Horizontal run on a stove pipe

[BillD]

I am installing a Quad 5700 in a finished basement and I want to use the existing chimney in the house. It's approx a 35 foot chimney, 12" diameter, interior, and masonry -- an unused flue that I guess used to vent an old coal burner. It is in good condition and has great draft in the winter. My problem is that the stovepipe has to pass through a small furnace room to get to the chimney. It has to cross a distance of about 10 feet horizontally with a 2 foot rise. To preserve heat, I am using Class A for this run. The other 'uh-oh' is that it's not a straight shot -- I have to cut diagonally across the furnace room, which means I need to put in a bend after coming through the near wall and a second bend to get into the chimney.

I have called Quadrafire and they thought it would be OK as long as the horizontal was less than 1/3 of the chimney's vertical. However, it was not specifically addressed in the manual.

Is this likely to work? Can Class A be used for a horizontal run, or just for a vertical chimney? Duratech describes certain minimum slopes on their website -- but that seems to be for chimney applications.

Any help is greatly appreciated. I did search the Q&A but couldn't find this as being previously addressed.

bill

 

[MountainStoveGuy]

Quadra fire didnt have a problem with you hooking up to a existing masonry chimney? As far as i know that unit is only listed for sl300 or duraplus chimney. 10 foot horizontal will never spell good draft, expecially if your going to dump it into a 12x12 clay chimney. Bad idea in my opinion. also, you will only find 30* and 15* elbows in class a. i dont have my charts here at home but that would be a hell of a rise for a 10 foot run.

 

[begreen]

Seems like double-wall would suffice and be more manageable as long as clearance to combustibles is honored and the pipe is well supported. But I'll wait for the pros and inspector to weigh in for the final judgement.

 

[MountainStoveGuy]

you cant get a 2 foot rise with 10 foot horizontal with a 30*'s or a 15* elbow. Class a doenst come in 45*'s and 90*'s The double wall would be plenty safe, but i think you will be on here this winter asking why your 7100 smokes up the house.

 

[BillD]

The 30' elbow wouldn't be pointing up -- it would be pointing to the side (and a little up) as I have to cut diagonally across the room. It's a narrow furnace room I'm crossing -- and I have to get almost diagonally from one corner across to the other.

I know you can't put two elbows together on a chimney (ie to make a 45' to get around a rafter or something) but can I do that if I need a tighter turn go get across the room? I might need a 60' coming into the room, and a 60' to get into the chimney --

According to the manual the 5700 is OK into a masonry chimney. And the flue may be 12 x 8 -- I have to double check that.

bill

 

[MountainStoveGuy]

Bill, correct on the 5700, i read that as a 7100. my bad. I will let others comment on the chimney. My opinion still stays the same. It might be possible to do that, but i dont think you would have very good draft, and it would be a pain to clean.

 

[BrotherBart]

Changed my mind. Doing a little calculating.

 

[MountainStoveGuy]

I would be courious what your local installer/dealer told you. Dont forget that basements are typically under negative pressure. This wont help. No mattter how close you follow the rules, basements are somewhat harder to get good established draft in. If possible, i would keep your pipe as strait as possible, and with as few elbows as possible. Now, alot of my advice on here comes from a high altitude perspective. Your install would not even be considered here. So i tend to be a little conservative.

 

[BillD]

The dealer initially thought I would have to go up 2 feet for every foot over (up at a 60'angle on the 'horizontal' run) but then realized he didn't account for the vertical of the chimney. He's thinking it will be touch and go. The installer thinks it should work. He thought the interior chimney being warm already was worth the traverse to get to it. He says if more draft is needed, could always add a liner to the chimney.

I will be ducting in the combustion air from outside.

 

[MountainStoveGuy]

one more warning, with that outside air kit, its possible to get reverse draw. Here is the scenario, you chimney is cold, you light a fire. The flue has lots of restriction anyway with the long horizontal and elbows. A little wind comes up and reverses the draw. The heat and smoke will take the path of least resistance. I would recommend a passive system, like the condar asv-90. (broken link removed to http://www.condar.com/asv.html) What your trying to accomplish is equalizing the pressure in the basement best you can. This is not a combustion air issue, its a pressure issue. You house is basicly a big chimney, the attic is positive, the mail level in neutral, and the basement is negative. Thats due to the natural draft of a house. You want to get that netrual line as low in the house as possible.

 

[elkimmeg]

according to your manual in has to default to NFPA211 or the vent manufacture's listing or both
Neither code or manualy list a section where I think it will work section? Here is a direct paste from your manual

CHIMNEY CONNECTOR IS TO BE USED ONLY WITHIN THE ROOM, BETWEEN THE STOVE AND CEILING OR
WALL. THE CONNECCONCEALED SPACE,
I see no mention where it is permissable to pass threw the boiler room. Infact one could deduce it is not permitted to do so.
I see no mention of elevating the pitch of the connector in code or manufactures specs. I would assume, it is in the section,
I think it will work.




For optimal performance, masonry chimneys used to vent this
appliance should be lined with a 6" (152mm) stainless steel
liner. Installations into a clay flue without a stainless steel liner
may reduce draw which affects performance, cause the glass
to darken and produce excessive creosote.

Unfortunately Qudrafire has not read the NFPA 2003 edition of the code concerning cross-sectional flue requirements.
If The liner is 12/ 12 a HT2100 liner is required Per code. If it is 12/8 and is exposed to the outside, then again a full liner is required to satisfy code


It is best to have the chimney inspected by a
professional, and be sure to have the chimney cleaned before

Again this is required by code not an option. My post here is not to discourage one, but in order for a stove to function saftely,it must be installed correctly. Marginal I think it is ok, non tested approaches, is not the way to go. Why waste your money on a stove, that at best might preform marginally? and is questional code compliant installation.

 

[MountainStoveGuy]

elk, i think he was talking about passing class A through the boiler room, not connector. I agree with the cross sectional area, if i had all that strangeness going on inthe boiler room, i would definalty line the chimney.

 

[MountainStoveGuy]

ohh and ofcourse that exposed class A should be chased into somthing so people cant hit it.

 

[BillD]

StoveGuy -- I checked out the link for the passive venting system (thanks). I'm not sure this house would need one -- it was built in 1920 and it is not well sealed at all. However I am certainly not an expert. I was venting from the outside just for efficiency. I see your point about the risk of backdraft.

I just ran home over lunch and measured the chimney -- it is approx 11" x 6.5" or 7". This appears to be within the guidelines of the manual ["The flue should be checked to determine that it is not too large for the stove. NFPA 211 allows the cross-sectional area of the flue to be no more than 3 times the crosssectional area of the flue collar of the stove (28 x 3 = 84 square inches)."] if I am measuring correctly. They do recommend a liner for chimneys greater than 6" and I may need one. However like I said before this is an interior chimney so it is warm.

It seems that this is something that there might be an equation for, like I should be able to tell before it is set up whether or not it will work, or at what temperatures outside it will work for. I am in northern Minnesota so the winter air is cold and sea-level dense.

Elk, I appreciate your input as well. I agree with you completely that the installation should be done properly and by code. I don't want my family to be at risk because of careless work. (Why I hired an installer.)

 

[MountainStoveGuy]

Its more to equalize the atmospheric pressure near the stove, so the flue doesnt become the supply air for the basement. As far as outside air kits are concerned. I usually dont recommend them unless your in a mobile home, and only then because its federal law. They can be dangerous, expecially in a basement install. Im shure others will comment on this. No matter how leaky your house is, the basement still has less pressure then the attic, which makes a enviroment for downdrafts. Listen to the local proffesional that is in your home and can see exactly what he is doing. And above all, get 2 more opinons from local installers. A perfectly legal install which is safe, doenst mean that it will draft. Let us know how it goes.

 

[webbie]

Is this likely to work? Can Class A be used for a horizontal run, or just for a vertical chimney? Duratech describes certain minimum slopes on their website -- but that seems to be for chimney applications.

Any help is greatly appreciated. I did search the Q&A but couldn't find this as being previously addressed.

bill

If original chimney was lined it would greatly help- in fact, it must be lined to meet cross-sectional code. Horizontal connector should probably be packed (not air cooled) class A. Rise may not be that important as long as you slope it as much as possible. May not require chase in boiler room type situation.

Should be set up for easy cleaning of both horizontal and vertical chimneys....without taking any of the liner or class A out.

Those are my first thoughts and reflect what some others have mentioned.

 

[elkimmeg]

bill what is the total distance of the horrizontal run and how many bends. It is true the more pitch the better chance to draft

With that length run, as Craig said double wall to the class A insulated filled. and get a couple of oppinions

Bill I was not trying to be negative but to make you think out your situation. You will be spending a good chunk of money.

 

[BillD]

Elk, I will come off of the stove vertically with double wall stovepipe 1 foot length, then a 90 bend and a 1 foot horizontal (actually a slight incline) into the cinderblock wall (that is framed for a wall on the stove side of the room, so there is a thimble). Class A picks up where it passes into the wall -- which is about about a foot thick -- then I come off of that with what will probably be a 60 bend to the left (and slightly up for the incline), run 10 or 11 feet straight to another 60* bend that goes into the chimney on the far wall of the room.

I have to talk to the installer about how he proposes to make this accessible for cleaning. I think he had considered a T for a cleanout but felt that avoiding the 90* of that would provide better draft.

bill

 

[Shane]

A horizontal turn? I'll be amazed if this works. With the draft provided by a 35' chimney it might work. I have to say honestly though from what you're explaining, I would not take your job, too much risk that it won't work.

 

[BillD]

Is there a way to calculate an answer, or does this have to be a 'try and see'? Seems the output of the stove should be a known value, perhaps based on the temperature of the burn, and the chimney draft should be something that can be fairly closely estimated (with wind effect probably hard to account for). I saw a reference somewhere that the horizontal should not exceed 1/3 of the chimney height, and that every 90* bend reduces effective chimney height by 5 feet -- so some of this stuff has been quantified. The only other variable is the outdoor temp (affecting air density), and I imagine the colder it is outside the stronger the draft from a heated chimney (?).

Also, in a horizontal run, do the turns make a big difference above and beyond the total length of the horizontal? Isn't all the pull coming from the vertical of the chimney, and offset by the "resistance" of moving a large horizontal tube of air?

 

[MountainStoveGuy]

a simple rule, 90* worth of elbows cost you 5 feet of verticle chimney. example: a 10 foot chimney with 2 90*'s is like having no chimney at all. [in theroy]

 

[Shane]

A horizontal elbow is bad news though. How many inches of water column do you have on the existing chimney? I don't mean to sound critical but that is alot of 90 bends on top of a horizontal 60 degree left turn (if I'm reading your post correctly) that's going to cause all sorts of resistance. I would speculate that a horizontal turn like that would take around 10' of height off of your chimney.

 

[BillD]

I wish I could draw a picture. Right now I don't have any horizontal 90's. It comes up off of the stove and turns into a wall, passing through it. Lets say that points North. It then takes a horizontal 60* bend to the northwest; there is an incline along this run. When it reaches the chimney, there is another 60* bend to make the pipe point north again and that goes direct into the chimney.

 

[BillD]

Shane -- I calculate the draft on my chimney based on 500 degree exhaust temp to be .234 inches -- but I don't have a tool to measure it.

bill

 

[MountainStoveGuy]

Dont you need somewhere in the neighborhood of .08? this is posed as a question because i dont dont draft readings to often.