stove fills the house with smoke upon shutdown

[huntNJ]

Hello all, Ethan from NJ here with my first post. I have 2 Quadrafire Castile pellet stoves. One insert and one freestanding, which I installed about 18 years ago. The problem I'm having is the freestanding unit will fill the house with smoke when it shuts down (intermittently) as if there was a power failure. Embers burning in the fire pot but no combustion or convection fans running, smoke exiting from the air wash gap in the door. This seems to occur when the stove shuts down when commanded by the programmable thermostat.
I have performed a thorough cleaning of the unit and vacuumed out the exhaust vent. Being an intermittent problem, it's hard to reproduce.
There hasn't been any power failure issues (I have a standby Generac), and I've gone over everything I can think of. I'm stumped with this one, and I can't trust this stove to run over night without killing me in my sleep! Any suggestions would be appreciated, Thanks.

 

[peeler23]

How much rise do you have on your chimney/vent pipe? If you don't have enough a natural draft won't be created, allowing smoke to come back into the house

 

[huntNJ]

Hi peeler, thank you for replying. I have a horizontal vent in both stoves, no rise required per the instalation manual. This is a new problem. I've never experienced this in either one of my stoves unless I have a power outage, but that is no longer a problem with a standby generator.

 

[peeler23]

My manual also says no rise required, but does recommend atleast 3 feet rise because of this reason. I had the same issue as you, but it greatly depended on which way the wind was blowing whether I would get smoke in the house or not. Adding a 90 and 2 feet of pipe outside before another 90 and the termination cap fixed my problem. I'm very new to pellet stoves so hopefully someone else can chime in with some advice

 

[huntNJ]

My manual also says no rise required, but does recommend atleast 3 feet rise because of this reason. I had the same issue as you, but it greatly depended on which way the wind was blowing whether I would get smoke in the house or not. Adding a 90 and 2 feet of pipe outside before another 90 and the termination cap fixed my problem. I'm very new to pellet stoves so hopefully someone else can chime in with some advice

Thanks, definitely will keep that suggestion in mind. It certainly wouldn't hurt.

 

[bogieb]

The fact that your exhaust fan is not running during shut down seems to be the issue, not the lack of rise - especially since this is a new problem. Unfortunate I don't know what would cause the problem of it turning off too soon.

It would seem as if that programmable thermostat has developed an issue since that is the only time it happens.

 

[gfreek]

The fact that your exhaust fan is not running during shut down seems to be the issue, not the lack of rise - especially since this is a new problem. Unfortunate I don't know what would cause the problem of it turning off too soon.

It would seem as if that programmable thermostat has developed an issue since that is the only time it happens.

Something is shutting off the combustion blower too early, leaving burning embers and smoke..

 

[huntNJ]

I also suspected the thermostat. I changed the batteries (tested weak) and I'll monitor the operation.
It was my feeling also that the combustion fan is shutting down prematurely. The only thing I feel could cause that would be the control box or snap disc #3, but the disc isn't tripped. The control box is pricy but might have to bite the bullet and try it.

 

[jzm2cc]

The thermostat turning off will initiate the control module count down to turning off the exhaust blower after the auger is turned off. Have you timed how long this takes on a couple shutdowns? However this should be the same amount of minutes ( Thinking its 10-15 minutes to allow for pellets to burn completely in burn pot.) I'd begin with that test before replacing anything.

 

[huntNJ]

Great suggestion! I will time a few shut down cycles and see what happens.
One important point I forgot to mention. After complete shutdown (again intermittently) the combustion blower will kick back on and off a few times without calling for heat or dropping pellets. It will run for a minute or two then stop until the next call for heat.

 

[jzm2cc]

Assuming the wiring is correct and no phantom issues. I have to wonder if the control board is flaky. There is a triac that controls the exhaust blower and usually they are either good or bad, not an intermittent functioning device. If the stove is cold with an intermittent operating exhaust fan and nothing else coming on I'd try to determine if the motor is getting normal voltage (thinking 85-115Vac) as in the software is turning on triac, or is it low voltage (<85Vac like a triac that's going bad and allowing current flow to exhaust motor but not in a normal way). If it were me I'd try to compare the different triacs to see if there is contrast with resistance between them to see if the exhaust one is subpar. This is done with module removed and plastic cover removed assuming you are familiar with a multi-meter.

 

[huntNJ]

Thanks, yes I am familiar with a DVOM, and it's a good suggestion. Prior to opening up the suspect control box, I will just swap it out with my other Castile stove and monitor. If the trouble travels to the insert, I'll know the board is bad. I should have started there in the first place. Over thinking things as usual!