Integrated Gas Controller - Carrier WeatherMaker 48FC04-07 Installation Instructions Manual

Integrated Gas Controller

This unit contains an Integrated Gas Controller (IGC)
board. The IGC control board uses a flue gas pressure switch
that senses pressure drop in the heat exchanger due to the
combustion inducer. See Fig. 43.
FLUE GAS
PRESSURE
SWITCH
FLUE GAS
PRESSURE
SENSE TUBE
Fig. 43 — Flue Gas Pressure Switch and Pressure
Sense Tube (Typical Location)
Locking
Tab Connector
Locking
Tab Connector
Spade
Connect Ignitor
Fig. 44 — IGC Board Component Layout
When the thermostat calls for heating, power is sent to W
on the Integrated Gas Controller (IGC) board. An LED (light
emitting diode) on the IGC board turns on and remains on
during normal operation. A check is made to ensure that the
rollout switch and limit switch are closed, and that the pres-
sure switch is open. If the check was successful, the induced
draft motor is energized. When the pressure in the heat ex-
changer is low enough to close the pressure switch, the igni-
tion activation period begins. Once ignition occurs, the IGC
board will continue to monitor the condition of the rollout
switch, the limit switches, the pressure switch, and the flame
sensor. Assuming the unit is controlled through a room ther-
mostat set for "fan auto," 45 seconds after ignition occurs, the
indoor fan motor will energize, and the outdoor air dampers
will open to their minimum position. If the "over temperature
limit" opens prior to the start of the indoor fan blower, the
IGC will shut down the burners, and the control will shorten
the 45 second delay to 5 seconds less than the time to trip the
limit. For example, if the limit trips at 37 seconds, the control
will change the "fan on delay" from 45 seconds to 32 sec-
onds. Once the "fan on delay" has been modified, it will not
change back to 45 seconds unless power is reset to the con-
trol. On units with 2 stages of heat, W2 closes and initiates
power to the second stage of the main gas valve when addi-
tional heat is required.
When the thermostat is satisfied, W1 and W2 open and the
gas valve closes, interrupting the flow of gas to the main
burners. If the call for W1 lasted less than 1 minute, the heat-
ing cycle will not terminate until 1 minute after W1 became
active. If the unit is controlled through a room thermostat set
for fan auto, the indoor fan motor will continue to operate for
an additional 45 seconds, then stop. An LED indicator is pro-
vided on the IGC to monitor operation.
See Fig. 44 for IGC board component layout. Fig. 45 is a
typical IGC control wiring diagram.
Overcurrent Fuse
Redundant Gas
25
Protection
Valve Relay