BK 40 billowing smoke out of the bottom of stove at cold start

[nobodyspecial]

New to the forum world figure I would start here.
last year I installed a new (2020) epa BK 40 . First and foremost the stove is great. When lighting the stove while she is dead cold is has a ton of smoke spillage from under it . Any help would be appreciated. Thanks

 

[sundance]

@bkvp might be able to comment.

 

[bkvp]

New to the forum world figure I would start here.
last year I installed a new (2020) epa BK 40 . First and foremost the stove is great. When lighting the stove while she is dead cold is has a ton of smoke spillage from under it . Any help would be appreciated. Thanks

In order for that to happen, you have tremendous negative draft on cold start. Some very quick questions:
How tall is chimney from stove top to cap?
Does cap have spark arrestor screen?
Is your black pipe single wall or double wall?
Any elbows or offsets in chimney?
Are you opening bypass when starting?
If you give me some of this or post pictures of install, it will be very helpful.

BKVP

 

[CaseyForrest]

Ill add... Are you completely closing the door on cold starts or do you leave it cracked?

How quickly are you closing the bypass?

 

[bbxlr8]

Welcome - you came to the right place and can learn a lot from the great people on here. I have.

I have a very tall run (27') through a masonry chimney and initially struggled on a cold start when the temp differential is high - i.e. really cold outside... It drove me crazy, and several times I smoked out the entire basement & up into the house - Very, VERY bad plan.

• Per above It basically reverts and you can think of it as cold air actively flowing down backwards towards the inside. I got to the point where I could stick my hand in the cold stove and feel it and just know it was going to give me trouble.
• Very windy conditions can aggravate the situation.
• Properly sized SS liners are the usual suggested solution.

Without going into changes in the pipe or design etc. Here is what I learned to crutch my situation:

1. You need to quickly generate enough heat to overcome the negative flow. Monitoring the flame and judging the air need by opening the door a bit helps.
2. I use a bunch of lightly wadded newspaper, & maybe some really dry small kindling. I also use an accelerant - some will say "don't do that" and I get it; but it works for me.

During serious polar vortex type weather and I have to do a cold start (super rare these days, but an example is where I used to travel and the wife struggled, etc) & I do not want to ever smoke it out again- I do the following in order of severity:

1. Use a plumbing soldering propane torch and leave it in the stove - cracked open a bit.
2. IF i don't want to mess around with that, I go to my propane torpedo heater to git er done. Never, ever fails after that

Being aware & using a progression of the above, I have not had this issue again in many years, again this is without any changes to the chimney, new liner etc.

 

[nobodyspecial]

@bkvp might be able to comment.

Ill add... Are you completely closing the door on cold starts or do you leave it cracked?

How quickly are you closing the bypass?

Ill add... Are you completely closing the door on cold starts or do you leave it cracked?

How quickly are you closing the bypass?

Fire box door cracked, bypass does not get closed until T stat reads active.

Ill add... Are you completely closing the door on cold starts or do you leave it cracked?

How quickly are you closing the bypass?

f

In order for that to happen, you have tremendous negative draft on cold start. Some very quick questions:
How tall is chimney from stove top to cap?
Does cap have spark arrestor screen?
Is your black pipe single wall or double wall?
Any elbows or offsets in chimney?
Are you opening bypass when starting?
If you give me some of this or post pictures of install, it will be very helpful.

BKVP

 

[CaseyForrest]

Is the chimney lined or does it dump directly into the chimney?

ETA: Looks like new windows... Perhaps the house is getting tight and you need some air supply. Try cracking one of the windows near the stove when starting it.

 

[nobodyspecial]

In order for that to happen, you have tremendous negative draft on cold start. Some very quick questions:
How tall is chimney from stove top to cap?
Does cap have spark arrestor screen?
Is your black pipe single wall or double wall?
Any elbows or offsets in chimney?
Are you opening bypass when starting?
If you give me some of this or post pictures of install, it will be very helpful.

BKVP

24ft top of stove to chimney cap in this order, 36” vertical rise ( single wall not insulated, I had it wrapped with zero clearance insulation, took it off to see if it made a difference one way or another it didn’t) two 45s insulated to a 32” snout/service T insulated to a 21ft 8”insulated SS liner in a masonry chimney capped with SS cap with spark cage.
Thank you for all the replies already. I really appreciate it.

 

[nobodyspecial]

Is the chimney lined or does it dump directly into the chimney?

ETA: Looks like new windows... Perhaps the house is getting tight and you need some air supply. Try cracking one of the windows near the stove when starting it.

 

[nobodyspecial]

The house is getting better all the time as far as being tight/ insulation wise so my thoughts were the same. I opened the windows to let her breathe a bit better, nothing. So I went a step further and opened the overhead door 10’ away and still nothing.

 

[bbxlr8]

Very similar physical situation to mine - check out what I do to mitigate it in post above.

 

[bkvp]

View attachment 975766View attachment 975767View attachment 975768View attachment 975768View attachment 975769


Fire box door cracked, bypass does not get closed until T stat reads active.

f

Thanks for the pictures. I must first ask what is above (on the other side) of the tin you have on the ceiling? How close is that venting (ignoring the metal) to a combustible surface? Like a floor joist? DBL wall reduces clearances to 8-9" but your single wall requires 18" of clearance to a combustible surface.

The owners manual, in four places, encourages the use of double wall stove pipe to help maintain stack temps. I appreciate your observations of wrapping the pipe with insulation. I can't qualify how that is or is not better than dbl wall because I have no data. However, it does appear with that entire chimney located on the exterior wall, cold air is going to be a challenge. That cap is not one that I think (bot an expert on caps) would normally be associated with a wood stove, but rather a wood chimney/fireplace. The liner dropped down inside, you say that it is insulated. Was it a wrap that was applied to the venting on the outside or an insulating material between two layers of metal?

The suggestion to use a torch or weed burner to warm the stack has been used for decades, although not a great solution.

 

[nobodyspecial]

Thanks for the pictures. I must first ask what is above (on the other side) of the tin you have on the ceiling? How close is that venting (ignoring the metal) to a combustible surface? Like a floor joist? DBL wall reduces clearances to 8-9" but your single wall requires 18" of clearance to a combustible surface.

The owners manual, in four places, encourages the use of double wall stove pipe to help maintain stack temps. I appreciate your observations of wrapping the pipe with insulation. I can't qualify how that is or is not better than dbl wall because I have no data. However, it does appear with that entire chimney located on the exterior wall, cold air is going to be a challenge. That cap is not one that I think (bot an expert on caps) would normally be associated with a wood stove, but rather a wood chimney/fireplace. The liner dropped down inside, you say that it is insulated. Was it a wrap that was applied to the venting on the outside or an insulating material between two layers of metal?

The suggestion to use a torch or weed burner to warm the stack has been used for decades, although not a great solution.

Anything in the 18” clearance is wrapped in zero clearance insulation. Double wall liner with insulation in between.

 

[nobodyspecial]

Anything in the 18” clearance is wrapped in zero clearance insulation. Double wall liner with insulation in between.

The double wall stove pipe doesn’t have near the insulation value as the zero clearance insulation I had on it , unless of course it is insulated double wall pipe.

Anything in the 18” clearance is wrapped in zero clearance insulation. Double wall liner with insulation in between.

what does a wood stove chimney cap look like?

 

[bkvp]

 

[nobodyspecial]

View attachment 976086

Thank you

 

[Yarz]

Has any of this helped you, nobodyspecial?

I have a powerful negative draft when everything is cold as well, and have smoked out my basement several times.

Now, I prepare the fire, then light paper in my chimney's cleanout T, (so the heat has no choice but to go straight up the vertical part of the chimney, starting the draft going upward - It will actually suck the burning paper upward when it reverses), and then immediately light the fire.

I know with the liner, you can't get access to the tall vertical part of your chimney, but can you reach into the first part from inside your stove?

 

[loadthestove]

I have very similiar problem with my stove.On cold start I have to open a window next to stove until chimney get warm.After that i have no problems.