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269434-UUM-A-0407
Unitary Products Group 7
9 RED FLASHES: Indicates reversed line voltage polarity or grounding
problem. Both heating and cooling operations will be affected. Check
polarity at furnace and branch. Check furnace grounding. Check that
flame probe is not shorted to chassis.
10 RED FLASHES: Gas valve energized with no call for heat. Check
gas valve and gas valve wiring.
11 RED FLASHES: This indicates that a primary or auxiliary limit switch
has opened its normally-closed contacts and has remained open for
more than five minutes. This condition is usually caused by a failed
blower motor or blower wheel.
12 RED FLASHES: This code indicates an open igniter circuit, which
could be caused by a disconnected or loose wire or by a cracked or bro-
ken igniter.
STEADY ON RED: Control failure. Replace control board.
60-MINUTE AUTOMATIC RESET FROM LOCKOUT: This control
includes a “watchdog” type circuit that will reset from a lockout condition
after 60 minutes. Operational faults 6,7,8 will be reset. This provides
protection to an unoccupied structure if a temporary condition exists
causing a furnace malfunction. An example would be a low incoming
gas supply pressure preventing unit operation. When the gas pressure
is restored, at some point the “watchdog” would restart the unit and pro-
vide heat for the house.
NOTE: If a flame is detected the control flashes the LED for 1/8 of a
second and then enters a flame stabilization period.
DIAGNOSTIC FAULT CODE STORAGE AND
RETRIEVAL
The control in this furnace is equipped with memory that will store up to
five error codes to allow a service technician to diagnose problems
more easily. This memory will be retained even if power to the furnace
is lost. This feature should only be used by a qualified service tech-
nician.
The control stores up to five separate error codes. If more than five
error codes have occurred since the last reset, only the five most recent
will be retained. The furnace control board has a button, labeled "LAST
ERROR" that is used to retrieve error codes. This function will only work
if there are no active thermostat signals. So any call for heating, cooling
or continuous fan must be terminated before attempting to retrieve error
codes.
To retrieve the error codes, push the LAST ERROR button. The LED on
the control will then flash the error codes that are in memory, starting
with the most recent. There will be a two-second pause between each
flash code. After the error codes have all been displayed, the LED will
resume the normal slow green flash after a five second pause. To
repeat the series of error codes, push the button again.
If there are no error codes in memory, the LED will flash two green
flashes. To clear the memory, push the LAST ERROR button and hold it
for more than five seconds. The LED will flash three green flashes when
the memory has been cleared, then will resume the normal slow green
flash after a five-second pause.
IGNITION CONTROL
Normal flame sense current is approximately
3.7 microamps DC (µa)
Low flame signal warning starts at 1.5 microamps.
Low flame signal control lockout point is
0.1 microamps DC (µa)
FIGURE 7: Furnace Control Event Schedule
Thermostat Calling for Heat
Thermostat Satisfied
(Seconds)
THERMOSTAT
INDUCER
IGNITOR
MAIN VALVE
HUMIDIFIER
ELECTRONIC
AIR CLEANER
CIRCULATING
BLOWER
OFF
OFF
OFF
OFF
OFF
OFF
OFF
ON
ON
ON
ON
OFF
OFF
OFF
OFF
ON
ON
ON
OFF
OFF
OFF
OFF
OFF
OFF
OFF
15 Sec.
Post
Purge
Fan on Delay
30 Seconds
0
2
17 22
52
0
60, 90, 120, 180 SEC.
Selectable Fan Off Delay