Tight clearance help with Englander 28-3500

[Badfish740]

Ok folks, I'm pretty close to installing a 28-2500 in my basement to mostly replace my oil heat. The problem is the overhead clearance for the chimney pipe exiting to the outside. With the horizontal run of pipe passing through a thimble installed an old window opening (the most convenient way for a few reasons) the top of the horizontal pipe will end up within 8" of the floor joists-the only combustible surface. My solution is to run Class A all the way into the house and to use a tee to make the 90 degree turn down to the outlet of the stove as seen in the crude diagram attached. The pipe coming out of the stove will be as follows:

Stove to Class A adapter - Is there such a thing? Can I modify a stovepipe to Class A adapter in order to make it work?

Vertical 18" section of Class A

Class A Tee

Horizontal 36" section of Class A

Class A Tee

8 Vertical 36" sections (24 feet) of Class A

Will it be detrimental to have a tee rather than a 90 just 18" above the outlet of the stove? Is it detrimental to have two tees in a chimney system altogether? Would I be able to remedy the problem by increasing the chimney height to 27 feet?

 

[stee6043]

I installed Supervent (Selkirk) and yes, there is a Class A to stove pipe adapter. I ultimately did what you're looking at but instead of the Tee I used a 15 degree elbow after I passed through the wall, two sections of Class A, a Class A to stove pipe adapter and then a standard stovepipe 90 to make my connections at my unit...

I think it would be better for your draft to angle out of the house rather than use the T directly above the furnace. How long is your horizontal run? I think the general rule is to have at least 1" rise for every 12" of run. I believe Selkirk recommends you not exceed 24" of horizontal pipe when you pass through a wall...

 

[mattinpa]

Obviously, check with code first. But to answer your questions, (personal experience not suggestions) I would
first say do a draft test. Light a match or paper torch at the end of your pipe run and see how it draws. I have
2 angles in my setup, and it draws incredibly good. I used 90's instead of tee's, but can't see how it would be
any different. Also, with being so close to your floor, why not make your combustable into a noncombustable by
screwing up a thin concrete board or fireproof material? Just my .02

 

[M1sterM]

I concur with a couple of the other suggestions, so here's my summarized recommendations/answer.

1. Use an adjustable 90 elbow that is set at 45 degrees out the top of the furnace (this is what I did, I don't have a picture to post, but if you need it, let me know and I'll try to get one).

2. Install another 90 elbow that is set at 45 degree at the wall thimble (which should incorporate the Class A to single-wall adapter that is standard with the kit. It doesn't need to be right at the thimble, but can go very near the furnace while using Class A as the "connector" to the outside chimney, but see my note/caution, below).

3. Cut to length the single wall connector that will be installed at a 45 degree between the 2 elbows.

4. Install a barrier/shield above the thimble where the 18 inch clearance can't be met, but ensure that you use spacers between the floor joists and the shield. You could even get/fabricate an additional shield that attaches to the single wall pipe for additional peace of mind.

Notes: You are only supposed to have a 2-foot max piece of Class-A penetrating vertically through the wall thimble into the house (read the Supervent install instructions). Your proposed install raises a concern to me because of that.

Also, I like having a bit of single wall coming right out of the furnace in case of a power outage to allow some of the heat to dump out into the room.


Hope this helps, and post a pic when you're all done. I love my ESW Add-on, and I'm sure you will too! As I write this, our low last night was somewhere around -5 F, and we were staying at 67+ in the house running the Add-on as a stand alone unit!

 

[Badfish740]

I never really thought of shielding the floor joists-but here is the dilemma. It's my understanding that one must have an air gap with no "conductors" in between such as fasteners like screws or nails connecting the shield to the combustible surface. So while it's no problem to slap up a sheet of concrete board or hardi-board, how do you do that without exposing the fasteners to heat? I suppose I could screw metal studs perpendicular across the floor joists and then glue the hardi-board to the studs using a high strength construction adhesive. If I did that how close could I run the single wall pipe?

 

[M1sterM]

I never really thought of shielding the floor joists-but here is the dilemma. It's my understanding that one must have an air gap with no "conductors" in between such as fasteners like screws or nails connecting the shield to the combustible surface. So while it's no problem to slap up a sheet of concrete board or hardi-board, how do you do that without exposing the fasteners to heat? I suppose I could screw metal studs perpendicular across the floor joists and then glue the hardi-board to the studs using a high strength construction adhesive. If I did that how close could I run the single wall pipe?

Well, that (gluing to metal studs) doesn't really solve the problem too much, unless you're considering the adhesive to be sufficient to thermally isolate the board and the metal studs (which I wouldn't). However, I'm 95% sure that I saw a reference somewhere to not worry about the fasteners themselves causing thermal bridging, as long as the spacers themselves are non-combustible. You could stack small squares of cement board, or use electric fence insulators, or some type of ceramic spacers. Hopefully someone else can chime in with a reference about the fasteners.