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stove won't draft

Hi--

I recently installed a small woodstove on my boat--not a navigator, unfortunately, but a little Norwegian stove called a Trolla. (Is this site only for navigator people? I'd really appreciate some advice!) I can't get my stove to draft--whenever I open the door, smoke fills the cabin, even after its been burning hot for a hours.

I used heavy (1/8" walls) stainless pipe, and it only has 2 45 degree elbows in the run. The stove came fitted for 3.5" pipe, and the ID on my stainless is roughly a 1/4" under that, so I wondered if such a small diameter pipe could be a part of the problem.

The other potential source for the problem is that the stove itself isn't level from front to back. It sits on top of my water tank, and once I filled my tank--combined with the weight of the stove/heat shields etc--the boat is listing some (and the berth itself is cantered), which might cause the smoke to rise toward the door instead of to the back of the stove. (I'm on a slip now, so have the boat set for winter living, not sailing...).

Also, my companionway hatch is rather high, so I wondered if the source of fresh air being so much higher than the stove could be a cause of the problem.

I have roughly three feet of pipe above deck. It's not higher than my boom, but my neighbor, who has a Little Cod, has less pipe, and no draft problems.

Thanks for any ideas.

jon

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Re: stove won't draft

J,

First, I think the pipe size may be too small. From the quick look I did, I found that the outlet is sized for 4.5" pipe. Reducing it down to 3.25 will have a big impact. I'd measure the outlet circumference and determine what size pipe would truly fit OVER the oval/circular collar. I'd get this right first before I made any comment on why it's not running as you'd like it to. A/NSW

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Re: stove won't draft

Hi Andrew, thanks a bunch for the thoughts. My first guess was the stove pipe, too, but I wasn't sure. This model has a collar that measures around 3.5" ID and just under 4" OD. I'd thought the pipe was supposed to fit inside the collar, not over, so there's my first big mistake--I'd used the 3.5" measurement to go from.

Even a half inch in diameter is a fairly large percentage of the total area of the pipe when we're dealing with flow, isn't it?

Thanks again. I really appreciate your time.

jon

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Re: stove won't draft

J,

At the stove collar is the only place where one switches "the rule" about pipe ABOVE going down INTO the pipe below. It is usually so hot there that creosote would not dare drizzle out. The reduced pipe size will have an effect but you also likely have other issues going. Overall you just need to confirm with a piece of incense (smoke source) that you don't have a negative pressure or flow of air out of the boat when the wind blows. When this happens all your chimney is doing is supplying "make up air" to the cabin and overriding the hot updraft. This checking can be done w/o the stove running and if you have flow out the stove, you will need to adjust things to stop the inrush of air down the chimney.
Well intended, fine mesh spark screens can also clog quickly and kill flow. Your thick, long, uninsulated pipe on deck might prove to be a great creosote condenser. You might have to insulate that portion to stop it from doing that in very cold weather. Study your flow to see where things are working in reverse is your main task though to start. A/NSW

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Re: stove won't draft

Andrew--


Thanks a bunch. I ripped out my thick-walled pipe and ran 4" pipe throughout... the stove's running a ton better, and I got rid of about 50 lbs of weight on board. I'm also playing with the indoor/outdoor pressure discrepancies, and that's helping.

Last question (maybe): does the stove pipe hat make much difference as far as draft goes? It seems that a good one would make a difference, but I've heard conflicting reports.

Thanks again for the insights.

jon

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