Mixed advice on SS liner in prefab chimney

[wahoowad]

Hello! Newbie here. I know this must be a frequent question but I did search the archives and FAQ and didn't see a direct answer. My apologies if I missed something.

I just purchased a Jotul 3CB. I have a prefab "out and up" style chimney according to some things I read here. This is a zero clearance setup with a 8 inch stainless steel inner pipe inside a larger 10 or 12 inch pipe. It is a 2 story chimney and goes straight up. I am aware of numerous clearance topics, etc but have a question specifically about whether I need an additional 6 inch stainless steel flex liner installed. The fireplace store owner's son was adamant I needed it - he seemed to live strictly by the manufacturers instructions. Hard to fault him there. The owner said he was walking on thin ice discussing it but felt I would be fine using a reducer to convert the 6 inch stovepipe to fit the 8 inch pipe at my damper. My neighbor has used the simpler method (reducer stright to 8 inch pipe) for his woodstove and said I should do the same.

I appreciate your opinions. My thanks to the webmaster for making this forum possible!

 

[Eric Johnson]

You need a Class A chimney to connect to an airtight woodstove or insert. Anything less is a violation of code and adversely affect your homeowners' insurance policy (read: no check). Fireplace chimneys are not built to the same high standards as wood stoves, so it's doubtful that you have a Class A chimney. And that's pretty much the end of the story. The good news is that you should be able to run a 6" Class A stainless liner right up the middle of the existing chimney and be OK

 

[wahoowad]

An article on this site seems to describe my chimney, and it calls it a Class A (type 2). Here is a link to the article https://www.hearth.com/what/installstove.html#anchor1678812

What about my installation is different than the description made of a Class A chimney on that page? I don't know, I'm asking.

 

[wg_bent]

Eric is right on here. The other issue is that your draft will likely not be appropriate. Volume of air in a 6" pipe is much smaller than an 8" and the stoves are designed to be efficient with a 6".

The 0 clearance chimneys also are not rated for the kind of heat a wood stove can put out. They are designed to move large volumes of air along side the fire gasses and are cooled this way. Woodstoves severely limit the amount of air going up the chimney, so the prefab would not be cooled properly.

It's different with a masonry chimney since they do not need to be cooled, but the volume issues still apply. My install is into a prefab, and when I go to bed at night and think of all the heat that stove is generating, I'm real glad that there is a single continuous piece of pipe from the stove to above the existing chimney.

The liners aren't that expensive. Do it the right way!!

 

[webbie]

Hello! Newbie here. I know this must be a frequent question but I did search the archives and FAQ and didn't see a direct answer. My apologies if I missed something.

I just purchased a Jotul 3CB. I have a prefab "out and up" style chimney according to some things I read here. !

This is the confusing part.....
If you have an "out and up" 8 inch flue with a tee where it goes out, then you have a generic class A chimney and it is OK to connect to it...

BUT, if you have a fireplace...a pre-fab fireplace with a chimney you want to connect to, then you have to line it. In addition, you have other potential problems such as clearance to the pipe or the stove.

As others mentioned, there are other articles and posts here concerning this....

 

[wahoowad]

I was told the heat up the chimney is LESS with a wood stove which is why a 6 inch pipe was specified. This smaller volume traps more heat than the larger 8 inch pipe and keeps the creosote down.

Regardless, I am leaning towards installing the 6 inch flex pipe but can't find any DIY places to buy one. My dealer will do it for a small fortune, although I clean my own chimney and am quite confident I can install it just fine if I could find a reasonable place to buy it from....? Any idea what this stuff costs per foot for a DIYer?

 

[wahoowad]

Craig,

My prefab has a 8 inch flue and it is all 8 inch pipe straight up. I guess this means it is non Class A? I do not think there is any tee or anything in it.

I have taken steps, or purchased necessary stovepipe to mitigate any other clearance issues I have.

 

[Extendaboo]

Craig,

My prefab has a 8 inch flue and it is all 8 inch pipe straight up. I guess this means it is non Class A? I do not think there is any tee or anything in it.

I have taken steps, or purchased necessary stovepipe to mitigate any other clearance issues I have.

Yes, you must line it.

The key is this...prefabs take a lot of air up with the fire, therefore the chimney stays cool. When you put a stove in, you are now limiting the air going up and have the potential of higher stack temps. Other issues: Prefabs are usually hardly ever used, so the chimneys are not put to the test as much.

Bottom line, you must line it for safety. You will be much happier and sleep better.

 

[saichele]

Just google 'Chimney liner' or 'felxible chimney liner' or something similar. There are about half a dozen major online vendors.

I had remarkably good service and good prices from an outfit called Hartshearth.com, 8" round 316-Ti alloy for 20/ft. They have some born-again overtones, but also were the cheapest I found and they delivered before they said they would, which hasn't been my general experience in this industry.

Steve

 

[wg_bent]

I put in a Forever flex liner in mine. Sharpest thing on the planet I think. Flexable is a relative term. I think it's a good product, and I suspect representative of all products in this market, but...WOW.

 

[wahoowad]

Above Eric says "The good news is that you should be able to run a 6” Class A stainless liner right up the middle of the existing chimney and be OK"

Does this mean the liner itself is classified Class A? And that properly installing it through my existing chimney pipe creates a Class chimney? Does it require being insulated to be considered Class A?

Thanks again for the advice!

 

[Eric Johnson]

As I understand it, (though maybe elkimmeg or Craig could verify this), the chimney you have is insulated, it's just that the existing ss interior lining is not designed to take the heat that a Class A chimney is. If you put an uninsulated liner into the existing 8" opening, you basically upgrade what you've got to meet the code.

 

[wahoowad]

Thanks for the clarification, Eric. Hopefully someone can confirm as you mentioned.

One thing Ihave not done is measure my damper/flue width. I have assumed it was the same 8 inches as my current stainless steel pipe. I am not even sure how to remove the damper. Hopefully I can dissassemble it and not permanently cut it out. I'd like to be able to return the existing fireplace and chimney to current conditions when I move and take my stove.

 

[wahoowad]

elkimmeg, can you confirm/refute the point Eric thought you could address?

 

[elkimmeg]

I think the entire post replies has given you good advice That's why I stayed out of it
There are two types of insulated chimneys one with packed insulation and one with a dead air space.
The packed one is best. Do you know which you currently have also how old is it? final piece of the puzzel is your chimney's
location interior or exterior explain please. how clean is your existing chimney?
With this additional info I will make a decision, based upon code and years of practical experience And with your reply model stove and perposed liner and manufacturer. I will look out the specs from both and post my oppinoins

 

[wahoowad]

I have a 1987-era Majestic (MBUC I think) prefab. The current chimney is exterior to the house but in a large uninsulated chase - an 8 inch SS inner pipe with a 10" outer pipe. It is dead air space. I want to put in a Jotul F3CB using a 6" doublewall stovepipe out the back of the Jotul, to a tee, and up the flue with a 6" SS flex liner. I am good with the clearances around the hearth and with the 6 inched around the double-wall stovepipe.

Thanks!

 

[elkimmeg]

Exterior chimneys draft the poorest. Since the chase is not insulated and the original pipe is air spaced insulated.
The question now is to insulate the liner. It can be answered two ways some liner manufactures as part of their listings require insulation They use 304 ss and need the insulation to comply to the UL 103. Some only require insulation in exterior chimnys and allow or list no insluation requirement in a lined interior masonry chimney. Part of the insulation requirement is reduction to combustiables as the insulation achieves that as well as keeping the heat in and enhancing draft. SS 316 HT 2100 liner may not require insulation it is of a higher grade and thicker ss the insulation is not needed to comply to UL 103. The other part of figuring your situation out is your climate. How cold does your average Jan temps get. The further north and colder, insulation benifits
increase. Money is also a consideration insulation cost more. Factor this in, your stove may opperate ok without an insulated liner,
but the lingering question you will be asking youeself. How much heat am I loosing heating the chimney and not my home? How much more effecient would my stove be, using an insulated liner. Inspection wise. I require the liner installation requirements when I do my inspection. If insulation is part of the listing for your chimney location, then it is required to pass inspection. You might try to see how it works without insulation then plan accordingly to insulate next year. Work would be duplicated, pulling the existing liner and re installing it for blanket applications insulation, or you could opt for poured in insulation. One other piece of advice,remember to install spacers along the linner to keep it supported and centered in the chimney. The snake approach, creates way too much bends and obstructions to obtaining a good draft flow. Boy I wish I could afford such a nice stove, the Jotul. Me I am stuck with re-habing older stoves. Money is tight, when kids can't manage there spending. Dad is always there to bail them out. They cost me more than when 2 were in college. I thought once the youngest graduated, I could create breathing room. Don't co-sign on auto loans. I ended up with a pretty expensive sports car I never drove. Cost me 8 grand to learn that lesson. 6 more grand to pay for the additional credit courses to complete the diplomia from Villanova. I had thought she graduated. Then 11.5 grand for a new well 750 ft deep all this happened this year. Unfortunately that was not all.

 

[wahoowad]

Thanks for the detailed feedback, elk!