New 6" stove with existing 8" stovepipe

[stokedalaska]

I currently have an older Jotul Combifire #4 wood stove that I would like to upgrade to an EPA certified, non-catalytic, clean burning wood stove.

The current stove is configured with 8" metalbestos stove pipe which extends through the first floor, second floor, then through an unheated attic, for a total length of 24' with no bends. The stove pipe is in good condition and has only been used occasionally in the fifteen years since it's installation. We cleaned the stovepipe recently and got about a grapefruit sized mass of creosote (last cleaning was about 5 years earlier). It looks like there is an adapter right at the stove that increases from 6" or 7" to the 8" stove pipe (this is what came with the house).

We live in Alaska and would like the stove to be capable of being a primary heat source in winter. Our house is 2 stories and is just over 1000 square feet.

A few questions:

- Could we expect good (and safe) performance if we use the current 8" ID stove pipe? Or would it be more desirable to install a 6" single wall pipe inside the current stove pipe (or even consider that after seeing how a new stove performs at 8".) I've read a few new stove manuals that will first say "A six inch diameter flue is required for proper performance" but then later stats "If the area of the flue is greater than the collar, it should never be more than two and 1/2 (2.5) times greater." My research seems to find that a long straight length helps to promote good draft.

- Also, some of the 1000 square foot models are not EPA certified, and we'd have to bump up to a 1500 or 1800 square foot model for EPA certified (and eligible for the tax credit); however would the larger model be oversized and not work as efficiently if we have to damp it down, or would it be more appropriate taking into account where we live (winter temps typically in -20's, and dip into -30's)?

 

[learnin to burn]

You should be fine using the 8 inch pipe. 6" pipe is 28sq in. and 8" is 50sq in. well below the 2.5 x greater which would be 70 sq in.

If you want to heat exclusively with wood you will defiantly want something larger than something rated for 1000 sq ft. unless you have the time to put wood in it every 3 hours. You will see a wide variety of responses on this too. I would suggest something with a 2.5 to 3 sq ft. fire box.

 

[sapratt]

One thing I was told is its better to have to big of a stove and build smaller fires. Then to have to small of one and run it wide open all the time.
That is something to think about also.

 

[stokedalaska]

Thanks for the feedback so far! I am open to more opinions as well.

Some local fireplace stores recommended replacing the 8" with 6" (which would cost way more than the stove). My hunch is that they wanted to CYA and/or make a bigger sale.

But it is important to me to make a step in the right direction of efficiency and of course to be safe.

 

[sapratt]

If the chimney you have will work why replace it. That is how I look at it.

 

[learnin to burn]

They were trying to sell you something you didn't need (IMO). I ran my Regency with 6 inch pipe to an 8 inch wall thimble to an outside 7x7 clay flue without an ounce of issue. Your going strait up and out which is ideal.

 

[monkey]

Hi,was reading your post about going from 6inch to 8inch and not having any problems ,this what i had until recently,but could get stove to work
right. Every time i would open door to add and/or start fire i would fill house full of smoke, finnaly i got tired of that and changed the pipe from
the top of the to 8inch,as the top of stove had a 6inch hole so i put a 6 to 8inch adapter on it and ran 8inch pipe to where it went into the wall
and chimney,now i can start a fire leave door open until it gets going and when i open door to add more wood smoke will not come into room,thank's

 

[pen]

They were trying to sell you something you didn't need (IMO). I ran my Regency with 6 inch pipe to an 8 inch wall thimble to an outside 7x7 clay flue without an ounce of issue. Your going strait up and out which is ideal.

I have the same setup as learning to burn, and make out fine as well. If I am trying to have a fire at say about 50 degrees, the stove doesn't draft as well as my buddies who has 6in all the way.

But, if the chimney is in good shape, you should be good to go.

At the very least, you are safe to try it. If it doesn't work well, then plan B.

Oh, also, I'd be looking at the 1500 square foot model if I were you. My Englander 30 can be run on less than a full load of wood, and puts out significantly less heat and still get good burn times. This is characteristic of many of the modern stoves. I think you'll be OK w/ one a little bigger and you DEFINITELY want one that is certified for the tax credit. If it's not, you won't be getting any of the modern goodies like secondary burn tubes and a true baffle plate.

good luck

pen

 

[tickbitty]

I'm not as experienced as some on here but I am under the impression that it is good to get a stove where your square footage falls somewhere in the middle of the stated range for the stove. If you have vaulted ceilings or anything like that, that cubic footage should also be considered.

For going from 6" to an 8" flue, I think it might be more of a concern if you were in a one story house, because the draft might not end up being appropriate for the new stove, but since you are in a two story house I think it's fine. (Or maybe the one story problem only arises when you are talking about going from an 8" DOWN to a 6"!)

Too bad you have to say goodbye to the old Jotul, they are so cool looking, like Easter Island statues!

 

[stokedalaska]

Ah, you know my Jotul well. Yes the Easter Islander looks is very cool indeed. But I am looking forward to a window, a flat top that can be used to heat things, and stuffing less wood into it!

Thank you all for your replies - this is great stuff!

 

[begreen]

The old combifire was a serious heater. Odd looking, but it could heat.

I think there are several stoves that can handle the straight up 8 pipe. Go for at least a 2 cu ft stove. PE stoves work over a wide temperature range. The will burn steadily with a stove top temp of 450 or can be cranked up to 700. We have one fellow in Wyoming that has the biggest PE in the same sized house, says it is staying comfortable at below zero. https://www.hearth.com/econtent/index.php/forums/viewthread/47182/ And yet I am running the same stove in a 2000sq ft house in a mild climate.

 

[stokedalaska]

Any opinions on outside air kits? Would the reasons for installing one be first to improve your draft and secondly so you don't draw cold air into the house? When I run my kitchen vent hood or my clothes dryer, I figure they must suck in a lot more cold air than a wood stove wood, so wonder if it makes much of a difference.

And thanks BeGreen; I'll look into the PE too, but was considering a steel stove. I actually like the basic look of the steel stoves (and the price is right too).

 

[begreen]

All PE stoves are steel stoves. The Alderlea line is cast iron clad, but inside they are the same steel stove as the rest of the PE line. T4=Vista, T5=Super, T6=Summit. The cast iron jacket on the Alderleas provides more mass to soften the heat and retain it longer. You might also look at the Blaze King line. They work well if you want a slow steady heat and their big stove uses an 8" flue.

There's a lot of opinions on OAKs. I would try the stove without one first.

 

[Valhalla]

My Oslo has a 6" to 8" adapter at the Selkirk Metalbestos previous stack from my Encore.
It burns great through the 22' straight up flue.

Excellent air control during all weather conditions.