Heil quaker gas furnace won't reach desired temperature

mperry

I have a Heil quaker gas furnace that keeps shutting down before reaching the entered temperature. I replaced the flame sensor but that obviously wasn't the problem. any suggestions are greatly appreciated.

bburd

Is the air filter clean? Are the return air intakes unobstructed? The burner could be shutting down from the high temperature limit switch.

EdTheHeaterMan

Does your Heil furnace ever get to the desired temperature? Or is this something that happens every cycle.

• Some thermostats are out of calibration. If you set the thermostat to 68° for example, and it always shuts off at 65° then there is a possibility that your thermostat is out of calibration by 3° and it is just shutting off normally. Thermostats are either blind or illiterate. they ccant actually see the numbers on the display, They can only open and close a set of contacts that power the burner relay
• There may be a heat anticipator on your thermostat that is shutting off the thermostat prematurely. That may have worked on the old gravity furnace because that old furnace took longer to heat up and to cool down. So the heat anticipator would have been set to "Anticipate" the overheating and shut the burner down early
• You could have a high limit control that is reaching the high temperature inside the duct or furnace that shuts the burner down. The blower will keep operating until the duct or furnace temperature drops. then the burner will restart as long as there is a call for heat
• You may have a fan motor that is overheating. That will make the blower fan stop after operating several minutes.  Then the furnace will overheat and shut off by the limit.  Eventually your furnace control may offer an error code and go into a reset condition.  By the time the furnace control resets in 15 minutes or 30 minutes, the blower fan motor cools down enough to operate on the next cycle and you are heating again.

There are 4 reasons, and you need to test differently to determine what it is. There are many more reasons than those 4 that could cause your issue.  Firing the parts cannon (flame sensor) without diagnosing can get expensive.   How are you with an electrical meter?

mperry

Thank you very much for taking the time to respond I appreciate it. I'm no expert with a meter but can work my way around one most of the time. I'm more than likely going to call a professional to come and repair the furnace. It's actually my sister's furnace and it's way out of my skill set and like you said can get expensive guessing at the problem. If it were a thermocouple I'd be all set but that's about my extent of knowledge with furnaces. But I appreciate your time and input Thank You