Thermostat faulty or something else?

[Latah11]

I am a first-time Newbie. I don’t know where to post my question, so will post it here and perhaps be directed to the proper forum.

We have a Whitfield pellet stove, bought new in 2004. No real problems until this last year. The stove would be burning, then go in to shut down mode (fans ramping up, pellets cease to feed, etc.), then when fire was nearly out, it would start feeding pellets again and start up again. It doesn’t seem to be able to shut down by itself, but when I turn the thermostat down or off, it does what it’s supposed to.....shuts down and fire goes out. If I don’t touch the thermostat and let it try to shut down by itself....it tries, but keeps starting up again and frequently a lot of smoke gathers in the chamber, then all of a sudden POOF, the fire ignites, sending a big puff of smoke into the room. Sometimes, the fan ramps up and down and the stove just acts crazy.

Since I can avoid all of this by manually turning down the thermostat, I am of the thinking the thermostat is faulty....sending bad messages to the stove. What do you think?

The stove is thoroughly cleaned at least twice a year, so I doubt it has anything to do with that.

 

[cncpro]

You're in the right place.

What type of thermostat ? If it's an electronic thermostat you can adjust the maximum number of "cycles" so the thermostat doesn't tell the stove to keep starting and stopping...

Regardless of what type I would think that you could test the thermostat's function with an electronic multimeter for continuity... You're just looking for the circuit to be closed when calling for heat then open when it's not...

If it is a cheap thermostat I'd replace it to see if it helps. If expensive I'd test it...

 

[compressedwoodsupplier]

I Know on some stoves if you have them hooked to a thermostat and you move the switch form thermostat to manual mode then you will mess up your board and may have to get a new board. But that being said try unplugging the stove to reset the board and try that. If the stove is heating up and then going out and then ramping back up after its almost out it could be your high temp switch on the unit acting like the stove is overheating

 

[Latah11]

The thermostat is a Honeywell.....just an ordinary "wired" unit, not remote, not fancy. We will focus on the thermostat to begin with and see if replacing it resolves the problem. If not, then we will explore the high temp switch theory.

Thanks for the suggestions. I am not anxious to call in a service man since they don't seem to know any more than we do!

 

[imacman]

You may have tried this already, but simply disconnect one of the wires on the stove that comes from the stat, and run the stove in "manual" mode....if it works correctly, you'll know where your problem is.

 

[Latah11]

Pellets are dry as can be....no problem there. As for the ignitor, will check it out. Thanks!

 

[begreen]

Which Honeywell? Depending on the unit, there are various ways to adjust the swing. If this is a T87, it's a little copper slider marked off in millivolts.

One thing I don't understand yet. If this is the thermostat, why did it just start becoming an issue? Or has this been a problem for awhile?

 

[Latah11]

The Honeywell thermostat is a T81. The stove started doing this a couple of years ago, but only infrequently. With the passage of time it has gotten worse and now it has become a problem. We had a pellet stove service man come out last year to clean the stove and I mentioned to him what was happening. He said it could be a variety of things, but thought cleaning the stove would solve the problem. It didn't. I'm not looking forward to operating the stove manually. I rely on the thermostat to run the stove during the night and at times I am not home.

 

[Latah11]

Thanks for the information on how to test the thermostat. I will have my grandson read all of these posts so he knows how to test things. He replaced his combustion fan on his pellet stove last winter and did a great job. He is concerned that our combustion fan may be going out, which would cause the smoke accumulation in the burn chamber, but that could be a seperate problem from the stove not being able to shut completely down and trying to start up again. Somehow, I think it's all connected, but being a woman and not having much knowledge of mechanical or electronic things, I'd like to get as much information as possible. I hope I've explained the problem so you can understand what's happening. I'll describe it again so things might be clearer:

Say the stove is off. I turn the thermostat up till it starts the stove. The stove feeds pellets which ignite and the fire is burning normally. The fans ramp down and the stove burns correctly. After running for some time (I assume the selected temperature has been reached), the pellets stop feeding and the fan ramps up. Now, the fire will begin to go out and eventually the fan should shut off, but that doesn't happen. Just as the fire is about out, it starts feeding pellets again and the ignitor comes on and starts the pellets smoking. Sometimes, the fire ignites, and sometimes it doesn't. When it just sits there a smokes, the burn chamber fills with an excessive amount of smoke. When the fire does ignite, there is a "poof" and smoke is forced out in to the room. This doesn't happen every time, but enough to be a problem. Then, the fire will burn normally for a few minutes (anywhere from 1 minute to 5 or 10 minutes) and then it tries to shut down again. Sometimes it will shut down by itself and stay off for a few minutes before it starts up again, and sometimes it just starts up before the fan has shut off.

It's like it's receiving a message to shut down and when it has nearly completed that process, it receives a message to start up again.

 

[Latah11]

EVER CLEANED THE EXHAUST PIPE OR CHIMNEY?

That is one thing we are adamant about doing....at least twice a year. Amazing how much stuff collects. Yes, they are cleaned thoroughly.

My grandson mentioned that the "proof switch" could be the culprit. We will perhaps start with that and go from there. All suggestions or ideas are certainly appreciated! I will have him read each and every post!!

 

[summit]

disconnect the two wires that hook into the tstat from the terminal on the tstat, and wire- nut them together. the stove should run. let it run for enough time to get past it's start up cycle time out (usually 15-30 minutes), and then remove the wire nut and seperate the wires... if the stove shuts down normally when you do this, then it is working fine, and you just need a new tstat. (sometimes the anticipator settings on the two wire tstats can be a little funky and / or faulty leading to this kind of issue.)