Wood Furnace limit switch issue

[HadleyPA]

Wood furnace limit switch

I read all the time, don’t post much but am looking to see if anybody has any ideas. Put in wood furnace about 9 years ago. Had to replace limit switch that controls power to blower about a month ago because it was not shutting off. It would come on fine but would run for hours and blow cold air until I bumped the switch and then it would jump and shut off. After getting new one all was well till last night. It did it again. Ran for about 6 hours straight. I finally went down and bumped it and it shut off. Worked fine after that. When working normal it is on for about 20 minutes and then off for 10-20 depending on fire. Any ideas on what the heck caused it to stay again other than the new switch going bad?

 

[olyman]

Wood furnace limit switch

I read all the time, don’t post much but am looking to see if anybody has any ideas. Put in wood furnace about 9 years ago. Had to replace limit switch that controls power to blower about a month ago because it was not shutting off. It would come on fine but would run for hours and blow cold air until I bumped the switch and then it would jump and shut off. After getting new one all was well till last night. It did it again. Ran for about 6 hours straight. I finally went down and bumped it and it shut off. Worked fine after that. When working normal it is on for about 20 minutes and then off for 10-20 depending on fire. Any ideas on what the heck caused it to stay again other than the new switch going bad?

guy on here.. whitespider..look him up,,and pm him..

 

[kingOFgEEEks]

Is your limit switch installed through a hole drilled into the plenum? Make sure that it is centered in the hole, so the probe can turn freely (assuming yours is that type).

Is it one of these?

 

[Gugi47]

Can be a defective switch from new. I see that many times.
Give me the manufacture, model # and serial# and I will find out for you if is a defective batch.

 

[Gugi47]

If you have a Honeywell. You have to set you switch on and off just like this:

Before 100 fan OFF and after 100 fan ON

 

[kingOFgEEEks]

I took the cover off of mine the other night, just to blow the dust out of it. When I put it back on, I must have accidentally put the cover on just a little crooked, and it pushed the 'on' button in. That made it run really funny, as it would stay on for a long time, then shut off, turning back on for only 2-3 seconds before stopping again. I was sitting against the 'off' limit, so when it got too cold, it would turn off, and then as soon as enough heat built up for it to run, it would try to start, but cool off very quickly.

The limit switches are great, but can be finicky.

 

[HadleyPA]

Kingofgeeks- Yes mine is exactly like that. I installed it about a month ago and it worked fine for the past month and then screwed up last night. I also never put the cover on this one or the last one that I put on 7-8 years ago. The button was the first thing I checked when I went down in the middle of the night and it was pulled out meaning not on manual.

Joseph Veress- It is a Honeywell switch and let me tell you they are getting expensive as I was told buy local hardware owner where I bought it that they are the only ones making them now so they are charging whatever they think we will pay. When I changed it 7-8 yrs ago it was around 25-30 bucks, this last one was $160! I will get serial and model tonite when I get home. I did set the limits for on/off just like I set it the last time I changed it. Took me a couple days to get it where I was happy but it has been fine ever since till last night.

Thanks for all the suggestions by the way.

 

[Gugi47]

Check all the wires to be tight.

 

[Homelite410]

I have had my switch go cold and the "limit tab" will return too far and switch the blower on when its cold.

 

[Whitespider]

Which fan is blowing continuous??
The draft blower (if it has one) or the circulation blower??
And does Honeywell blower controller/limit switch control those blowers directly or through a relay setup??
*

 

[HadleyPA]

IT is a Honeywell switch and I looked on the box it came in and the only #'s are L4064B2228, 20201, and 141112. I have no idea which of these are model or serial #'s it did not say. IT is a 5" long by 3/4" model if that helps. I jiggled all the wires and everything is tight.
No draft inducer fan, heat circulation fan.
It is not connected to the regular furnace blower, I let them work independent of each other.
Last night it seemed to work okay. I talked to the wife at lunchtime today before she had to leave for work and she said the blower had been kicking off/on like normal.
Maybe it was just an anomaly but it makes me nervous that if it fails to kick off whose to say it may not kick on sometime.
Thanks for all the help.