Jotul Castine Protected Wall ??

[hsvbama]

Just installed a Jotul Castine and have a question on the clearance. Its a corner orientation with brick on bottom and sides. There is plenty of ceiling clearance but the back corners are approx 5.5" from the brick. Jotul manual says 8" with single pipe and no rear heat shield for protected wall. I checked and the brick has a 1" gap from the wall sheathing, but it also has some type of non-paper backed insulation in the gap. Note that the previous owner had an older pre-EPA stove installed at this location and used it for years. My clearance with the brick is easily 8" from the combustible wall, but Im worried about the insulation. My pipe is straight up 3', 90 turn, through wall, 90 on exterior, and 15' vertical run. If I put a 45 elbow and a short horizontal run at the interior 90, I can slide the stove out from the wall. How would that affect my draft? The problem is that the pre-existing hole in the wall (brick on both sides) is very close the corner. Thus the need to get the stove close for an up and through with the one 90 elbow. Hopefully that is not too confusing. Thanks!

 

[edthedawg]

If the brick is gapped behind, and the gap is filled or faced with a non-combustible material, and the full clearance to the first combustible layer meets your manual requirements - then you should be fine. Post a photo of the install!

 

[fossil]

The gap between the masonry and the combustible wall is really supposed to be a ventilated airspace. Free flow of air there will promote the establishment of a natural convective flow continually removing heat and dispersing it out the top to help keep the combustible wall from becoming too hot. If anything, I'd make an attempt, if feasible, to just remove the insulation that somebody stuffed in there. It won't burn, but it's kinda defeating the purpose of the air gap. I certainly don't think there's anything about the situation that warrants reconfiguring the piping...especially if doing so would add yet another direction change. I, too, would enjoy seeing a pic of the installation. Rick

 

[begreen]

To be an NFPA 211 wall shield I believe the air space is required with at least a 1" gap at the bottom and top. The insulation defeats this air space, much like stuffing insulation around a class A pipe would. Remove the insulation.

What's the thickness of the brick, or more importantly, what is the distance from the back corner of the stove to the wall behind the brick? Does the wall shield go floor to ceiling with an air gap at bottom or top? Jotul calls for 25" from single-wall stovepipe to unprotected walls, or 12" from protected vertical surfaces.

 

[hsvbama]

Thanks for the responses! I will take some pics and post tonight. I went ahead and put the 45 degree elbow in-line which bumped the back corners from 5.5 to about 8-10" from the wall. Im at work and cant remember the specific numbers. Draft seems to be fine. We burned the stove all weekend with no problems. The wall surface temps seem to be down, though it got pretty warm during the last long burn at around 500-600F stove top temp. I could put my hand on the brick for 4+ seconds without getting burned, but again, it was very warm. Keep in mind that is 4" of brick from the insulation filled gap and another 1" from the wall sheathing. Im mainly worried about the insulation getting too hot. Not sure what material it is but does not have paper backing. With respect to removing the insulation, there is brick on the back side of both walls (corner of brick exterior). So removing is out of the question.

The brick is approx 4" thick and goes from floor to approx 7-8' up the wall (on 2 sides) with a top air gap. The ceilings are high (+2' from brick top) so the vertical clearance from the horiz single pipe is easily >18". The pipe exits the side wall at approx 6.5'. I dont think there is 25" of clearance from vertical single pipe to the side wall sheathing. The wall surface temps are very low in the pipe area (above the stove) and in the back. The main problem area seems to be along the sides near the bottom and about 3/4 up the box height. I would guess the back stove corners are approx 14-15" from the combustible wall sheathing behind the brick (including the insulation filled gap).

I will post pics and better dimensions later. Possible options are adding the rear heat shield or putting a short run between the 45 and 90 elbows. I could get another 2-4 inches of corner clearance, but this puts the stove near the front edge of the hearth, which will not look as good.

 

[hsvbama]

Here are some pics of the castine install. Note that I let the wife talk me into a golden mustard wall color. We are just getting started on that part. Back to the stove, the pics show the front view and from the side. The side gives you a good view of the horiz run from the wall. It hits a 45 elbow pointing to the front, straight into the 90, and then down into the stove. It should be clear how the 45 buys me a few more inches away from the corner. I could get a few more inches there, but prefer not to unless necessary. The draft does not seem too bad. Sometimes a little slow to start but really kicks once its going. I really love the stove!

I took some better measurements. Front of the brick to the wall sheathing including the insulated gap is 5". The stove back corner clearance to the brick is 9.5" (14.5" with brick and gap). Approx 15" from the vertical pipe to the side brick (so 20" to the wall sheathing). Thats about it. Looks like it comes down to whether or not I can count the brick as a protected surface for the sheathing. I agree that the insulation defeats the purpose of the air gap. Though, the gap is open at the top. If using the unprotected wall numbers, can I count the brick/gap in the clearance or is it from the front of the brick surface? Should I consider purchasing the heat shield? Will the rear heat shield lower the brick surface temps on the side? Lastly, should I be worried about the insulation being combustible? It does not look like typical wall insulation. No paper and compact/dense.

Any comments/suggestions would be much appreciated. Thanks!

 

[begreen]

Pictures help. It's a great setting for the stove. But I'm not seeing any top and bottom wall shield air vents to allow circulation. This should be treated as a brick wall which still gives a 33% reduction from the maximum clearances. No need to disturb the insulation from what I see, that was a red herring.

 

[hsvbama]

Thanks BeGreen. So I can take a 33% reduction in the max clearance (unprotected wall, single pipe) and meet the requirement as measured from the inner wall sheathing (1st combustible material)? Or is the insulation considered combustible?

BTW, is that reduction specified in NFPA 211 or maybe just a rule of thumb calculation for brick? Sorry for all the questions. Just trying to get my facts straight. I still need to get with my insurance company and want to make sure Im meeting the requirements.

 

[begreen]

The clearance is as per the diagram in the manual, from the back corner to the nearest combustible in the wall assembly. We can't see what is under or behind the brick. So I would assume that behind the underlayment for brick are wood studs. If yes that is the nearest combustible. If the underlayment is paper-backed drywall, then that is the nearest combustible. The insulation should not be combustible, but if it is paper-backed, the paper is combustible.

In the case of the Castine, this would be dimension 'C' = 18". With the brick the distance can be reduced to 12". From the picture it looks ok.

Here is a chart from the NFPA regs:

https://www.hearth.com/econtent/index.php/wiki/NFPA_Wall_Clearance_Reductions/

 

[hsvbama]

Thanks! I can see behind the brick from the top side and there is definitely an insulation filled gap, then sheathing, and then the studs for the main house wall. Looks like Im good either way. Thanks again for the clarification and regs link!