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| Probable Causes: | Recommended Actions: | |
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1. |
Exhaust fan not running. | Check to make sure the exhaust fan is turned on. Check the exhaust fan for mechanical damage. Check relay 1933CR to see if its energized. Click here for device location Check exhaust fan motor starter. |
| 2. | Combustion Air Blower motor is stopped. | Find out why the Combustion Air Blower stopped, correct the condition and restart the blower. If the blower will not start, check control relay 1931CR to see if it is energized. Click here for device location If the control relay is energized, check motor starter 252M to see if it is pulled in. Click here for device location Replace malfunctioning components as needed. |
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3. |
Combustion air pressure is low. | If this is the problem, the gas train will kick-out for all burners. Check the Combustion Air Blower filter to make sure it is clean. Replace the filter if dirty. Check pressure switch 1942PS to make sure it is set properly (20" WC) and operating correctly. Replace the pressure switch if necessary. Click here for device location  Do not attempt to re-start the PreWash Unit until the combustion air problem is corrected. |
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4. |
Burner gas pressure is high. | Check for a blown regulator valve. Check pressure switch 1942BPS to make sure it was properly reset (if starting furnace). Check to make sure switch is set properly (2" PSI) and operating correctly. Replace the pressure switch if necessary. Click here for device location |
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5. |
Burner gas pressure is low. | Check incoming gas pressure to see if it is really low. Verify that all incoming gas shutoff valves are fully open. Check for a malfunctioning pressure regulator. Check to see that the Maxon Valve is operating correctly. Check pressure switch 1942APS to make sure it was properly reset (if starting furnace). Check to make sure switch is set properly (20" WC) and operating correctly. Replace the pressure switch if necessary. Click here for device location |
| 6. | Pilot is not lit. | Relight the pilot. If the pilot will not light, check the following: Check to see if solenoid valve 1958SV is operating properly. It may be sticking or not working at all. Click here for device location Check for a burned out flame rod 1953FD. Replace if necessary. Click here for device location Check for a malfunctioning Pilot Ignition Transformer 1955XF. Click here for device location If the problem still exists, replace Flame Relay 1951FR with one known to be good. Click here for device location |
| 7. | Faulty microswitch inside Maxon Valve. | Check the microswitch located inside the Maxon Valve to see if it's operating properly. Check the linkage inside the Maxon valve for mechanical damage. |
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8. |
Faulty control relay. | If the problem still exists, check control relay 1942CR to see if it is energized. This relay must be energized in order to get the "Prewash Burner Interlocks" input. Click here for device location |