Carrier Weathermaster 48P2030-100, Controls, Start-Up, Operation, Service, And Troubleshooting

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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 func-
tion is proven, the ignition activation period begins. The burn-
ers 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 re-
set 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 sec-
onds 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 de-
lay 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 fol-
lowed 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 mo-
tor 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.
Table 58 — TR1 Board LED Indicators
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 de-
termine which state to command the induced-draft motor and
main gas valve. See Table 58.
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), regard-
less of the unit size. The boards provide control for variable
heating output for the gas heat section.
Similar to the staged gas heat option, each IGC board is con-
trolled separately. The IGC functions are not affected by the
modulating gas control logic. When a call for gas heat is initi-
ated, 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 receives 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 con-
ditioner 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.
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 fol-
lowed and the gas will remain on for a minimum of 1 minute.
RELOCATE SAT FOR HEATING-LINKAGE APPLICATIONS
If
Configuration

HEAT

LAT.M is set to YES, the supply
air temperature thermistor ( Temperatures

AIR.T

SAT )
must be relocated downstream of the installed heating device.
This only applies to two-stage gas or electric heating types
( Configuration

HEAT

HT.CF =1 or 2).
Determine a location in the supply duct that will provide a fair-
ly uniform airflow. Typically this would be a minimum of 5
equivalent duct diameters downstream of the unit. Also, care
should be taken to avoid placing the thermistor within a direct
line-of-sight of the heating element to avoid radiant effects.
Run a new two-wire conductor cable from the control box
through the low voltage conduit into the space inside the build-
ing and route the cable to the new sensor location.
Installing a New Sensor
Procure a duct-mount temperature sensor (Carrier P/N
33ZCSENPAT or equivalent 10,000 ohms at 25C NTC [nega-
tive temperature coefficient] sensor). Install the sensor through
the side wall of the duct and secure.
Re-Using the Factory SAT Sensor
The factory sensor is attached to the left-hand side of the sup-
ply fan housing. Disconnect the sensor from the factory har-
ness. Fabricate a mounting method to insert the sensor through
the duct wall and secure in place.
Attach the new conductor cable to the sensor leads and termi-
nate in an appropriate junction box. Connect the opposite end
inside the unit control box at the factory leads from MBB J8
terminals 11 and 12 (PNK) leads. Secure the unattached PNK
leads from the factory harness to ensure no accidental contact
with other terminals inside the control box.
TEMPERING MODE
In a vent or cooling mode, the economizer at minimum posi-
tion may send extremely cold outside air down the ductwork of
the building. Therefore, it may be necessary to bring heat on to
LED
DESIGNATION
RESULT/ACTION
ON 24 VAC Supplied to TR1
SR Input received from IGC2, starts timer no. 1
MR
Modulating Gas Valve modulated except during
fixed output delay time
FR IDM2 operates at high speed
CR
Modulating Gas Valve operates in high pressure
stage