1 RED FLASH: This indicates that flame was sensed when there was not a call for heat. With this fault code the control will turn on both the inducer motor and supply air blower. A gas valve that leaks through or is slow closing would typically cause this fault.
2 RED FLASHES: This indicates that the normally open pressure switch contacts are stuck in the closed position. The control confirms these contacts are open at the beginning of each heat cycle. This would indicate a faulty pressure switch or miswiring.
3 RED FLASHES: This indicates the normally open pressure switch contact did not close after the inducer was energized. This could be caused by a number of problems: faulty inducer, blocked vent pipe, bro- ken pressure switch hose or faulty pressure switch.
4 RED FLASHES: This indicates that a primary or auxiliary limit switch has opened its normally closed contacts. With this fault code the control will operate the supply air blower and inducer. This condition may be caused by: dirty filter, improperly sized duct system, incorrect blower speed setting, incorrect firing rate or faulty blower motor.
5 RED FLASHES: This fault is indicated if the normally closed contacts in the rollout switch opens. The rollout control is manually reset. If it has opened, check for proper combustion air, proper inducer operation, and primary heat exchanger failure or burner problem. Be sure to reset the switch after correcting the failure condition.
6 RED FLASHES: This indicates that after the unit was operating, the pressure switch opened 4 times during the call for heat. If the main blower is in a “Delay on” mode it will complete it, and any subsequent delay off period. The furnace will lock out for one hour and then restart.
7 RED FLASHES: This fault code indicates that the flame could not be established. This
8 RED FLASHES: This fault is indicated if the flame is lost 5 times (4 recycles) during the heating cycle. This could be caused by low gas pressure, dirty or faulty flame sensor or faulty gas valve. The furnace will lock out for one hour and then restart.
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 including the transformer ground. Check that flame probe is not shorted to chassis.
10 RED FLASHES: Gas flow 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
4 AMBER FLASHES: Y present with no G call. Normally, both Y and G are energized on a call for cooling. If a Y signal is present with no G sig- nal, check to see that the wire from the G terminal on the board to the wall thermostat has not broken or disconnected.
STEADY ON RED: Control failure. Replace control board.
NOTE: If a flame is detected the control flashes the LED for 1/8 of a second and then enters a flame stabilization period.
IGNITION CONTROL (P/N
Low flame signal warning starts at 1.5 microamps.
Low flame signal control lockout point is
0.9 microamps DC (µa)
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 is 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
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
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| Thermostat Calling for Heat | |
(Seconds) | 0 2 | 17 | 22 | 52 | |
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| Fan on Delay |
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| 30 Seconds |
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| ON |
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THERMOSTAT | OFF |
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INDUCER |
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| ON |
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| OFF |
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| ON |
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IGNITOR | OFF |
| OFF |
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MAIN VALVE |
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| ON |
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| OFF |
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| ON |
HUMIDIFIER | OFF |
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| OFF |
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ELECTRONIC |
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| ON |
AIR CLEANER | OFF |
| OFF |
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CIRCULATING |
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| ON |
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BLOWER | OFF |
| OFF |
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Thermostat Satisfied
0
OFF |
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15 Sec. | OFF |
Post |
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Purge |
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| OFF |
OFF
OFF
OFF
60, 90, 120, 180 SEC. OFF Selectable Fan Off Delay
FIGURE 9: Furnace Control Event Schedule
Unitary Products Group | 7 |