Gas and Oil Home Heating Furnaces - Gas furnace not lit
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lmluo
05-24-05, 08:19 AM
I have a Byant 383KAV gas furnace(11 year old) and it stopped firing up.
The led flashes 3 short and 1 long, I take it meaning code 31.
And 31 is according to the label on the furnace:
Pressure, Draft Safegurd or Auxiliary-Limit switch(when used) did not close or reopened. Check for
- Proper vent sizing and condesate pitich
- Vent restriction or high winds
- Defective inducer motor or start capacitor
- Defective pressure switch or connection. If it opens after trial ignition period blower will come on for 90 seconds recycle delay
- Inadequate combustion air supply
- Low inducer voltage
- Disconnected or obstructed pressure tubing
I did component test and draft motor, blower, hot surface ignitor all came on
though the motor was not consistent, sometimes it came on just very briefly not reaching full speed, sometimes longer and seems to be full speed.
I also checked Draft Safeguard terminals and they are closed. There is no auxiliary switch.
The two things I am not sure are the pressure switch and the inducer motor.
My question is
How does the pressure switch suppose to work?
It's normally open. When does it close?
How can I be sure if inducer motor is defective?
If it's defective how easy is it to replace it?
Thanks
Limin
The led flashes 3 short and 1 long, I take it meaning code 31.
And 31 is according to the label on the furnace:
Pressure, Draft Safegurd or Auxiliary-Limit switch(when used) did not close or reopened. Check for
- Proper vent sizing and condesate pitich
- Vent restriction or high winds
- Defective inducer motor or start capacitor
- Defective pressure switch or connection. If it opens after trial ignition period blower will come on for 90 seconds recycle delay
- Inadequate combustion air supply
- Low inducer voltage
- Disconnected or obstructed pressure tubing
I did component test and draft motor, blower, hot surface ignitor all came on
though the motor was not consistent, sometimes it came on just very briefly not reaching full speed, sometimes longer and seems to be full speed.
I also checked Draft Safeguard terminals and they are closed. There is no auxiliary switch.
The two things I am not sure are the pressure switch and the inducer motor.
My question is
How does the pressure switch suppose to work?
It's normally open. When does it close?
How can I be sure if inducer motor is defective?
If it's defective how easy is it to replace it?
Thanks
Limin
Grady
05-25-05, 07:45 PM
If this furnace is piped with pvc pipe, make sure there are no obstructions & the pipe is pitched AT LEAST 1/4" per foot of run sloped up from the furnace. Many times the pipe will sag for one reason or another & trap water causing an obstruction. No sure of the sequence of operation on your equipment but most have to start with the pressure switch open & then it must close. If it does not go thru this sequence, the furnace will not light.