What are the proper chimney hight deductions for horizontal runs of pipe?

[MountainStoveGuy]

Well the subject line tells all. Trying to help a member with his chimney set up, it looks like there is about a 3' run. I dont remember the deduction for that run. Also, in wood venting, the first 90* in the system doenst count against you, the second counts as 5' of deduction. Does the reversed flue collar count as the free one? or is the T going up the chimney count as the first one? The point im getting at, lets say you have a 15 foot chimney. If you take 1 foot off per foot of horizontal run, that would equal a 12 foot chimney, then the second 90* (if it applies in this situation) would deduct 5 more. So now your 15' chimney acts like a 7' chimney. So the unknown in my book is the penalty for the horizontal run assuming that you have a 1/4" of rise per foot.

 

[BrotherBart]

Ok guy. Ya asked for it. Go here to find out more than you wanted to know and also that that 90 degree six inch elbow is equivilant to 11 feet, not 10.

(broken link removed to http://tinyurl.com/ekjek)

 

[webbie]

MSG, I don't think any of these are hard and fast rules, rather a way to point out the possible effect of too many turns or too short of a chimney. If these numbers were correct, I'd have seen a LOT of chimneys that are negative!

As far as the reversing flue collar, I would not count it. Every stove is different inside and we'd have to start with counting the baffle as one!

A stove venting out the rear into a tee which is the bottom of the class A chimney would only have one deduction in my opinion. I never did use any of these calcs in the real world....except to inform customers why their stoves may not have been working correctly.

 

[MountainStoveGuy]

guidlines are all im after. Yes, i have calculated more then a few chimneys to be negative after the deductions, and typically they dont work well with that math adds up. have you looked at JBinKC's photo thread? I think the real culprit might be the level or less then level horizontal run. I think he has a 15 foot chimney, with the one elbow deduction you have ~10' chimney. the stove he has draft sensitive, and if there is no rise on that pipe then there isnt a chance in he!! of it working properly. If you use the deduction as a guildline, he still doenst have enough even with a good slope on the chimney.

 

[elkimmeg]

MSG Now you know why I wiki a primer prior to a stove purchase. IT's situations like this we should add to the wiki. Not every location or chimney can support a stove. You are right there is a certaint deduction to horrizontal run I never posted it here because feeding more code restrictions is not well recieved There is also the 180 degree in bends limit. All manufactures try to discourage elbows and bends and place a short length to the connector pipes. The 1/4" per foot rise is min more the better much better. The rerar mount tee is not considered a bend and there is language the first bend is not factored. This is also true. A stove faced with an imediate 90 degree bend is worst then running straight then into a bend. it has a chance to gain momentum and power threw a bend up higher than at fuel collar exit. All this and we have many trying to opperate at less the min verticle length and height.. I has got to wonder how any of these steups passed inspections. And what about the installer being paid to install a stove non compliant?
That installer should be held accountable to know, min verticle height does not exist. He should never install a stove if it can not be code compliant. How do these stoves get installed? How do they pass inspections? Are you telling me people are being paid to install non permitted non compliant stoves? Where is the inspectors when you need them? Oh that's right we are doing it illegally so he is not susposed to know? Well I did not know a permit was required? what about the first page on every manual informing you it is I guess you must have3 skipped over that section.. I do my best to help you here, But I can't help ones that do not want help

If you continue allowing unlicenced un supervised installers to continue installing non compliant installations It is hard for use inspectors to help you Had you talked to me prior to you install you would not be in this position