Furnace cycling on and off because of APS
#1
02-15-21, 11:02 PM
Furnace cycling on and off because of APS
Sorry if a repeat, first one didn't go.
Carrier condensing
My furnace runs for a while then shuts down for a while. Maybe 10 minutes on then 15 off, and repeat over and over. I can make it run continuous by bypassing the air pressure switch. I have replaced the draft blower motor thinking maybe the draft was weak. No change. I put my hand next to the exhaust and I feel a good draft. When it runs everything seems good, flame color etc. I can't figure out what would make the air pressure switch shut it down after a while. My house only gets up to 55 degrees. I might replace the switch but doubt that is the issue. Any thoughts?
Carrier condensing
My furnace runs for a while then shuts down for a while. Maybe 10 minutes on then 15 off, and repeat over and over. I can make it run continuous by bypassing the air pressure switch. I have replaced the draft blower motor thinking maybe the draft was weak. No change. I put my hand next to the exhaust and I feel a good draft. When it runs everything seems good, flame color etc. I can't figure out what would make the air pressure switch shut it down after a while. My house only gets up to 55 degrees. I might replace the switch but doubt that is the issue. Any thoughts?
#2
02-16-21, 03:50 AM
From your description it seems the pressure switch is operational but maybe not to specification. Replacing the switch would be a cost saver versus obtaining the instruments to test the switch to specification or contracting for the same. Does the thermostat control the heating system normally when you bypassed the pressure switch?
#3
02-16-21, 05:02 AM
Member
DO NOT bypass safety controls. They are doing there job. I’ve seen fires caused by doing such things.
what’s the model number?
what’s the model number?
#4
02-16-21, 07:41 AM
Roughneck, I couldn't agree with you more. However I doubt there isn't a technician or DIYer out there that hasn't bypassed a device as part of their diagnostics. The DIYer in the above post, based on his words, seems to have knowledge of how a furnace control should operate and the consequences of his actions.
#5
02-16-21, 08:51 AM
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The most common cause of pressure switch is vent pipe slope. The fact your furnace will run for about 10 minutes after a 15 minute rest tends to indicate a possible condensate drainage issue. If the vent has a slight belly in it somewhere that could certainly cause your issue.
#7
02-16-21, 01:40 PM
Member
What is the model number of the furnace? Is it one of those affected by a class action lawsuit? That one of the symptoms is solids in the condensation?
#8
02-16-21, 02:40 PM
Gee, I wonder. Model # 398aaw036060d
I had the heat exchanger replaced a few years ago and at the time the guy who did it said the exchanger was under warranty but his labor was not.
I had the heat exchanger replaced a few years ago and at the time the guy who did it said the exchanger was under warranty but his labor was not.
#9
02-16-21, 03:57 PM
Member
That unit isn’t affected.
However, drain cleaning is something that should be done during preseason maintenance that needs to be done every year.
However, drain cleaning is something that should be done during preseason maintenance that needs to be done every year.
#11
02-16-21, 09:54 PM
Group Moderator
It's almost impossible to bypass the pressure switch. If you short around it..... the board will show a "closed" pressure switch and will not light. It needs to see the pressure switch open on a call for heat and then go short when the inducer runs. It's designed so that it can't be bypassed permanently. It can be bypassed as a one shot test.
#12
02-16-21, 10:02 PM
Right, I discovered that. First time I did it I was measuring voltages and finding where the fault was and just jumped it. Next time on cold start it didn't like it, but I already had got some heat into the house.
Lee
Lee
