Wood stove clearance

[Nick]

My new wood stove lists 15" to combustible surfaces at the rear. Anyone know how far I can cut that back to a stud wall faced with cement board and ceramic tiles?

Thanks

Nick..

[Pop]

Go to NFPA site; lots of info t here. Can't find my link to it; Google for it. Also try "wood stove"+clear while you're there for other good info.

Pop

[SQLit]

call the manufacture or it should be listed in the instructions.

[xrongor]

i believe you should have an air space between the 'facing' and the actual wall, along with vents to allow the air to flow behind the facing.

randy

[HerHusband]

Nick,

If the cement board and ceramic tile are attached directly to the stud walls, I don't believe there is ANY reduction in the clearances. The heat can transfer directly through the tile/backer to the studs.

On the other hand, if the backer/tile is spaced away from the wall about an inch (with non-combustable spacers), the clearances CAN be reduced. I don't recall how much right now, you would need to check with the wood stove manufacturer and/or your county officials about that.

Anthony

[Evon]

Depends on how quickly you want to burn the house down! I would NOT reduce the distance and I would put 1" noncombustible spacers in the back board. Remember, when you are sleeping or away from home - the fire has it's own way. I've use wood stoves all my life and always have a healthy respect for "Murphy's Law".

[Edwin Pawlowski]

There are approved methods of doing it. Check your local codes, check with experienced people at a stove shop as they should have the right materials. Doing it the wrong way can be a very expensive lesson. In most cases, there must be an air gap between the board and the wall but it has been a few years since I've kept up with that sort of thing. This is something you don't want to cheat on. That stove can easily be cranking along at 600+ degrees.

[George E. Cawthon]

Good points but if a stove has a surface temp of

600 degrees it is burning way too hot. That's way too hot for the stack also.

[George E. Cawthon]

I'm missing the op's first comment so I'm putting it here. The installation instructions for a new stove should state that. In addition the county/city building codes will state it. A 1" space with some airflow should about cut the required distance in half. The surface temp of my ceramic shield (actually light weight cement with ceramic tiles (also a 1" space to the drywall) would get high enough one couldn't hold a hand on it, but probably never exceeded 160 degrees. Removal of that back after 20 years of use showed no heat damage to the drywall.

If one doesn't give a hoot about the code requirement but is just interested in safety, installation of a thin metal shield (or you can even try it with aluminum foil) 2-3 inches from the stove back will provide the greatest safety. Think stove -- metal shield-- wall. 3" between the stove and the shield and 2-3" between the shield and the wall will result in an wall temp of less than 110 degrees at any normal stove operating temperature. Thin shiny metal is the best. I'm not necessarily recommending this, but it proves that the safety recommendations are not realistic. A metal shield (and some stove makers sell them as accessories) with an air spacing is far superior safety wise than any ceramic against the wall.

[Edwin Pawlowski]

I run my stove at 400 on a regular basis. At least once a day, I crank it up to 600+ for about 15 minutes to clear out the creosote. Been doing that for 24 years now on a cast iron Vermont Castings. While I don't run it there for long, it can easily reach those temperatures and you have to allow for it.

[George E. Cawthon]

What exact surface is your thermometer measuring?

[Edwin Pawlowski]

The top cast iron surface. Actually, it is a griddle if I choose to cook on it, machined smooth, right over the fire. Great for making pot roast or stews. Ed..

[nicksanspam]

Thick works better, IMO, but thin is cheaper.

Ts Tw | R | 2/3

600 -- --> --*---www-------www--- 70 I | | 1/3 ---www--- 70

If the stove temp is 600 F, I = 0.1714x10^-8(600+460)^4 = 2164 Btu/h-ft^2. A 90% reflective shield would absorb about 10% of this, ie 216 Btu/h-ft^2. The linearized radiation conductance R = 1/(4x0.1714x10^-8(70+460)^3x0.1) = R9.8, with 2/3 airfilm conductances. Here's one equivalent circuit:

Ts Tw 1/3 | 9.8 | 2/3 ---www---*---www-------www--- 70 F | | 142 F = 70+216x1/3 --- _ | -

What are the shield and wall temps Ts and Tw?

Nick

[George E. Cawthon]

ok. but hopefully the rear surface (vertical) doesn't get that hot. Damn typing with one hand is hard, smacked myleft thumb with a hammer. gonna be a blue thumbnail.

[nicksanspam]

It's just Ohm's law, with different units:

I = (142-70)/(1/3+9.8+2/3) = 6.7 Btu/h, so Tw = 70 + 6.7x2/3 = 74.4 F, and Ts = 74.4 + 6.7x9.8 = 139.7.

Nick