Carrier 48LC 14, Инструкции по обслуживанию и техническому обслуживанию

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Heating
In the Heating Mode (W1 on the thermostat), the ISC board sends
power to W on the IGC board. The ISC board sees W1=ON and
also expects IFO=ON. However, the IFO is not ON immediately
as the Integrated Gas Controller (IGC) board has to work thru its
operating sequence. Thus, the ISC board will turn on a momentary
LED (light-emitting diode). The indoor fan is not turned on by the
ISC board.
The IGC board starts its gas ignition process. An LED 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. If the check was successful, the induced draft motor is en -
ergized, and when its speed is satisfactory, as proven by the “hall
effect” sensor, the ignition activation period begins. The burners
will ignite within 5 seconds. If the burners do not light, there is a
22 second delay before another 5 second attempt. This sequence is
repeated for 15 minutes or until the burners light. If, after the
15 minutes, the burners still have not lit, heating is locked out. To
reset the control, break 24VAC power to the thermostat.
When gas ignition occurs, the IGC board will continue to monitor
the condition of the rollout switch, the limit switches, the “hall ef -
fect” sensor, as well as the flame sensor. Once gas ignition is con -
firmed, the IGC board has a 45 second built in delay before it
sends an IFO=ON signal to the ISC board. Assuming the unit is
controlled through a room thermostat set for fan auto, the indoor-
fan motor will energize and the outdoor-air dampers will open to
their minimum position. The delay will allow for the gas section to
come to temperature before turning on the indoor fan. This will
prevent the unit from blowing cold air into the space. Once the
ISC board sees IFO=ON, the VFD controlled indoor fan is set to
high speed and the LED error is cleared. If, for some reason the
over temperature limit opens prior to the start of the indoor fan
blower, the unit will shorten the 45 second delay to 5 seconds less
than the time from initiation of heat to when the limit tripped. Gas
will not be interrupted to the burners and heating will continue.
Once the fan ON delay has been modified, it will not change back
to 45 seconds until power is reset to the control.
When W1 is turned OFF, the IGC board turns off the gas valve.
The IGC board has a delay time before it turns IFO=OFF. At this
time, the ISC board sees W1=OFF and IFO=ON. The ISC will
keep the indoor fan ON. Once the IGC board delay times out, the
ISC board will see W1=OFF and IFO=OFF, which then turns the
indoor fan OFF.
If the call for W1 lasted less than 1 minute, the heating 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. If the over temperature limit opens after the indoor mo -
tor is stopped, but within 10 minutes of W1 becoming inactive, on
the next cycle the time will be extended by 15 seconds. The maxi -
mum delay is 3 minutes. Once modified, the fan OFF delay will
not change back to 45 seconds unless power is reset to the control.
A LED indicator is provided on the IGC to monitor operation.
When additional heat is required, W2 closes and initiates power to
the second stage of the main gas valve. When the thermostat is sat -
isfied, the gas valve closes, interrupting the flow of gas to the main
burners.