Service Manual

42
COOLING OPERATION WITH A COMMUNICATING THERMOSTAT AND
CONVENTIONAL SINGLE STAGE A/C
The call for cooling will be communicated via the
ClimateTalk™ protocol.
The Y1 terminal of the IFC becomes an output via the
on board Y1 relay
The IFC does not provide short cycle protection.
The circulator operates as commanded by the com-
municating thermostat.
COOLING OPERATION WITH A COMMUNICATING THERMOSTAT AND
OUTDOOR UNIT
The furnace receives the CFM demand from the com-
municating outdoor unit.
CALL FOR COOL WITH CALL FOR HEAT PRESENT – DUAL FUEL
DEFROST OPERATION
While in defrost, the standard light off sequence will
be followed. The IFC will then fire at 100% for the
remainder of the defrost call.
While in defrost the circulator will use the selected
heat speed.
FAN MODE
CONVENTIONAL THERMOSTAT
Two seconds after G request becomes active without Y1
request, IFC will run the circulator at the appropriate speed
(as selected by the DIP switches), unless circulator is run-
ning as a result of Heat or Cool mode. The circulator speed
required by the heat or cool demand always has priority
over G speed.
COMMUNICATING THERMOSTAT
If a conventional G request is present without a heat or cool
request from the communicating thermostat, the circulator
will run at the selected fan speed.
HUMIDITY CONTROL
HUMIDIFIER OUTPUT – CONVENTIONAL THERMOSTAT
One set of isolated relay contacts are wired to a pair of
terminals for connection to a humidifier. When the inducer
is on the IFC closes the humidifier relay contacts, except
from the calibration routine where the humidifier relay con-
tacts are always open.
HUMIDIFIER OUTPUT – COMMUNICATING THERMOSTAT
One set of isolated relay contacts are wired to a pair of
terminals for connection to a humidifier. Upon receipt of a
Humidification Requested Demand the IFC will:
Close the humidifier relay contacts
Energize the circulator at the circulation speed (G
speed) unless the circulator is commanded to a dif-
ferent speed by a heat demand.
DEHUMIDIFICATION – CONVENTIONAL THERMOSTAT
DEHUM functionality is enabled by a DIP switch set-
ting.
The IFC varies circulator speed operation based on
the DEHUM signal from the thermostat
If 24VAC (R) is not connected to DEHUM (through a
Humidistat) and both Y1 and O terminals are ener-
gized, then the IFC control reduces the cooling CFM
by 15%.
If both Y1 and O terminals are not energized, the
DEHUM signal is ignored
DEHUM is ignored during any heating request.
LEARN PUSH-BUTTON
Pressing the learn button re-sets the communicating net-
work and allows the IFC to search for communicating equip-
ment The press and release of the button starts the same
learning process as during power-up of the system.
CLIMATETALK™ COMMUNICATION LEDS
The IFC has two LEDs :
Red communications LED – Indicates the status of
the network
OFF is normal condition.
2 slow flashes on power-up: ON for ¼ second, OFF for
¾ second, ON for ¼ second, OFF.
Continuous slow flash indicates communication fail-
ure: ON for ¼ second, OFF for ¾ second…
Green receive LED – Indicates network traffic
Fast, sporadic flashes indicates normal bus commu-
nication.
ON solid indicates a Data 1 / Data 2 miswire.
OPERATION