Download Service Literature 80MGF SERIES UNITS
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80MGF Corp. 9801−L2 Revised 08−2004 Service Literature 80MGF SERIES UNITS 80MGF series units are mid−efficiency gas furnaces manufactured with tubular heat exchangers formed of aluminized or stainless steel. 80MGF units are available in heating capacities of 45,000 to 140,000 Btuh and cooling applications up to 5 tons. Refer to Engineering Handbook for proper sizing. Units are factory equipped for use with natural gas. A kit is available for conversion to LPG operation. All 80MGF units built proir to September 98 use electronic (direct spark) ignition. 80MGF−11 model units are equipped with the Lennox SureLight ignition system. The 80MGFX unit meets the California Nitrogen Oxides (NOx) Standards and California Seasonal Efficiency requirements. All units use a redundant gas valve to assure safety shut−off as required by A.G.A. or C.G.A. The heat exchanger, burners and manifold assembly can easily be removed for inspection and service by simply disconnecting gas, unplugging wiring harness and spark wires and removing four screws holding the heat exchanger in place. Then the heat exchanger slides out of the cabinet. All specifications in this manual are subject to change. Procedures outlined in this manual are presented as a recommendation only and do not supersede or replace local or state codes. In the absence of local or state codes, the guidelines and procedures outlined in this manual (except where noted) are recommended only and do not constitute code. Units may be installed in upflow, downflow or horizontal position. The heat exchanger is designed for upright or horizontal use only. When the unit is installed in the downflow position, the heat exchanger is field removed and reinstalled so it is upright when the cabinet is inverted. No field conversion is required when the unit is installed in the horizontal position. Introduction . . . . . . . . . . . . . . . . . . . . . . . . Specifications . . . . . . . . . . . . . . . . . . . . . . Blower Data . . . . . . . . . . . . . . . . . . . . . . . Parts Identification . . . . . . . . . . . . . . . . . . I Unit Components . . . . . . . . . . . . . . . . . . II Installation . . . . . . . . . . . . . . . . . . . . . . . 1 2 5 7 9 19 TABLE OF CONTENTS III Start Up . . . . . . . . . . . . . . . . . . . . . . . . . Preliminary Seasonal Checks . . . . . Heating Start Up . . . . . . . . . . . . . . . . IV Heating System Service Checks . . . V Typical Operating Characteristics . . . VI Maintenance . . . . . . . . . . . . . . . . . . . . VII Wiring and Sequence of Operation . VIII SureLight Control Troubleshooting . Page 1 19 20 20 20 22 24 26 40 © 1998 Lennox Industries Inc. SPECIFICATIONS Model No. 80MGF2(X)-45 80MGF2-60 80MGF3(X)-60 80MGF2-75 80MGF3(X)-75 Input Btuh (kW) 45,000 (13.2) 60,000 (17.6) 75,000 (22.0) Output Btuh (kW) 36,900 (10.8) 49,200 (14.4) 61,700 (18.1) A.F.U.E. 80.1% 80.5% California Seasonal Efficiency 75.4% 76.4% Flue size connection diameter in. (mm) round 75.9% 30 - 60 (17 - 33) 76.8% 45 - 75 (25 - 42) .50 (125) Gas Piping Size I.P.S. Natural or LPG/propane 1/2 (13) in. 9x7 10 x 7 9x7 10 x 7 229 x 178 254 x 178 229 x 178 254 x 178 1/4 (187) 1/3 (224) 1/4 (187) 1/3 (224) Tons 1, 1-1/2 or 2 2, 2-1/2 or 3 1, 1-1/2 or 2 2, 2-1/2 or 3 kW 3.5, 5.3 or 7.0 7.0, 8.8 or 10.6 3.5, 5.3 or7.0 7.0, 8.8 or 10.6 mm Blower motor output hp (W) Shipping weight lbs. (kg) 1 package 130 (59) Electrical characteristics 135 (61) 120 volts 60 hertz 1 phase (less than 12 amps) All models Optional Accessories (Must Be Ordered Extra) LPG/propane kit LB-69845L (38K84) Twinning Kit 15L3801 5 lbs. (2 kg) Up Flow/Horizontal Filter and Filter Rack Kits Up−Flow/Horizontal N & sizeoffilters− No. i f filt in. i (mm) ( ) Down flow Down-flow Filt Kit Filter 76.8% 4 (102) High static certified by A.G.A./C.G.A. in wg. (Pa) Nominal cooling th t can b that be added dd d 80.0% 3 (76) Temperature rise range F (C) Blower wheel nominal di diameter t x width idth 80.1% Single (32J02) Ten Pack (66K64) (1) 16 x 20 x 1 (406 x 508 x 25) Catalog No. LB-69843A (32J01) 3 lbs. (1 kg) No. & Size of Filters in. (mm) (2) 16 x 20 x 1 (406 x 508 x 25) Down-flow Combustible Floor Base LB-79239A (67J91) 10 lbs. (4 kg) Sidewall Power Venting Kit 79J15 25 lbs. (11 kg) Hanging Bracket Kit Annual Fuel Utilization Efficiency based on U.S. furnaces. Polyurethane frame type filter is furnished with kit. Filters are not furnished with kit and must be ordered extra. LB-69957 (46J66) 15 lbs. (8 kg) DOE test procedures and according to Page 2 FTC labeling regulations. Isolated combustion system rating for non-weatherized SPECIFICATIONS continued Model No. 80MGF4(X)-75 80MGF3/4(X)-100 80MGF4/5(X)-100 Input Btuh (kW) 75,000 (22.0) 100,000 (29.3) Output Btuh (kW) 61,700 (18.1) 82,000 (24.0) A.F.U.E. 80.0% 80.1% 80.0% California Seasonal Efficiency 76.3% 76.5% 77.0% Flue size connection diameter in. (mm) round 4 (102) Temperature rise range F (C) 45 - 75 (25 - 42) 35 - 65 (19 - 36) .50 (125) .65 (162) High static certified by A.G.A./C.G.A. in wg. (Pa) Gas Piping Size I.P.S. Natural or LPG/propane Blower wheel nominal di diameter t x width idth 1/2 (13) in. 12 x 8 12 x 9 305 x 203 305 x 229 1/2 (373) 3/4 (560) Tons 2, 2-1/2, 3, 3-1/2 or 4 3-1/2, 4, 5 or 6 kW 7.0, 8.8, 10.6, 12.3 or 14.1 12.3, 14.1, 17.6 or 21.1 mm Blower motor output hp (W) Nominal cooling th t can b that be added dd d Shipping weight lbs. (kg) 1 package 140 (64) Electrical characteristics 175 (79) 120 volts 60 hertz 1 phase (less than 12 amps) All models Optional Accessories (Must Be Ordered Extra) LPG/propane kit LB-69845L (38K84) LB-69845K (81J14) Twinning Kit 15L3801 5 lbs. (2 kg) Up Flow/Horizontal Filter and Filter Rack Kits Up−Flow/Horizontal No. & sizeoffilters− in. (mm) Down flow Down-flow Filter Kit Single (32J02) Ten Pack (66K64) (1) 16 x 20 x 1 (406 x 508 x 25) Catalog No. LB-69843A (32J01) 3 lbs. (1 kg) No. & Size of Filters in. (mm) Down-flow Combustible floor Base (2) 16 x 20 x 1 (406 x 508 x 25) LB-79239A (67J91) 10 lbs. (4 kg) Sidewall Power Venting Kit LB-79239B (67J92) 10 lbs. (4 kg) 79J15 25 lbs. (11 kg) Hanging Bracket Kit Annual Fuel Utilization Efficiency based on U.S. furnaces. Polyurethane frame type filter is furnished with kit. Filters are not furnished with kit and must be ordered extra. Single (46J14) Ten Pack (66K65) (1) 20 x 20 x 1 (508 x 508 x 25) LB-69957 (46J66) 15 lbs. (8 kg) DOE test procedures and according to Page 3 FTC labeling regulations. Isolated combustion system rating for non-weatherized SPECIFICATIONS continued Model No. 80MGF3/4-120 80MGF4/5-140 80MGF4/5(X)-120 Input Btuh (kW) 120,000 (35.2) 140,000 (41.0) Output Btuh (kW) 98,400 (28.8) 114,800 (33.6) A.F.U.E. California Seasonal Efficiency 80.0% 80.1% 80.0% Not Available 75.5% Not Available Flue size connection diameter in. (mm) round Temperature rise range F (C) 45 - 75 (25 - 42) High static certified by A.G.A./C.G.A. in wg. (Pa) .50 (125) Gas Piping Size I.P.S. Natural or LPG/propane in. (mm) Blower wheel nominal diameter x width in. 1/2 (13) 12 x 9 305 x 203 305 x 229 1/2 (373) 3/4 (560) Tons 2, 2-1/2, 3, 3-1/2 or 4 3-1/2, 4, 5 or 6 kW 7.0, 8.8, 10.6, 12.3 or 14.1 12.3, 14.1, 17.6 or 21.1 mm Shipping weight lbs. (kg) 1 package 190 (86) 175 (79) Electrical characteristics 120 volts 60 hertz 1 phase (less than 12 amps) All models Optional Accessories (Must Be Ordered Extra) LPG/propane kit LB-69845K (81J14) Twinning Kit 15L3801 5 lbs. (2 kg) Up−Flow/Horizontal Filter and Filter Rack Kits No. & sizeoffilters− in. (mm Single (46J14) Ten Pack (66K65) (1) 20 x 20 x 1 (508 x 508 x 25) Catalog No. Down-flow Filter Rack .65 (162) 12 x 8 Blower motor output hp (W) Nominal cooling that can be added 5 (127) 4 (102) No. & Size of Filters Down-flow Combustible Floor Base Single (58J93) Ten Pack (66K66) (1) 20 x 20 x 1 (508 x 508 x 25) LB-69843A (32J01) 3 lbs. (1 kg) in. (2) 16 x 20 x 1 mm (2) 406 x 508 x 25 LB-79239B (67J92) 10 lbs. (4 kg) Sidewall Power Venting Kit LB-79239C (67J93) 12 lbs. (5 kg) 79J15 25 lbs. (11 kg) Hanging Bracket Kit LB-69957 (46J66) 15 lbs. (8 kg) Annual Fuel Utilization Efficiency based on U.S. DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non-weatherized furnaces. Polyurethane frame type filter is furnished with kit. 2 in. x 5 in. (51 mm x 127 mm) flue adaptor furnished with -140 input furnaces for connection to furnace induced draft blower. Filters are not furnished with kit and must be ordered extra. Page 4 BLOWER PERFORMANCE DATA 80MGF2-45, 80MGF2-60 AND 80MGF2-75 BLOWER PERFORMANCE Air Volume at Various Blower Speeds External Static Pressure High Medium-High Medium-Low Low in. w.g. Pa cfm L/s cfm L/s cfm L/s cfm L/s 0 0 1270 600 980 460 770 365 570 270 .05 12 1245 590 975 460 770 365 565 265 .10 25 1220 575 975 460 770 365 565 265 .15 37 1195 565 965 455 765 360 560 265 .20 50 1170 550 960 455 760 360 560 265 .25 62 1140 540 950 450 760 360 555 260 .30 75 1110 525 940 445 760 360 550 260 .40 100 1060 500 910 430 750 355 545 255 .50 125 990 465 880 415 740 350 540 255 .60 150 900 425 810 380 690 325 530 250 .70 175 800 380 740 350 630 295 520 245 NOTE All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished) in place. Also see Filter Air Resistance table 80MGF3-60 AND 80MGF3-75 BLOWER PERFORMANCE Air Volume at Various Blower Speeds External Static Pressure High Medium-High Medium-Low Low in. w.g. Pa cfm L/s cfm L/s cfm L/s cfm L/s 0 0 1425 670 1240 585 1000 470 800 380 .05 12 1415 670 1230 580 995 470 800 380 .10 25 1400 660 1220 575 990 465 795 375 .15 37 1385 655 1200 565 985 465 795 375 .20 50 1370 645 1180 555 980 460 790 375 .25 62 1350 635 1160 545 970 460 780 370 .30 75 1330 630 1140 540 955 450 770 365 .40 100 1280 605 1095 515 925 435 750 355 .50 125 1210 570 1040 490 900 425 720 340 .60 150 1135 535 985 465 860 405 680 320 .70 175 1070 505 920 435 800 380 630 300 NOTE All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished) in place. Also see Filter Air Resistance table Page 5 80MGF4-75, 80MGF3/4-100 AND 80MGF3/4-120 BLOWER PERFORMANCE Air Volume at Various Blower Speeds External Static Pressure High Medium-High Medium Medium-Low Low in. w.g. Pa cfm L/s cfm L/s cfm L/s cfm L/s cfm L/s 0 0 1830 865 1600 755 1325 625 1070 505 880 415 .05 12 1815 855 1585 750 1320 625 1070 505 880 415 .10 25 1800 850 1570 740 1315 620 1070 505 880 415 .15 37 1875 885 1550 730 1310 620 1065 505 875 415 .20 50 1750 825 1530 720 1300 615 1060 500 875 415 .25 62 1725 815 1515 715 1290 610 1050 495 870 410 .30 75 1700 800 1500 710 1275 600 1040 490 870 410 .40 100 1650 780 1460 690 1245 590 1020 480 860 405 .50 125 1600 755 1420 670 1210 570 1000 470 840 395 .60 150 1550 730 1380 650 1170 550 980 460 820 385 .70 175 1480 700 1330 630 1130 535 960 455 790 375 NOTE All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished) in place. Also see Filter Air Resistance table 80MGF4/5-100, 80MGF4/5-120 AND 80MGF4/5-140 BLOWER PERFORMANCE Air Volume at Various Blower Speeds External Static Pressure High Medium-High Medium Medium-Low Low in. w.g. Pa cfm L/s cfm L/s cfm L/s cfm L/s cfm L/s 0 0 2450 1155 2160 1020 1970 930 1700 800 1500 710 .05 12 2440 1150 2155 1015 1965 925 1695 800 1500 710 .10 25 2430 1145 2150 1015 1960 925 1690 800 1495 705 .15 37 2415 1140 2135 1010 1950 920 1685 795 1495 705 .20 50 2400 1135 2120 1000 1940 915 1680 795 1490 705 .25 62 2380 1125 2105 995 1930 910 1675 790 1480 700 .30 75 2360 1115 2090 985 1915 905 1670 790 1470 695 .40 100 2310 1090 2050 965 1870 880 1650 780 1440 680 .50 125 2260 1065 2000 945 1810 855 1610 760 1410 665 .60 150 2180 1030 1950 920 1750 825 1560 735 1370 645 .70 175 2100 990 1890 890 1700 800 1520 715 1330 630 NOTE All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished) in place. Also see Filter Air Resistance table FILTER AIR RESISTANCE cfm (L/s) in. w.g. (Pa) 0 (0) 0.00 (0) 200 (95) 0.01 (2) 400 (185) 0.03 (7) 600 (280) 0.04 (10) 800 (375) 0.06 (15) 1000 (470) 0.09 (22) 1200 (560) 0.12 (30) 1400 (655) 0.15 (37) 1600 (750) 0.19 (47) 1800 (845) 0.23 (57) 2000 (935) 0.27 (67) 2200 (1030) 0.33 (82) 2400 (1125) 0.38 (95) 2600 (1220) 0.44 (110) Page 6 80MGF PARTS IDENTIFICATION and ORIENTATION VENT ADAPTER CABINET TOP HEAT EXCHANGER ASSEMBLY FLUE BOX COMBUSTION AIR BLOWER PRESSURE SWITCH 80MGF CABINET PRIMARY LIMIT FRONT ACCESS PANEL NOx TURBULATOR BURNER ASSEMBLY TRANSFORMER CONTROL BOARD SECONDARY LIMITS CABINET BOTTOM BLOWER ASSEMBLY DOOR INTERLOCK SWITCH FIGURE 1 HEATING COMPONENTS (shown in horizontal position) PRIMARY LIMIT ROLLOUT SWITCH (2) COMBUSTION AIR PROVE SWITCH MANIFOLD Left Bottom BURNERS Back Front Top Right HEAT EXCHANGER GAS VALVE COMBUSTION AIR BLOWER COLLECTOR FIGURE 2 Page 7 80MGF BURNER ASSEMBLY (Shown With SureLight ignitor) SURELIGHT IGNITOR ROLLOUT SWITCHES BURNER BOX TOP VEST PANEL UPPER BURNER MOUNTING RAIL LOWER BURNER MOUNTING RAIL FLAME SENSOR BURNER HEAT EXCHANGER PRIMARY LIMIT Top Back ORIFICE Left GAS VALVE Right Front BURNER BOX MANIFOLD Bottom FIGURE 3 80MGF BLOWER DOOR COMPONENTS − BLOWER ACCESS (SureLight MODEL SHOWN) To Access Blower: 1− Turn off power to unit and disconnect L1 and L2 line voltage power. 2− Disconnect thermostat wiring connections from furnace control board. 3− Disconnect blower leads from control board. 4− Disconnect J1 from P1. 5− Disconnect 6 pin P156 from control board. 6− Disconnect 9 pin P58 from control board. 7− Disconnect sensor wiire from center of board. 8− Remove screws (2) and lift panel from unit. 4 7 5 Top 3 Right 6 8 2 1 FIGURE 4 Page 8 Back Left Front Bottom I−UNIT COMPONENTS (Figures 1, 2, 3) 80MGF unit components are shown in figure 1. The blower controls, gas valve and burners can be accessed by removing the front access panel. A separate blower access door is located behind the front access panel. Electrical control components are mounted to the blower access door. 80MGF units are factory equipped with bottom return air panels. The panels are designed to be field removed as required for bottom air return. Indentations on side of units, show where side air return opening should be cut during installation. A−Blower Door Components (Figure 4) Electrical burner control and blower control components are located on the outside surface of the blower access door. Jackplugs allow the blower door to be easily removed for blower service. Located on the blower door are the unit transformer (T1), the furnace control (A3) and door interlock switch (S51). Furnace control (A3) combines the function of a burner ignition control and blower control. 1− Control Transformer (T1) A transformer located on the blower door provides power to the low voltage section of the unit. Transformers on all models are rated 30VA with a 120V primary and a 24V secondary. 2−Door Interlock Switch (S51) A door interlock switch rated 16A at 125VAC is located on the blower access door. The switch is wired in series with line voltage. When the blower door is removed the unit will shut down. 3− Ram Control (A3) The furnace control combines burner ignition functions with blower control functions. Some early model 80MGF units utilize a furnace control manufactured by RAM Electronics Corporation. The RAM" board is a printed circuit board which controls the blower, gas valve, combustion air blower and ignition spark. It also monitors the flame, limit and gas valve operation. The control has a non−adjustable, factory preset on" fan timing (45 seconds). Fan off" timings are adjustable. The board utilizes both 120 and 24VAC. See figure 5. The board is also equipped with a diagnostic LED for use when troubleshooting the unit. When the furnace is idle (blower off and no heating or cooling demand), the diagnostic LED flashes at a slow steady rate. On a call for heat, the diagnostic LED begins flashing at a fast rate and the combustion air blower is energized. The LED flashes different codes to indicate problem con- ditions. The diagnostic LED lights red (not flashing) to indicate control board failure. Table 3 shows how to interpret the other LED modes. Pre-Purge On a call for heat, the combustion air blower begins operating. If the combustion air prove switch closes, the combustion air blower continues to operate for 45 seconds (pre-purge) before allowing ignition. Pre-purge allows the heat exchanger to be cleared of combustion products and to introduce fresh air for combustion. If the combustion air prove switch does not close, the combustion air blower continues to run indefinitely (until the prove switch closes). Post-Purge After a demand, the combustion air blower continues to operate for 5 seconds (post-purge) before stopping. Postpurge allows the heat exchanger to be cleared of combustion products. Ignition Control The ignition control is a direct spark ignition control module integral to the furnace control. See figure 5. When there is a call for heat, the control delays ignition until combustion air blower operation has been proved and pre-purge period has elapsed. It then opens the gas valve and generates a spark to ignite the burners. Trial for ignition lasts for 7 seconds. At the same time, the control begins monitoring the flame sensor. If the flame current is too weak (less than 1 microamp) or if the burners do not ignite (within the 7 second ignition trial), the control will shut off spark and the combustion air blower and de-energize the gas valve. Flame current should be between 1 and 5 microamps to keep the gas valve open. See figure 23. The control will attempt to ignite the burners up to two more times. Each time the control restarts the ignition sequence, it begins with a 45 second pre-purge. If flame is not sensed after the third trial, the control locks out. Lockout means that the control shuts off the gas valve, spark and combustion air blower for 60 minutes. At the end of 60 minutes the control completely resets and will attempt ignition up to three times. The control can be manually reset before the end of 60 minutes by momentarily turning off power to the unit. Page 9 DANGER Shock hazard. Spark related components contain high voltage. Disconnect power before servicing. Control is not field repairable. If control is inoperable, simply replace entire control. Can cause injury or death. Unsafe operation will result if repair is attempted. RAM CONTROL (A3) SPARK OUTPUT 24VAC VOLT TERMINAL CONNECTIONS LINE VOLTAGE TERMINAL CONNECTIONS See Table 2 for Terminal Functions See Table 2 for Terminal Functions FAN-OFF TIMING SWITCHES THERMOSTAT CONNECTIONS DIAGNOSTIC LED FIGURE 5 TABLE 1 Furnace Control A3 Limit Response During Operation Response Condition Loss of Flame Sensed Before End of 45 second Blower On Delay (3 or Fewer Trials for Ignition) Combustion Air Blower Gas Valve Supply Air Blower Diagnostic LED On On (Spark Starts Within 0.8 seconds) On Fast Flash Blower Control and Timings DANGER Loss of Flame Sensed After 45 second Blower On Delay (3 or Fewer Trials for Ignition) On Loss of Flame Sensed (More Than 3 Trials for Ignition) Off Off Off 2 Flashes Flame Sensed Without Demand On Off On 5 Flashes Primary or Secondary Limit Open On Off On 4 Flashes Rollout Switch Open On Off On 4 Flashes Combustion Air Prove Switch Open On Off On 3 Flashes Off Then On With Spark After PrePurge When flame is sensed, the indoor blower starts after a 45 second delay. Gas valve remains open and blower continues to run until demand stops, flame sensor senses loss of flame, a limit opens or the prove switch opens. If any of these events occur during a thermostat demand, the gas valve closes and the diagnostic LED registers the error condition (table 1). On Electrical Shock Hazard. This control contains field adjustable switches and also contains line voltage. Make sure power is disconnected before making any field adjustments or performing any service procedure. Fast Flash NOTEIf fan off" time is set too low, residual heat in heat exchanger may cause primary limit S10 to trip resulting in frequent cycling of blower. If this occurs, adjust blower to longer time setting. Fan ON" timing (time that the burners operate before the supply air blower starts) is fixed at 45 seconds and cannot be adjusted. Page 10 Fan OFF" timings (time that the blower operates after a heating or cooling demand has been satisfied) are determined by the arrangement of switches on the furnace control board. See figure 5. To adjust fan off " timings, gently reposition the switches to a new timing position. Figure 6 shows the various fan off" timings and how switches should be positioned. 80MGF−1, −2, −3, −4 and −6 units are shipped with a factory fan off" setting of 180 seconds. 80MGF−5 and −7 units are shipped with factory "off" setting of 60 seconds. Fan off" time will affect comfort and efficiency and is adjustable to satisfy individual applications. The fan off" timing is initiated after a heating or cooling demand but not after a blower demand (that is, when indoor thermostat switch is changed from ON to AUTO and heating/cooling demand is not present, the blower stops immediately). TABLE 2 C Screw Strip Screw Strip Screw Strip Screw Strip Early Units 1/4" Spade Later Units Screw Strip LOCATED ON FURNACE CONTROL (A3) Fan-Off Timings Switch 1 2 Timing Seconds Off Off On Off On Off 90 120 180 On On 240 FIGURE 6 Diagnostic LED The furnace control is equipped with a diagnostic LED used for troubleshooting the unit and the control. LED functions are shown in table 3. TABLE 3 Furnace Control A3 Diagnostic LED Meaning Remedy Steady On Control Failure Replace Control Slow Flash Normal Operation and No Call For Heat ---- Fast Flash Normal Operation with Call For Heat ---- 24VAC Common Two Flashes Control Lockout Failed to Sense or Sustain Flame. Check Gas Valve, Burners, Spark Electrode and Wire, Flame Sensor. Replace Control If All OK. Three Flashes Pressure Switch Open Failed to Prove Combustion Blower Operation or Blocked Vent. Repair or Replace as Necessary. Four Flashes Open Limit Check Primary Limit, Rollout Switches and Secondary Limits. Find source of Overtemperature. If all OK, Reset or Replace Limits as Necessary. Five Flashes Flame Sensed and Gas Valve Not Energized. Check Gas Valve. If OK, Check Flame Sensor. FURNACE CONTROL A3 TERMINAL DESIGNATIONS Terminal Type Function Y G R W FAN-OFF TIME ADJUSTMENT SWITCHES Cooling Demand Blower Demand 24VAC to Thermostat Heating Demand 120VAC HOT AUX 1/4" Spade 1/4" Spade CMB BLWR 1/4" Spade Line Voltage In Line Voltage Out (Switched) Switched 120VAC to Combustion Air Blower ACB HEAT 1/4" Spade Switched 120VAC to Blower Heating Tap ACB COOL 1/4" Spade Switched 120VAC to Blower Cooling Tap VALVE 24VAC HOT GROUND FLAME SENSE 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade PSW 1/4" Spade HI LIMIT IN 1/4" Spade HI LIMIT OUT 1/4" Spade 24VAC to Gas Valve 24VAC In From Transformer To Cabinet Ground Flame Microamp Sensing 24VAC In From Pressure Switch Switch Open: Prohibits Ignition Switch Closed: Allows Ignition 24VAC In From Limits Limit Open: Closes Gas Valve Limits Closed: Allows Ignition 24VAC to Limit Train and Pressure Switch ROLLOUT IN 1/4" Spade 24VAC In From Rollout Switches LED State Page 11 4− EGC Control (A3) Some early model 80MGF units are equipped with an integrated ignition/blower control (EGC−1 or EGC−2) which controls ignition, safety circuits, blower operation, fan off timing, and allows for thermostat connection and troubleshooting. The EGC is a printed circuit board which is divided into two sections, 120 and 24VAC. Line voltage comes into the board on the 120VAC side. See figure 8. Terminal designations are listed in tables 5 and 6. Ignition Control 80MGF units use the EGC direct spark integrated ignition control. The EGC controls and monitors the entire sequence of operation. On a call for heat from the thermostat the control monitors the combustion air blower pressure switch. The control will not begin the heating cycle if the pressure switch is closed (by-passed). Once the pressure switch is determined to be open, the combustion air blower is energized. When the differential in pressure across the pressure switch is great enough, the pressure switch closes and a 15 second pre-purge period begins. After the pre-purge period, the gas valve will open and ignition (spark) will be attempted for 10 seconds. After ignition, the control initiates a ten second flame stabilization period. The flame stabilization period allows the burners to heat up and the flame to stabilize. Once flame is established, the control will constantly monitor the burner flame using flame rectification. Flame failure response time is 0.8 seconds. If the initial attempt for ignition fails, the sequence is repeated up to five times. After the fifth trial, the control goes into Watchguard"*. During watchguard mode, the entire unit will be de-energized for one hour. After one hour the control will repeat the ignition sequence. Watchguard may be manually reset by breaking and remaking thermostat demand. when no voltage should be present, the control de-energizes the combustion air blower which terminates voltage to the valve. The system goes into hard lock-out which is reset only by removing power to the unit. If flame is sensed when no flame should be present, the control will energize the combustion and indoor blowers. The unit will remain locked in this sequence until the flame is no longer sensed or the main power is turned off to reset the control. DANGER Shock hazard. Avoid personal injury. Make sure to disconnect power before changing fan off" timing. Blower Operation / Fan Off Timings Fan off" timing (time that the blower operates after the heat demand has been satisfied) can be adjusted by moving the jumper on the EGC blower control board. Figure 7 shows the various fan off" timings and how jumper should be positioned. To adjust fan off " timing, gently disconnect jumper and reposition across pins corresponding with new timing. Unit is shipped with a factory fan off" setting of 180 seconds. Fan on" time is factory set at 45 seconds following the opening of the main gas valve and is not adjustable. Fan off" time will affect comfort and efficiency and is adjustable to satisfy individual applications. The fan off" timing is initiated after a heating demand but not after a cooling demand. NOTEIf fan off" time is set too low, residual heat in heat exchanger may cause primary limit S10 to trip, resulting in frequent cycling of blower. If this occurs, adjust blower to longer fan off" time setting. *NOTE−If flame is established beyond the 10 second flame stabilization period then lost, the control resets for five more ignition trials. The control can be reset five times during one unsatisfied thermostat demand, providing a maximum of 25 trials for ignition. Safety Circuits During the entire heating demand the control monitors the safety circuits. If the primary or secondary heating limits open, the control de-energizes the main gas valve and combustion air blower while the indoor blower remains energized. When the limit automatically resets, the ignition sequence also resets. If either of the limits trip five consecutive times during one unsatisfied thermostat demand, the control will go into watchguard for one hour. The control monitors main valve voltage. If voltage is sensed FAN-OFF TIME ADJUSTMENT TIMING JUMPER 180 To adjust fan-off timing: Remove jumper from EGC and select one of the other pin combinations to achieve the desired time. 60 TIMING PINS (seconds) Leave jumper off for 240 second fan-off timing. 120 90 FIGURE 7 Thermostat Connection Thermostat wires are connected to the terminal strip found on the EGC control board. Page 12 Troubleshooting TABLE 4 The EGC control board is equipped with two diagnostic green LEDs to indicate the mode of failure. The LED lights are marked DIAG #1 and DIAG #2. The codes are given in table 4. On the EGC−1 only, the last failure code is stored in memory and may be retrieved by depressing and holding the memory recall button. When this button is depressed, the LEDs will signal the last failure code in memory. Power must be restored to the control (depress blower interlock switch) within one minute of blower access panel removal in order to retain memory. To clear the memory of the stored failure code, remove main power and short the jumper next to the diagnostic button for five seconds. EGC DIAGNOSTIC CODES DIAG #1 DIagnostic Condition DIAG #2 Simultaneous Flash Simultaneous Flash On Flash Flash Off Alternate Flash Alternate Flash Off Flash Flash On Continuous On Continuous On EGC−2 INTEGRATED CONTROL 8 * * * 9 10 11 12 13 14 * * * 15 16 Power ON". Normal Operation. Increased flash rate indicates there is a heating demand. Primary or Secondary Limit Switch Open. Auto-Reset Switch. Pressure Switch Watchguard, pressure switch opened during operation or condensate drain blocked. Watchguard, burners failed to ignite. Flame sensed without valve energized. Roll-out Switch Open. Manual-Reset Switch. Circuit board self-check failure or ignition/blower control is wired incorrectly. NOTE: EGC−1 board will have terminal (#15) for 7 ACB low speed. NOTE: EGC−1 board will have terminal (#16) for ACB Heat speed. 6 5 4 DIAGNOSTIC LEDS DIAGNOSTIC MODULE BLOWER TIME ADJUSTMENT JUMPER THERMOSTAT TERMINAL STRIP (DETACHABLE) 1 EDGE CONNECTION 2 7 8 5 3 24VAC PLUG P20 4 6 9 3 2 1 RED DIAGNOSTIC BUTTON DIAGNOSTIC CODE ERASE JUMPER (EGC−1 only. Depress button and hold (Remove power to control and short pins for for display of last failure code.) 10 seconds to erase previous code.) FIGURE 8 Page 13 TABLE 5 BLOWER CONTROL A15 TERMINAL DESIGNATIONS Terminal Designation Type Function (See fig. 8) R Screw Strip G Screw Strip W Screw Strip Y Screw Strip C 1 2 3 4, 5, 6 Screw Strip 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 7 1/4" Spade 8 9 10 11 12, 13 14 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 15 1/4" Spade 16 1/4" Spade 24VAC to Thermostat (Red) Manual Fan Input from Thermostat (Green) Heat Demand Input from Thermostat (White) Cool Demand Input from Thermostat (Yellow) Common Ground to Thermostat 24VAC Hot from Transformer 24VAC Return to Transformer 24VAC Ground 120VAC Return − 120VAC Common 120VAC Return − 120VAC Common Input Combustion Blower (Line Voltage) Heat Only Accessory (Line Voltage) 120VAC Hot to Transformer 120VAC Hot Input Accessories (Line Voltage) ACB Cool Speed (Line Voltage) EGC−1 ACB Low Cont. Speed (Line Voltage) EGC−2 ACB Heat Speed (Line Voltage) ACB Heat Speed (Line Voltage) 5−Flame Sensor (−11 models) A flame sensor is located on the left side of the burner support. See figure 9. The sensor is mounted on a bracket in the burner support and the tip protrudes into the flame envelope of the left−most burner. The sensor is fastened to burner supports and can be removed for service without removing any part of the burners. During operation, flame is sensed by current passed through the flame and sensing electrode. The SureLight control allows the gas valve to remain open as long as flame signal is sensed. NORMAL FLAME SIGNAL u 0.7 MICROAMPS LOW FLAME SIGNAL v 0.7 MICROAMPS MINIMUM FLAME SIGNAL v 0.15 MICROAMPS 1/4 in. 7 mm 1/32 in. 0.79 mm BURNER FLAME TABLE 6 Rollout Switch Out Spare Gas Valve Common Pressure Switch Return Hi Limit Return / Pressure Switch Out Flame Sensor Gas Valve Out High Limit Out Rollout Switch Return DANGER Shock hazard. Disconnect power before servicing. Control is not field repairable. If control is inoperable, simply replace entire control. Can cause injury or death. Unsafe operation will result if repair is attempted. 3/16 in. 4.7 mm SIDE VIEWSENSOR END VIEW FIGURE 9 NOTE − The 80MGF furnace contains electronic components that are polarity sensitive. Make sure that the furnace is wired correctly and is properly grounded. EGC CONTROL JACK/PLUG 20 TERMINAL DESIGNATIONS Pin # Function 1 2 3 4 5 6 7 8 9 11/16 in. 18 mm 1/32 in. 0.79 mm 6− SureLight Ignition System A3 (−11 models) All 80MGF−11 model units are equipped with the Lennox SureLight ignition system. The system consists of ignition control board (figure 11 with control terminal designations in table 10) and ignitor (figure 12). The board and ignitor work in combination to ensure furnace ignition and ignitor durability. The SureLight integrated board controls all major furnace operations. The board also features two LED lights for troubleshooting and two accessory terminals rated at (4) four amps. See table 9 for troubleshooting diagnostic codes. Table 7 and 8 show jack plug terminal designations. Units equipped with the SureLight board can be used with either electronic or electro−mechanical thermostats without modification. The SureLight ignitor is made of durable silicon−nitride. Ignitor longevity is also enhanced by voltage ramping by the control board. The board finds the lowest ignitor temperature which will successfully light the burner, thus increasing the life of the ignitor. Page 14 TABLE 7 SureLight BOARD J156 (J2) TERMINAL DESIGNATIONS PIN # FUNCTION 1 Ignitor 2 Not Used 3 Ignitor Neutral 4 Combustion Air Blower Line Voltage 5 Not Used 6 Combustion Air Blower Neutral TABLE 8 SureLight BOARD J58 (J1) TERMINAL DESIGNATIONS PIN # FUNCTION 1 Primary Limit In 2 Gas Valve Common 3 Roll Out Switch Out 4 Gas Valve 24V 5 Pressure Switch In 6 Pressure Switch and Primary Limit Out 7 Not Used 8 Roll Out Switch In 9 Ground ELECTROSTATIC DISCHARGE (ESD) Precautions and Procedures CAUTION Electrostatic discharge can affect electronic components. Take precautions during furnace installation and service to protect the furnace’s electronic controls. Precautions will help to avoid control exposure to electrostatic discharge by putting the furnace, the control and the technician at the same electrostatic potential. Neutralize electrostatic charge by touching hand and all tools on an unpainted unit surface, such as the gas valve or blower deck, before performing any service procedure. a−Electronic Ignition On a call for heat the SureLight control monitors the combustion air blower pressure switch. The control will not begin the heating cycle if the pressure switch is closed (by− passed). Once the pressure switch is determined to be open, the combustion air blower is energized. When the differential in the pressure switch is great enough, the pressure switch closes and a 15−second pre−purge begins. If the pressure switch is not proven within 2−1/2 minutes, the control goes into Watchguard−Pressure Switch mode for a 5−minute re−set period. After the 15−second pre−purge period, the SureLight ignitor warms up for 20 seconds after which the gas valve opens for a 4−second trial for ignition. 80MGF units with board 63K89, 24L85 or 56L83: the ignitor stays energized for the first second of the 4−second trial. Units with board 97L48: ignitor stays energized for the full 4−second trial for ignition. If ignition is not proved during the 4−second period, the control will try four more times with an inter purge and warm−up time between trials of 35 seconds. After a total of five trials for ignition (including the initial trial), the control goes into Watchguard−Flame Failure mode. After a 60−minute reset period, the control will begin the ignition sequence again. The SureLight control board has an added feature that prolongs the life of the ignitor. After a successful ignition, the SureLight control utilizes less power to energize the ignitor on successive calls for heat. The control continues to ramp down the voltage to the ignitor until it finds the lowest amount of power that will provide a successful ignition. This amount of power is used for 255 cycles. On the 256th call for heat, the control will again ramp down until the lowest power is determined and the cycle begins again. b−Fan Time Control The fan on time of 45 seconds is not adjustable. Fan off time (time that the blower operates after the heat demand has been satisfied) can be adjusted by flipping the dip switches located on the SureLight integrated control. The unit is shipped with a factory fan off setting of 90 seconds. Fan off time will affect comfort and is adjustable to satisfy individual applications. See figure 10. FAN-OFF TIME ADJUSTMENT 60sec. 90sec. 120sec. 180sec. To adjust fan−off timing, flip dip switch to desired setting. FIGURE 10 Page 15 The SureLight board is equipped with two LED lights for troubleshooting. The lights are found just above the 24VAC terminal strip see figure 8. The diagnostic codes are listed below in table 9. TABLE 9 DIAGNOSTIC CODES MAKE SURE TO ID LED’S CORRECTLY: REFER TO INSTALLATION INSTRUCTIONS FOR CONTROL BOARD LAYOUT. LED #1 LED #2 DESCRIPTION SIMULTANEOUS SLOW FLASH SIMULTANEOUS SLOW FLASH Power − Normal operation Also signaled during cooling and continues fan. SIMULTANEOUS FAST FLASH SIMULTANEOUS FAST FLASH Normal operation − signaled when heating demand initiated at thermostat. SLOW FLASH ON OFF SLOW FLASH ALTERNATING SLOW FLASH ALTERNATING SLOW FLASH SLOW FLASH OFF ON ON ON OFF SLOW FLASH ON OFF ON FAST FLASH SLOW FLASH SLOW FLASH FAST FLASH ALTERNATING FAST FLASH ALTERNATING FAST FLASH Primary or Secondary limit open. Units with board 63K8901 or 24L85: Limit must close within 5 trials for ignition or board goes into one hour limit Watchguard. Units with board 56L83 or 97L48: Limit must close within 3 minutes or board goes into one hour limit Watchguard. Pressure switch open or has opened 5 times during a single call for heat; OR: Blocked inlet/exhaust vent; OR: Condensate line blocked; OR: Pressure switch closed prior to activation of combustion air blower. Watchguard − burners fail to ignite. Flame sensed without gas valve energized. Rollout switch open. OR: 9 pin connector improperly attached. Circuit board failure or control wired incorrectly. Main power polarity reversed. Switch line and neutral. Low flame signal. Measures below .7 microAmps. Replace flame sense rod. Improper main ground or line voltage below 75 volts; OR: Broken ignitor; OR: Open ignitor circuit. NOTE − Slow flash equals 1 Hz (one flash per second). Fast flash equals 3 Hz (three flashes per second). Drop out flame sense current < 0.15 microAmps SureLight Ignitor SURELIGHT INTEGRATED CONTROL BOARD SURELIGHT IGNITOR FIGURE 12 TABLE 10 TERMINAL DESIGNATIONS ACB COOL Blower − Cooling Speed (Line Volt) ACB HEAT Blower − Heating Speed (Line Volt) PARK Alternate Blower Speeds (Dead) Continuous Low Speed Blower ACB LOW Accessory Terminal (Line Volt) ACC TX 120VAC Hot to Transformer HOT 120VAC Hot Input HTG ACC Heat Only Accessory (Line Volt) 120VAC Neutrals NEUTRALS 24VAC Hot from Transformer 24VAC HOT 24VAC RTN 24VAC Return from Transformer FLAME SENSE Flame Sense Terminal FIGURE 11 Page 16 B−Blower Motors and Capacitors All 80MGF units use direct drive blower motors. All motors used are 120V permanent split capacitor motors to ensure maximum efficiency. See table 11 for ratings. TABLE 11 80MGF BLOWER RATINGS 120V 1PH BLOWER MOTOR 80MGF2 80MGF3 80MGF3/4 80MGF4 80MGF4/5 80MGF5/6 HP 1/4 1/3 1/2 1/2 3/4 3/4 CAP 5MFD 370V 5MFD 370V 7.5MFD 370V 7.5MFD 370V 40MFD 370V 40MFD 370V SUPPLY AIR BLOWER AND SECONDARY LIMITSSECONDARY LIMITS (S21) Top Back Left Front Bottom Right tive. If pressure becomes less negative (signifying an obstruction) the pressure switch opens. When the pressure switch opens, the furnace control (A3) immediately closes the gas valve to prevent burner operation. D−Flame Rollout Switches (S47) Flame rollout switch is a high temperature limit located on top of the burner box. Each furnace is equipped with two identical switches. One switch is located over the leftmost burner and the other switch is located over the rightmost burner. The limit is a N.C. SPST manual-reset limit connected in series with the ignition control A3. When S47 senses rollout, the ignition control immediately stops ignition and closes the gas valve. If unit is running and flame rollout is detected, the gas valve will close and ignition control will be disabled. Rollout can be caused by a blocked flue or lack of combustion air. The switch is factory set and cannot be adjusted. The setpoint will be printed on the side of the limit. The switch can be manually reset. To manually reset a tripped switch, push the reset button located on the control. ROLLOUT SWITCH (S47) MANUAL RESET BUTTON BLOWER MOTOR FIGURE 14 MOTOR CAPACITOR E−Primary Limit Control (S10) To Remove Blower From Unit: Remove Bolts and Wiring Jackplugs. Then Slide Out Front of Unit. LIMIT CONTROL FOR 80MGF SERIES UNITS FIGURE 13 THIS TYPE AUTO-RESET LIMIT IS USED FOR THE PRIMARY LIMIT (S10) AND RIGHT SECONDARY LIMIT (S21) (see FIGURE 13) C−Combustion Air Blower (B6) All 80MGF units use a combustion air blower to move air through the burners and heat exchanger during heating operation. The blowers will use either a shaded pole 120V motor or a C−frame 120V motor. Shaded pole and C−frame motors do not use run capacitors. The motor operates during all heating operation and is controlled by furnace control A3. The motor also operates for a period before burner ignition (pre−purge). The pre−purge time is 45 seconds for 80MGF units equipped with the RAM control and 15 seconds for units equipped with the EGC control. With either the RAM, EGC or SureLight control board, the motor will operate 5 seconds after the gas valve closes (post-purge). A pressure switch connected to the combustion air blower housing is used to prove combustion air blower operation. The switch monitors air pressure in the blower housing. During normal operation, the pressure in the housing is nega- FIGURE 15 The primary limit (S10) on 80MGF units is located in the middle of the heating vestibule panel. When excess heat is sensed in the heat exchanger, the limit will open. If the limit is tripped, the furnace control energizes the supply air blower and closes the gas valve. The limit automatically resets when unit temperature returns to normal. The switch is factory set and cannot be adjusted. The switch may have a different setpoint for each unit model number. However, the setpoint will be printed on the side of the limit. There are two types of primary limit. See figures 15 and 16. Page 17 F−Secondary Limit Controls (S21) The secondary limit (S21) on 80MGF units is located in the blower compartment in the back side of the blower housing. When excess heat is sensed in the heat blower compartment, the limit will open. If the limit is tripped, the furnace control energizes the supply air blower and closes the gas valve. The limit automatically resets when unit temperature returns to normal. The switch is factory set and cannot be adjusted. Two limits are supplied in each furnace and each limit is a different style (figures 15 and 16). The setpoint will be printed on the side of the limit. If stick limit (Figure 16) suffers from nuisance trips and the furnace is in the horizontal position, replace with limit kit no. 50L98. LIMIT CONTROL (S21) (S10) FOR 80MGF SERIES UNITS G−Spark Electrode and Flame Sensor (Models with EGC or Ram control only) Figure 17 shows the arrangement of flame sensor, spark electrode and burners. The Ram and EGC ignition control uses direct spark to ignite the rightmost burner and the burners cross-light to the left. The flame sensor uses flame rectification to sense combustion. A flame retention ring in the end of each burner is used to maintain correct flame length and shape and to keep the flame from lifting off the burner head. Figure 18 shows the gap between tip of the electrodes and the burner surface. H−Gas Valve THIS TYPE AUTO-RESET LIMIT IS USED FOR THE LEFT SECONDARY LIMIT (S21) (see FIGURE 13) LIMIT SPADE CONNECTORS LIMIT INSULATING COVER The 80MGF uses a gas valve manufactured by Honeywell or WhiteRodgers. The valve is internally redundant to assure safety shut−off. If the gas valve must be replaced, the same type valve must be used. 24VAC terminals and gas control knob are located on top of the valve. All terminals on the gas valve are connected to wires from the electronic ignition control. 24V applied to the terminals energizes the valve. Inlet and outlet pressure taps are located on the valve. A regulator adjustment screw is located on the valve. Refer to figures 19 or 20 for location of valve features. INSULATING COVER (s) FIGURE 16 An LPG changeover kit is available from Lennox. The kit includes burner orifices and a regulator conversion kit. TYPICAL BURNER/ELECTRODE ORIENTATION DIRECT SPARK MODELS ONLY 1/8"(+1/64") SPARK ELECTRODE UPPER BURNER MOUNTING RAIL GROUND BURNER MANIFOLD FLAME RETENTION RING FIGURE 17 Page 18 LOWER BURNER MOUNTING RAIL 23/32 in. (18 mm) Top Right ORIFICE FLAME SENSOR Left Bottom The switch is a single-pole single-throw pressure switch electrically connected to the furnace control. The purpose of the switch is to prevent burner operation if the combustion air blower is not operating. SPARK ELECTRODE TO BURNER GAP BURNER 5/16 in. (7 mm) PROVE SWITCH COMBUSTION AIR BLOWER PROVE SWITCH Normally Open Closes on Negative Pressure SPARK ELECTRODE SPARK ELECTRODE FLAME SENSOR TO BURNER GAP BURNER 5/16 in. (7 mm) Sensing Tube Attaches to Top Side Of Blower Back PROVE SWITCH FLAME SENSOR Left FIGURE 18 Top Right Front Bottom WHITE RODGERS 36E SERIES GAS VALVE FIGURE 21 MANIFOLD PRESSURE ADJUSTMENT SCREW On start-up, the switch senses that the combustion air blower is operating. It closes a circuit to the furnace control when pressure inside the combustion air blower increases above pressure switch set point (In. negative w.c.). The pressure sensed by the switch is relative to atmospheric pressure. If the flue becomes obstructed during operation, the switch senses a loss of negative pressure (pressure becomes more equal with atmospheric pressure) and opens the circuit to the furnace control and gas valve. The switch trip pressure is different depending on unit model number. The trip pressure is printed on the side of the limit. The switch is factory set and is not field adjustable. It is a safety shut-down control in the furnace and must not be bypassed for any reason. MANIFOLD PRESSURE OUTLET GAS VALVE SHOWN IN OFF POSITION FIGURE 19 HONEYWELL VR8205 SERIES GAS VALVE MANIFOLD PRESSURE OUTLET MANIFOLD PRESSURE ADJUSTMENT SCREW II−PLACEMENT AND INSTALLATION Make sure unit is installed in accordance with installation instructions and applicable does. ON III−START-UP OFF GAS VALVE SHOWN IN OFF POSITION FIGURE 20 I−Combustion Air Blower Prove (Pressure) Switch (S64) 80MGF series units are equipped with a combustion air prove switch located on the vestibule panel. The switch is connected to the combustion air blower housing by means of a flexible silicone hose. It monitors air pressure in the combustion air blower housing. BEFORE LIGHTING smell all around the appliance area for gas. Be sure to smell next to the floor because some gas is heavier than air and will settle on the floor. Use only your hand to turn the gas control knob. Never use tools. If the knob will not turn by hand, do not try to repair it, call a qualified service technician. Force or attempted repair may result in a fire or explosion. Page 19 A−Preliminary and Seasonal Checks C−Safety or Emergency Shutdown 1− Inspect electrical wiring, both field and factory installed for loose connections. Tighten as required. 2− Check voltage at disconnect switch. Voltage must be within range listed on the nameplate. If not, consult the power company and have voltage condition corrected before starting unit. B−Heating Start-Up 1 − STOP! Read the safety information at the beginning of this section. 2 − Set thermostat to lowest setting. 3 − Turn off all electrical power to appliance. 4 − This appliance is equipped with an ignition device which automatically lights the burners. Do not try to light the burners by hand. 5 − Remove access panel. Turn off unit power. Close manual and main gas valves. D−Extended Period Shutdown Turn off thermostat or set to UNOCCUPIED" mode. Close all gas valves (both internal and external to unit) to guarantee no gas leak into combustion chamber. Turn off power to unit. All access panels, covers and vent caps must be in place and secured. IV−HEATING SYSTEM SERVICE CHECKS A−A.G.A./C.G.A. Certification All units are A.G.A. and or C.G.A. design certified without modifications. Refer to the 80MGF Operation and Installation Instruction Manual Information. B−Gas Piping Gas supply piping should not allow more than 0.5"W.C. drop in pressure between gas meter and unit. Supply gas pipe must not be smaller than unit gas connection. WARNING Shock and burn hazard. Compounds used on gas piping threaded joints should be resistant to action of liquefied petroleum gases. 80MGF units are equipped with a direct spark ignition system. Do not attempt to light manually. 6 − White Rodgers 36E Gas Valve −− Switch gas valve lever to OFF. See figure 19. Honeywell VR8205 Gas Valve −− Turn knob on gas valve clockwise to OFF. Do not force. See figure 20. 7 − Wait five (5) minutes to clear out any gas. If you then smell gas, STOP! Immediately call your gas supplier from a neighbor’s phone. Follow the gas supplier’s instructions. If you do not smell gas go to next step. 8 − White Rodgers 36E Gas Valve −− Switch gas valve lever to ON. Honeywell VR8205 Gas Valve −− Turn knob on gas to ON. Do not force. valve counterclockwise 9 − Replace access panel. 10− Turn on all electrical power to unit. 11− Set thermostat to desired setting. 12− If the appliance will not operate, follow the instructions To Turn Off Gas To Unit" and call your service technician or gas supplier. C−Testing Gas Piping IMPORTANT In case emergency shutdown is required, turn off the main shut-off valve and disconnect the main power to unit. These controls should be properly labeled by the installer. When pressure testing gas lines, the gas valve must be disconnected and isolated. Gas valves can be damaged if subjected to more than 0.5psig (14" W.C.). See figure 22. If the pressure is equal to or less than 0.5psig (14"W.C.), use the manual shut−off valve before pressure testing to isolate furnace from gas supply. Turning Off Gas To Unit 1 − Set thermostat to lowest setting. 2 − Turn off all electrical power to unit if service is to be performed. 3 − Remove access panel. 4 − Switch lever on White Rodgers gas valve to OFF; turn knob on Honeywell valve clockwise to OFF. Do not force. 5 − Replace lower access panel. Page 20 GAS PIPING TEST PROCEDURE MANUAL MAIN SHUT−OFF VALVE WILL NOT HOLD TEST PRESSURE IN EXCESS OF 0.5 PSIG (14"W.C.) CAP GAS VALVE FIELD PROVIDED LINE PRESSURE TAP FIGURE 22 When checking piping connections for gas leaks, use preferred means. Kitchen detergents can cause harmful corrosion on various metals used in gas piping. Use of a specialty Gas Leak Detector is strongly recommended. It is available through Lennox under part number 31B2001. See Corp. 8411−L10, for further details. Do not use matches, candles, flame or any other source of ignition to check for gas leaks. D−Testing Gas Supply Pressure When testing supply gas pressure, connect test gauge to inlet pressure tap (field provided). See figure 22. Check gas line pressure with unit firing at maximum rate. Low pressure may result in erratic operation or underfire. High pressure can result in permanent damage to gas valve or overfire. For natural gas units, operating pressure at unit gas connection must be a minimum of 4.5" W.C. For L.P. gas units, operating pressure at unit gas connection must be a minimum of 9.0" W.C. On multiple unit installations, each unit should be checked separately, with and without other units operating. Supply pressure must fall within range listed in previous paragraph. E−Check Manifold Pressure After line pressure has been checked and adjusted, check manifold pressure. Move pressure gauge to outlet pressure tap located on unit gas valve (GV1). Checks of manifold pressure are made as verification of proper regulator adjustment. Manifold pressure for the 80MGF can be measured at any time the gas valve is open and is supplying gas to the unit. Normal manifold pressure for natural gas units is 3.5 in. w.c. For LP/propane gas the correct manifold pressure is 9.0 in. w.c. The gas valve is factory set and should not require adjustment. All gas valves are factory regulated. See table 12. Manifold Adjustment Procedure: 1− Connect a test gauge to outlet pressure tap on gas valve. Start unit and allow 5 minutes for unit to reach steady state. 2− While waiting for the unit to stabilize, notice the flame. Flame should be stable and should not lift from burner. Natural gas should burn blue. L.P. gas should burn mostly blue with some orange streaks. 3− After allowing unit to stabilize for 5 minutes, record manifold pressure and compare to values given in table 12. NOTE−Shut unit off and remove manometer as soon as an accurate reading has been obtained. Take care to replace pressure tap plug. F− Proper Gas Flow (Approximate) Furnace should operate at least 5 minutes before checking gas flow. Determine time in seconds for two revolutions of gas through the meter. (Two revolutions assures a more accurate time.) Divide by two and compare to time in table 13 below. Adjust manifold pressure on gas valve to match time needed. NOTE− To obtain accurate reading, shut off all other gas appliances connected to meter. IMPORTANT For safety, connect a shut-off valve between the manometer and the gas tap to permit shut off of gas pressure to the manometer. TABLE 12 GAS VALVE REGULATION Unit (Fuel) Natural L.P. TABLE 13 GAS METER CLOCKING CHART Seconds for One Revolution Natural LP 80mgf g Unit 1 cu ft 2 cu ft 1 cu ft 2 cu ft Dial Dial Dial DIAL −45 80 160 200 400 −60 60 120 150 300 −75 48 96 120 240 −100 36 72 90 180 −120 30 60 75 150 −140 25 50 64 128 Natural−1000 btu/cu ft Operating Pressure (outlet) in. W.C. 3.5 +0 −0.3 9.0 + 0.5 Page 21 LP−2500 btu/cu ft the ignition control sensor connection and the negative (−) lead of the meter to the sensor wire. See figure 23. 2− Set thermostat for a heating demand and check flame signal with unit operating. See table 16 for microamp reading for the various control boards used. G−High Altitude Derate NOTE−In Canada, certification for installation at altitudes over 4500 ft. (1372m) above sea level is the jurisdiction of the local authorities. 80MGF−1 through −8 Models This unit does not require gas pressure adjustment, or pressure switch change when operating at elevations of 0 to 7500 ft. (0 to 2248m). Check gas line pressure with unit firing. The minimum pressure as shown on the nameplate for natural and propane gases must be maintained. No orifice change is required. FLAME SIGNAL TEST D.C. MICROAMP METER IGNITION CONTROL FLAME SENSOR SENSOR WIRE NOTE−This is the only permissible field derate for this appliance. FIGURE 23 80MGF−9, −10 and −11 Models Table 14 shows manifold pressure settings for installations at different altitudes. Refer to table 15 for pressure switch replacement for models at elevations of 4500 feet (1372m) and greater. ALTITUDE feet (m) GAS FUEL Natural 3.5 (0.87) Propane/LP 9.5 (2.36) 4500 − 5500 (1372 − 1676) Natural 3.4 (0.86) Propane/LP 9.2 (2.29) 5500 − 6500 (1676 − 1981) Natural 3.3 (0.82) Propane/LP 8.9 (2.21) 6500 − 7500 (1372 − 2286) Natural 3.2 (0.80) Propane/LP 8.6 (2.14) Unit Model 80MGF−45 80MGF−60 80MGF−75 80MGF−100 80MGF−120 80MGF−140 TABLE 15 Pressure Switch Part Number No Change No Change 88J8001 18L2401 18L2401 No Change 0 − 4500 (0 − 1372) TABLE 16 MICROAMP SIGNAL DROP OUT SIGNAL Ram 1.0 to 5.0 t1.0 EGC 1.0 to 5.0 v.45 SureLight w.70 v.15 CONTROL TABLE 14 MANIFOLD PRESSURE in. W.C. (kPa) SENSE" TERMINAL Flame signal may rise above 5 microamps for the first few seconds after ignition then level off within the range. WARNING Fire and explosion hazard. These instructions MUST be followed exactly. Can cause a fire or explosion resulting in property damage, personal injury or loss of life. V−TYPICAL OPERATING CHARACTERISTICS A−Blower Operation and Adjustment NOTE− The following is a generalized procedure and does not apply to all thermostat controls. 1− Blower operation is dependent on thermostat control system. H−Flame Signal A microamp DC meter is needed to check the flame signal on the primary ignition control. Flame (microamp) signal is an electrical current which passes from the furnace control through the sensor electrode during unit operation. Current passes from the sensor through the flame to ground to complete a safety circuit. To Measure Flame Signal: 1− Place meter in series between furnace control and sensor wire. Connect the positive (+) lead of meter to 2− Generally, blower operation is set at thermostat subbase fan switch. With fan switch in ON position, blower operates continuously on heating speed. With fan switch in AUTO position, blower cycles with demand or runs continuously while heating or cooling circuit cycles. 3− Depending on the type of indoor thermostat, blower and entire unit will be off when the system switch is in OFF position. B−Temperature Rise Temperature rise for 80MGF units depends on unit input, blower speed, blower horsepower and static pressure as marked on the unit rating plate. The blower speed must be set for unit operation within the range of AIR TEMP. RISE °F" listed on the unit rating plate. Page 22 TABLE 17 To Measure Temperature Rise: 1 − Place plenum thermometers in the supply and return air plenums. Locate supply air thermometer in the first horizontal run of the plenum where it will not pick up radiant heat from the heat exchanger. 2 − Set thermostat to highest setting. 3 − After plenum thermometers have reached their highest and steadiest readings, subtract the two readings. The difference should be in the range listed on the unit rating plate. If the temperature is too low, decrease blower speed. If temperature is too high, first check the firing rate. Provided the firing rate is acceptable, increase blower speed to reduce temperature. To change blower speed taps see the Blower Speed Taps section in this manual. C−External Static Pressure 1 − Measure tap locations as shown in figure 24. 2 − Punch a 1/4" diameter hole STATIC PRESSURE in supply and return air pleTEST nums. Insert manometer MANOMETER hose flush with inside edge of hole or insulation. Seal around the hose with per80MGF UNIT magum. Connect the zero end of the manometer to the FIGURE 24 discharge (supply) side of the system. On ducted systems, connect the other end of manometer to the return duct as above. For systems with non−ducted returns, leave the other end of the manometer open to the atmosphere. 3 − With only the blower motor running and the evaporator coil dry, observe the manometer reading. Adjust blower motor speed to deliver the air desired according to the job requirements. 4 − External static pressure drop must not be more than 0.5" W.C. 5 − Seal around the hole when the check is complete. BLOWER SPEED SELECTION Factory Connected Speed Taps Unit Speeds Available Cool (Black) Heat (Red) 80MGF2-45 2 4 4 80MGF2-60 2 4 4 80MGF3-60 2 4 4 80MGF2-75 2 3 4 80MGF3-75 2 4 4 80MGF4-75 2 4 5 80MGF3/4-100 2 4 5 80MGF4/5-100 2 5 5 80MGF3/4-120 2 3 5 80MGF4/5-120 2 5 5 80MGF4/5-140 2 3 5 TABLE 18 BLOWER SPEED SELECTION HI LOW ◊ ◊ 2 ◊ 2 2 3 ◊ 3 3 4 4 4 TAPS AVAILABLE 3 4 5 5 6 5 MOTOR PLUG SPEED TAP DESIGNATION 5 − Depress harness connector tab to release wire terminal. Select connector location for new speed (refer to unit wiring diagram). Insert wire terminal until it is securely in place. See figure 25. 6 − Replace harness connector to motor. BLOWER SPEED TAP SELECTION Leadless motors only HARNESS CONNECTOR D−Blower Speed Taps Leadless Motors Blower speed tap selection is accomplished by changing the taps at the blower motor harness connector. Disconnect harness connector from motor to expose speed selectors. Blower speed selections are listed in table 17. To Change Blower Speed: 1 − Turn off electric power to furnace. 2 − Remove front panel and blower access door. See figure 4. 3 − Disconnect blower motor harness from motor. 4 − Select desired speeds for heating and cooling. (Red = heating, Black = cooling, White = common). See table 17. Page 23 DEPRESS TAB TO RELEASE WIRE TERMINAL. SELECT CONNECTOR LOCATION FOR NEW SPEED (REFER TO UNIT WIRING DIAGRAM). INSERT WIRE UNTIL IT IS SECURELY IN PLACE. FIGURE 25 MOTOR E−Blower Speed Taps Leaded Motors −11 Models A−Cleaning Heat Exchanger and Burners Blower speed tap changes are made on the SureLight control board. See figure 8. Unused taps must be secured on dummy terminals "PARK M1" and or "PARK M2" on the SureLight board. The heating tap is connected to the "ACB HEAT " terminal and the cooling tap is connected to the "ACB COOL" terminal. The continuous blower tap is connected to the "ACB LOW" terminal. To change existing heat tap, turn off power then switch out speed tap on "ACB HEAT" with tap connected to "PARK M1" or "PARK M2". See table 19 for blower motor tap colors for each speed. TABLE 19 NOTE−Use papers or protective covering in front of furnace while cleaning furnace. Due to dimples designed in the heatexchanger, cleaning is not recommended. Removal is for inspection only. Burners Burners and burner flame should be inspected at the beginning of each heating season. Clean burners, if necessary, as outlined below: 1 − Turn off electrical and gas supply to unit. 2 − Remove burner box top. 3 − Remove burner retaining bracket. 4 − Remove burners. 5 − Clean burner insert with bottle brush as shown in figure 26. NOTE−Use papers or protective covering in front of furnace while cleaning furnace. CLEANING BURNERS BURNER BOTTLE BRUSH VI−MAINTENANCE At the beginning of each heating season, the system should be checked as follows: Filters All 80MGF filters are installed external to the unit. Filters should be inspected monthly and cleaned or replaced when necessary to assure proper furnace operation. See table 20 for filter sizes. Replacement filters for 80MGF-45/60/75 units must have a minimum velocity rating of 400 FPM. Replacement filters for 80MGF-100/120/140 units require a minimum velocity rating of 625 FPM. TABLE 20 MODEL NUMBER FILTER SIZE 80MGF−45/60/75 16" X 20" X 1" 80MGF−100/120/140 20" X 20" X 1" FIGURE 26 6 − Use bottle brush to clean inside of each burner. 7 − Replace burners and burner retaining bracket, making sure burners are properly seated in slots on tray and orifice in manifold. 8 − Check electrode gap using appropriately sized twist drills or feeler gauges. Gap should be between 2.79 to 3.56mm (0.110 and 0.140 inches). 9 − Reinstall burner box top. CAUTION Some soaps used for leak detection are corrosive to certain metals. Carefully rinse piping thoroughly after leak test has been completed. Do not use matches, candles, flame or other sources of ignition to check for gas leaks. WARNING Blower door must be securely in place when blower and burners are operating. Gas fumes, which could contain carbon monoxide, can be drawn into living space resulting in personal injury or death. 10 − Restore electrical power and gas supply. Follow lighting instructions on front of unit. Check the following: appearance of burner flame, burner pressure, gas flow and temperature rise. Make adjustments, if necessary. See adjustments section. B−Supply Air Blower 1 − Check and clean blower wheel. 2 − Motors used on the Lennox 80MGF series units are permanently lubricated and need no further lubrication. Page 24 C−Flue and Chimney Flue must conform to all AGA/GAMA venting requirements. Flue pipe deteriorates from the inside out and must be disconnected in order to check thoroughly. Check flue pipe, chimney and all connections for tightness and to make sure there is no blockage or leaks. D−Electrical CAUTION Potential for gas leaks, fire or explosion. Some soaps used for leak detection are corrosive to certain metals. Carefully clean piping thoroughly after leak detection has been completed. Can cause damage to piping resulting in gas leaks, fire or explosion. 1 − Check all wiring for loose connections. 2 − Check for correct voltage. 3 − Check amp−draw on blower motor. HEAT EXCHANGER REMOVAL (unit shown in horizontal position) REMOVE SCREWS (4) Left Back Bottom Top Front Right SLIDE ENTIRE ASSEMBLY OUT OF CABINET FIGURE 27 Page 25 VII−WIRING AND SEQUENCE OF OPERATION 5 3 2 6 1 4 8 7 80MGF WITH RAM CONTROL 1- When disconnect is closed, 120V is routed through door interlock switch (S51) to feed the line voltage side of the furnace control (A3) and transformer T1 primary. Door interlock switch must be closed for A3 and T1 to receive voltage. 2- T1 supplies 24VAC to terminal 24VAC" on A3. In turn, terminal R" of A3 supplies 24VAC to terminal RC" of the indoor thermostat (not shown). 3- When there is a call for heat, W1 of the thermostat energizes W of the furnace control with 24VAC. 4- CMB BLWR of the blower control energizes the combustion air blower (B6). When the combustion air blower nears full speed, combustion air prove switch (S18) closes. 5- When S18 closes, assuming the flame rollout switch (S47) primary limit (S10) and secondary limits (S21) are closed, the furnace control begins a 45 second time-delay (pre-purge). 6- At the end of the pre-purge cycle, the furnace control simultaneously opens the gas valve and sends high voltage to the spark electrode. 7- When flame is sensed, the furnace control begins a 45 second delay before energizing the indoor blower. 8- When heat demand is satisfied, W1 of the thermostat de-energizes W of the furnace control and the furnace control immediately de-energizes the gas valve. The combustion air blower runs for 5 seconds (post-purge) before being de-energized. Also, the indoor blower runs for a designated period (90−240 seconds) as set by switches on furnace control. Page 26 80MGF TROUBLESHOOTING SEQUENCE NORMAL HEATING MODE ABNORMAL HEATING MODE LED: SLOW FLASH RATE THERMOSTAT CALLS FOR HEAT LED: FAST FLASH RATE FLAME OFF? YES CONTROL SELF−CHECK OKAY? YES HI LIMIT SWITCH CLOSED? LOCKOUT: MAIN VALVE OFF COMB. AIR AND SYSTEM FANS ON RESET THERMOSTAT LED: 5 flash if flame sensed with valve off LED: Steady on if control board failure NO NO CHECK TO SEE IF MAIN VALVE IS OFF. SEQUENCE HOLDS UNTIL HI LIMIT CLOSES. LED: 4 flashes. NO YES PRESSURE SWITCH OPEN? NO YES COMBUSTION AIR BLOWER ON? PRESSURE SWITCH CLOSED? CHECK TO SEE IF MAIN VALVE IS OFF. SEQUENCE HOLDS UNTIL PRES. SWITCH OPENS. LED: 3 flashes. NO CHECK TO SEE IF MAIN VALVE IS OFF. SEQUENCE HOLDS UNTIL PRES. SWITCH CLOSES. LED: Fast flash rate. NO MAIN VALVE AND SPARK ARE OFF. INCREMENT TRIAL REGISTER THREE TRIALS COMPLETED? YES PREPURGE (45 seconds) IGNITION TRIAL (7 seconds) −− START IGNITION SPARK, OPEN MAIN GAS VALVE. INCREMENT TRIAL REGISTER. HAS FLAME BEEN REGISTERED WITHIN 7 SECONDS? YES IGNITION RESET PERIOD COMBUSTION & SYSTEM FANS OFF. IS 60 MIN. RESET PERIOD COMPLETE? LED: Fast flash rate. YES SYSTEM FAN ON. (Fixed 45−second delay) FLAME SENSE OKAY? MAIN VALVE AND SPARK OFF. NO NO YES START IGNITION SPARK (IN 0.8 SEC. MAXIMUM). HAS FLAME BEEN DETECTED WITHIN 7 SEC.? FLAME CONTINUOUSLY CHECKED? YES ROLLOUT SWITCHES CLOSED NO SEQUENCE HOLDS. MAIN VALVE OFF. COMBUSTION AND SYSTEM FANS ON. RESET OR REPLACE ROLLOUT SWITCH. LED: 4 flashes. YES HI LIMIT SWITCH CLOSED? YES NO PRESSURE SWITCH CLOSED? NO YES THERMOSTAT OPENS MAIN VALVE OFF. COMBUSTION & SYSTEM FANS ON. SEQUENCE HOLDS UNTIL SWITCH CLOSES. LED: 4 flashes for hi limit. LED: 3 flashes for pressure switch. LED: SLOW FLASH RATE SWITCH CLOSED YES COMB. AIR BLOWER OFF (5 sec. delay) NO COMBUSTION FAN ON. SYSTEM FAN OFF. (AFTER DELAY TO OFF INTERVAL COMPLETED.) FAN OFF (After selected 90, 120, 180, or 240 delay)? LED: Fast flash rate. Page 27 YES 80MGF TROUBLESHOOTING SEQUENCE − COOLING LED: Slow flash rate. REMAINS UNCHANGED THROUGHOUT COOLING CYCLE. THERMOSTAT CALLS FOR COOLING. COMPRESSOR CONTACTOR AND SYSTEM FAN ENERGIZED AT COOLING SPEED AFTER 1 SECOND DELAY. THERMOSTAT OPENS. COMPRESSOR OFF. SYSTEM FAN OFF AFTER COMPLETING SELECTED DELAY INTERVAL (At dip switches). 80MGF TROUBLESHOOTING SEQUENCE − FAN ONLY LED: Slow flash rate. REMAINS UNCHANGED THROUGHOUT SEQUENCE. MANUAL FAN SELECTION MADE AT THERMOSTAT. CONTROL ENERGIZES SYSTEM FAN AT HEATING SPEED. THERMOSTAT CALLS FOR HEAT. YES NO THERMOSTAT CALLS FOR COOLING. YES SYSTEM FAN REMAINS ON HEATING SEQUENCE AND RUNS THROUGH COMPLETION. NO SYSTEM FAN SWITCHED TO COOLING SPEED. COOLING SEQUENCE RUNS TO COMPLETION. SYSTEM FAN ON AT HEATING SPEED UNTIL MANUAL FAN IS SWITCHED OFF AT THERMOSTAT. SLOW FLASH FAST FLASH 2 FLASH 3 FLASH 4 FLASH 5 FLASH STEADY ON LED CODES NORMAL OPERATION. NO CALL FOR HEAT. NORMAL OPERATION. CALL FOR HEAT. . SYSTEM LOCKOUT. FAILURE TO DETECT OR SUSTAIN FLAME. PRESSURE SWITCH OPEN OR CLOSED. HIGH LIMIT OR ROLLOUT SWITCH OPEN. FLAME SENSED AND GAS VALVE NOT ENERGIZED. CONTROL BOARD FAILURE. Page 28 80MGF WITH EGC−2 IGNITION CONTROL 1 − When disconnect is closed, 120V is routed through door interlock switch (S51) to feed the line voltage side of the ignition control (A3) and transformer T1 primary. Door interlock switch must be closed for A3 and T1 to receive voltage. 2 − T1 supplies 24VAC to terminal 24VAC" on A3. In turn, terminal R" of A3 supplies 24VAC to terminal R" of the indoor thermostat (not shown). 3 − When there is a call for heat, W1 of the thermostat energizes W of the ignition control with 24VAC. 4 − CAB of the ignition control energizes the combustion air blower (B6). When the combustion air blower nears full speed, combustion air prove switch (S18) closes. 5 − When S18 closes, assuming primary limit (S10) and secondary limit (S21) are closed, a 15 second pre−purge begins. After the pre−purge period the ignition control starts ignition spark and opens main gas valve. 6 − After 45 seconds, ignition control (A3) energizes the indoor blower (B3). 7 − When heat demand is satisfied, W1 of the thermostat deenergizes W of the ignition control and the gas valve is immediately de-energized. The combustion air blower immediately stops. The indoor blower runs for a designated fan off" period (60−240 seconds) as set by jumper on ignition control. Page 29 80MGF WITH EGC−2 HEATING SEQUENCE OF OPERATION ABNORMAL HEATING MODE NORMAL HEATING MODE GAS VALVE OFF. COMB. BLOWER ON. INDOOR BLOWER ON HEAT SPEED. SEQUENCE HOLDS UNTIL NO FLAME SENSED OR MAIN POWER IS INTERRUPTED AND RESET. DIAG. CODE: 1− FLASHING; 2−OFF (FLAME SENSED WITHOUT VALVE ENERGIZED) CONTROL MAIN POWER ON" FLAME OFF? NO YES CONTROL SELF−CHECK OKAY? YES ROLL−OUT SWITCH CLOSED NO GAS VALVE, COMB. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. REMOVE POWER TO RESET CONTROL. DIAG. CODE: BOTH ON (CONTROL SELF−CHECK FAILURE OR INCORRECT WIRING) NO YES LED: SLOW FLASH RATE GAS VALVE, COMB. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. SEQUENCE HOLDS UNTIL ROLL−OUT SWITCH IS MANUALLY CLOSED. DIAG. CODE: 1−ON; 2−FLASHING (FLAME ROLL−OUT OPEN) THERMOSTAT CALLS FOR HEAT LED: FAST FLASH RATE COMB. AIR BLOWER PRESSURE SWITCH OPEN? YES COMBUSTION AIR BLOWER ON? HTG ACC. TERM. ENERGIZED. YES PRESSURE SWITCH CLOSED WITHIN 2.5 MIN.? NO GAS VALVE, COMB. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. SEQUENCE HOLDS UNTIL PRESSURE SWITCH CLOSES OR THERMOSTAT RESETS CONTROL. DIAG. CODE: 1−OFF; 2−FLASHING (C.A.B. PRESSURE SWITCH OPEN) NO YES YES COMB. AIR BLOWER PREPURGE (15 seconds) IGNITION TRIAL (10 seconds) −− START IGNITION SPARK, OPEN MAIN GAS VALVE. HAS FLAME REGISTERED WITHIN 10 SECONDS AFTER IGNITION TRIAL? YES IS FLAME SENSED AFTER 10 SECOND FLAME RECTIFICATION PERIOD? YES GAS VALVE OFF. COMB. BLOWER ON. INDOOR BLOWER (WITH 45 DELAY) ON. HAS CONTROL FAILED FLAME SENSE 5 TIMES DURING ONE HEAT DEMAND? IF YES, SYSTEM GOES INTO 60 MIN.WATCHGUARD. DIAG. CODE: 1−ALT. FLASHING / 2−ALT. FLASHING IF NO, GO TO COMB. AIR BLOWER ON?" NO NO HAS CONTROL RESET IGNITION SEQUENCE 5 TIMES IF YES, SYSTEM GOES INTO 60 MIN. WATCHGUARD. DIAG. CODE: 1−ALT. FLASHING / 2−ALT. FLASHING IF NO, GO TO COMB. AIR BLOWER ON?" INDOOR AIR BLOWER ON. (Fixed 45−second delay) PRIMARY/SECONDARY LIMITS MONITORED IN HEAT CYCLE. ARE SWITCHES CLOSED? NO GAS VALVE OFF. COMB. BLOWER OFF. INDOOR BLOWER ON UNTIL LIMIT CLOSES. DIAG. CODE: 1−FLASHING / 2−ON (LIMIT OPEN) IS LIMIT NOW CLOSED? YES YES PRESSURE SWITCH CLOSED? PRESSURE SWITCH WATCHGUARD CONDITION: GAS VALVE, COMB. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. DIAG. CODE: 1−OFF / 2−FLASHING (C.A.B. PRESSURE SWITCH OPEN) IS 5 MINUTE RESET PERIOD COMPLETE? NO YES HAS PRIMARY LIMIT OPENED 5 TIMES DURING ONE UNSATISFIED HEAT DEMAND. IF YES, SYSTEM GOES INTO 60 MIN.WATCHGUARD. DIAG. CODE: 1−FLASHING / 2−ON IF NO, GO TO COMB. AIR BLOWER ON?" THERMOSTAT OPENS LED: SLOW FLASH RATE COMB. AIR BLOWER OFF (5 sec. delay) HTG ACC. TERM.DE−ENERGIZED. GAS VALVE, COMB. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. DIAG. CODE: 1−OFF / 2−FLASHING NO (C.A.B. PRESSURE SWITCH OPEN) HAS C.A.B. PRESSURE SWITCH CLOSED IN 2.5 MINUTES? INDOOR AIR BLOWER OFF (After selected 60, 90, 120, 180, or 240 delay)? YES Page 30 80MGF WITH EGC−2 COOLING SEQUENCE OF OPERATION LED: Slow flash rate. REMAINS UNCHANGED THROUGHOUT COOLING CYCLE. THERMOSTAT CALLS FOR COOLING. COMPRESSOR CONTACTOR AND SYSTEM FAN ENERGIZED AT COOLING SPEED AFTER 1 SECOND DELAY. ACC TERMINAL ENERGIZED. THERMOSTAT OPENS. COMPRESSOR OFF. SYSTEM FAN AND ACC TERMINAL OFF AFTER 0 SECONDS. 80MGF WITH EGC−2 MANUAL CONTINUOUS FAN SEQUENCE OF OPERATION LED: Slow flash rate. REMAINS UNCHANGED THROUGHOUT SEQUENCE. CONTINUOUS FAN SELECTION MADE AT THERMOSTAT. CONTROL ENERGIZES SYSTEM FAN AT HEAT SPEED. ACC TERMINAL ENERGIZED. HTG ACC. TERM. ENERGIZED WITH COMB. AIR BLOWER. THERMOSTAT CALLS FOR HEAT. YES NO SYSTEM FAN REMAINS ON HEATING SPEED AFTER SELECTED DELAY. ACC TERM. REMAINS ENERGIZED. THERMOSTAT CALLS FOR COOLING. YES NO SYSTEM FAN SWITCHED TO COOLING SPEED. ACC TERMINAL REMAINS ENERGIZED. THERMOSTAT OPENS. SYSTEM FAN SWITCHED OFF AFTER DELAY. ACC TERMINAL DE−ENERGIZED. THERMOSTAT OPENS. SYSTEM FAN SWITCHES TO CONTINUOUS SPEED AND ENERGIZES ACC TERMINAL. BOTH REMAIN ON UNTIL CONTINUOUS FAN IS SWITCHED OFF AT THERMOSTAT. Page 31 80MGF WITH EGC−1 IGNITION CONTROL 1 − When disconnect is closed, 120V is routed through door interlock switch (S51) to feed the line voltage side of the ignition control (A3) and transformer T1 primary. Door interlock switch must be closed for A3 and T1 to receive voltage. 2 − T1 supplies 24VAC to terminal 24VAC" on A3. In turn, terminal R" of A3 supplies 24VAC to terminal R" of the indoor thermostat (not shown). 3 − When there is a call for heat, W1 of the thermostat energizes W of the ignition control with 24VAC. 4 − CAB of the ignition control energizes the combustion air blower (B6). When the combustion air blower nears full speed, combustion air prove switch (S18) closes. 5 − When S18 closes, assuming primary limit (S10) and secondary limit (S21) are closed, a 15 second pre−purge begins. After the pre−purge period the ignition control starts ignition spark and opens main gas valve. 6 − After 45 seconds, ignition control (A3) energizes the indoor blower (B3). 7 − When heat demand is satisfied, W1 of the thermostat deenergizes W of the ignition control and the gas valve is immediately de-energized. The combustion air blower immediately stops. The indoor blower runs for a designated fan off" period (60−240 seconds) as set by jumper on ignition control. Page 32 80MGF WITH EGC−1 HEATING SEQUENCE OF OPERATION ABNORMAL HEATING MODE NORMAL HEATING MODE GAS VALVE OFF. COMB. BLOWER ON. INDOOR BLOWER ON HEAT SPEED. SEQUENCE HOLDS UNTIL NO FLAME SENSED OR MAIN POWER IS INTERRUPTED AND RESET. DIAG. CODE: 1− FLASHING; 2−OFF (FLAME SENSED WITHOUT VALVE ENERGIZED) CONTROL MAIN POWER ON" FLAME OFF? NO YES CONTROL SELF−CHECK OKAY? YES ROLL−OUT SWITCH CLOSED NO GAS VALVE, COMB. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. REMOVE POWER TO RESET CONTROL. DIAG. CODE: BOTH ON (CONTROL SELF−CHECK FAILURE OR INCORRECT WIRING) NO YES LED: SLOW FLASH RATE GAS VALVE, COMB. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. SEQUENCE HOLDS UNTIL ROLL−OUT SWITCH IS MANUALLY CLOSED. DIAG. CODE: 1−ON; 2−FLASHING (FLAME ROLL−OUT OPEN) THERMOSTAT CALLS FOR HEAT LED: FAST FLASH RATE COMB. AIR BLOWER PRESSURE SWITCH OPEN? NO YES GAS VALVE, COMB. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. SEQUENCE HOLDS UNTIL PRESSURE SWITCH CLOSES OR THERMOSTAT RESETS CONTROL. DIAG. CODE: 1−OFF; 2−FLASHING (C.A.B. PRESSURE SWITCH OPEN) COMBUSTION AIR BLOWER ON? HTG ACC. TERM. ENERGIZED? YES PRESSURE SWITCH CLOSED WITHIN 2.5 MIN.? YES COMB. AIR BLOWER PREPURGE (15 seconds) NO YES IGNITION TRIAL (10 seconds) −− START IGNITION SPARK, OPEN MAIN GAS VALVE. HAS FLAME REGISTERED WITHIN 10 SECONDS AFTER IGNITION TRIAL? YES IS FLAME SENSED AFTER 10 SECOND FLAME RECTIFICATION PERIOD? YES GAS VALVE OFF. COMB. BLOWER ON. INDOOR BLOWER (WITH 45 DELAY) ON. HAS CONTROL FAILED FLAME SENSE 5 TIMES DURING ONE HEAT DEMAND? IF YES, SYSTEM GOES INTO 60 MIN.WATCHGUARD. DIAG. CODE: 1−ALT. FLASHING / 2−ALT. FLASHING IF NO, GO TO COMB. AIR BLOWER ON?" NO NO HAS CONTROL RESET IGNITION SEQUENCE 5 TIMES IF YES, SYSTEM GOES INTO 60 MIN. WATCHGUARD. DIAG. CODE: 1−ALT. FLASHING / 2−ALT. FLASHING IF NO, GO TO COMB. AIR BLOWER ON?" INDOOR AIR BLOWER ON. (Fixed 45−second delay) PRIMARY/SECONDARY LIMITS MONITORED IN HEAT CYCLE. ARE SWITCHES CLOSED? NO GAS VALVE OFF. COMB. BLOWER OFF. INDOOR BLOWER ON UNTIL LIMIT CLOSES. DIAG. CODE: 1−FLASHING / 2−ON (LIMIT OPEN) IS LIMIT NOW CLOSED? YES YES PRESSURE SWITCH CLOSED? PRESSURE SWITCH WATCHGUARD CONDITION: GAS VALVE, COMB. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. DIAG. CODE: 1−OFF / 2−FLASHING (C.A.B. PRESSURE SWITCH OPEN) IS 5 MINUTE RESET PERIOD COMPLETE? NO YES HAS PRIMARY LIMIT OPENED 5 TIMES DURING ONE UNSATISFIED HEAT DEMAND. IF YES, SYSTEM GOES INTO 60 MIN.WATCHGUARD. DIAG. CODE: 1−FLASHING / 2−ON IF NO, GO TO COMB. AIR BLOWER ON?" THERMOSTAT OPENS LED: SLOW FLASH RATE COMB. AIR BLOWER OFF (5 sec. delay) HTG ACC. TERM. DE−ENERGIZED. GAS VALVE, COMB. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. DIAG. CODE: 1−OFF / 2−FLASHING NO (C.A.B. PRESSURE SWITCH OPEN) HAS C.A.B. PRESSURE SWITCH CLOSED IN 2.5 MINUTES? INDOOR AIR BLOWER OFF (After selected 60, 90, 120, 180, or 240 delay)? YES Page 33 80MGF WITH EGC−1 COOLING SEQUENCE OF OPERATION LED: Slow flash rate. REMAINS UNCHANGED THROUGHOUT COOLING CYCLE. THERMOSTAT CALLS FOR COOLING. COMPRESSOR CONTACTOR AND SYSTEM FAN ENERGIZED AT COOLING SPEED AFTER 1 SECOND DELAY. ACC TERMINAL ENERGIZED. THERMOSTAT OPENS. COMPRESSOR OFF. SYSTEM FAN AND ACC TERMINAL OFF AFTER 0 SECONDS. 80MGF WITH EGC−1 MANUAL CONTINUOUS FAN SEQUENCE OF OPERATION LED: Slow flash rate. REMAINS UNCHANGED THROUGHOUT SEQUENCE. CONTINUOUS FAN SELECTION MADE AT THERMOSTAT. CONTROL ENERGIZES SYSTEM FAN AT LOW SPEED. ACC TERMINAL ENERGIZED. HTG ACC. TERM. ENERGIZED WITH COMB. AIR BLOWER. THERMOSTAT CALLS FOR HEAT. YES NO SYSTEM FAN SWITCHES TO HEAT SPEED AFTER SELECTED DELAY. ACC TERM. REMAINS ENERGIZED. THERMOSTAT CALLS FOR COOLING. YES NO SYSTEM FAN SWITCHED TO COOLING SPEED. ACC TERMINAL REMAINS ENERGIZED. THERMOSTAT OPENS. SYSTEM FAN SWITCHED OFF AFTER DELAY. ACC TERMINAL DE−ENERGIZED. THERMOSTAT OPENS. SYSTEM FAN SWITCHES TO CONTINUOUS SPEED AND ENERGIZES ACC TERMINAL. BOTH REMAIN ON UNTIL CONTINUOUS FAN IS SWITCHED OFF AT THERMOSTAT. Page 34 80MGF WITH SURELIGHT IGNITION CONTROL 1 − When there is a call for heat, W1 of the thermostat energizes W of the furnace control with 24VAC. 2 − S10 primary limit switch and S47 rollout switch are closed. Call for heat can continue. 3 − SureLight control energizes combustion air blower B6. Combustion air blower runs until S18 combustion air prove switch closes (switch must close within 2−1/2 minutes or control goes into 5 minute Watchguard Pressure Switch delay). Once S18 closes, a 15−second pre−purge follows. 4 − SureLight control energizes ignitor. A 20−second warm−up period begins. 5 − Gas valve opens for a 4−second trial for ignition. 6 − Flame is sensed, gas valve remains open for the heat call. 7 − After 45−second delay, SureLight control energizes indoor blower B3. 8 − When heat demand is satisfied, W1 of the indoor thermostat de−energizes W of the SureLight control which de−energizes the gas valve. Combustion air blower B6 continues a 5−second post−purge period, and indoor blower B3 completes a selected OFF time delay. Page 35 SURELIGHT CONTROL HEATING SEQUENCE OF OPERATION NORMAL HEATING MODE ABNORMAL HEATING MODE POWER ON GAS VALVE OFF. COMBUSTION AIR BLOWER ON. INDOOR BLOWER ON. LED #1 ALTERNATING FAST FLASH LED#2 ALTERNATING FAST FLASH CHECK FOR BROKEN IGNITOR OR OPEN IGNITOR CIRCUIT CONTROL SELF−CHECK OKAY? NO COMBUSTION AIR BLOWER ON FOR 1 SECOND. GAS VALVE OFF. COMBUSTION AIR BLOWER OFF. INDOOR BLOWER DELAY OFF. LED #1 ON LED #2 ON (RESET CONTROL BY TURNING MAIN POWER OFF.) YES TURN INDUCER ON FOR 1 SECOND. IS POLARITY REVERSED? SIGNAL IMPROPER GROUND AT LED. SIGNAL HOLDS UNTIL UNIT IS PROPERLY GROUNDED. POLARITY REVERSED. LED #1 −− FAST FLASH LED #2 −− SLOW FLASH NO NO YES IS THERE PROPER GROUND? IS VOLTAGE ABOVE 75 VOLTS? NO LOW VOLTAGE SIGNAL AT LED HOLDS UNTIL VOLTAGE RISES ABOVE 75 VOLTS. YES NO ROLLOUT SWITCH CLOSED? YES GAS VALVE OFF. COMBUSTION AIR BLOWER OFF. INDOOR BLOWER OFF WITH DELAY. LED #1 −− ON. LED #2 −− SLOW FLASH. SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES. GAS VALVE OFF. COMBUSTION AIR BLOWER ON. INDOOR BLOWER ON HEATING SPEED. LED #1 −− SLOW FLASH LED #2 −− OFF NO BURNER OFF? (CONTINUOUS FLAME CHECK) YES NORMAL OPERATION: LED #1 −− SLOW FLASH LED #2 −− SLOW FLASH THERMOSTAT CALLS FOR HEAT: LED #1 −− FAST FLASH LED #2 −− FAST FLASH YES NO IS COMBUSTION AIR PRESSURE SWITCH OPEN? YES IS COMBUSTION AIR BLOWER ENERGIZED? (HTG ACC TERMINAL IS ENERGIZED WITH C.A.B.) YES NO HAS COMBUSTION AIR PRESSURE SWITCH CLOSED IN 2.5 MINUTES? YES 15-SECOND COMBUSTION AIR BLOWER PREPURGE INITIATED BY CLOSED PRESSURE SWITCH. YES CONTINUED NEXT PAGE Page 36 GAS VALVE OFF. COMBUSTION AIR BLOWER OFF. INDOOR BLOWER OFF WITH DELAY. LED #1 OFF LED #2 SLOW FLASH (Sequence holds until pressure switch closes or thermostat resets control.) PRESSURE SWITCH IS IN WATCHGUARD MODE. GAS VALVE OFF. COMBUSTION AIR BLOWER OFF. INDOOR BLOWER OFF WITH DELAY. LED #1 −− OFF. LED #2 −− SLOW FLASH. IS 5-MINUTE RESET PERIOD COMPLETE? NORMAL HEATING MODE ABNORMAL HEATING MODE 15-SECOND COMBUSTION AIR INDUCER PREPURGE INITIATED BY CLOSED PRESSURE SWITCH. NO IS VOLTAGE ABOVE 75 VOLTS? YES IS THERE A PROPER GROUND? YES YES YES NO IGNITOR WARM-UP −− 20 SECONDS. YES NO NO LEDS SIGNAL ALTERNATING FAST FLASH IS IGNITOR INTACT AND CONNECTED? 4-SECOND TRIAL FOR IGNITION. GAS VALVE OPENS. IGNITOR ENERGIZED FOR 1 SECOND AFTER VALVE OPENS. NO FLAME SENSED DURING THIS PERIOD. BOARD 97L48 ONLY: IGNITOR ENERGIZED FOR THE FULL 4−SECOND TRIAL FOR IGNITION. GAS VALVE OFF. COMBUSTION AIR INDUCER ON. INDOOR BLOWER OFF. NO HAS CONTROL FAILED TO SENSE FLAME FOR FIVE CONSECUTIVE TRIES DURING A SINGLE HEAT DEMAND? YES NO YES FLAME STABILIZATION PERIOD. 4 SECONDS FLAME RECTIFICATION CURRENT CHECK. CAN FLAME BE PROVEN WITHIN 4 SECONDS AFTER GAS VALVE OPENS? (u0.15 microamps) IGNITION WATCHGUARD MODE. GAS VALVE OFF. COMBUSTION AIR INDUCER OFF. INDOOR BLOWER OFF WITH DELAY LED 1 ALT. SLOW FLASH LED 2 ALT SLOW FLASH IS 60-MINUTE RESET PERIOD COMPLETE? YES YES NO YES LOW FLAME SIGNAL (Does not affect operation of control) LED #1 −− SLOW FLASH LED #2 −− FAST FLASH NO FLAME SIGNAL ABOVE 0.7 MICROAMPS? YES INDOOR BLOWER ON DELAY BEGINS (45 seconds.) YES NO PRIMARY AND SECONDARY LIMIT SWITCHES CLOSED? NO HAS CONTROL RESET IGNITION SEQUENCE FOUR TIMES? FLAME PRESENT? GAS VALVE DE−ENERGIZED. COMBUSTION AIR INDUCER DE−ENERGIZED.INDOOR BLOWER ON UNTIL SWITCH CLOSES.LED #1 −− SLOW FLASH. LED #2 −− ON. IS LIMIT SWITCH CLOSED? YES LIMIT SWITCH WATCH GUARD MODE. GAS VALVE OFF. COMB. AIR INDUCER OFF. INDOOR BLOWER OFF WITH DELAY. LED#1−SLOW FLASH LED#2− ON. IS 60MINUTE RESET PERIOD COMPLETE.? YES NO YES HAS PRIMARY/SECONDARY LIMIT RESET. (See table 9 DIAGNOSTIC CODES for limit reset operation) GAS VALVE POWER OFF. COMBUSTION AIR INDUCER POWER OFF. INDOOR BLOWER OFF WITH DELAY LED #1 −− ON. LED #2 −− SLOW FLASH. SEQUENCE HOLDS UNTIL ROLLOUT SWITCH IS RESET NO ROLLOUT SWITCH CLOSED? YES COMBUSTION AIR PRESSURE SWITCH CLOSED? YES THERMOSTAT DEMAND SATISFIED. YES LED #1 & #2 SIMULTANEOUS SLOW FLASHES. YES NO YES GAS VALVE DE−ENERGIZED. COMBUSTION AIR INDUCER ON. INDOOR BLOWER OFF WITH DELAY LED #1 −− OFF. LED #2 −− SLOW FLASH. HAS CAB SWITCH CLOSED IN 2.5 MINUTES? NO YES COMB. AIR INDUCER CONTINUES 5-SECOND POST PURGE AFTER T’STAT DEMAND IS SATISFIED. INDOOR AIR BLOWER COMPLETES SELECTED OFF" DELAY BEFORE SHUTTING OFF. ACB.HEAT SPEED, HTG ACC TERM. AND ACC TERM. OFF. Page 37 5-MINUTE PRESSURE SWITCH WATCHGUARD MODE. YES SURELIGHT CONTROL COOLING SEQUENCE OF OPERATION NORMAL COOLING MODE ABNORMAL COOLING MODE POWER ON IGNITION CONTROL MAIN POWER ON. GAS VALVE OFF. COMBUSTION AIR BLOWER OFF. INDOOR BLOWER OFF WITH NORMAL DELAY. SIGNAL CIRCUIT BOARD FAILURE AT LED. INTERRUPT MAIN POWER TO RESET CONTROL. NO CONTROL SELF DIAGNOSTIC CHECK. IS CONTROL OPERATING NORMALLY? YES TURN INDUCER ON FOR 1 SECOND. YES IS POLARITY REVERSED? SIGNAL IMPROPER GROUND AT LED. SIGNAL HOLDS UNTIL UNIT IS PROPERLY GROUNDED. SIGNAL POLARITY REVERSED AT LED. NO NO YES IS THERE PROPER GROUND? IS VOLTAGE ABOVE 75 VOLTS? ROLLOUT SWITCH MONITORED CONTINUOUSLY. IS ROLLOUT SWITCH CLOSED? NO LOW VOLTAGE SIGNAL AT LET HOLDS UNTIL VOLTAGE RISES ABOVE 75 VOLTS. NO GAS VALVE OFF. COMBUSTION AIR BLOWER OFF. INDOOR BLOWER OFF WITH NORMAL DELAY. SIGNAL CIRCUIT BOARD FAILURE AT LED. SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES. NO GAS VALVE OFF. COMBUSTION AIR BLOWER OFF. INDOOR BLOWER OFF WITH NORMAL DELAY. SIGNAL CIRCUIT BOARD FAILURE AT LED. SEQUENCE HOLDS UNTIL FLAME IS NOT SENSED. YES CHECK FOR MAIN BURNER FLAME SENSE. IS MAIN BURNER FLAME OFF? LED: SLOW FLASH RATE REMAINS UNCHANGED THROUGHOUT COOLING CYCLE. THERMOSTAT CALLS FOR COOLING. COMPRESSOR CONTACTOR AND SYSTEM FAN ENERGIZED WITH 0-SECOND DELAY. ACB COOL SPEED AND ACC. TERMINAL IS ENERGIZED. THERMOSTAT OPENS. COMPRESSOR OFF. SYSTEM FAN AND ACC. TERM. OFF WITH 0-SECOND DELAY. Page 38 SURELIGHT CONTROL CONTINUOUS LOW SPEED FAN SEQUENCE OF OPERATION LED: SLOW FLASH RATE REMAINS UNCHANGED THROUGHOUT SEQUENCE. MANUAL FAN SELECTION MADE AT THERMOSTAT. CONTROL (G) ENERGIZES SYSTEM FAN AT ACB LOW SPEED. ACC. TERMINAL IS ENERGIZED. THERMOSTAT CALLS FOR HEAT (W). NO HTG ACC. TERM. ENERGIZES WITH COMB. AIR BLOWER. YES BOARD NO. 63K8901 SYSTEM FAN DE−ENERGIZED. SYSTEM FAN ENERGIZES ON ACB HEAT SPEED AFTER NORMAL DELAY. THERMOSTAT CALLS FOR COOLING. NO YES BOARD NO. 24L85, 56L83, 97L48 SYSTEM FAN SWITCHES TO ACB HEAT SPEED AFTER NORMAL DELAY (fan remains energized) SYSTEM FAN SWITCHED TO ACB COOL SPEED. ACC. TERM. REMAINS ON. THERMOSTAT OPENS. COMBUSTION AIR AND HTG ACC TERMINAL DE−ENERGIZE. THERMOSTAT OPENS. BOARD 63K89: SYSTEM FAN OFF. ACC. TERM. OFF. (AFTER OFF DELAY COMPLETED). BOARDS 24L85, 56L83 AND 97L48: SYSTEM FAN SWITCHES TO LOW SPEED AFTER NORMAL DELAY. (fan remains energized) MANUAL FAN SELECTION MADE AT THERMOSTAT. CONTROL (G) ENERGIZES SYSTEM FAN AT ACB LOW SPEED. ACC. TERM. ENERGIZED. Page 39 VIII−Troubleshooting−SureLight Control PROBLEM: 1 UNIT FAILS TO OPERATE IN THE COOLING, HEATING, OR CONTINUOUS FAN MODE Condition Possible Cause 1.1 1.1.1 − Both diagnostic lights fail to light up. Main voltage 120V not supplied to unit. LED#1−Off LED#2−Off ACTION 1 − Check for correct wiring of 120V to power make up box and transformer. ACTION 2 − Check 24V wiring to control board. 1.1.3 Circuit breaker tripped or fails to close. ACTION 1 − Replace circuit breaker if it is reset but does not have continuity. ACTION 2 − If circuit breaker still trips, check for short. 1.1.4 Door interlock switch failure. ACTION 1 − Check that door switch is activated when door is closed. ACTION 2 − Check wire connections to switch, replace loose connectors. ACTION 3 − Check continuity of switch in closed position. Replace if malfunctioning 1.1.5 Transformer Failure. ACTION 1 − Check that transformer output is 24V. Replace if malfunctioning Failed control board. − Diagnostic lights flash the roll−out code. LED#1−On, LED#1 O LED#2−Slow LED#2 Slow Flash 1.3 − On initial power−up the comb. air blower does not energize. − Diagnostic lights flash the reverse polarity code. ACTION 1 − Check 120V main voltage. Determine cause of main power failure. 1.1.2 Miswiring of furnace or improper connections. 1.1.6 1.2 Corrective Action / Comments 1.2.1 Roll−out switch open. ACTION 1 − If all the above items have been checked, replace board. ACTION 1 − Manually reset the roll−out switch by pushing the top button. ACTION 2 − Determine the cause of the roll−out switch activation before leaving furnace. 1.2.2 Roll−out switch failure. ACTION 1 − Check continuity across roll−out switch. Replace roll−out switch if switch is reset but does not have continuity. 1.2.3 Mis iring or improper connections at Miswiring roll−out switch. ACTION 1 − Check wiring connections to switch. switch 1.2.4 Nine pin connector failure ACTION 1 − Check 9−pin connector for proper connection to control board. ACTION 2 − Check continuity of the multi plug pin. 1.3.1 120V main power polarity reversed. ACTION 1 − Check the 120V has line and neutral correctly input into control. ACTION 2 − Reverse the line and neutral at the 120V field connection. LED#1−Fast Flash, LED#2−Slow Flash. 1.4 1.4.1 − On initial power up the combustion Open combustion air blower motor air blower does not energize. − Diagnostic lights flash normal power circuit. on operation. LED#1−Slow Flash LED#2−Slow Flash 1.4.2 Failed combustion air blower motor. Page 40 ACTION 1 − Check for 120V to combustion air blower. If no power, check wire and connections. ACTION 1 − If power is present at blower, replace blower. PROBLEM 1: UNIT FAILS TO OPERATE IN THE COOLING, HEATING, OR CONTINUOUS FAN MODE Condition 1.5 − On initial power−up the combustion air blower remains energized. g − Diagnostic Di ti lilights ht flflash h th the iimproper main ground. LED#1−Alternating Fast Flash LED#2−Alternating Fast Flash Possible Cause Corrective Action / Comments 1.5.1 Improper ground to the unit. ACTION 1 − Check that the unit is properly grounded. ACTION 2 − Install a proper main ground to the unit 1.5.2 6−Pin connector is improperly attached to the circuit board. ACTION 1 − Check 6−pin connector for proper installation. Correctly insert connector into control. 1.5.3 Line voltage is below 75V. ACTION 1 − Check that the line voltage is above 75V. Determine cause of voltage drop and supply correct voltage to the control. PROBLEM 2: UNIT FAILS TO OPERATE IN THE COOLING OR HEATING MODE, BUT COMBUSTION AIR BLOWER OPERATES CONTINUOUS. UNITS WITH CONTROL BOARDS DATE CODED AFTER NOV.1 1997, WILL OPERATE IN COOLING WITH COMBUSTION AIR BLOWER CYCLING 5 SECONDS ON 55 SECONDS OFF, BUT NOT IN THE HEATING MODE. Condition 2.1 − On initial power−up the combustion air blower remains energized. − Diagnostic lights flash the improper main ground. − Units with control boards date coded after Nov.1 Nov 1 1997; combustion air blower will cycle 5 seconds on 55 seconds off. Possible Cause Corrective Action / Comments 2.1.1 Open ignitor circuit. ACTION 1 − Check for correct wiring and loose connections in the ignitor circuit. Check multi − plug connections for correct installation. 2.1.2 Broken or failed ignitor. ACTION 1 − Unplug ignitor and read resistance across ignitor. If resistance does not read between 10.9 and 19.7 ohms, replace the ignitor. LED#1−Alternating Fast Flash LED#2−Alternating Fast Flash PROBLEM 3: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER DOES NOT ENERGIZE Condition 3.1 − Unit operates with a cooling or continuous fan demand. − Combustion air blower will not start with a Heating demand. − Diagnostic g lights g flash the limit failure mode. d LED#1−Slow Flash, LED#2−On Possible Cause Corrective Action / Comments 3.1.1 Primary or secondary (if equipped) limit open. ACTION 1 − Check continuity across switch(es). Switches reset automatically upon cool down. ACTION 2 − Check for restrictions on blower inlet air (including filter) and outlet air. Determine cause for limit activation before placing unit back in operation. 3.1.2 Miswiring of furnace or improper connections at limit switch(es). ACTION 1 − Check for correct wiring and loose connections. Correct wiring and/or replace any loose connections. 3.2 3.2.1 − Unit operates with a cooling and continuous fan demand. Miswiring of furnace or improper con− Combustion air blower will not start nections to combustion air blower. with a Heating demand. − Diagnostic lights flash the pressure switch failure code. LED#1−Off, LED#2−Slow Flash 3.2.2 Pressure switch stuck closed. Page 41 ACTION 1 − Check for correct wiring and loose connections. Correct wiring and/or replace any loose connections. ACTION 1 − Check that the pressure switch is open without the combustion air blower operating. Replace if malfunctioning PROBLEM 3: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER DOES NOT ENERGIZE (CONT.). Condition Possible Cause 3.3 − Unit operates with a cooling and con3.3.1 tinuous fan demand. Miswiring of furnace or improper con− Combustion air blower will not start nections to combustion air blower. with a Heating demand. − Diagnostic lights flash the pressure switch failure code 2.5 2 5 minutes after heating demand. 3.3.2 Combustion air blower failure. LED#1−Off, LED#2−Slow Flash Corrective Action/Comments ACTION 1 − Check for correct wiring and loose connections. Correct wiring and/or replace any loose connections. ACTION 1 − If there is 120V to combustion air blower and it does not operate, replace combustion air blower. PROBLEM 4: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER ENERGIZES, IGNITOR IS NOT ENERGIZED. Condition Possible Cause Corrective Action/Comments 4.1 − Unit operates with a cooling and continuous fan demand. − Combustion air blower energizes with a heating demand. demand − Diagnostic lights flash the pressure switch failure code 2.5 minutes after heating demand. 4.1.1 Pressure switch does not close due to incorrect routing of the pressure switch tubing. ACTION 1 − Check that the pressure switch tubing is correctly routed. Correctly route pressure switch tubing. 4.1.2 Pressure switch does not close due to obstructions in the pressure tubing. ACTION 1 − Remove any obstructions from the pressure tubing and/or taps. 4.1.3 Pressure switch tubing damaged ACTION 1 − Check pressure switch tubing for leaks. Replace any broken tubing. LED#1−Off LED#2 Slow Flash LED#2−Slow 4.1.4 Pressure switch does not close due to a low differential pressure across the pressure switch. ACTION 1 − Check the differential pressure across the pressure switch. This pressure should exceed the set point listed on the switch. ACTION 2 − Check for restricted inlet and exhaust vent. Remove all blockage. ACTION 3 − Check for proper vent sizing and run length. See installation instructions. ACTION 4 − Check voltage to combustion air blower. 4.1.5 Wrong pressure switch installed in the unit, or pressure switch is out of calibration. ACTION 1 − Check that the proper pressure switch is installed in the unit. Replace pressure switch if necessary. 4.1.6 Miswiring of furnace or improper connections at pressure switch. ACTION 1 − Check for correct wiring and loose connections. Correct wiring and/or replace any loose connections. 4.1.7 Pressure switch failure. ACTION 1 − If all the above modes of failure have been checked, the pressure switch may have failed. Replace pressure switch and determine if unit will operate. Page 42 PROBLEM 5: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER ENERGIZES, IGNITOR IS ENERGIZED. (CONT.) Condition Possible Cause Corrective Action/Comments 5.1 5.1.1 Check that gas is being supplied to the unit. ACTION 1 − Check line pressure at the gas valve. Pressure should not exceed 13" WC for both natural and propane. Line pressure should read a minimum 4.5" WC for natural and 8.0"WC for propane. 5.1.2 Miswiring of gas valve or loose connections at multi−pin control amp plugs or valve. ACTION 1 − Check for correct wiring and loose connections. Correct wiring and/or replace any loose connections. 5.1.3 Malfunctioning gas valve or ignition control. ACTION 1 − Check that 24V is supplied to the gas valve approximately 35 seconds after heat demand is initiated. ACTION 2 − Replace the valve if 24V is supplied but valve does not open (check for excessive gas line pressure before replacing gas valve). ACTION 3 − Replace the control board if 24V is not supplied to valve. − Unit operates with a cooling and continuous fan demand. − Combustion air blower energizes with Heating demand. − Ignitor is energized but unit fails to light. LED#1−Alternating Slow Flash LED#2−Alternating Slow Flash PROBLEM 6: BURNERS LIGHT WITH A HEATING DEMAND BUT UNIT SHUTS DOWN PREMATURELY Condition Possible Cause Corrective Action/Comments 6.1 − Burners fire with a heating demand. − Burners light but unit shuts off prior to satisfying T−stat demand. − Diagnostic lights flash the pressure switch code. 6.1.1 Low pressure differential at the pressure switch. ACTION 1 − Check for restricted vent inlet or exhaust. Remove all blockage. ACTION 2: Check for proper vent sizing. See installation instructions. LED#1−Off LED#2−Slow Flash 6.2 − Combustion air blower energizes with a heating demand. − Burners B light li ht but b t fail f il to t stay t lit lit. − After 5 tries the control diagnostics flash the watchguard burners failed to ignite code. LED#1−Alternating Slow Flash LED#2−Alternating Slow Flash 6.2.1 Sensor or sense wire is improperly installed. ACTION 1 − Check that sensor is properly located (page 10) and that the sense wire is properly attached to both the sensor and the control. 6.2.2 Sensor or sense wire is broken. ACTION 1 − Check for a broken sensor. ACTION 2 − Test continuity across the sense wire. If wire or sensor are damaged replace the component. 6.2.3 Sensor or sensor wire is grounded to the unit. ACTION 1 − Check for resistance between the sensor rod and the unit ground. ACTION 2 − Check for resistance between the sensor wire and the unit ground. ACTION 3 − Correct any shorts found in circuit. 6.2.4 Control does not sense flame. ACTION 1 − Check the microamp signal from the burner flame. If the microamp signal is below 0.70 microamps, check the sense rod for proper location or contamination. ACTION 2 − Replace, clean, or relocate flame sense rod. If rod is to be cleaned, use steel wool or replace sensor. DO NOT CLEAN ROD WITH SAND PAPER. SAND PAPER WILL CONTRIBUTE TO THE CONTAMINATION PROBLEM. NOTE: Do not attempt to bend sense rod. Page 43 PROBLEM 6: BURNERS LIGHT WITH HEATING DEMAND BUT UNIT SHUTS DOWN PREMATURELY (CONT.) Condition 6.3 − Combustion air blower energizes with a heating demand. − Burners light. − Roll−out switch trips during the heating demand. − Diagnostic lights flash roll−out failure. LED#1−On LED#2−Slow Flash 6.4 − Combustion air blower energizes with a heating demand. − Burners light roughly and the unit fails to stay lit. − Diagnostic lights flash watchguard flame failure. LED#1−Alternating Slow Flash LED#2−Alternating Slow Flash Possible Cause Corrective Action/Comments 6.3.1 Unit is firing above 100% of the nameplate input. ACTION 1 − Check that the manifold pressure matches value listed on nameplate. See installation instructions for proper procedure. ACTION 2 − Verify that the installed orifice size match the size listed on the nameplate or installation instructions. ACTION 3 − Check gas valve sensing hose to insure no leaks are present. ACTION 4 − Check the input rate to verify rate matches value listed on nameplate. 6.3.2 Gas orifices leak at the manifold connection. ACTION 1 − Tighten orifice until leak is sealed. NOTE: Be careful not to strip orifice threads. ACTION 2 − Check for gas leakage at the threaded orifice connection. Use approved method for leak detection (see unit instructions). 6.3.3 Insufficient flow through the heat exchanger caused by a sooted or restricted heat exchanger. ACTION 1 − Check for sooting deposits or other restrictions in the heat exchanger assembly. Clean assembly as outlined in instruction manual. ACTION 2 − For 80MGF gas furnaces, check for proper combustion and flow. CO2 should measure between 6.0% and 8.0% for natural and 6.5% and 8.5% for L.P. CO should measure below .04% (400PPM) in an air−free sample of flue gases. 6.3.4 Burners are not properly located in the burner box. ACTION 1 − Check that the burners are firing into the center of the heat exchanger openings. Correct the location of the burners if necessary. 6.4.1 Recirculation of flue gases. This condition causes rough ignitions and operation. Problem is characterized by nuisance flame failures. ACTION 1 − Check for proper flow of exhaust gases away from intake vent. Remove any obstacles in front of the intake and exhaust vent which would cause recirculation. ACTION 2 − Check for correct intake and exhaust vent installation. See instructions 6.4.2 Improper burner cross−overs ACTION 1 − Remove burner and inspect the cross−overs for burrs, or any restriction or if crossover is warped. Remove restriction or replace burners. Page 44 PROBLEM 6: BURNERS LIGHT WITH HEATING DEMAND BUT UNIT SHUTS DOWN PREMATURELY (CONT.) 6.5 − Combustion air blower energizes with a heating demand. − Burners light. − Diagnostic lights flash watch guard flame failure. − NOTE" Unit might go into 60 minute Watchguard mode depending on intermittent nature of sensor signal. 6.5.1 Loose sensor wire connection causes intermittent loss of flame signal. ACTION 1 − Check that the sensor is properly located. ACTION 2 − Check that the sense wire is properly attached to both the sensor and the control. Pay extra attention to the pin connectors. LED#1−Alternating Slow Flash LED#2−Alternating Slow Flash PROBLEM 7: CONTROL SIGNALS LOW FLAME SENSE DURING HEATING MODE Condition 7.0 − Unit operates correctly but the diagnostic lights flash low flame sense code code. LED#1−Slow Flash LED#2−Fast Flash Possible Cause Corrective Action/Comments 7.1.1 Sense rod is improperly located on the burner. ACTION 1 − Check the sense rod for proper location on the burner. Properly locate the sense rod or replace if rod cannot be located correctly. 7.1.2 Sense rod is contaminated. ACTION 1 − Check sense rod for contamination or coated surface. Clean the sense rod with steel wool or replace sensor. DO NOT USE SAND PAPER TO CLEAN ROD. SAND PAPER WILL CONTRIBUTE TO THE CONTAMINATION PROBLEM. PROBLEM 8: INDOOR BLOWER FAILS TO OPERATE IN COOLING, HEATING, OR CONTINUOUS FAN MODE Condition 8.0 − Indoor blower fails to operate in continuous fan, cooling, or heating mode. Possible Cause Corrective Action/Comments 8.1.1 Miswiring of furnace or improper connections at control or indoor blower motor. ACTION 1− Correct wiring and/or replace any loose connections. Check for correct wiring and loose connections. 8.1.2 120V is not being supplied to the indoor air blower or blower motor failure. ACTION 1 − Check for 120V at the various calls for indoor blower by energizing "Y", "G", and "W" individually on the low voltage terminal strip. Note that when "W’ is energized, the blower is delayed 45 seconds. If there is 120V to each motor tap but the blower does not operate, replace the motor. 8.1.3 Defective control board ACTION 1 − If there is not 120V when "Y", "G", or "W" is energized, replace the control. PROBLEM 9: RF STATIC DURING TIME FOR IGNITION Condition Possible Cause Corrective Action/Comments 9.0 − AM radio interference 9.1.2 Ignitor operation ACTION 1− Call Technical Support, Dallas Page 45 SERVICE NOTES Page 46