Yearly thread about liners, when to direct connect them , and when to use insulation.

[MountainStoveGuy]

OK, so lets see where to start this. Most manufactures produce literature that says you can direct connect chimneys as long as the surface area of the existing chimney is no more then 3 times the area of the appliance being hooked up if its a internal chimney, or 2 times the area if its a external chimney. This rule assumes that the chimney you have is rated to UL1777 which states that the chimney should be able to handle 3 10 minute chimney fires at 2100*. Well guess what, none do. Most clay tile chimneys are constructed wrong (95%+) so UL1777 states that all inserts and stoves that are connected to solid fuel clay liners must be lined and insulated. So what does this really mean?

You can never dump a stove or insert in to a clay flue liner.

You must insulate every installation. The insulation is there to protect the home from a chimney fires, not improve draft. But insulation improves draft substantially and protects the home at the same time.

You can never hook up a solid fuel appliance to a factory built fireplace or factory built flue. Its not tested and not approved. Factory buillt chimneys are listed to 1700* not 2100*. And the manufacture of the pre fab chimneys never had there chimneys tested to operate with a liner installed. So technically, there is not a approved installation on zero clearance fireplaces for any thing other then the zero clearance fireplace that is attached to it. Just because a insert manufacture states that there insert can be installed in a ZC, does not mean the ZC can take a insert. Not one ZC fireplace is listed to use a insert or liner so its totally not legit to do this. Most companies ignore this rule.

ANY thing out of these guidelines is technically an illegal install, but that does not mean that we do not take educated risks when we veer from these rules. Most installs are not up to code, the only ones that are, are the ones that are installed in clay flue tile liners with insulation and a stainless steel liner. IF the liner is rigid, then you must use stainless rivets to connect the rigid to the flex sections. If your installation does not sound like this. then technically, its wrong.

 

[Todd]

So your saying that insert manufactures don't have them tested in ZC fireplaces? How do they get approved without testing? Doesn't the stove manual supersede code? Of course the ZC manufactures won't state a liner or insert is approved for their fireplace, they don't see any of the money from that deal.

 

[MountainStoveGuy]

thats exactly what i am saying. its not a secret either. Inserts technically can not be installed in ZC fireplaces. The insert can be approved, but not a single fireplace is approve for the use of a insert in them, nor there chimneys. Zero Clearance fireplaces are one of the most strict, most regulated appliance in our industry.

 

[Todd]

Interesting, you would think some lawyers would take advantage of this and sue?

 

[CarbonNeutral]

If I printed your (excellent) post and showed it to some of the shops that I have had experience with, I wonder what the look on their face would be?

 

[MountainStoveGuy]

They know. We do it too. It doesnt make it right, but they know. Every company that does these installations are liable for these installations. I would sleep better if we didnt. If we cant get insulation down there we wont do it. I think that keeps us pretty protected in the real world, but our ass is still hanging out there.

 

[MountainStoveGuy]

I also need to clarify this does not apply to all pre fab flues, HT pipe, other wise known as class A, is rated for the 2100* rating and does not require insulation. To bad none of the ZC fireplaces use this type of pipe. What is interesting, is that there are different ratings for HT pipe as well. The canadian standard, is one continoius 30 minute burn at 2100*. the US version is three ten minute tests at 2100*. I think the US is going to adopt the canadian standard some time in the near future.

 

[BrotherBart]

I know what the codes are and the reason for them but what still fascinates me is that I can have thirty feet of non-UL tested/listed 24 gauge tin stove pipe in my living room but inside that brick encased tile flue with three sides not even touching the house that 1/2 inch of flimsy ass insulation wrapped around that liner is gonna save the world. :coolsmirk:

Good post and a needed one MSG but the ironies still get me.

 

[jtp10181]

are the ones that are installed in clay flue tile liners with insulation and a stainless steel liner.

I am pretty sure most liners are also listed as safe with insulation even without a clay liner, as long as its a masonry chimney structure.

 

[wendell]

Well, it appears I am SOL. I have 35 feet of uninsulted 6" flex running through my utility chimney and due to the variance in the tile liner, am quite sure I don't have a 1" air gap. The installer did inspect the chimney and it is in very good shape but if 95% aren't built correctly, it sounds like I am playing a little Russian Roulette?

I guess at this point, I just need to make sure I burn good wood and keep my chimney spotless?

 

[MountainStoveGuy]

are the ones that are installed in clay flue tile liners with insulation and a stainless steel liner.

I am pretty sure most liners are also listed as safe with insulation even without a clay liner, as long as its a masonry chimney structure.

That is correct.

 

[MountainStoveGuy]

On of the reasons we use rigid liner is to keep the liner off of the sides of the chimney to insure a proper air gap around the liner and chimney. This is not necessary, but its good practice IMO.

 

[jtp10181]

At least I have someone to back me up now, when I tell all these people they need insulation on their liner for it to be safe.

Maybe if two people say the same thing they will believe us

All you have to do is read some brochures and talk to the liner manufacturer a little to figure it out.

 

[MountainStoveGuy]

yep, but its real black and white, the listing company does not leave much to the imagination...... Its strange, one of the most important issues of hearth installation is one of the most over looked. The Zero clearance firebox installations are crazy too. Most of the inserts are installed with the surround panels covering the cooling vents on the zc fireplace. Very dangerous situation. You know pyrosis and carbonization is going on with the studs on top of the fireplace...

 

[woodgeek]

Appreciate the post MSG, and I get/appreciate the code intent--protecting idiots that will load a chimney with heavy creosote to get a (hypothetical) 30 minute chimney fire (or three 10 minute fires) at realistic temps--2100°F.

I guess when I got into the wood burning thing, I noticed that we have two layers of safety, 1) we avoid any (non-miniscule, detectable) chimney fires by using the correct fuel, correct operation and scheduled cleaning AND 2) we have an installation that can reliably survive a maximal chimney fire.

The scariest stories on here (including web's from a while back) are from installations which light off framing WITHOUT a chimney fire, but just extended normal operation. So the testing data I want to see is about steady state temps on the outside of tile lined masonry chimneys with say, a direct connect and various invisible defects (e.g. not missing mortar or tiles, but mortar filled air space). Equivalently, how bad is a liner in a '1700F' ZC chimney under steady state normal operation?

 

[MountainStoveGuy]

The liner in a 1700* chimney cant be that bad... the Quadrafire 7100 FP fireplace is designed with one. That alone scares me. How is it that every other epa fireplace requires 2100* pipe and the monstrous 7100 doesn't? (im pretty sure SL300 chimney is 1700*). I am not sure of the rating, but if the standard for liners was 1700* instead of 2100*, and they kept the insulation clause in there it would be fine. However, if it where 1700* and people abuse the insulation installation like they do now, i think would would have serious problems. I think the 2100* pipe is overkill, but i also think that it protects people better when its not installed per UL1777.