Blaze King Ashford Smoke Leak in Back

[MikeVT]

This is my second season with the Ashford 30.2. Overall, it is amazing - best stove I’ve had. But (here we go), twice in the last week smoke started coming out of the back - immediately rectified when I opened a window to neutralize the air pressure differential between inside and outside. I’ve done this a couple times now, so I do know the air pressure difference is a big factor, which makes me think the updraft got weak enough to stop pulling the smoke up the pipe with “force.” That said, I’m still surprised smoke is coming out the back, as I would think the smoke wouldn’t have any escape other than up the pipe (and in that case would likely “over power” and potential downdraft).

It is very strange I’ve been through 1.5 seasons without this happening before. I cleaned every nook and cranny of the stove and pipe before this season. But, I never removed the cover on the back (says “no user serviceable parts, don’t open”).

I uploaded a video of it occurring here:

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. Note how quick it stops (and smoke goes up pipe) when the window is opened (air pressure equalizes).

 

[stoveliker]

That is the air inlet. So that icould be a draft reversal due to cold air in the chimney sinking down.
I presume this was on a cold start?

Get a propane torch and aim it into the open bypass for 20 secs before you light the stove (with the same torch).

Or if it was a pressure issue, make sure all fans (kitchen, bath) are off.
You may need an outside air kit.

Do you have CO detectors?

 

[DuaeGuttae]

Please tell us more about when the smoke leakage occurs. Is it on a cold start with the bypass damper open, or is it during an active burn with the damper closed? If during an active burn, does it happen when you've just adjusted the thermostat or at some other point?

Your window test does seem to indicate a draft issue. Have you checked the cells on your catalyst to make sure that they're clear? A high draft due to a tall chimney or cold temperatures can sometimes pull ash into the catalyst and clog it. I've had some buildup on mine in the past. You can't pull the cat to inspect without having interam gasket on hand with which to replace the one that will fall apart, but you can look at the face of the cat and see if you see any ash clogging. It can be lightly brushed on the surface or vacuumed gently. Don't run anything through the cells.

Another area of potential blockage could be the chimney cap. If the weather has been usually cold even for Vermont, it might be hard for the flu gases to stay above the condensation point all the way to the top of the chimney. I've even heard of water vapor freezing on a chimney cap. Are you able to see the cap from the ground, perhaps with a good pair of binoculars or a camera that will zoom? How tall is the chimney?

Others will be along who may have even more suggestions, but you've come to the right place to get help. Folks will help you get it sorted.

Just to reiterate, though, you do have functioning smoke and carbon monoxide detectors installed, right?

 

[MikeVT]

Thanks for the input so far! To answer the questions/add some info:

- This is happening during active burns, stove temp is in the normal range, damper closed, t-stat mid way
- It has never happened during cold starts, and I never struggle to get it going
- Chimney is about 21’…16’ of single wall inside the room (high ceilings, clearance from wall is > code), 5’ of triple wall through the attic/above the roof, with cap
- We do have smoke/CO detectors. Thankfully this happened when we were home, and we’ve temporarily stopped burning unless we have a day with someone always home who can monitor

I did remove the cat to clean that off before season, but I haven’t checked it recently, so maybe some ash has clogged it this season? Is there any part of the air intake behind that rear cover I should take a look at/clean?

I thought about the outside air kit in the beginning, but decided to see how it went first. And it went great for 1.5 seasons. So, while that may help solve this problem and isn’t off the list, I suspect there’s something else going on that truly started this issue, given the amount of burns we’ve had with zero issue.

 

[tabner]

When you say you removed the cat to clean it, did you wrap a new gasket around it before putting it back in? I don't think removing the cat to clean it is advised, usually you would only remove it to replace it. It requires a new gasket every time it's removed.
Any exhaust fans in the house? Bathroom fan or over the oven? or dryer maybe kicking on and sucking air out of the house? Just thinking maybe something is clicking on and creating a quick negative pressure environment.

 

[MikeVT]

I sure didn’t replace the gasket…did not know about that issue. Oops, maybe that is the culprit. The house is very tight (new build, overboard on insulation gameplan), so negative pressure is probably fairly common. But, given the 1.5 seasons of zero issues, I imagine it’s at least historically not enough of a delta to prevent an updraft…until now.

Back to the cat gasket - do you advise ordering a new gasket, then replacing that once it gets here? It seems kind of crazy a brand new gasket would be dead the second it’s removed, but maybe this is just a replacement and learned my lesson to just clean cat while it’s installed

 

[stoveliker]

Gaskets swell to seal when they get hot.
Yes, order interam gasket.
I suspect an air exhausting device switched on, possibly while having lower draft due to cat clogging or flue or cap obstruction.

Did you have any new additions to the home, and is your chimney taller than any roof you have? (Wind gusts curving down into the flue could be a cause.)

You may also have had a backpuff.

Is your wood as dry as previous years?

 

[DuaeGuttae]

Yes, as others have said, you do want to order interam gasket and apply it around the perimeter of the cat. You tape it in place with masking tape that will be burn off when you fire it up. I'll see if I can find a picture that BKVP once posted for me.

Since you're going to be pulling the cat when you gasket it properly, take the opportunity to clean from both sides. It can have buildup midseason, and sometimes you can't see it all from the front,.

I'm no chimney expert, but I do wonder if your flue gases run below the condensation point given your long run of single wall pipe and your well insulated house. We also live in a new build, and we run our stove on low the vast majority of the time because our house maintains the temperature so well. I have to look for opportunities to do a high burn longer than the initial burn in period, but we have double wall insulated for our entire run. Do you remember how much soot or creosote you got out of the pipe when you did your last cleaning? Even better if you have a picture you can post, and people can evaluate how things look.

If you have a sooteater or some other system you can use from inside your house, since you're having to have the stove shut down anyway, a midseason cleaning is a good idea. This winter has been colder for us than last year, and we've burned a lot more wood. So far things are drafting well, but you certainly could have a clogged cat or clogged cap midseason, and it's definitely worth investigating.

In a well insulated house if it's also well sealed, you might run very close to the edge of having the air you need for a sufficient draft. It could very well be an exhaust fan or dryer pushing you into negative pressure territory. I also wonder about your other heating system, whether it's been cycling during this cold weather, and if that could be a culprit.

I don't think that there's any sign of anything wrong in the thermostat/air intake area of the stove. You should be just fine concentrating on the cat, pipe, and cap at this point as well as considering whether there could be a new contributor to negative pressure in the house while the stove is running.

 

[stoveliker]

If you clean the cat, do not put brushes into the channels; you'll sweep out the precious metals on the surfaces that do the catalytic work for you.
If you use compressed air, use very low pressure (for the same reason).
Best to use a soft brush over the surface, and a (shop) vacuum to suck out any ashes.

 

[Highbeam]

Chimney is about 21’…16’ of single wall inside the room (high ceilings, clearance from wall is > code), 5’ of triple wall through the attic/above the roof, with cap

Ouch. Most manuals forbid any more than 10' of single wall pipe. Then you have air cooled triple wall above that to further cool the flue gasses. Does the cap have a bird screen in it? Those things clog up really fast and with your cold flue that could be a regular maintenance item, like more than once per year.

 

[DuaeGuttae]

Here's a link to a thread where BKVP posted a picture of taping the interam gasket to the cat before installation. I've done the process once, and it was surprisingly easy.

Post in thread 'Question about chimney after first cleaning'

Feb 4, 2025

Thanks for the input. I think when the burning season is over, we'll have to investigate the pipe removal as a cleaning option. I like the five-gallon bucket system.

If I have interam gasket on hand, is there harm in removing the combustor to clean. I know there's a danger that comes with damage from dropping it or something, but is it fragile in other ways? I figured it would be an opportunity to brush off the back as well when we do the next cleaning, but aside from the gasket issue, is it not a good idea to remove it for inspection?

Go ahead. But grab some 2" wide masking...

• BKVP

 

[BKVP]

A snip from OP Video. Thermostat set quite low. Instead of opening the window, turn up the thermostat and increase heat in the stack.

Incidentally, how tall is your total chimney stove to cap?

BKVP

 

[BKVP]

BTW, I have added some more videos...copy and paste into youtube. I think the gasketing video is posted as well.

OregonBowGuy

Share your videos with friends, family, and the world

www.youtube.com

BKVP

 

[begreen]

Replace the single-wall stove pipe. That will keep the flue gases much hotter, improving draft, safety, and family health. Draft reversal can be dangerous. There should also be less creosote buildup with this change to double wall.

 

[MikeVT]

Gaskets swell to seal when they get hot.
Yes, order interam gasket.
I suspect an air exhausting device switched on, possibly while having lower draft due to cat clogging or flue or cap obstruction.

Did you have any new additions to the home, and is your chimney taller than any roof you have? (Wind gusts curving down into the flue could be a cause.)

You may also have had a backpuff.

Is your wood as dry as previous years?

I pulled the cat out - gasket was a felt-like material, and it did look in rough shape (probably from when I put the cat back in without paying attention to a gasket). I’m picking up a new one today, so hopefully that solves the problem. The cat had some ash stuck to the front, so vac’d that off as well.

I’ll inspect the cap with a drone later, but all was good when I looked at everything close up at beginning of the season. The cap sits about roofline height. Wood is very dry.

 

[MikeVT]

Replace the single-wall stove pipe. That will keep the flue gases much hotter, improving draft, safety, and family health. Draft reversal can be dangerous. There should also be less creosote buildup with this change to double wall.

I had that thought, but previously had blown it off because everything had been working well (last year at least). I’ll put that on the list, but probably not happening right away. Hopefully the cat gasket can solve it for now.

 

[MikeVT]

BTW, I have added some more videos...copy and paste into youtube. I think the gasketing video is posted as well.

OregonBowGuy

Share your videos with friends, family, and the world

www.youtube.com

BKVP

Thank you, very helpful!

 

[stoveliker]

I'm not sure it's the cat or its gasket.
You had smoke out the inlet, but "never had trouble getting the stove going". Clogged cats would give trouble getting the stove going,

I think you had a back puff and are operating with low room pressures (due to whatever reason), and you opening the window that stopped the smoke may just have been enough to get the flow going normally again after the backpuff.

Mix of two things, back puff and low pressure in the room, is my best guess.

 

[Highbeam]

I’ll inspect the cap with a drone later, but all was good when I looked at everything close up at beginning of the season. The cap sits about roofline height. Wood is very dry.

Bird screens can clog fast and dry fuel does not prevent it, we're halfway through the burn season now so it is totally possible your screens are clogged.

Unless you have some goofy local law requiring the screen I would recommend removing it. The screens were an option when I bought my duravent systems.

I agree that your cat gasket has nothing to do with the smoke flowing from the back.

 

[DuaeGuttae]

I'm not sure it's the cat or its gasket.
You had smoke out the inlet, but "never had trouble getting the stove going". Clogged cats would give trouble getting the stove going,

I think you had a back puff and are operating with low room pressures (due to whatever reason), and you opening the window that stopped the smoke may just have been enough to get the flow going normally again after the backpuff.

Mix of two things, back puff and low pressure in the room, is my best guess.

I agree that the gasket isn't likely the issue, though it's good that it's getting corrected, and that negative pressure is probably involved, but I'm curious about the statement that "Clogged cats would give trouble getting the stove going." Since the bypass damper is open when getting the stove going, wouldn't it light up normally but then have trouble after the bypass damper is flipped? Would a clogged cat contribute to a backpuff?

 

[DuaeGuttae]

Bird screens can clog fast and dry fuel does not prevent it, we're halfway through the burn season now so it is totally possible your screens are clogged.

Unless you have some goofy local law requiring the screen I would recommend removing it. The screens were an option when I bought my duravent systems.

I agree that your cat gasket has nothing to do with the smoke flowing from the back.

I've had a clogged screen on my cap before, and it's entirely reasonable to check for it partway through the season, especially if experiencing draft trouble or smoke rollout. I think it was the reason we first bought a sooteater many years ago as we needed to clean it out when there was snow on our roof. I'm glad you're able to get a drone up there, @MikeVT .

Even if you do find a clog on your cap, I'd be cautious about removing the screen itself. You can perhaps make the holes bigger if it's excessively restrictive, but I think it's a good idea to have something to keep birds out. I know that Highbeam doesn't have a problem with birds, but we folks who live on the east coast seem to have more likelihood of birds or squirrels in our chimneys in the spring. I even watched a pair of Eastern Bluebirds make repeated attempts to get through my screen this spring. I was working in the garden, and it was kind of astounding just how persistent they were being. Thankfully my screen did keep them out.

 

[stoveliker]

I agree that the gasket isn't likely the issue, though it's good that it's getting corrected, and that negative pressure is probably involved, but I'm curious about the statement that "Clogged cats would give trouble getting the stove going." Since the bypass damper is open when getting the stove going, wouldn't it light up normally but then have trouble after the bypass damper is flipped? Would a clogged cat contribute to a backpuff?

Getting going with the bypass open indeed not affected but for me getting going is also a warm reload when the new load needs to get going, but the bypass is already closed
Flue warm bypass closed,. And the load getting going means it's not the cat.
If he meant only cold start, then yes.

Backpufs can happen when the cat is partially clogged.

 

[bigealta]

When i get backpuffs with NW winds only in Utah, the puffs are "Puffs". Smoke puffs, then nothing then another puff usually bigger or snaller than the previous puff. Then it randomly changes with each puff with no puffing between puffs.

Back puffs for me are wind driven
The smoke in the video seems very steady and constant. Nothing like what i've experienced.

Smoke puffs are a different thing than negative pressure driven smoke leakage/downdrafts which it looks like what is happening.

Is the OP 100% sure a furnace, dryer, bath vent, kitchen vent, attic fan, or anything else that blows air to the outside is not running when they experience this smoking?

 

[stoveliker]

I've had a backpuff with my BK and while it starts as a puff it took a while to stop - presumably due to the path length of the smoke (and thus the reservoir of smoke near the air inlet).

But yes, negative pressure is likely playing a role. Could be a larger role.
But I think he said no fans were running. If it's negative lower floor pressure (i.e. home system,.not fan driven) then, it should be hard to start a stove imo.

Tough to be sure from here...

 

[bigealta]

If there are no fans running it Kind of feels like a partial blockage? Maybe just big enough to slow the already weakish draft to turn into a down draft?