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Normal Heat Mode - Conventional Single
Stage Thermostat
Refer to Fig. 12 on page 22 for the operating sequence
diagram.
Call for Heat
A call for heat is signaled by the thermostat closing the
contacts between R and W1.
Upon a call for heat, the following occurs:
— After a successful Light Off and expiration of the
ignition stabilization period, the Inducer adjusts to the
low firing rate speed.
— After expiration of the heat fan on delay, the IFC
adjusts the circulator to the appropriate speed (CFM).
— If a discharge air sensor is present, the circulator
adjusts to maintain the target discharge air
temperature.
— The IFC remains in this state until the selected 2nd
stage on delay expires or the call for heat is removed.
When the 2nd stage on delay expires:
— The Inducer adjusts to the mid firing rate speed.
— The IFC adjusts the circulator to the appropriate speed
(CFM).
— If a discharge air sensor is present, the circulator
adjusts to maintain the target discharge air
temperature.
— The IFC remains in this state until the selected 3rd
stage on delay expires or the call for heat is removed.
When the 3rd stage on delay expires:
— The Inducer adjusts to the high firing rate speed.
— The IFC adjusts the circulator to the appropriate speed
(CFM).
— If a discharge air sensor is present, the circulator
adjusts to maintain the target discharge air
temperature.
— The IFC remains in this state until the call for heat is
removed.
Cooling Mode
Refer to Fig. 13 on page 23 for the operating sequence
diagram.
NOTES:
1.
If a call for heat and a call for cool are present
simultaneously, the call for heat is serviced.
2.
The circulator runs at the highest speed per the
thermostat request.
Single Stage Cooling
A call for cooling is signaled by:
— The shorting of R to Y1.
— The shorting of R to Y1 and G simultaneously.
Upon a call for cooling:
— The compressor and condenser fan energize directly
from the Y1 terminal pass-through signal from the
thermostat.
— The IFC does not directly control the compressor and
does not provide short cycle protection.
— The circulator energizes two seconds after the cool
request.
S9240F1004 MODULATING HOT SURFACE IGNITION INTEGRATED FURNACE CONTROL
13
— The circulator starts according to one of the selectable
ramping profiles.
When the cool request is satisfied, the circulator de-energizes
per one of the selectable ramping profiles.
Two Stage Cooling
The two stage cooling jumper
enable two stage cooling control.
A call for 1st stage cooling is signaled by:
— The shorting of R to Y1.
— The shorting of R to Y1 and G simultaneously.
A call for 2nd stage cooling is signaled by:
— the shorting of R to Y2 while a valid call for first stage
cooling exists.
Upon a call for two stage cooling:
— The compressor and condenser fan energize directly
from the Y1 and Y2 terminals pass-through signal from
the thermostat.
— The IFC does not directly control the compressor and
does not provide short cycle protection.
— The circulator energizes at the low cooling speed two
seconds after the 1st stage cool request is detected
and switches to high cooling speed immediately after
the 2nd stage cool request is detected.
— The circulator starts and operates according to the
selected ramping profile.
— When the cool requests are satisfied, the circulator
de-energizes per the selected ramping profile.
Fan Mode
Refer to Fig. 14 on page 24 for the operating sequence
diagram.
— If the IFC is not currently servicing another circulator
request, the circulator energizes at the fan speed
when R is shorted to G and de-energizes when the
request is removed.
— The circulator speed is determined by the dip switch
settings. See "DIP Switches" on page 7.
— If the IFC is servicing a fan request and a call for heat
or a call for cooling occurs, the circulator remains
energized at the continuous fan speed until it is
requested to move to the speed required by the heat
or cool demand.
Call for Compressor Heat
b
Removing the "O" jumper
in a heat pump system. The thermostat generates the "O"
signal. No signal on "O" with 24 Vac on Y1 or Y1+Y2 from the
thermostat indicates a call for compressor heat for stage 1 or
stage 2 respectively.
These 24 Vac signals directly control a one or two stage heat
pump.
— No heat fan on delay is present for compressor heat.
— The circulator energizes without delay when
compressor low or high heat is requested.
— Compressor heat calls and fossil fuel calls can be
serviced simultaneously. The circulator energizes at
the speed requested by the compressor or fossil fuel
heat sequence, whichever is higher.
a
See jumper W915 in Table 4 on page 7.
b
See jumper W951 in Table 4 on page 7.
a
on the IFC must be clipped to
indicates that the IFC is being used
69-2088—01
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