Ceiling support box clearance

[strategy400]

So I'm installing my chimney. I've got the duravent 6 inch round ceiling support box. My plan is to insert 6 inch single wall slip connector into this support box. What's bugging me is how can I insert single wall into this support box where there is ~3 inches to combustibles and the single wall pipe calls for 18 inches. And I'm pretty sure a lot of people use this configuration. It defies logic. Has anyone used this and shot a temperature of your ceiling?

 

[Highbeam]

That 18” is measured horizontally. The closest thing horizontally from the single wall pipe is the side wall. Hope your ceiling box is not too close to the wall.

The stub that hangs down is Class A so only needs 2” clearance which is provided by the ceiling support box.

 

[begreen]

It looks like the adjacent wall may be closer than 18". I would use double-wall stove pipe. It's better quality and will keep the flue gases hotter heading up to the chimney cap.

PS: In this case the clearance to single-wall is measured horizontally, but it is measured vertically in the case of a horizontal run of stove pipe.

 

[strategy400]

Thanks for the replies. OK that has to be the case. The picture is an example of the pieces I'm using. Mine is a corner install and the manufacturer calls for 18 inches from the wall (duravent black). Mine will be 20 inches from each wall. Its just the ceiling that seemed weird to me. If it gets too toasty I'll swap in some double wall later.

 

[Highbeam]

Thanks for the replies. OK that has to be the case. The picture is an example of the pieces I'm using. Mine is a corner install and the manufacturer calls for 18 inches from the wall (duravent black). Mine will be 20 inches from each wall. Its just the ceiling that seemed weird to me. If it gets too toasty I'll swap in some double wall later.

I’ll be curious how you do that upgrade. The first duravent starter piece of single wall snaps into that ceiling box. I don’t know how to get it out to put in double wall stuff. You’ll see what I mean when you install it if you haven’t.

I have a single wall system in the shop with 10’ of single wall and I lose 200 degrees of skin temperature ( approximately 400 internal loss) over that 10’ which makes flue temps quite low and prone to creosote if I don’t keep the stove hot.

 

[strategy400]

There will be 5 feet of single wall between stove and ceiling then 12 feet of class A double wall above that through the attic and out the roof. 5 feet attic 7 feet outside. Hopefully 5 feet of single wall won't cool it too much.