New woodstove and smoke in the house

[programme]

I recently installed a Hearthstone Eclipse to replace a Hearthstone I stove that my wife and I used for nearly 20 years. We burn between 4 and 5 cords of hardwood per winter, with a fire most days between November through May. I have a older open post-and-beam house (3000 sq.ft.) with a central masonry wall in the middle of the house that acts as thermal storage for passive solar and also contains a masonry flue. Twenty years ago when the wall was built I had an idea about increasing efficiency out of a woodstove, so I had the 8" dia masonry flue inlet located about 16 feet above the floor, and I connected the outlet of the Hearthstone 1 to the masonry flue with 16 feet of single wall 8" metal flue ending in a 90 degree bend into the masonry flue. (The masonry flue then runs horizontal for 2', turns 90 degrees, and then goes vertical for about 16 feet out of the roof. The total height of the flue is about 35 feet.) Most of the masonry wall (30') is inside of the house, with about 5 feet extending above the roof. The Hearthstone I and the flue worked very well, with a good draw and very little flue gas residue buildup over that time. The exhaust plume coming out of the top of the flue was always well defined and the plume aggressively moved up and away from the house. With the new stove I've noticed two changes: 1) smoke from the new stove seems to just barely makes it out of the flue, and often settles back around the house; and 2) there are black streaks coming down the outside of my exposed chimney that I'm assuming is creosote that is growing at an alarming rate. I suspect that all this is the likely result of much cooler flue gas from the new stove. One issue we are having is a smoke smell in the house -- noticeable when starting a fire but more of an issue when refueling the stove. I've caulked flue joints that I thought were leaking, but the smell of smoke hasn't changed. Using metal flue sections I raised the height of the outside flue, but this hasn't elimated the smoke problem. I just found your website, have read some articles and I now suspect that the smoke smell isn't originating inside, but rather is infiltrating from the outside, returning back into the house through somewhat leaky construction. I think that I can improve the situation (and increase the flue gas temperature) by using a couple of your recommendations (building better fires (hotter) and making sure to allow time for refueling to come up to temperature). I'm more concerned, however, that a signficant part of the issue with smoke is the long run of single wall flue inside the house that worked well with the hotter exhaust gasses from the Hearthstone I, but probably isn't a good idea with the new stove. I think that I should replace the single wall flue with a better insulated product (double wall?) to better preserve a higher flue temperature. Would you agree?

 

[struggle]

I am not familiar with the stove you speak of but if you are running in on an 8" pipe into a masonry chimney then that would explain the lack of draft. Or is it an 8" flue all the way up to the top of the chimney?

Does the new stove have a 6" outlet and you adapted it to a 8" pipe? An 8" pipe would have almost twice the cross sectional area that a 6" would have which could significantly reduce you draft.

You would be best served to run and the exact same size diameter pipe that the stove call for the entire run of the chimney.

 

[begreen]

Could this be a Hearthstone Equinox stove? The Eclipse is not familiar to me either. Do you have a thermometer on the stove? It sounds like it is being run too cool.

If you look into the new stove's manual, I think you might find that Hearthstone says not to use single-wall pipe for heat recovery. The new stove is more efficient in extracting heat, which means cooler flue gases than the older stove. This is from the Equinox manual:

"We do not recommend long runs of stovepipe to increase heat dispersal. Longer lengths of stovepipe or more connecting elbows than necessary increase the chances of draft resistance and the accumulation of creosote buildup."

 

[oconnor]

You are descibing a low draft situation, and lots of things can effect it. Hot fires and dry wood are needed to avoid the condensation of creosote in the flue.

As well, look into what else could cause poor draft - is your cleanout door allowing air into the flue and droping temps? As you mentioned, double wall will help stack temps therefore draft. If the stove is intended for 6" pipe, put you need to increase the diameter, do it at the connection with the chimney, not at the stove. This will preserve the intent of the 6" flue in the area where you can. Does the problem still occur if you reload with a window open in the room? If the open window fixes the issue, you have learned that stack effect in your house may be influencing draft. If it doesn't help, look towards wet wood and other sources of cool flue.

Get yourself a flue gas thermometer, preferably a probe type, so you can have an idea of performance. My thermomter is great at letting me know when I have grabbed a stick of wood that wosn't dry enough yet - I can't get it to heat up if my wood isn't truly seasoned.

Laspt tip - recommend you edit your post with a few paragraph breaks - it will make other folks more likely to read it and answer with some suggestions.

Hope these help

 

[Jags]

I think that I should replace the single wall flue with a better insulated product (double wall?) to better preserve a higher flue temperature. Would you agree?

You are approaching this very methodically. I do agree that you should get rid of the single wall to begin with.

Sounds like a slow draft. Hot fires, keeping the stack up to temp, eliminate bends, good dry wood, these are just some of the things that can improve that.

EDIT: and don't buy into the idea that you HAVE to completely shut down the primary air on your stove. Each setup requires little tweaks.

 

[programme]

Thanks for your comments and suggestions. Yes, it is a Hearthstone Equinox (not an Eclipse -- I mixed up the astronomical reference). I don't have a thermometer -- I'll get one. The stove comes with an 8 "diameter outlet, so it's 8" flue pipe from the stove up. I wish the dealer who did the install had suggested replacing the single wall with double wall -- it would have cost a little more, but would have been a better choice. Brent, I read through the guide. I'll do the window test tonight.

I was told when we bought the stove that the performance would be quite different due to advances in stove technology over our first stove. When I heard this I thought, "yeah, right -- it's just burning wood". We're burning less than half the wood. The heat output has been as good or better.