Download Carrier WEATHER MASTER 48P2 Specifications

Modulating Gas Control Boards (SC30 and TR1) Logic —
All gas modulating units are equipped with one timer relay
board (TR1) and one signal conditioner board (SC30), regardless the unit size. The boards provide control for variable heating output for the gas heat section.
Similar with staged gas heat option, each IGC board is controlled separately. The IGC functions are not affected by the
modulating gas control logic. When a call for gas heat is initiated, W on the IGC board and the timer relay board (TR1) are
energized. The LED on TR1 board will be turned on. See
Table 58 for LED explanation.
When TR1 received an input from the IGC board, the relay
board starts Timer no. 1 or start-up sequence: sets the gas valve
stage and the inducer motor speed, and enables the signal conditioner board SC30. During Timer no. 1, the SC30 board
keeps a fixed heating output. When Timer no. 1 expires, the
modulating gas control boards start Timer no. 2. Throughout
the duration of Timer no. 2, the boards determine which state to
adjust the capacity output to satisfy the heat demand. When
Timer no. 2 expires, the boards receive a capacity input from
the SCB board and continuous modulate the heat output until
the mode selection sensor is satisfied.
in parallel. For staged gas heat, each board is controlled separately. When energized, an LED on the IGC board will be
turned on. See Table 57 for LED explanations.
Each board will ensure that the rollout switch and limit
switch are closed. The induced-draft motor is then energized.
For units equipped with 2-stage or staged gas heat the speed of
the motor is proven with a Hall Effect sensor on the motor. For
units equipped with modulating gas heat the motor function is
proven with a pressure switch. When the motor speed or function is proven, the ignition activation period begins. The burners ignite within 5 seconds. If the burners do not light, there is a
22-second delay before another 5-second attempt is made. If
the burners still do not light, this sequence is repeated for 15
minutes. After 15 minutes have elapsed and the burners have
not ignited then heating is locked out. The control will reset
when the request for W (heat) is temporarily removed.
When ignition occurs, the IGC board will continue to monitor the condition of the rollout switch, limit switches, Hall Effect sensor or pressure switch, and the flame sensor. Forty-five
seconds after ignition has occurred, the IGC will request that
the indoor fan be turned on.
The IGC fan output (IFO) is connected to the indoor fan input on the MBB which will indicate to the controls that the indoor fan should be turned on (if not already on). If for some
reason the overtemperature limit switch trips prior to the start
of the indoor fan blower, on the next attempt the 45-second delay will be shortened by 5 seconds. Gas will not be interrupted
to the burners and heating will continue. Once modified, the
fan delay will not change back to 45 seconds unless power is
reset to the control.
The IGC boards only control the first stage of gas heat on
each gas valve. The second stages are controlled directly from
the MBB board for staged gas. For units equipped with modulating gas heat, the second stage is controlled from the timer relay board (TR1). The IGC board has a minimum on-time of 1
minute.
In modes such as Service Test where long minimum on
times are not enforced, the 1-minute timer on the IGC will still
be followed and the gas will remain on for a minimum of 1
minute.
Staged Gas Heat Board (SCB) — When optional staged or
modulating gas heat is used, the SCB board is installed and
controls additional stages of gas heat. The SCB also provides
additional sensors for monitoring of the supply-air and limit
switch temperatures. For units equipped with modulating gas
heat, the SCB provides the 4 to 20 mA signal to the SC30
board that sets the modulating gas section capacity. This board
is located in the main unit control box.
Timer Relay Control Board (TR1) — The TR1 is used on
modulating gas heat equipped units only. It is located in the gas
heat section and is used in combination with the SC30 to provide control of the modulating gas heat section. The TR1 receives an input from the IGC, initiates a start-up sequence,
powers the SC30, sets the induced-draft motor speed, and provides the main gas valve high fire input. When the start-up sequence is complete, the TR1 checks the input from the SC30 to
determine which state to command the induced-draft motor
and main gas valve. See Table 58.
Signal Conditioner Control Board (SC30) — The SC30 is
used on modulating gas heat equipped units only. It is located
in the gas heat section and is used in combination with the TR1
to provide control of the modulating gas heat section. The
SC30 is powered by an output from the TR1. It receives a
capacity input from the SCB, provides a capacity output to the
modulating gas valve, and provides an output to the TR1 to
determine which state to command the induced-draft motor
and main gas valve. See Table 58.
Table 57 — IGC LED Indicators
ERROR CODE
Normal Operation
Hardware Failure
Fan On/Off Delay Modified
Limit Switch Fault
Fame Sense Fault
Five Consecutive Limit Switch Faults
Ignition Lockout Fault
Ignition Switch Fault
Rollout Switch Fault
Internal Control Fault
Software Lockout
LED INDICATION
On
Off
1 Flash
2 Flashes
3 Flashes
4 Flashes
5 Flashes
6 Flashes
7 Flashes
8 Flashes
9 Flashes
NOTES:
1. There is a 3-second pause between error code displays.
2. If more than one error code exists, all applicable error codes will
be displayed in numerical sequence.
3. Error codes on the IGC will be lost if power to the unit is
interrupted.
Table 58 — TR1 Board LED Indicators
LED
RESULT/ACTION
DESIGNATION
ON
24 VAC Supplied to TR1
SR
Input received from IGC2, starts timer no. 1
Modulating Gas Valve modulated except during
MR
fixed output delay time
FR
IDM2 operates at high speed
Modulating Gas Valve operates in high pressure
CR
stage
The IGC boards only control the first stage of gas heat on
each gas valve. The second stages are controlled directly from
the MBB board. The IGC board has a minimum on-time of 1
minute.
In modes such as Service Test where long minimum on
times are not enforced, the 1-minute timer on the IGC will still
be followed and the gas will remain on for a minimum of 1
minute.
RELOCATE SAT FOR HEATING-LINKAGE APPLICATIONS — If ConfigurationoHEAToLAT.M is set to YES,
the supply air temperature thermistor (TemperaturesoAIR.T
o SAT) must be relocated downstream of the installed heating
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