Overdraft problems

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New Member
Nov 29, 2022
New York
I have a Hotblast 1557M that I use for wood burning in our basement. I know its notoriously not the greatest at burning wood but it does the job and I'm not in the market to replace it yet. Our stove though BURNS the wood up like crazy. The draft in it is crazy, I usually have the bottom air vent closed or just barely cracked. On the door is another air supply with a bimetallic door on it that opens and closes as the temp changes. Even with minimal air in, this thing rips through wood.

In addition when I close the flue damper to about 75% closed it still rips! Any suggestions? My flue pipe is 6" SS double wall. It comes out the stove, up 3' to a 90° then about 3' outside through the basement wall, then 90° up probably about 25'. So theres likely over 30' of chimney which makes me think its overdrafting. Is there a better way to control this than the manual damper?
I'd start by burning coal in it. It wasn't designed to burn wood. Coal wants the air to move up from the bottom. Air from the bottom turns the woodstove into a forge.
I'd start by burning coal in it. It wasn't designed to burn wood. Coal wants the air to move up from the bottom. Air from the bottom turns the woodstove into a forge.

I burn wood because I have access to all the firewood I want for free (minus chainsaw and splitter gas). I appreciate the suggestion but I'm looking for suggestions on ways to make it more efficient with wood.
What does your fire box bottom look like? If it’s for burning coal it’s probably has metal grates open to below where the air comes up through your wood causing short burn times. Maybe try laying some fire bricks over the grates to reduce that forge like air supply. I did this a long time ago to an old coal stove and it helped but it didn’t burn very clean and had to sweep often.
You can stop air from coming up from the bottom, and close down the upper damper more than 75%. Making sure the wood is as dry as possible will ensure that the heat from the wood isn’t being used to boil off water.

It’s not going to be what it wasn’t designed to be.

Be wary of choking it down too much as it could allow the flue gasses to cool and condense inside the chimney, causing creosote.
Install a barometric damper with good seal and explosion relief

Overdraft problemsOverdraft problems
looking for suggestions on ways to make it more efficient with wood.
It will never be efficient on wood...but the suggestions already made are good ones...but not sure why an explosion proof baro is needed...if it's gonna backpuff, smoke will come out of every crack crevice and seam...you're not gonna stop it.
That said, get a cheap manometer to check/monitor your draft...the Dwyer Mark II model 25 is a good one and not expensive...once you have that hooked up you can set your draft with the key damper, maybe...it might take both a baro, and a key damper also in real cold weather.
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The Hotblast is essentially a newer version of the Clayton I used for years. It used to be a "wood or coal furnace", until the need to dodge EPA regs made it "coal only". The difference is the words "coal only" in the instructions. I had a similar experience with mine. Tall chimney, in my case straight up, and I could get enough airflow through the thing to about empty the ash drawer onto the rooftop.

The instructions with mine clearly stated not to use a damper. I couldn't see how that ever worked, and I installed a key damper that I kept 90% closed - just shy of causing it to leak smoke. That was my solution, and it worked for me. It still drew harder than was ideal, but "good enough". I never saw mine backpuff. There was always too much flow going through the thing for that. Later instructions said maybe a baro damper. I just glanced at the instructions for the 1557m and it specifies a manual damper AND a baro damper.

This design doesn't combust very efficiently and also puts a tremendous amount of heat up the chimney, so no way around it, it's going to go through wood. The answer to that is one of the new tech furnaces. I replaced mine with the Kuuma. That worked! It burns every bit of the fuel, and I can put my hand on the single wall pipe while it is in operation.

I do miss that the Clayton was drop-dead easy to start! I could throw a basket full of junk mail in, a little kindling, or even just some smaller splits, and logs on top of that. One match, then close the damper at about 2 minutes and walk away. It would be at full output in about 10 minutes!
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The 1557 is not a good coal burner. Been there done that, the firebox is v'd and not good for coal. Maybe others have had luck but not me!