BK Strong plastic smell when warming up stove from "inactive" zone

[jdr7]

We're in our second year of running our Blaze King Princess 32. Very recently, and only 2-3 times, we're sometimes getting a strong paint/glue/chemical odor when the cat is inactive and heating up. For example, we'll fill it before bed and set the thermostat to 90% low. When we wake up, and see the cat is below the "inactive" zone. There is plenty of wood left, so I open the bypass and turn it on high, to let it warm up to the "active" zone (then obviously close the bypass damper).

For the first 5 minutes, when I open the bypass damper and turn it on high, the indoor part of the chimney appears to be "off-gassing" or emitting some kind of steam off of it. And the whole house smells like plastic or burning glue, sort of like when we had to break the stove in the first time. It also makes a bunch of crackling sounds and pops.

This is the only time it happens, and it's only happened 2-3 times, but has me concerned. It only happens when it's very low (maybe even below the normal "inactive" range) and being brought back up to heat. Any ideas? Anybody experience this before? We've had it for 2 years and only now is it starting to do this under these conditions. Thanks in advance!

Edit: here are our uneducated guesses:

1. We almost never burn it even on medium for 8hrs let alone high, (PA has been mild). We got the chimney cleaned before starting up this season, so doubt it's this, but maybe some creosote build up from burning on low so much? And we should run on high for like 8hrs to help clean out residual in the chimney?

2. Is it just that when it's below inactive, it's going from so cold, to so hot, so fast that it's sort of reheating the paint/glue? It smells like our break-in fires.

 

[stoveliker]

I do think the chimney is getting too hot and is possibly too dirty.

You need to avoid it dropping into the inactive zone if you have much fuel left. Draft is lower when it's warmer (or when the cap is clogged), therefore more heat needs to go up the flue to sustain draft. I.e. you need to run a bit higher.

Do you have a flue probe? If that hits 550- 600 F, close the bypass even if the cat gauge still reads inactive.


Is your wood dry enough?

 

[moresnow]

For example, we'll fill it before bed and set the thermostat to 90% low. When we wake up, and see the cat is below the "inactive" zone. There is plenty of wood left, so I open the bypass and turn it on high, to let it warm up to the "active" zone (then obviously close the bypass damper).

Find the low set point that allows active cat all night. Your 90% closed is likely waaaaaay to low. Setting to low can definitely make the stove stink. Each unique stove install has its own "low set point" that needs to be found. If you're snuffing the cat overnight, you are setting much too low in my opinion.
What is your procedure at the overnight loading? Are you charring the reload for 15-30 minutes prior to turning down? As directed in your manual?

 

[jdr7]

I do think the chimney is getting too hot and is possibly too dirty.

You need to avoid it dropping into the inactive zone if you have much fuel left. Draft is lower when it's warmer (or when the cap is clogged), therefore more heat needs to go up the flue to sustain draft. I.e. you need to run a bit higher.

Do you have a flue probe? If that hits 550- 600 F, close the bypass even if the cat gauge still reads inactive.


Is your wood dry enough?

Thanks! Our wood is very dry (avg is 13-15% moisture). To your point, it does seem to only happen when the needle drops below even the "inactive range", so we will try turning the thermostat to 1/4 or 1/3 at night and see if that keeps it warmer. I thought we could get away with turning thermo. to "low" especially after a full refill. It's just a shame it won't stay active if we turn it really low - we don't need all that heat at night.

To clarify: is it just the dramatic temperature change it's going through in 5-10 minutes (when we go full heat when we wake up)? So we could either run it hotter at night, or maybe warm it up slower? Or do you think we should run an 8hr burn on high to clear things out?

 

[jdr7]

Find the low set point that allows active cat all night. Your 90% closed is likely waaaaaay to low. Setting to low can definitely make the stove stink. Each unique stove install has its own "low set point" that needs to be found. If you're snuffing the cat overnight, you are setting much too low in my opinion.
What is your procedure at the overnight loading? Are you charring the reload for 15-30 minutes prior to turning down? As directed in your manual?

Thanks - I honestly did not know it was possible to go so low. When we go low during the day (to help get 24hr burn times) we do end up having to kick it up for a while so it keep it form going inactive. I suspect that's what happening at night, but we obviously aren't awake to turn the thermostat up and keep it warm. We will try to keep it higher (maybe 1/4) and see if that does the trick.

When we reload, we fill the firebox and always burn for 20 minutes on high to char, then we lower the thermostat. So when we go to bed, it's a fresh load that's been charred, and the cat reads like 3/4 high in Active. We turn it low (not as low as possible which is ALL the way left, but a couple notches above that). During the day when we do that, we're good for hours - but we DO have to occasionally kick it higher to keep it active. So yeah - maybe it's just going out, and then the temperature increase is too dramatic.

 

[moresnow]

My low set point is around the half way point. Somewhat dependent on outside temps/conditions.
Run loads at different settings until you find the sweet spot. Mark the dial at that spot. Easy peasy!

 

[jdr7]

My low set point is around the half way point. Somewhat dependent on outside temps/conditions.
Run loads at different settings until you find the sweet spot. Mark the dial at that spot. Easy peasy!

Oh wow! That's crazy, you mean you set the thermostat at halfway overnight? Thanks btw - I did not know we had to find this point, and were just letting it get to low.

 

[stoveliker]

I agree; one has to find the lowest point where the cat stays active on your flue and in your home.

Having it smolder a long time with an inactive cat will deposit junk in the chimney.
Getting it active again with a charred load flaming thru the bypass will make the pipe sound, but waiting until the cat goes active will put a lot of flame in there, which is a concern if it's dirty. Best to close the bypass when the flue probe says 550-600 F.

Clearing out the chimney with a high fire is not possible - well, it is but that's called a chimney fire. Don't try that.

 

[DonTee]

I think finding the low point on the temp gauge is something that isn’t talked about enough. I’d have to reread the manual to see what they say about it in there.

I think it’s much easier with a flue temp probe. For my stove i try to keep it above 250 degrees flue temp. At that temp the cat will stay active until the fuel is burned to embers.

On my stove about 1/3 of the way up is the low point. Besides the charring phase, my stove spends all its time between 1/3 and 2/3 on the temp control

 

[moresnow]

Oh wow! That's crazy, you mean you set the thermostat at halfway overnight? Thanks btw - I did not know we had to find this point, and were just letting it get to low.

Just reloaded at 18.5 hrs. Setting was just over half way to wide open. Food for thought.

 

[stoveliker]

I had 21 hrs with the tstat at 3.30 o'clock this past week.

A lot depends on how you fill the stove.
You gotta play stove Tetris.

 

[Highbeam]

I think finding the low point on the temp gauge is something that isn’t talked about enough. I’d have to reread the manual to see what they say about it in there.

I think it’s much easier with a flue temp probe. For my stove i try to keep it above 250 degrees flue temp. At that temp the cat will stay active until the fuel is burned to embers.

On my stove about 1/3 of the way up is the low point. Besides the charring phase, my stove spends all its time between 1/3 and 2/3 on the temp control

It is important to find the setting so that you get maximum burn times but do not stall the cat. I stay a little warmer yet for a margin of error and to make sure my flue temperatures stay warm all the way to the top.

The manual really doesn’t address this issue. It’s too bad because a stalled cat allows a lot of pollution to slip by and a lot of rapid creosote accumulation. It’s like a really bad smoke dragon.

 

[jdr7]

Thanks for your help everyone! As @Highbeam and others mentioned, the manual definitely doesn't cover this well so this was news to us. It's been over a year, but I believe the manual simply said to do the char burn (20~ min) then set your preferred temp. Obviously we knew to keep the cat active during the day, but thought if it faded out at night we were just conserving.

All that to say, we took your advice, reloading before bed and setting to a much higher temp (about 4:00). Woke up this morning and temp was low, but still active. Kicked it on high to warm up, and no problems at all. During the day I've found we can easily leave it at 2 or 3o'clock, but usually it will start to fade and we'll have to kick it up for an hour.

Thanks again for your help. I'm guessing we'll probably be in need of a good chimney sweep after this year running it so low every night 😅

 

[BKVP]

If you wake up in the morning, the cat is inactive and there is fuel left in the stove, you are running the stove too low. Put in less fuel, run the stove hotter and fine tune so that the cat remains active until you are down to the last of the coals.

BKVP

 

[Todd]

Might want to inspect your cat as well. Brush it off and blow some low pressure air through. A good high burn may help as well.