Never had a wood stove. Don’t know their limits. Question is: how horizontal can the stove pipe go before it turns vertical? Or even not purely horizontal…slope up is ok. I’ve seen one that’s set 2′ outside of a fireplace where the pipe then runs through the chimney flue, so I’m guessing 2′ is doable. Is 4′? 6′? What are the limits? Would a pipe sloped to 45 degrees work as well as one vertical? How about up, over, and then up again? What governs what works and what doesn’t?
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I know the number of ELs reduces draft drastically.
Thats my 2cents.
I'll bet it took me four minutes longer to type mine than it did you yours...;)
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LOL
My benefit of being unedumacated...been burning wood for 30 yrs. and thats about all I know (G).
There are a lot of variables, like how many elbows and how sharp a turn do they make. Each typical 90° reduces the draft by about 15%.
The horizontal run works as a percentage of the total vertical lift and related 5o the size of the flue.
It can get pretty complicated There are old churches and Grange halls with 20' of horizontal run that worked fine for decades because they burned hot and had a lot of vertical lift. There are stove insert runs of two feet and only 14' lift that clog up yearly and smoke in every low pressure system...
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Where does one find answers on how that works? For example, we could angle this so there'd be just one 75 or 80 degree angle, plus the 10 or 15 degree off horizontal run would be well insulated so the smoke wouldn't cool much on the run. But it's an area in which I don't have much experience, and don't know all the factors that affect it.
One idea would be compareing it to dust collection systems used in shops.
Onieda Air Systems is one that comes to mind, they calc. duct length and els and static pressure drops and cfm and stuff.
Maybe?
But it's an area in which I don't have much experience, and don't know all the factors that affect it.
IIRC, NFPA 211 deals with all things related to solid fuel. It is all fire protection related, but a lot of prevention is making sure things flow properly and the "rules" are outlined in it.
While a chimney with great draft will work fine with a long horizontal run attached to it today, tomorrow it may not from the overnight creosote build up.
All chimneys do not draft equally, so what works in one house may not work in the other, even though all the rules were followed. Wood stoves vary greatly as well.
I can't remember all the rules, but the bottom line is to keep the horizontal runs as short as possible and as few elbows as possible. Four feet is a long horizontal run for an "airtight" stove, but I believe permissable. You're on the right track sloping the near horizontal runs as much as possible and keeping them as warm as possible. If possible, use "tees" rather than elbows when going from horizontal to verticle. That way, when creosote drops from the verticle runs, it can fall into the resovoir created by the 3rd leg of the tee (capped of course) instead of blocking the elbow.
If you have a fairly long horizontal run, it might be worth using double wall black pipe (it's primary use is reducing clearance to combustables) to keep the exhaust warmer as you indicated.
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There are pros and cons on the Ts.
They make it easier to clean, but they slow air flow inside, so increase the need for cleaning.
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Twenty some years ago, I had a source....I think from Duravent or one of the metal flue suppliers
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There are old churches and Grange halls with 20' of horizontal run that worked fine for decades because they burned hot and had a lot of vertical lift.
I remodeled an old church that was built in 1880 - the main hall was approx 30' X 75', 12' high ceilings. They had a wood burning stoves at each end of the main room, the flue went strait up out of the stove, at about 8' high it elbowed off at 90° and ran horizontal for about 25' to 30' where it went into a chimney.
I'm betting that even with that heating system one of our good ole fashioned 20° below zero February mornings there was still enough chill to keep one attentive to the sermon, regardless of the message!
Doug
Edited 7/26/2007 10:51 pm ET by DougU
I went to kindergarten in a one room schoolhouse where part of every students duty was to carry in some coal. The older kids had to rattle the grate around in the burner and feed the monster.I remember some mornings where it was necesary to keep your heavy clothes on for a while
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I remember some mornings where it was necesary to keep your heavy clothes on for a while
The cool air keeps the mind awake and alert! Helped you be a better student. Hell those kids over at those fancy schools with their furnaces were probably half asleep when they needed to be paying attention!
Doug
What governs what works and what doesn't?
draw -
there's a cookstove in my kitchen where the exhaust path goes over, down, under, back, and finally up - if your chimney has the draw, you can send the exhaust thru the basement (not recommended)
draw is a factor of heated air being lighter and rising (think hot air balloon) -- the taller the chimney, the greater the draw, everything else being equal - the tighter the seal of the pipe, the better the draw -
what kind of chimney are you dealing with?
cold (outside) masonry chimneys are poorly suited for occasional woodstove use -
interior masonry chimneys are better, but still work better if in continous use -
SS insulated chimneys warm very quickly (don't condense or precipitate creosote), draw well, and clean easily - my choice -
horizontal runs are mainly an issue with establishing draft - the cookstove I referenced earlier has a 'flapper door' that allows you to bypass the oven so to allow starting the fire and establishing the draw before asking the exhaust to go 'over and down and under' -
if you have a good drawing chimney, you can put the stove about anywhere and pipe the exhaust -
Here's a good piece from TEMCO.
http://www.hearth.com/econtent/index.php/articles/chimneys_an_unexact_science/
Check the manufacturers website. These days they all have downloadable PDF files that give you the specs on this stuff and it's different for every stove. the old Ashley Trash burners we heated the first architectural office I worked in back in 76 had one of those and you could stuff it full of blueprints, wet brush and old sneakers and it would draw up down and out. With the Jotul Castines we install today that would be a definite no-no.
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I think when you look at the owners manual for fireplaces and stoves it tells you how to run the pipe.
Martin
Another thing to think about is how difficult it is to clean. It's nice to have a straight shot up through the roof from an elbow. That way you can detach the elbow and get a straight shot to the roof. The horizonal section over to the stove would be short and easier.
That's how my last stove was set up although I never had it cleaned. I burn hot fires so I've never had a problem.
If you do have to clean it a lot of elbows would be a pain.