Chimney Pipe Condensation

This question is about our SF-250, it's been burning 24/7 for about a month, it is located in the basement.

Exhaust Setup:

1) There's about a 6' run of 6" stove pipe with two adjustable elbows set at 45 degree each in order to make the attachment to the 6" SS flexible liner.
2) The is a baro-damper inline in the 6' run of stove pipe about 18" from the chimney collar.
3)From the connection of the stove pipe, the SS flexible liner makes a 24' run through an old brick masonry chimney to the top. There is 2' of of exposed stove pipe at the top with a SS chimney cap to give me clearance above the roof line.
4) The stove pipe is run with the crimped ends leading away from the stove - which I understood was acceptable for coal burning, but should be reversed for wood burning.
5) The stove is highly efficient; between the stove pipe and stove, I'm seeing 80%. I usually have to run the stove above 500F to get over 100F on the stove pipe. So by the time the smoke leaves the top of the chimney, it is condensing, and even icicles have formed on my chimney cap.

Problem:

Within the past two days, I have suddenly noticed a sizable amount of brownish slightly pungent liquid dripping from the stove pipe fittings. This I assume to be creosote? I have occasionally burned a log or two in this unit. But not enough to justify this I believe.

On a side note, the weather has been cold the past 5 or 6 days, it's been around 7 degrees outside with winds between 40-60 MPH. This weather seems to have really brought this issue to the forefront.

I have trouble believing it's just creosote because of the amount of watery fluid leaking all of the sudden.

Possible Solution:

I'm heading out to get a chimney brush today to do a cleaning. I'm also going to reverse the fitting on the stove pipe so it funnels any liquid back into the stove. I will also get a couple of creosote soot sticks to burn, and stop burning any wood in the stove except for fire starters. I'm going to seal the baro-damper.

Is the cap causing a problem with excessive condensation with these temps? I was reading on an HVAC forum that a cap can cause excessive condensation on low exhaust temps.

Is there a way to increase stack temps on this unit without over firing it? Possibly adjusting the secondary dampers in some manner?

Am I missing anything?

Your Alaskan Sub-bit coal probably has a lot of moisture in it, and it could very well be condensing in the flue...especially that last 2 feet of pipe. If the condensation runs down the liner and mixes with soot/flyash...that would account for the dirty water you are seeing.

I would ditch the baro completely, it is only lowering your stack temperatures. You could also try running it without the cap...the last thing you want is a flue blocked from ice.

Rob R. wrote:Your Alaskan Sub-bit coal probably has a lot of moisture in it, and it could very well be condensing in the flue...especially that last 2 feet of pipe. If the condensation runs down the liner and mixes with soot/flyash...that would account for the dirty water you are seeing.

I would ditch the baro completely, it is only lowering your stack temperatures. You could also try running it without the cap...the last thing you want is a flue blocked from ice.

Thanks Rob, it is an easier fix than I initially thought given I've only burned about 5 or 10 4" logs in the unit over the course of a month. Not thinking about it at the time, and given the low pipe temps, I probably shouldn't ever burn any wood in the thing - it was build to burn coal, and does it quite well. Thanks again, I was stressed this morning seeing the huge puddle under the pipe this morning.

I remember other forum members saying that the SF250 would load up with creosote pretty quickly; the heat exchanger does a pretty good job of lowering the stack temperatures. I would save the wood for starting the fire.

It could be condensation from the high moisture coal. It's not creosote, if anything the brown liquid is soot/flyash mixed with condensate. You could either remove the baro or just keep it in place and increase the draft setting (move the weight) so that under almost all conditions it doesn't open.

Berlin wrote:It could be condensation from the high moisture coal. It's not creosote, if anything the brown liquid is soot/flyash mixed with condensate. You could either remove the baro or just keep it in place and increase the draft setting (move the weight) so that under almost all conditions it doesn't open.

Thanks Berlin. I crawled up to the chimney top and saw that there was some snow and ice accumulated at the base of the flashing below the cap. The snow and ice had been melting and working in between an opening and dripping back down the liner. That's probably part of the problem. I probably need to lose the cap at this point just to get us by, and reduce the condensate. We're planning to rebuild the chimney in Spring.

Thanks again everyone, I was really stumped this morning when I found a puddle of brown water under the pipes.

If you rebuild it, use block or brick and a tile liner with a larger than normal air space between the flue and the inside of the masonry chase. fill this space with vermiculite or expanded pearlite.

My coal has the same issue. I now keep a ton inside at 50*. And bring in about 100lbs of it at a time to set near the stove. This warms it up and dries it out. The first day I had my stove going it poured water.

oh and it has been around -10 for a week here and 70* in the house. With the boiler turned off and nothing but burning black rock!

Have you picked up any coal lately? did Aurora up the price?

murphyslaw wrote:My coal has the same issue. I now keep a ton inside at 50*. And bring in about 100lbs of it at a time to set near the stove. This warms it up and dries it out. The first day I had my stove going it poured water.

oh and it has been around -10 for a week here and 70* in the house. With the boiler turned off and nothing but burning black rock!

Have you picked up any coal lately? did Aurora up the price?

Thanks for your thoughts.

I really need to build a coal bin in the basement, but there's just too much else to do right now. I do have parts of the pile I shovel out with fair amounts of moisture on it. I bring it inside over night, but it's not always enough to dry it out. I'm going to pull the chimney cap off today. I pulled the cap off the other stack, and it is performing better.

When I picked up 6 tons 2.5 months ago, Aurora said they would be bumping the price up, but when we just called a couple days ago to arrange another load, the price was still the same - $80/Ton.

Just out of curiosity, you said your sole source of heat is coal right not - what amount of coal are you burning, and how many sq/ft are you heating?

I am burning the hitzer 82 now. Going threw the contents of a 35gal trash can of coal a day. Running the stove at about 350-400 Down stares where the stove is is 78* up stares is 72* I have used about 1/2-5/8 of a ton since I installed it.

And its a '81 2300sqft split level. with crappy windows and poor insulation.

How does the Hitzer do at burning off the volatiles from the coal? They claim that the secondary burn chamber helps clean up the smoke...I'm curious how it is working for you.

I am very pleased with it! As long as you don't load it to the hilt it works great. My load routine is to load the back half. Then in an hr or so load up the front. This gives it time to burn the gasses off the back half's fresh coal. I have yet to have a complaint from a neighbor. It smokes a little on reload, but after about 30-45min it cleares up and its just a light smoke like any other wood fireplace.

I installed a Selkirk Metalbestas HT chimney. The through the wall adapter to chimney pipe has the crimp toward the stove. This is so the condensation falls into the stove and not on any other surface. I do not have a baro installed.

We have a Hitzer 55 and I mix 1 stove to 1/2 nut. This gives a nice even burn throughout including the corners. When we bought the stove this was recommended by the seller, who has the same stove because the nut did not burn well in the corners. I am careful not to get the bigger chunks in the corners and this seems to work well. Loading is right up to the top of the brick with a little mound of the larger chunks in the middle.

If this the coal that I saw an analysis for it contains ~30% water,which doesn't dry out

because it is in the layer spaces inside the coal.The BTU's are fairly low because all of

that water has to be heated to evaporate to be lost up the flue.This probably accounts

for the lower heat output in the stove, 212* steam does carry many BTU's so the stove

does not radiate much heat.

BigBarney

As long as I keep my stove hot I do not have this issue. But when I started it up it drained about 2cups worth. Since it has been running I have not had an issue. But would imagine if I let it cool to under 200* it may start back up. Have been running at 400* since day 3. Keeping the down stairs at 78 and up stairs at 72. I LOVE IT!