Stainless steel flex inside SS class A chimney?

[SlimTidy]

This is my first post here so thanks in advance for any help. I purchased a used Lopi 400 and am installing it where a wood stove used to be. I was told by a reputable dealer to run 3" SS flex through my existing almost brand new 6" class a chimney. I used an adapter at the cathedral ceiling box that hooks but doesn't seal to the box and it has a collar that is 3" that the flex pipe clamps to.
I realize now after this is all installed that there would have been a better way to do this and that would have been to get a 3-6" adapter that actually seals into the existing 6" and leave everything be from there up.
I don't want to uninstall now and spend the money on this new adapter. Am I being unreasonable?
The possible issues that I see are that I need to join the 3" liner to the 6" chimney at the roof to prevent weather and smoke from entering as well as sealing this ceiling adapter as good measure.
I was hoping to rig some of this up to run for the season and then next year pull the liner and buy the correct ceiling adapter.
Does this sound safe?

Appliance exhaust is 3"
From the appliance to the ceiling box I have the recommended duravent twist lock piping. It's a little over 7' from the stove exhaust to the box.
The 6" SS class a pipe runs for about 8-9' above the ceiling box.
Thanks again!

 

[alternativeheat]

This is my first post here so thanks in advance for any help. I purchased a used Lopi 400 and am installing it where a wood stove used to be. I was told by a reputable dealer to run 3" SS flex through my existing almost brand new 6" class a chimney. I used an adapter at the cathedral ceiling box that hooks but doesn't seal to the box and it has a collar that is 3" that the flex pipe clamps to.
I realize now after this is all installed that there would have been a better way to do this and that would have been to get a 3-6" adapter that actually seals into the existing 6" and leave everything be from there up.
I don't want to uninstall now and spend the money on this new adapter. Am I being unreasonable?
The possible issues that I see are that I need to join the 3" liner to the 6" chimney at the roof to prevent weather and smoke from entering as well as sealing this ceiling adapter as good measure.
I was hoping to rig some of this up to run for the season and then next year pull the liner and buy the correct ceiling adapter.
Does this sound safe?

Appliance exhaust is 3"
From the appliance to the ceiling box I have the recommended duravent twist lock piping. It's a little over 7' from the stove exhaust to the box.
The 6" SS class a pipe runs for about 8-9' above the ceiling box.
Thanks again!

View attachment 144223

Well first you probably should get the proper adapter , it just makes sense in terms of safety and not leaking.. But I don't know that the rig that you are describing is either unsafe or will leak for sure.

Many stoves can run in 6" pipe after a short run of 3" or even 4" pellet vent, the pipe you have is safe. Anyway if you ran another liner it would be 4" not 3" as your evl would probably require that. The only restriction here, in what you want to do is if the install instructions say not to run the venting into larger than X size. We have a lot of folks here running stoves in an old stainless and approved for wood, wood stove 6" stainless vent with no issues. Some questions can arise when dumping into large clay mason vents over 6 inches and against a particular makers diagrams but 6" stainless usually works out fine. I would do it personally and see how it runs.. And too you already have 7' of 3" pellet vent that should establish good drafting /pressures for your stove. However, that said and back to this adapter, I think you will find the vast majority here using the correcting attaching fixtures. With pellet stoves-- if it can leak it will and if it leaks you will smell smoke in the house. If you have a solid connection that won't break loose on you, is approved for pellet burning etc then you still need to get it sealed , probably with good healthy amounts of red RTV or venting high heat tape. I'm not recommending that just saying if you continue you need it sealed up.

 

[Harvey Schneider]

One issue with adapting to the larger vent is that it is not easy to clean from the bottom. A brush that reasonably passes through the 3 or 4 inch section will not clean the walls of the larger section.
I have a 4" stainless flex running through a much larger stainless fireplace flue. The installer capped the fireplace flue with a flat plate and a proper termination for the 4". To prevent leaks and drafts the bottom of the large flue was packed with mineral wool.

 

[SlimTidy]

I agree that the right adapter is the right way to go. I am just confused by some saying to run this flex and some not. I would absolutely say now that I read about it that it is not ideal.
I see in the manual that it looks like you only need to step up to 4" pipe on vertical runs exceeding 15'. I am really close to that but possibly under so I will have to measure. If I am under the 15' I will probably let it go for the season and then get the adapter next year. I will also seal both terminations thoroughly and attach my old rain cap again. So far it doesn't necessarily sound like it would be unsafe but certainly not ideal.
Now to measuring.

 

[alternativeheat]

I agree that the right adapter is the right way to go. I am just confused by some saying to run this flex and some not. I would absolutely say now that I read about it that it is not ideal.
I see in the manual that it looks like you only need to step up to 4" pipe on vertical runs exceeding 15'. I am really close to that but possibly under so I will have to measure. If I am under the 15' I will probably let it go for the season and then get the adapter next year. I will also seal both terminations thoroughly and attach my old rain cap again. So far it doesn't necessarily sound like it would be unsafe but certainly not ideal.
Now to measuring.

Measure and get back to us, not that we are nosy or anything ! NO not us !!

 

[SlimTidy]

Okay I'm back from the roof! I have almost literally exactly the 15' from the top of the appliance outlet to the top of the stack on the roof. I would say with a tolerance of 10-12". Now I get that if I were off by 12" the wrong way that I would technically be out of tolerance but I am not sure if that would be enough to make this necessarily unsafe for the season.
I attached some pics of what I have temporally rigged at the top to keep most smoke and weather out but this will need to be redone of course.
Now if I button that up, cut that 3" flex flush and install the rain cap back on I am worried I may have another problem. I am only getting about 2" clearance from where I would cut that flex flush up to the underside of the rain cap. That clearance is obviously fine for a wood stove because the exhaust isn't necessarily forced, though I understand in theory it is in fact forced by the draft. However I can feel the force from the pellet stove exhaust up there and it feels pretty powerful, I guess because it is being mechanically pushed. I never had the need to feel the force when the wood stove was there but I feel like it would have been less.
I couldn't find anything in the owners manual that I found online for the stove. I don't see anything specific to the rain cap clearances other than it having to be located 24" above the lower slope of the roof which I have. My concern obviously is the blowback of that exhaust forced back down toward the 3" liner and the 6" chimney. I am worried about both smoke which could easily be solved by thoroughly sealing all joints but also and most importantly because of the danger, cost and the fact that I wouldn't see or smell it happening and that is what if that clearance being too small would be putting too much resistance on my exhaust blower??
Maybe I am over thinking this, it's not like it will be blocked but I am just not sure if 2" is enough....that's what she said. Have to stay focused here!
Here is the manual
http://www.lopistoves.com/TravisDocs/93508046.pdf
And I attached some more pics as well.
Thanks again!

 

[SlimTidy]

I also just realized that my home made cap that I have to redo anyhow may have some clearance left in it that I could steal. I only need that cap to have 2" or so down over so I can seal it so I could cut that collar down some. I can't remember if I was able to push it all the way down flush or not, probably not because I had to make a relief cut to even get it to slide over. This may solve everything.
Back to the roof!

 

[SlimTidy]

I was right. If I cut the collar of that cap down to 1" I then gain one and will have 3" from the top of the liner to the bottom of the rain cap.

 

[alternativeheat]

Ok so you already have the 3" liner installed and you are at 15 ft total which is fine per install instructions. You didn't mention before you had it in already or I didn't catch it.. So what is this issue with the hook up inside the house ? You have it running, a CO detector will pick up anything remotely deadly and smoke you can smell that before a smoke detector will go off. You should have one Smoke/Co combo detector within about 15 ft of the stove anyway.

 

[SlimTidy]

I guess my main concern now is the clearance from the top of the flue to the bottom of the rain cap. Is the 3" I can get enough or will that put too much back pressure on my exhaust blower? I can't find any specs but the rain caps I see are about 5" of clearance. I would only be taking an inch away from the clearance that was there when the woodstove was installed but that didn't have a forced exhaust either. Other than that I think I feel pretty comfortable with the setup.

 

[alternativeheat]

I guess my main concern now is the clearance from the top of the flue to the bottom of the rain cap. Is the 3" I can get enough or will that put too much back pressure on my exhaust blower? I can't find any specs but the rain caps I see are about 5" of clearance. I would only be taking an inch away from the clearance that was there when the woodstove was installed but that didn't have a forced exhaust either. Other than that I think I feel pretty comfortable with the setup.

I don't know that there is any particular advertised or commonly advised spec on that clearance. But I would think that like with water flow that a space equal to the diameter of the flowing pipe is sufficient. I'm pretty sure my 4" liner top that has about 4" clearance with screen but sorry I'm not going up 26 ft to measure it !! LOL.. An remember any cross wind will increase flow and the cap can spill fumes in 360 deg otherwise. That's one reason I went up instead of out at my house.

 

[SlimTidy]

It was in front of me this whole time. Hydrodynamics Haha. Great point though and I actually think I skimmed something to that effect for measuring for a custom fit cap. I'll triple check but if I have the full 3" of clearance than I should be good.
Thanks for the input

 

[alternativeheat]

It was in front of me this whole time. Hydrodynamics Haha. Great point though and I actually think I skimmed something to that effect for measuring for a custom fit cap. I'll triple check but if I have the full 3" of clearance than I should be good.
Thanks for the input

glad it works for ya.