Install Question for Unlisted Stove

[Alex C]

Last winter, I installed an Old Mill wood stove I did a restoration on. The majority of the install went without a hitch. I used clearances for an unlisted stove since I didn't have a UL tag. All my clearances are legit, if anything they all actually exceed the requirements. I thought for sure I did absolutely everything right. Somehow, I missed the memo on having the entire bottom of the side walls be 1" up from the base of the hearth for air flow. I don't know how I didn't notice it in the diagrams. I do have the 1" air gap around the sides and top. I am trying to decide if I need to modify some cuts along the bottoms. Any thoughts? The wall seemed to stay cool last year as I was always checking. Here is a photo of the install.

 

[begreen]

Nice install. Yes NFPA211 requires a ventilated wall shield to get down to the 12" clearances. That means air need to be able to freely convect behind the shield. Static air will still offer some protection, but not as much.

 

[Alex C]

Yes NFPA211 requires a ventilated wall shield to get down to the 12" clearances.

Suppose I ought to get acquainted with a right angle grinding saw, then? Maybe cut some 1" slots along the base? I think I need to keep the ends of each wall intact to carry the load of the cement board and tiles.

 

[begreen]

Slots or holes should suffice. Some folks are able to do this on the backside of the wall and then put a grille on the hole.

 

[DougA]

If you have to make the holes to pass inspection for insurance, that is not going to be easy. I would get a 1/4" or larger ceramic bit and drill a series along the bottom. I think it's the same as a glass bit but not the same as a concrete bit at all. I did a 1" hole in ceramic tile with the correct bit and it was a perfect hole without chipping. A grinder will make a mess IMHO.

Another option is drilling holes from the basement up into that 1" gap. Going to be a challenge to get the exact location but WAY easier to drill a hole through the floor.

If you have no problems with insurance, I might consider just a few holes and put a thermometer in one to check the temps when burning hot. If they are well within a safe range, I'd leave it.

 

[Alex C]

Another option is drilling holes from the basement up into that 1" gap. Going to be a challenge to get the exact location but WAY easier to drill a hole through the floor.

Interesting point! My house is actually a cabin which is on wood piles. I can access under the house fairly easily. And, I took out a gas heater that used to be on that wall and the 5/8" hole where the gas service came in through the floor is still open, which I had thought may help induce cool air behind the clearance wall.

If you have no problems with insurance, I might consider just a few holes and put a thermometer in one to check the temps when burning hot. If they are well within a safe range, I'd leave it.

I am having a new insurance company come do a walk through before this heating season. I will see what they have to say and address any problems they may have.

Does the fact that I exceed all the clearances in the NFPA211 help my case? my clearance to the combustible wall is almost 18" from the stove because the single wall pipe higher up was my limiting factor, not the stove itself.

 

[begreen]

I wouldn't introduce outdoor air behind the shield. That would be inefficient, like leaving a window open. You want room air to recirculate behind the wall shield. The fact that you have 18" clearances helps. I was thinking 12". See what the insurance company says. At the most you may need to slip some roxul or micore board behind the shield, in between the spacers to get the 12.6.2.1 (b) 50% clearance reduction. That would be easier.

 

[Alex C]

I agree that the efficiency is certainly not as good once you start introducing air in from the arctic outside. I will see what they say. I built the hearth with 19-1/2" tiles, so the dimensions of the hearth were driven based on making fewer cuts and reducing oddball tile sizes, while meeting all the NFPA guidelines, so in most cases, all my clearances are exceeded. Thanks for your insight guys. Great forum, lots of knowledge.

 

[DougA]

If those are 12" tiles, the back of your stove appears to be much closer than 12" from the wall in the photo. What is supporting the wall tiles? If you've got a wood support for the wall tiles, your clearance theory just got blown apart.

Since your basement is cold, I'd go with begreen's idea and drill holes from the other side of the wall and put a vent on it to look good.

 

[Alex C]

Just to clarify, those are 19-1/2" tiles. They are huge. I've got just under 18" from combustible wall to the stove. I used 3/4" galvanized electrical conduit cut into 1" lengths, then screwed through the cement board and into the wall. I am way over my clearances side to side and I'm just at the ember protection up front.