Elbow Clearance to Ceiling?

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wjohn

Member
Jul 27, 2021
110
KS
I would like to use two 45 degree elbows right below my ceiling support box to gain some space in my corner installation (still well within clearance specs for the stove and pipe). I did a lot of searching, and this seems like a common thing to do. The sales guy where I bought my stove thought it would be no issue but the owner wasn't around, who I would trust to be much more knowledgeable about installations.

The question I was unable to answer in my seraching: Is the ceiling clearance dimension shown in my image not an issue? For example, the stove I am installing shows a 20" minimum clearance from pipe to ceiling if you were to run horizontally out the wall. This dimension would not meet 20" if I were to do this with the 45s right at the ceiling support box.

Screen Shot 2021-09-06 at 9.50.23 PM.png
 

MongoMongoson

Member
Feb 6, 2021
205
Wisconsin
Please let us know which stove you are installing. I would like to look at the manual.
 

wjohn

Member
Jul 27, 2021
110
KS
Specifically this is a Vermont Castings Aspen C3, but the question about the vertical clearance above the elbow is a general one that I think would apply to any stove.

Install manual: Link
 

wjohn

Member
Jul 27, 2021
110
KS
Are you using double wall black stove pipe? or single wall?

I used double wall insulated stovepipe and it said it needed only 8" from walls and ceiling
Single wall. The VC manual doesn't give any specs for vertical clearance to double wall, so I presume that means follow the double wall manufacturer's guidelines.
 
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MongoMongoson

Member
Feb 6, 2021
205
Wisconsin
In this case, it is not a general question because your manual specifies the clearance. In general, the acceptable clearance from single wall pipe to combustibles is 18".

I looked at your manual, and don't see anything to help answer your question. I thought maybe a second set of eyes could help.

You could always go with double-wall. It is a better product. Since I made the switch, I would not go back.
 

MongoMongoson

Member
Feb 6, 2021
205
Wisconsin
On second thought, the general rule probable does help you here. If you cut a stick 18" long, place one end perpendicular to the lower 45 elbow, anywhere, and can also touch a combustible surface with the other end of that stick... you are probably too close to the ceiling with a single wall 45 elbow.
 

kennyp2339

Minister of Fire
Feb 16, 2014
6,090
07462
DVL can be 6" to combustibles, if using single wall pipe and vented shield is needed, distance to a wall can be reduced to 6" and 9" respectively to the ceiling.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
26,053
central pa
On second thought, the general rule probable does help you here. If you cut a stick 18" long, place one end perpendicular to the lower 45 elbow, anywhere, and can also touch a combustible surface with the other end of that stick... you are probably too close to the ceiling with a single wall 45 elbow.
Not just perpendicular. If it is closer than 18 in any direction it is too close
 

wjohn

Member
Jul 27, 2021
110
KS
On second thought, the general rule probable does help you here. If you cut a stick 18" long, place one end perpendicular to the lower 45 elbow, anywhere, and can also touch a combustible surface with the other end of that stick... you are probably too close to the ceiling with a single wall 45 elbow.
That's my concern. However I see people doing the elbows right at the connector with single wall all the time (even on this site) and nobody ever mentions the vertical clearance, which is pretty obviously less than 18". That's why I was trying to figure out if I was missing something, or if lots of people are missing this.

I suppose the safe thing to do is either shield the sections that have less than 18" clearance to the ceiling, or drop a 6" or so piece of pipe between the bottom of the connector and then put the elbows on?

Here is what I would be looking at if I had installed as-is. I am under the trim flange coming vertically straight up from the elbow, but I am looking at 14" or thereabouts to combustibles right behind it.

20210907_094106.jpeg 20210907_094211.jpeg 20210907_094841.jpeg
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
26,053
central pa
That's my concern. However I see people doing the elbows right at the connector with single wall all the time (even on this site) and nobody ever mentions the vertical clearance, which is pretty obviously less than 18". That's why I was trying to figure out if I was missing something, or if lots of people are missing this.

I suppose the safe thing to do is either shield the sections that have less than 18" clearance to the ceiling, or drop a 6" or so piece of pipe between the bottom of the connector and then put the elbows on?

Here is what I would be looking at if I had installed as-is. I am under the trim flange coming vertically straight up from the elbow, but I am looking at 14" or thereabouts to combustibles right behind it.

View attachment 281700

View attachment 281701

View attachment 281702
You will need to should or go to double wall or drop the elbows down a little
 

begreen

Mooderator
Staff member
Nov 18, 2005
90,417
South Puget Sound, WA
You could try putting the offset down low, right off the stove. Our stove is set up that way. With 20' straight up flue, draft has not been an issue.
I second the suggestion for using double-wall stove pipe. It will draft better and is superior construction with its stainless inner liner.

45_flue_offest_web.jpg
 

Highbeam

Minister of Fire
Dec 28, 2006
19,300
Mt. Rainier Foothills, WA
Not just perpendicular. If it is closer than 18 in any direction it is too close

I'm trying to think this through and it can't be correct. Imagine a vertical single wall pipe going into a ceiling support box there is plenty of pipe within 18" of the ceiling when measured at an upward angle. I think it's supposed to be a perpendicular measurement.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
26,053
central pa
I'm trying to think this through and it can't be correct. Imagine a vertical single wall pipe going into a ceiling support box there is plenty of pipe within 18" of the ceiling when measured at an upward angle. I think it's supposed to be a perpendicular measurement.
Not if the support box is hanging down the proper amount
 

wjohn

Member
Jul 27, 2021
110
KS
You could try putting the offset down low, right off the stove. Our stove is set up that way. With 20' straight up flue, draft has not been an issue.
I second the suggestion for using double-wall stove pipe. It will draft better and is superior construction with its stainless inner liner.

View attachment 281703
I would do that, but my problem is that I want the offset inwards, so it would be over the top of the stove and severely limit being able to put a big pot of soup on it, for example. I also only have a floor to flue exit height of a bit over 14'.

I can always just go straight up and forget the elbows. I was just looking at ways to gain a little bit of space back in what is a pretty small house, since the Aspen C3 can be tucked in pretty close in the corner - closer than where my ceiling support will be.
 

wjohn

Member
Jul 27, 2021
110
KS
I'm trying to think this through and it can't be correct. Imagine a vertical single wall pipe going into a ceiling support box there is plenty of pipe within 18" of the ceiling when measured at an upward angle. I think it's supposed to be a perpendicular measurement.
Right. This is what I'm trying to wrap my head around. Would you be okay as long as you stayed directly under the main part of the ceiling support box (not the trim flange), for example?
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
26,053
central pa
I would do that, but my problem is that I want the offset inwards, so it would be over the top of the stove and severely limit being able to put a big pot of soup on it, for example. I also only have a floor to flue exit height of a bit over 14'.

I can always just go straight up and forget the elbows. I was just looking at ways to gain a little bit of space back in what is a pretty small house, since the Aspen C3 can be tucked in pretty close in the corner - closer than where my ceiling support will be.
So just run a short section of pipe above the elbows to move them down a bit
 

begreen

Mooderator
Staff member
Nov 18, 2005
90,417
South Puget Sound, WA
Bholler's suggestion makes sense. A 6" piece of stovepipe at the ceiling support connection would drop the corner of the elbow down to 20" away from the ceiling.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
26,053
central pa
Like 16”? That’s ridiculous. I think you have a misunderstanding.
No it doesn't have to be anywhere near that low. Since when does radiant heat only travel perfectly perpendicular to the surface?
 

wjohn

Member
Jul 27, 2021
110
KS
Bholler's suggestion makes sense. A 6" piece of stovepipe at the ceiling support connection would drop the corner of the elbow down to 20" away from the ceiling.
Right, I mentioned dropping at 6" piece in there earlier to get the clearance as one of my options. It's easy enough and addresses my install. But the single wall installs I have seen without a 6" straight piece here - they're all wrong?

I can't find any documentation clearly stating one way or the other. To me I do not have the 18" clearance to the ceiling (and Bholler's statements agree). Not that it's okay to do the elbows at the support box just because lots of people have done it - but I was wondering if I was missing anything. So far it sounds like it's not kosher.

I suppose you may not be throwing off as much heat towards the ceiling at the corner of an elbow in what is mostly a vertical run as you would be on a horizontal run but otherwise I can't think of any other significant difference.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
26,053
central pa
Right, I mentioned dropping at 6" piece in there earlier to get the clearance as one of my options. It's easy enough and addresses my install. But the single wall installs I have seen without a 6" straight piece here - they're all wrong?

I can't find any documentation clearly stating one way or the other. To me I do not have the 18" clearance to the ceiling (and Bholler's statements agree). Not that it's okay to do the elbows at the support box just because lots of people have done it - but I was wondering if I was missing anything. So far it sounds like it's not kosher.

I suppose you may not be throwing off as much heat towards the ceiling at the corner of an elbow in what is mostly a vertical run as you would be on a horizontal run but otherwise I can't think of any other significant difference.
Many of those installs may be with double wall pipe. Which in your case with 14' ceilings I would absolutely recommend.
 

Highbeam

Minister of Fire
Dec 28, 2006
19,300
Mt. Rainier Foothills, WA
No it doesn't have to be anywhere near that low. Since when does radiant heat only travel perfectly perpendicular to the surface?

Radiant heat travels in all directions of course but that is irrelevant. I'm trying to imagine how anybody could ever install a vertical single wall pipe to a ceiling support box and still comply with your "in any direction" interpretation. The single wall snaps directly into the box. 18" to "the first combustible surface" would mean that the box would have to hang nearly 18" below the ceiling which is ridiculous.

Just trying to make sense out of your interpretation. A little sniff test.
 

Highbeam

Minister of Fire
Dec 28, 2006
19,300
Mt. Rainier Foothills, WA
Bholler's suggestion makes sense. A 6" piece of stovepipe at the ceiling support connection would drop the corner of the elbow down to 20" away from the ceiling.
I'm concerned about the connection point to the ceiling support box. That point is just as hot.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
26,053
central pa
I'm concerned about the connection point to the ceiling support box. That point is just as hot.
Have you ever measured diagonally from a single wall pipe on a proper install? The box itself acts as a shield. And when we are talking about protecting from radiant heat how is the fact that it travels in all directions irrelevant?