Jotul F 55 Triple Wall Air Cooled Manufactured Chimney (Liner) Connection

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calinb

New Member
Apr 15, 2020
16
N. Central Idaho
Call it what ever you want it will never pass inspection and is a definite potential safety issue.
Agreed. It's a big unknown and hence a potential safety issue. Finding an alternate location to install a new chimney and the stove would probably be easier than correcting the factors that result in the unknowns and an alternate location would permit the option to use the propane stove, which I doubt meets code either but at least it's been running without burning the house down for the last 25 years!

Sadly, no one's been able to explain specifically and physically why modern ZC fireplaces with liners are sometimes okay with old AC metal chimneys. (Code doesn't provide reasons.) Of course my interest in the answer stands apart from the other issues specific to the non-conforming chimney and overhang / ceiling or whatever you want to call it.
 
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begreen

Mooderator
Staff member
Nov 18, 2005
89,791
South Puget Sound, WA
Let us know if you need help with the installation of the stove in an alternate location. Generally going straight up through the roof is the least expensive and best-performing option.
 

calinb

New Member
Apr 15, 2020
16
N. Central Idaho
Let us know if you need help with the installation of the stove in an alternate location. Generally going straight up through the roof is the least expensive and best-performing option.
Thanks, begreen!

The first prospect would be straight up through the roof but it's not near the peak of the roof so I have to take some measurements and figure out how high the chimney would terminate and the support required.
 

BKVP

Minister of Fire
Agreed. It's a big unknown and hence a potential safety issue. Finding an alternate location to install a new chimney and the stove would probably be easier than correcting the factors that result in the unknowns and an alternate location would permit the option to use the propane stove, which I doubt meets code either but at least it's been running without burning the house down for the last 25 years!

Sadly, no one's been able to explain specifically and physically why modern ZC fireplaces with liners are sometimes okay with old AC metal chimneys. (Code doesn't provide reasons.) Of course my interest in the answer stands apart from the other issues specific to the non-conforming chimney and overhang / ceiling or whatever you want to call it.
I'll try to explain...

When a factory built fireplace is designed and then safety tested, the chimney system is part of the test. That same system is then sold with the fireplace because all clearances (such as hearth, mantel) are established.

The air to fuel ratio for a fireplace is vastly different than a sealed unit, like your Jotul.

The stack temperatures can be much higher. It's 99.9% unlikely that a stove or fireplace manufacturer set up in the lab the alterations you have contemplated in order to establish the same required clearances.

If you home were to experience a loss due to a fire, then there is a 100% certainty that a fire inspector will determine your install was not legal.

Lastly, there is ZERO assurance the builder that installed the factory built fireplace venting system did so without taking any shortcuts.

Your propane heater will most likely never experience a chimney fire. However if a wood stove/liner did (and that most definitely can happen) you'll find out if it was installed correctly.

You're on the best path...a new location.
 

calinb

New Member
Apr 15, 2020
16
N. Central Idaho
I'll try to explain...

When a factory built fireplace is designed and then safety tested, the chimney system is part of the test. That same system is then sold with the fireplace because all clearances (such as hearth, mantel) are established.
Thanks, BKVP! That makes sense but looking at the Jøtul C 550 CB Rockland insert pre-fabricated chimney / liner instructions, it still doesn't appear to me that many chimney and liner variables are very well covered (as is also the case with a masonry chimney). There are still many degrees of freedom that fall within the approved requirements that appear to be quite relevant to me, but I guess the testing and installation criteria can be "looser" with an insert that's found to produce cooler exhaust than a stove.

The air to fuel ratio for a fireplace is vastly different than a sealed unit, like your Jotul.

The stack temperatures can be much higher. It's 99.9% unlikely that a stove or fireplace manufacturer set up in the lab the alterations you have contemplated in order to establish the same required clearances.
99.9% at least! I have little doubt that the F 55 was not tested with a chimney that had long expired from the marketplace by the time the F 55 was introduced.

Even though stove temperatures can be much higher than an insert, when I look at the "HomeSaver Factory-Built Liner Adaptor Supplemental Instructions" they imply that free standing wood stoves could, at least potentially, be approved with an AC factory-built chimney and liner. Of course that doesn't mean that any wood stoves have actually been approved in practice:

If a hearth stove will be connected to the liner, determine which type of tee will be used (see the liner installation instructions for specific recommended tees). If an insert will be connected to the liner, you may use a HomeSaver connector/adaptor to make the connection between the flex and the insert if it has a 6″ inside dimension flue collar.
If you home were to experience a loss due to a fire, then there is a 100% certainty that a fire inspector will determine your install was not legal.

Lastly, there is ZERO assurance the builder that installed the factory built fireplace venting system did so without taking any shortcuts.
Agreed here too... AND zero assurance that the chimney has never been subject to a chimney fire. These sorts of concerns would be applicable to even any previous owner code-acceptable HT/UL3 installations too. By the time these kinds of history unknowns are addressed, a new chimney is probably often the best option.
Your propane heater will most likely never experience a chimney fire. However if a wood stove/liner did (and that most definitely can happen) you'll find out if it was installed correctly.

You're on the best path...a new location.

I'm still rejecting tearing out the overhang. It turns out that there's no drywall behind the stone except at the edges. I'm not sure what's supporting it--maybe rebar. After tearing out a sizable amount of stone, replacement drywall would need to be installed and the ceiling completed and textured. If I'm going to need to do drywall work, I'd rather limit it and also avoid tearing out a sizeable amount of stone, which I find to be attractive. On the other hand, ceiling work should be very limited with a new chimney installation.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
25,667
central pa
Thanks, BKVP! That makes sense but looking at the Jøtul C 550 CB Rockland insert pre-fabricated chimney / liner instructions, it still doesn't appear to me that many chimney and liner variables are very well covered (as is also the case with a masonry chimney). There are still many degrees of freedom that fall within the approved requirements that appear to be quite relevant to me, but I guess the testing and installation criteria can be "looser" with an insert that's found to produce cooler exhaust than a stove.


99.9% at least! I have little doubt that the F 55 was not tested with a chimney that had long expired from the marketplace by the time the F 55 was introduced.

Even though stove temperatures can be much higher than an insert, when I look at the "HomeSaver Factory-Built Liner Adaptor Supplemental Instructions" they imply that free standing wood stoves could, at least potentially, be approved with an AC factory-built chimney and liner. Of course that doesn't mean that any wood stoves have actually been approved in practice:

If a hearth stove will be connected to the liner, determine which type of tee will be used (see the liner installation instructions for specific recommended tees). If an insert will be connected to the liner, you may use a HomeSaver connector/adaptor to make the connection between the flex and the insert if it has a 6″ inside dimension flue collar.

Agreed here too... AND zero assurance that the chimney has never been subject to a chimney fire. These sorts of concerns would be applicable to even a code-acceptable HT/UL3 installations too. By the time the concerns are addressed, a new chimney looks like the better option.


I'm still rejecting tearing out the overhang. It turns out that there's no drywall behind the stone except at the edges. I'm not sure what's supporting it--maybe rebar. After tearing out a sizable amount of stone, replacement drywall would need to be installed and the ceiling completed and textured. If I'm going to need to do drywall work, I'd rather limit it and also avoid tearing out a sizeable amount of stone, which I find to be attractive. On the other hand, ceiling work should be very limited with a new chimney installation.
As far as the approval of things involving prefab ul listed products like your chimney go. It isn't enough that the liner or insert manufacturer says it is ok. They cannot over ride the instructions for the original product. And I can gaurantee the instructions for your chimney don't allow for a liner. In addition inserts do not run cooler than stoves. They are simply stoves made to fit inside a fireplace.

What is the structure of that stone covered area?
 

calinb

New Member
Apr 15, 2020
16
N. Central Idaho
As far as the approval of things involving prefab ul listed products like your chimney go. It isn't enough that the liner or insert manufacturer says it is ok. They cannot over ride the instructions for the original product.
Yes. Irrespectively, just like the days when perhaps the majority of masonry chimneys were built, I don't think flexible liners even existed!
And I can gaurantee the instructions for your chimney don't allow for a liner.
Or, similarly, the stove! The F 55 does not include a liner as approved. It's pretty specific for pre-fab chimneys (HT / UL3) and modern liners are 1777, I believe, which isn't even mentioned.
In addition inserts do not run cooler than stoves. They are simply stoves made to fit inside a fireplace.
Hmm--that's actually what I originally suspected--just based on EPA data and the installation instructions that I've reviewed.
What is the structure of that stone covered area?
From what I can observe (including drilling a small hole from the room on the other side of the wall), it's all stone and grout all the way up to the chase section in the floor above. Out of curiosity, I might cut a larger hole from a closet into the conventional looking chase on the second floor and try to look down. I have discovered no wood or other visible structure behind the stone yet. Given other masonry projects around here that appear to be of similar vintage (including a 3000 gal water cistern), the people that put it in used a lot of rebar. I would not be surprised to find the stone drilled for rebar. It appears to be a claystone or sandstone or limestone (hmm--gotta drop some acid on it) and it might succumb to a masonry bit. It's been up for a long time but I don't know what holds it up yet! I don't think it's artificial stone, because no two pieces are even close to being alike in shape. This house was an original 1908 Homestead Act farmhouse and it's been upgraded a few times over more than a century so there's plenty that doesn't meet our codes today for sure! On the other hand, just try drilling into the old-growth forest lumber in its framing! It's amazing stuff that simply isn't available today. It's the second "old-growth home" that I've owned during my life.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
25,667
central pa
Yes. Irrespectively, just like the days when perhaps the majority of masonry chimneys were built, I don't think flexible liners even existed!
There were flexible liners around before prefab chimneys were available. And there are still lots of masonry chimneys built. They are more common than prefabs in many areas including here.

Or, similarly, the stove! The F 55 does not include a liner as approved. It's pretty specific for pre-fab chimneys (HT / UL3) and modern liners are 1777, I believe, which isn't even mentioned.
From the jotul manual.

"There are two types of approved chimneys:
1. A code-approved masonry chimney with a ceramic tileor listed steel flue liner.
2. A prefabricated chimney complying with therequirements for Type HT (2100°F) chimneys per UL 103or ULC S629."

So yes stainless liners in a masonry chimney are perfectly acceptable.

There is no way that stone structure is just masonry and rebar.
 

BKVP

Minister of Fire
And even when an insulated flex liner is used in a masonry chimney, NFPA211 requires clearances to combustible of 1" on an exterior wall and 2" on an interior wall. So ask yourself, did the mason remove all the wooden forms used in building the chimney?
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
25,667
central pa
And even when an insulated flex liner is used in a masonry chimney, NFPA211 requires clearances to combustible of 1" on an exterior wall and 2" on an interior wall.
Not when the liner is properly insulated. That gives you zero clearance to the outside of the masonry.