What to check after a backdraft?

[sacountry]

My BK40 (3 years old) backdrafted this morning. I had the t-stat set low overnight, as I normally do, and in the morning I turned it up, stirring the remaining wood to level it out across the box. I didn't add more wood, just shut the door. The CAT was still hot enough to remain engaged so I left the bipass alone. Never seen it before, but the stove backdrafted to the point that a puff of smoke emitted from it along with the audible pop/poof. The wood that was smoldering from overnight had ignited then the backdraft knocked it out but relit after a few moments. There were 2 more less violent backdrafts in short succession, then the now burning wood established the proper draft. I beleive my error was that I probably should have opened the bipass even though the CAT was hot.... at least until the wood was burning consitently again.

My question is what should I be checking following that first backdraft. Even though I was looking at the stove when it happened, I couldn't exactly tell where the puff of smoke left the box. As far as my burn habits, I clean the stack 2x per year. My stack has about 8' inside the home and 16' outside the home, all double walled. The stove has a fire typically burning from October to April. I cleaned the CAT about a year ago, arguably incorrectly using compressed air at a respectable distance away from the CAT.

 

[Dieselhead]

You should always open the bypass before opening the door. By not doing so your catalyst will disintegrate from thermal shock. Also more likely to get smoke billowing into the room.
As far as what to check, not much. I’ve had a few over the years with no evidence of damage. These stoves are pretty stout.

 

[stoveliker]

What happened was that the coals after stirring saw more air, produced more combustible gases, but the draft in the chimney was not enough yet (due to the chimney being relatively cool) to suck in enough air/oxygen to burn it, and/or suck out the gases at a sufficient rate to avoid this.
So eventually you had a build-up of combustible gases, slowly more oxygen came in, until it said poof.
This can happen.
This would less likely happen if you open the bypass (less combustibles accumulating in the firebox).

And I concur with the above; not opening the bypass leads to cold (room temp) air going in the cat when you open the door. That causes thermal shock and will kill a cat. *always* open the bypass before the door.
In fact, open the bypass, wait a bit (a minute, or 5 minutes - depending on the draft, depending on what you see happen in the firebox) to send some heat up the flue and get more draft. Then open the door. This will also help with less ashes whirling out when you stir coals etc. because they get sent up the flue with the draft.
And it saves your cat from desintegrating.

 

[DuaeGuttae]

I have read in Blaze King threads for a number of years now and have perused stove manuals as well, and so I have long understood that one always opens the bypass before opening the door. I was therefore surprised when reading the physical manual that came with my stove that the section on "Reloading Procedure" when the catalytic thermometer remains in the active zone does not actually state that one should open the bypass. It talks about turning the thermostat to high and letting the air flow stabilize, but it doesn't actually mention opening the bypass.

In fact, in step four, it seems to indicate that opening the bypass is optional. The exact wording is "Once loaded, latch the loading door shut and (if opened) close the bypass door immediately." I admit that I was surprised to find that. My husband has not read all the Blaze King information that I have, and I was concerned that he would open the door without opening the bypass, so I've emphasized to him that he should always open the bypass before opening the stove door to prevent thermal shock or smoke spillage. I just thought I'd mention this so that long-time BK users are aware that newbies following instructions in their manuals may not know to open that bypass.

Strangely enough the section in my manual that covers "Lighting the fire" doesn't seem to contain any instructions about how to use the bypass. I have not reread the whole manual, and it may be in there somewhere, though I have read it cover to cover more than once. I think my knowledge of operating these stoves has been heavily informed by Hearth.com over the years, and I'm grateful for that.

sacountry, I think you've gotten good advice from the posters above. I hope it helps.

 

[stoveliker]

@BKVP please read the post directly above mine for a potential improvement to the manual and thus (hopefully) operator actions?

 

[ManitobaSky]

The manual tells you to open the bypass in step 2 and 3.

 

[DuaeGuttae]

The manual tells you to open the bypass in step 2 and 3.
View attachment 333854

My printed manual does not actually have those steps. I've taken some photos of the "Bypass Door" paragraph. And "Lighting the Fire" and "Reloading Procedure" in the Operating Instructions. My manual was published in September of 2023, and it seems to me that new users of this stove would be hard pressed to understand the full use of the bypass from these pages. I'm not even saying that it's not somewhere else in the manual but it's not easily accessible in the pages that new users might check as a quick reference guide.

I've had the benefit of reading older manuals in my years of research and of hearing the wisdom from folks on this forum, and I'm grateful for that. From personal experience with this particular manual, though, I do think that others who have this same information in front of them may have difficulty really understanding the bypass. My own husband who is a careful reader and rule follower tells me that he did not understand the necessity of opening the bypass from this, only from my instructions.



The discussion of thermal cracking mentions to "Avoid flooding a hot, active combustor with cool room air when reloading" and one can infer that using the bypass would help avoid that, but it really is not spelled out in my manual in the operating instructions, and I imagine that there are other users who are in the same boat.

@sacountry , I'm sorry that this has turned quite so much into a focus on different versions of the manual. I'm afraid that I don't have any advice for your on what to check after some major backpuffing. Have you been running your stove since? How's it working?

 

[BKVP]

Good morning. It is a requirement of EPA rule that the manual mirror the way a stove was tested. We retested all model in the Spring of 2024. We tested the stoves with opening the bypass ANY TIME THE DOOR IS OPENED. A regulating agency, not EPA, suggested by testing with bypass door kept closed kept additional particulate matter from being collected during testing. (We've not opened bypass in all prior testing because it wasn't a requirement in the method.)

When we retested, the stoves mostly burned cleaner or about the same. Agency folks still scratching their heads...

BKVP

 

[Highbeam]

As far as checking, the only thing that really moves around is the perforated flame shield and sometimes the cat can walk out of the hole a little. You can reset these things with your hands.

 

[J10]

Good morning. It is a requirement of EPA rule that the manual mirror the way a stove was tested. We retested all model in the Spring of 2024. We tested the stoves with opening the bypass ANY TIME THE DOOR IS OPENED. A regulating agency, not EPA, suggested by testing with bypass door kept closed kept additional particulate matter from being collected during testing. (We've not opened bypass in all prior testing because it wasn't a requirement in the method.)

When we retested, the stoves mostly burned cleaner or about the same. Agency folks still scratching their heads...

BKVP

So how important is it in terms of catalyst care to always open the bypass when reloading hot?

 

[Dieselhead]

So how important is it in terms of catalyst care to always open the bypass when reloading hot?

Always That’s cat stove ownership 101..

 

[BKVP]

So how important is it in terms of catalyst care to always open the bypass when reloading hot?

Are there instances or installations where folks did not open the bypass when reloading, yes. Should you open the bypass, yes.

BKVP

 

[stoveliker]

This week was the first time I forgot to open the bypass... Reloaded, let it rip, wanted to close the bypass, and "oops".
I had wondered about the strange smoke rolling in the top front in the box with the door open just before the fire caught.

I guess my flue was warm enough so that there was sufficient draft despite the cat nearing the bottom of the active range, and hence smoke did not roll out. (Had there been smoke roll out, I'd immediately have realized that the bypass still was closed...)

Hit my head against the wall, felt stupid.
But things happen. It should not kill a cat in one time (especially if the cat was not very hot). At least, that's what I tell myself to sleep at night

But, even if doing it once doesn't hurt things, doing it a lot will shorten the life (of the wash coating on the substrate). So for your wallet's sake, open the bypass before letting in cold air.

 

[sacountry]

Thanks all. The stove definitely tells you what it likes and doesn't like. This backdraft said that I should have opened the bypass and left it there after the stirring / leveling the reminants wood in the box. I've been cautiously burning since that backdraft, looking/smelling for signs of smoke, not seeing any. Perhaps, and likely, the pressure what great enough that it pushed the door gasket with enough force to allow it to emit from there.

Now I need to spend some time researching here for the best CAT cleaning method. I'm leaning towards the vinegar and water soak.

 

[BKVP]

The process involving distilled water and vinegar does remove some of the over plating. (Deposits left from burning wood)

You will need new gaskets and please do the process outside if you want to stay married. Also be very careful handling the combustor. You will need to give it ample time to dry. After cleaning, drying and attaching new gaskets, can be placed back into service.

However, after only 3 burning seasons, it is likely the issue you encountered had more to do with volume of gases vs incoming air into the firebox.

A combustor can only handle a specific amount of gases, based upon surface area. In fact, combustor temps can soar when a "burned or charred" log breaks open and releases gases. If the air setting is set too low or the stove is very hot, the thermostat blade will have been closed by the bimetallic spring. Stirring the coals would have released a heap of gases and with the bypass closed, created a environment where the combustor could not keep up.

BKVP