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options
Figure 25.1 - Dirty Filter Pressure Switch and Air Flow
Proving Switch
Negative pressure
connector
Positive pressure connector
C
NO
(42) Proportional Temperature Controller – (OPT)
A proportional temperature controller is provided with Air Control
options GG, GH, GK or GM (Digits 20 & 21) and factory installed
in the electrical section. The controller compares the mixed
air temperature set point and the mixed air temperature from
the Proportional Temperature Controller Sensor. The controller
sends a 2-10 Vdc signal to the modulating damper actuator in
order to maintain the set point. The controller includes a set point
dial that must be field set to the desired mixed air temperature
(typically 55°F).
Figure 25.3 - Proportional Temperature Controller
Pressure adjustment set screw
(40) Motor Starter – (OPT)
The motor starter is factory installed in the electrical section.
A motor starter is required for all three phase motors and single
phase motors 1-1/2 Hp and greater. The motor starter current set
point dial is factory set to the motor full load amp draw listed on
the motor nameplate.
(40) Variable Frequency Drive – (OPT)
The VFD controller adjusts the motor rpm to vary the unit air
flow. The minimum air flow may be varied between 30 and 100%
of the full speed air flow depending on the controls selection of
the unit. The control changeover options are two speed, floating
building pressure sensing, and building management control.
The overload module of the motor starter is designed to trip to
protect the motor from exceeding the nameplate amps. If the
motor exceeds the amp draw on the current set point dial, the trip
condition is indicated by a red color in the trip indicator window.
The motor starter can be placed in the automatic or manual
reset positions. Automatic reset is accomplished by depressing
the “RESET” button and turning the button 1/4 turn. When in the
automatic reset position, if the overload module trips, the module
will reset itself once the overload relay has cooled. In the manual
reset position, if the overload module trips, the “RESET” button
must be depressed before the blower can operate.
The contractor module includes one (1) normally open auxiliary
contact. The contact rating is 10 amps.
If the factory installed motor starter option was not ordered with a
unit that has a three phase motor or single phase motor 1-1/2 Hp
or greater, a motor starter must be field supplied and installed.
Figure 25.2 - Motor Starter
A1
1
A2
3
L1
5
L2
13
L3
NO
CONTACTOR
MODULE
CURRENT
SET POINT
DIAL
4
T1
6
T2
14
T3
NO
(44) Blower Supply Power Terminal Strip – (STD)
The blower supply power terminal strip is located in the electrical
section. The terminal strip is labeled to match the electrical wiring
diagram provided with the unit. Supply power labeling ranges
from terminal numbers 80 to 99. All field wiring connections
should be made to the bottom side of the terminals to prevent
miswiring by modifying the factory wiring which is made to the
top of the terminal strip.
(45) Service Switches – (OPT)
The service switches are factory installed in the electrical
section. The service switches allow for service personnel to
independently test operation of the damper, blower, and furnace
without using jumper wires. The switches override the remote
monitoring panel and/or thermostats to energize each compo­
nent directly. All switches need to be reset to the “OFF” position
after testing otherwise the components will remain energized.
Figure 25.4 - Service Switches
TRIP
INDICATOR
WINDOW
2
(43) Warm-Up Stat – (OPT)
A warm-up stat is provided with Air Control options GK or GM
(Digits 20 & 21) and factory installed in the electrical section with
the sensor in the return air stream. The warm-up thermostat
monitors the return air temperature to the unit and prevents
the fresh air dampers from opening until the temperature of the
return air has reached the desired set point (typically 65°F or 5°F
below the room temperature).
RESET
A2
OVERLOAD
MODULE
A R
E
S
E
T
H
NO
98
2
NC
97
T1
4
95
T2
96
6
T3
(41) Mild Temperature Thermostat – (OPT)
The mild temperature thermostat is factory installed in the
electrical section. The mild temperature thermostat is designed
to lockout the burner during mild weather conditions which
prevents the burner from cycling. The thermostat must be field
set to the desired mild temperature condition (refer to the latest
revision of Modine Literature 75-540).
5-572.8
25