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Furnace short-cycling.... (turning on and off)

post #1 of 14
Thread Starter 
I've been noticing that since I've had my heat on these past few cold days, my furnace kicks off before it has even reached the set temp on the thermostat, and a min or two later, turns back on, and keeps doing it. I tested by jacking the temp from 65 to 75, and it ran straight for 20 mins, then again cut short of the temp.

Is this a thermostat issue, or something more serious with the furnace? I checked the filter and it's pretty clean. Also, could this constant on and off be damaging to the furnace? Thanks!!
post #2 of 14
Quote:
Originally Posted by Jay in the Bay View Post

I've been noticing that since I've had my heat on these past few cold days, my furnace kicks off before it has even reached the set temp on the thermostat, and a min or two later, turns back on, and keeps doing it. I tested by jacking the temp from 65 to 75, and it ran straight for 20 mins, then again cut short of the temp.
Is this a thermostat issue, or something more serious with the furnace? I checked the filter and it's pretty clean. Also, could this constant on and off be damaging to the furnace? Thanks!!


if it ran for 20 minutes without cutting out it sounds like a thermostat issue.

what brand of stat?
post #3 of 14
Thread Starter 
It's a RiteTemp touchscreen. They don't even make them anymore. I have a honeywell I am going to hopefully swap it out with tomorrow.

194
post #4 of 14
first thing after checking the filter would be the fire sensor, take it out rub it with some steel wool and put it back. it doesnt sound like a thermostat problem since it fires up when you call for heat.
post #5 of 14
Quote:
Originally Posted by Jay in the Bay View Post

It's a RiteTemp touchscreen. They don't even make them anymore. I have a honeywell I am going to hopefully swap it out with tomorrow.
194

yea they were junk, a good honeywell should cure the problem.wink.gif
post #6 of 14
Thread Starter 
Changed out the thermostat, but still short cycling. Might look into getting a pro to look at it. Any recs in the Monmouth County NJ area?
post #7 of 14
does new thermostat have a cycle per hour setting?
is it reaching set point?
what type of filter are you using, the 3M filters are very restrictive and can cause problems.
post #8 of 14
I know next to nothing about heating&cooling other than basic yearly servicing stuff, but this doesnt sound like a thermostat issue to me. all the thermostat does it call for heat and read temperature then turn off when it reaches the # it wants. the furnace is turning itself off for a reason. does it have any codes you can read? first things to check are that it is getting enough air, the flame sensor is clean and all the vents/drains/wires are connected and open and clean. if i was a betting man id say its something silly with the furnace.
post #9 of 14
Have a pro check the controller within the furnace.
post #10 of 14
I have a good guy who does all my work. I just had a new a/c and furance put it by him. PM me if you want a name & number.

Also, after getting this problem fixed,contact your gas company to see what a service contract costs. If you have one service call with parts, you covered your costs +.
post #11 of 14
I have baseboard hot water, not sure what you have. My system runs until it reaches a high temp/safety setting on the boiler and then shuts off until it cools down to another set point. The circulation pump is still running but the boiler is not. As the boiler cools it fires back up to heat the circulating water if the thermostat is still calling for heat. Not sure how forced hot air works but things can't run continuously unless you can remove the heat from the system as fast as it's being made. Just my $.02.

In rereading the OP it sounds like you have forced hot air. Are they supposed to run continuously until the stat stops calling for heat? Inquiring minds want to know.
post #12 of 14
Quote:
Originally Posted by Darth Baiter View Post

In rereading the OP it sounds like you have forced hot air. Are they supposed to run continuously until the stat stops calling for heat? Inquiring minds want to know.

yes

strange thing was in his OP he said when he turned the stat way up the furnace ran for 20 minutes without cycling..headscratch.gif

sounded like a thermostat issue to me, troubleshooting over the net is a pita.frown.gif
post #13 of 14
Sounds like it is cycling on limit.

Make sure everything that can reduce airflow is in such a condition that it doesn't impede airflow. IE the filter should be clean, the blower wheel should be clean, the secondary heat exchanger or ac coil (if applicable) should be clean. Make sure all the ducts are not damaged, it amazes me how many homes I've been in following other techs where I'd find ducts in an attic crushed with Christmas decorations or dampers closed or something that should be obvious and is missed.

The likelyhood of a lack of airflow being your problem is high, the likelyhood of it being a defective part is low. Something you can clean / open yourself is high.
post #14 of 14
I know I'm a little late in responding to this thread and I hope you got it fixed.
You had mentioned that it was short cycling,meaning the burner would come on and after several seconds the main blower wouldn't come on and the burner cut out?
After the heat exchanger cooled down the high limit switch should reset,then re light and it repeated the heating processes?if this is the symptom it could be one of the following.
A.
the blower motor or capacitor is dead.
B.
the fan/blower relay expired.(High limit/fan switch)
C
pending on how young the unit is it could be the main control board.


If you did get it fixed what was the problem?
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