Quadrafire CB1200 Applied AC Issue

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Dec 2, 2018
East Central Iowa
I wrote to Quadrafire but they won't talk to me. So I've copied the email below.

This is an intermittent issue, so calling a licensed service tech will not solve the problem. I need one of your "engineers" to reply to this.

For the last 8 months or so, my CB1200 will act as if I just plugged it into 120v AC. The exhaust fan will run for approximately 10 minutes, and the thermostat is OFF.

Please Note The Following:

Thermostat is OFF
No Red LED (Call for heat)
I've had two UPS's on the stove. The latest is a new $550 Sine Wave unit.
The 120v AC wall outlet has been double-checked.
The Power Cord has been replaced
Lastly, I purchased a brand new Control Board for the stove. The problem still exists.

I replaced the main 7A fuse a week ago, thinking the fuse might be intermittent. The exhaust fan started up again two nights ago.

I have ordered a new #3 Snap Disk in hopes that if it is intermittent, it might be the culprit. I haven't put it in yet.

The stove, when heat is called for, works fine. The Call light turns on, the Feed Motor turns on, the ignitor turns on, the pellets ignite, and the stove shuts down normally once the thermostat says that the room has reached the set temp.

What else (besides everything I mentioned above) could be causing the stove to think that 120v AC has just been applied?

Again, this is a very intermittent issue. I only know it happens when I happen to be in the room with the stove and hear the exhaust fan running. It could be doing it while I'm gone at work during the day, or asleep at night. As such, there's really no way for a service tech to "activate" the issue.

For background, I am a 69 y/o Electronics Engineering Technician, and a Ham Radio operator. So while I don't specifically have Pellet Stove experience, I am adept at troubleshooting. However, without a schematic of the "guts" of the Control Board, I don't have much of a way to troubleshoot possible causes for this, as I don't know how the control board senses the 120v Line to the stove, or what all is in-line with that function.

Does anyone on this forum have any ideas why the stove would intermittently think it was just plugged in? I welcome all input. Thanks in advance.
Unplug the stove and pull out the control board. Clean the contacts and reinstall. Maybe dirty contacts or poor connection?
Hello, ham operator here as well KB3GWQ. Have you disconnected the thermostat from the stove for a few days? Maybe there's something up with the thermostat that cause some residual just enough to start the exhaust but not stay on long enough for a real "call for heat".

I know you said there's no red light, but maybe it happens so quick like if you flip the t-stat on/off very quickly to force the exhaust on to clean the stove.
The stove is programed to start the exhaust fan as soon as it gets power, it will run for 10-12 min then shut down. If it is statically starting the combustion blower there is an issue with the thermostat, control board or wiring. Disconnect the thermostat for 24hrs and see if it repeats the issue.