Operating instructions

(3.) When thermostat is satisfied, furnace blower motor
BLWM continues operating on cooling speed for an
additional 90 sec.
c. Single-Speed Heat Pump Heating
(1.) The thermostat and accessory interface kit R to G-
and-Y/Y2 circuits start furnace blower motor
BLWM on heat pump high-heat speed (identical to
high-cool speed).
(2.) The EAC terminals EAC-1 and EAC-2 are ener-
gized with 115v when blower motor BLWM is
operating.
(3.) When thermostat is satisfied, furnace blower motor
BLWM continues operating on heat pump high-heat
speed for an additional 90 sec.
d. Two-Speed Heat Pump Heating
(1.) The thermostat closes R to G circuit for low heat
and starts furnace blower motor BLWM on heat
pump low-heat speed (identical to low-cooling
speed). Closing R-Y/Y2 circuit to furnace provides
blower motor BLWM heat pump high-heat speed.
NOTE: The furnace control CPU controls blower motor BLWM
speed by sensing only G (for heat pump low-heat speed) and Y2
(for heat pump high-heat speed).
(2.) The EAC terminals EAC-1 and EAC-2 are ener-
gized with 115v when blower motor BLWM is
operating on either heating speed.
(3.) When thermostat is satisfied, R to G or R to G-
and-Y2 circuits are opened. After opening R to
G-and-Y2 circuit, the furnace blower motor BLWM
continues operating on heating speed for an addi-
tional 90 sec.
(4.) Opening R-Y2 circuit reduces blower motor
BLWM speed to heat pump low-heat speed.
6. Defrost
a. When furnace control R to W/W1-and-Y/Y2 circuits are
closed, furnace control CPU continues blower motor
BLWM operation at heat pump heating speed until end
of prepurge period, then shuts off until end of HSI ignitor
on period (22 sec).
b. When installed with a heat pump, furnace control CPU
automatically holds blower off time to 22 sec during HSI
ignitor on period. After 17 sec of HSI ignitor on period,
a trial-for-ignition sequence occurs as described above
for gas heating. After flame is proved and without
blower on delay, blower motor BLWM then operates on
high-gas-heat speed during defrost. For both single-
speed and 2-speed heat pumps, defrost mode is in
high-gas heat only.
c. When furnace control R to W/W1 circuit is opened,
furnace control CPU begins normal inducer post-purge
period, and blower motor BLWM remains on for blower
off delay period. If R-G circuit remains closed, blower
motor BLWM reverts to continuous operation.
C. Start-Up Procedures
1. Component test—The furnace features a component test
system to help diagnose a system problem in case of
component failure. To initiate component test procedure,
ensure that there are no thermostat inputs to control and that
all time delays have expired. Short TWIN/TEST terminal to
ground or Com for 1 to 4 sec. See Fig. 14 for terminal
locations.
NOTE: The component test feature will not operate if control is
receiving any thermostat signals and until all time delays have
expired.
The component test sequence is as follows:
a. The furnace control checks itself, operates inducer motor
on low speed for 7 sec and on high speed for 7 sec, then
stops.
b. The hot surface ignitor is then energized for 15 sec, then
de-energized.
c. The blower motor operates on low-gas-heat/heat pump
low-heat/low-cool/continuous fan speed for 7 sec, then
stops.
d. The blower motor operates on high-gas-heat speed for 7
sec, then stops. The gas valve and humidifier terminal
HUM are not energized for safety reasons.
NOTE: The EAC terminals are energized when blower is ener-
gized.
e. The blower operates on heat pump high-heat/high-cool
speed for 7 sec, then stops.
2. After all connections have been made, purge gas lines and
check for leaks.
WARNING: Never purge a line into a combustion
chamber. Never use matches, candles, flame, or other
sources of ignition to check for gas leakage. Use a
soap-and-water solution to check for gas leaks. A failure
to follow this warning could result in fire, explosion,
personal injury, or death.
3. To operate furnace, follow procedures on operating instruc-
tion label attached to furnace.
4. With furnace operating, set thermostat below room tem-
perature and observe that furnace goes off. Set thermostat
above room temperature and observe that furnace restarts.
D. Adjustments
1. Set gas input rate.
Furnace gas input rate on rating plate is for installations at
altitudes up to 2000 ft.
In the U.S.A., input rating for altitudes above 2000 ft must
be reduced by 4 percent for each 1000 ft above sea level.
In Canada, input rating must be derated by 10 percent for
altitudes of 2000 ft to 4500 ft above sea level.
Furnace input rate must be within ±2 percent of input on
furnace rating plate.
a. Determine natural gas orifice size and manifold pressure
for correct input.
(1.) Obtain yearly heat value average (at installed alti-
tude) from local gas supplier.
(2.) Obtain yearly specific gravity average from local
gas supplier.
(3.) Verify furnace model. Table 10 can only be used for
model 331AAV Furnaces.
(4.) Find installation altitude in Table 10.
NOTE: For Canada altitudes of 2000 to 4500 ft, use U.S.A.
altitudes of 2001 to 3000 ft in Table 10.
(5.) Find closest natural gas heat value and specific
gravity in Table 10.
(6.) Follow heat value and specific gravity lines to point
of intersection to find orifice size and low- and
high-heat manifold pressure settings for proper
operation.
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