Trane furnace: flame turning on and off
#1
12-27-21, 04:11 PM
Trane furnace: flame turning on and off
I have a Trane XB80 furnace and a 5055-3797 White Rodgers control board where the flame keeps cycling on and off. I checked the high limit on the control board and it is reaching the limit and the limit switch is turning the flame off while the blower and the exhaust fan continue to run. It waits a while and then turns back on when it cools off. Is this normal or is the limit switch bad?
#2
12-27-21, 04:33 PM
Group Moderator
It is possible to be a bad switch but that's rare.
More than likely you have an airflow issue.
Dirty/clogged filter, dirty blower wheel, closed off registers, blocked return, dirty A/C coil.
More than likely you have an airflow issue.
Dirty/clogged filter, dirty blower wheel, closed off registers, blocked return, dirty A/C coil.
#3
12-27-21, 06:49 PM
Thanks Pete for your response. It feels like there is good airflow coming from the vents. Most of the vents in the house are open but I'll try opening all of them to see if it helps. I just changed the air filter and have the furnace panels off right now so it should be getting good air input. I haven't checked the A coil or the blower wheel.
#4
12-28-21, 04:41 AM
Member
I had a similar problem about a month ago. One of the high limit switches on my high efficiency furnace (mine has 2) kept tripping if the furnace ran for 20 minutes or longer. I had an HVAC tech come out and check the furnace and he said everything was working okay as far as air flow and combustion. I replaced the high limit switch and everything is working fine now. So, while it may be rare that they fail, it can happen.
#5
12-28-21, 06:02 AM
Thanks Bob for your response. I opened all of my vents in the house and installed my old programmable thermostat to eliminate the smart thermostat but nothing changed. I checked the exhaust stack as much as I could because it vents through the roof (it's an 80% furnace). It is still reaching the high limit and turning the flame off for a bit and then back on. Mine only takes about 5 minutes of running for it to reach the limit. The furnace is 16 years old so from everything I've been reading they only last 15 to 20 years. I'm wondering if it's worth fixing or replace.
#6
12-28-21, 12:56 PM
Group Moderator
You should let a service tech help you to make a decision. Furnaces are supposed to be cleaned every couple of years and at certain times the heat exchanger is checked for integrity. It's the condition of the heat exchanger that dictates immediate replacement.
Call your gas provider. They usually have good service guys that aren't out to sell you.
You could change the high limit switch. They aren't expensive.
It's usually the constant cycling that cause the limit switch to go bad.
Call your gas provider. They usually have good service guys that aren't out to sell you.
You could change the high limit switch. They aren't expensive.
It's usually the constant cycling that cause the limit switch to go bad.
#7
01-03-22, 11:04 PM
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Could it be a dirty flame sensor? Let's go through the steps. Tstat calls for heat....1 Inducer draft motor, 2 pressure switch, 3 gas valve, 4 ignition, 5 flame sensor, 5 fan motor, 6 limit and roll out switches
