Mantel shields - anyone know the regulations?

[cycloxer]

Does anyone know the particular regulations for mantel shields? Required dimensions? My stove is a bit too close to my mantel. I tried it without a shield and it is getting a bit too toasty for my liking when I run her up around 600 degrees. I have been playing around with temporary shields from sheet metal (as pictured) before I make the real deal. The temperature drop is quite remarkable behind the shield. I am not making a huge shield as I am very close to legal w/o it, but I would like to know the official rules for reference.

 

[Danno77]

I have a similar issue, don't know what to tell you. Glad to hear you notice a difference, because I need to fab one up before I put the mantel up.

 

[oconnor]

The official specs would be in the manual for the given stove. That said, I think you can add the shield at the top of the fireplace instead of on the mantel. You may be breaking the clearances for having the mantel above the stove, but given that it looks like your stove is entirely within the old fireplace, you don't have the radiant heat transfer from the stove to the mantel, and can likely reduce the distances based on principles at play, despite what the actual numbers from the manual say. The manuals numbers are based on a line of site distance, and the lintel of the fireplace is essentially a shield.

Take a look at one of Jotul's flush mount inserts manuals (The Rockland 550 comes to mind) and see what they say there to get a comparison of the two. Unless the mantel is getting too hot to place the back of your hand against for a moment, you are not at much risk of it lighting on fire.

 

[Danno77]

...That said, I think you can add the shield at the top of the fireplace instead of on the mantel...

that's what my plan is, seems like it would be a cleaner looking install....

 

[cycloxer]

Right. I could probably do without the shield, but I like to be safe. The mantel used to get pretty toasty when I raged good fires in the fireplace. The stove protrudes 2.5" from the brick face (tough to see from pics). I have a bit of radiation to the mantel, but not the full stove top surface. The manual states a clearance of 25" from the top of the stove. I have 18" to the stove top. With a 50% reduction, I easily make the distance. The test shield I used dropped the temps quite a bit. I initially put it on so that it only covered half of the stove and then I compared the sides. It's pretty cool how well it works. I might try your idea of a small shield attached to the lintel for the next test.

 

[begreen]

Good question, I haven't seen a spec, just recommendations. There are usually two choices, both should exceed the stove width. 1) the shield is attached to the lintel of the fireplace opening and angled upward to extend past the wood mantel above it by an inch. or 2) The shield should be attached under the mantel wood with 1" non-combustible spacers and extending 1" beyond the edge of the wood. Typically they turn upward at a 45° angle once past the wood. The upward part is only for about an inch.

 

[Ticmxman]

Good information on this topic:

https://www.hearth.com/talk/threads/41505/

 

[thinkxingu]

I'm not sure what the actual requirements are (sounds like 50% reduction in distance if using a mantle shield), but the one I put on keeps my mantle much cooler than without. In fact, it's not much warmer above the stove than on the ends.

S

 

[73blazer]

Not sure if this is the right section of the code, but best I can read it, mantels are not mentioned a whole lot in the book, the one section dealing with them states,
Accordng to NFPA211

11.2.5.3 Woodwork, such as wood trim, mantels, and other
combustible material, shall not be placed within 6 in. (152 mm)
of a fireplace opening.
11.2.5.4 Combustible material above and projecting more
than 11⁄2 in. (38 mm) from a fireplace opening shall not be
placed less than 12 in. (305 mm)

But that's in the masonry fireplace section which I don't think applies here? I'm not sure.
So according to that, it's 12" . WHich seems way to little (especially given for a masonry open fireplace where a flame can roll up and out of the open fireplace). But, your listed appliances stated clearance in the manual supersedes this.

In a more general section dealing with all kinds of solid fuel appliances,
You have to start with the listed appliances stated clearance in the manual, then

12.6.2.1 Clearances from listed and unlisted solid fuel–
burning appliances to combustible material shall be permitted
to be reduced if the combustible material is protected as
described in Table 12.6.2.1 and in Figure 12.6.2.1(a) through
Figure 12.6.2.1(f).

So, best I can read from the code, if you consider your mantel a ceiling, it can be protected with 24gauge sheet metal with an air clearance (1" best I can read from another section of the manual) and when you do that you can reduce by 50% the minimum clearance in the manual to not less than 18", which is where your mantel is at. It doesn't say where between the appliance and the combustible the shield has to be, so I think your free to place it anywhere in between, but not closer than 1" to the combustible or stove.

 

[cycloxer]

Yes I agree. My temporary shield makes a huge difference - so much so that I have left it in place. I am going to try a smaller version today and compare the temps. With the one I have in place, you can slide your hand between the shield and the mantel and feel how cool the mantel remains - and that is with this shield still very close to the wood at the ends. With a 1" gap it would work even better. As long as the shield is at least the same width as the stove you are covered. The temps are much hotter in the center than at the edges.

I'm building the shield for myself and not an inspector so I can can do pretty much whatever I want. The goal is the fabricate the smallest, least intrusive shield possible while still maintaining function and temperature reduction at the lower mantel surface. I'll paint it up in matte black, gap it, and secure it properly once I finalize the design.

 

[73blazer]

I'm building the shield for myself and not an inspector so I can can do pretty much whatever I want. The goal is the fabricate the smallest, least intrusive shield possible while still maintaining function and temperature reduction at the lower mantel surface. I'll paint it up in matte black, gap it, and secure it properly once I finalize the design.

Oh, well, I just posted the regulations for you because the post was entitled "anyone know the regulations". So, now you know!

I think what you got going is going to work just fine, code or no code. (but sounds like you'll be within code). I don't think a shield is really necessary at all, I mean how long would you have to hold a blow torch to that mantel before it caught on fire.

How close are you to 300C in that location?

Table 2 Summary of ignition temperature data
Type of test Ignition temperature (ºC)
Piloted Autoignition
a few grams plunged into a furnace 220-260
radiant heating of a largish specimen 296-497

But, if it helps you sleep at night, by all means, install the shield!

 

[cycloxer]

I put the thermo at the center of the temporary shield when the stove was cruising at 650 F and it indicated 200 F. Stove had been cruising for 4 hours at between 500-700 F.

 

[tickbitty]

The trim below my mantel is what I will need to shield, the manual does not have any particular specs for what or where the shield should be. (Lopi Republic Insert) Seems from my picture searches that for similar applications most people use a black metal shield (similar to the homesaver mantel shields) mounted at a 45 degree angle up at the top of their surround, a few or several inches under the mantel trim. Is that generally acceptable? The trim is 1/5" thick and it is over a foot below the mantel itself.

Even shielded, the trim will come to within 1/4" of the stated clearances, so I want to make sure the shield is what and where it's supposed to be.

 

[cycloxer]

I did more research and asked around. You want 1" of clearance between the shield and the combustible in order for it to be effective. More distance is better. All we can find so far is that the shield has to be at least the width of the stove it is shielding - more is better.

You are trying to protect against radiation (the reflected heat) and convection (the hot air). Radiation is protected via blocking the line of sight. Convection is protected by directing the hot air away from the surface (that is why some of the shields are angled).

I haven't finalized my design yet. I'm probably going to do a small piece of sheet painted black and secured to the underside of the mantel w/ a small lip. My mantel really doesn't get that hot, so I am making my shield fairly small.

 

[tickbitty]

Thanks. Yeah I have been looking at all the threads and it's just not that apparent, some people claim that if the shields are not installed just under the flat mantel using the ceramic spacers that it is not being done "to specifications" and might be wrong, but the clearance I am dealing with is not even my mantel, it's 1.5" thick trim so there's not really any way to use the mantel shield as intended UNLESS it can be done with that 45 degree angle as it is shown on so many people's pictures. The manuals do not seem to spec it out and only a couple of stoves have a shield made to go with theirs, the rest just don't seem to address it. I guess I will do one like everyone else does and hope it is OK!

 

[cycloxer]

The only reason you need a 1" gap is so that you don't heat up the air behind the shield too much. The shield itself is going to get hot and radiate towards your trim. A larger gap is better. Less than 1" is technically not permitted.

 

[tickbitty]

Yeah I think that my shield will end up 10 or 12 inches above the stove (depending on the size surround I choose) and it would still be like a foot below the trim itself.

 

[cycloxer]

Here is what I have come up with so far. I haven't painted it yet, but I am pretty happy with the design. It is fairly low profile and doesn't look too bad. I think once I spray it up with matte black paint you will hardly notice. I bent this up from an 8" x 24" sheet of 22 gauge steel that I got at the Blue Box. Then I used some spacers and screwed it into the bottom of the mantel. The shield is spaced off about 1" and is pitched up slightly away from the mantel to deflect the convection currents away from the combustible. Total cost for the project was about $10 and some of my time. It seems to deflect the heat quite well.

 

[derecskey]

Looks good. personally, if it were me, I think I'd run it the length of my mantel. It would give more of a "it was built that way" impression. It's a case where, to me, more material (running to both ends) would actually draw less attention than a 24" wide piece just in the middle.

 

[cycloxer]

Yeah I thought of that, but I don't like any mantel shields so I went for a minimalist approach. I'll post another pic once I have it painted up to see if it blends in more. I just wanted a little bit of a shield for safety. I am kind of on the fence as to whether my situation really necessitates a shield, but I opted for the safer route. It does work.

 

[elmoleaf]

At a minimum, it probably should be at least the width of the stove...which looks wider than 24". Probably the width of the old fireplace opening would be sufficient.

 

[cycloxer]

Yeah it is about the same width as the portion of the top plate of the stove that is exposed. I measured the temps at the center and at the edges. The center is where the heat is concentrated and the edges are about 50-75 degrees colder. I've seen a max temp of about 200 in the center when I have the stove burning at 650. I consider doing a wider plate, however, this seems to be doing the trick. I don't have a ton of radiation from the stove top because the majority of it is inside my fireplace opening (stove sticks out 2"). So my shield can be smaller as a result.

 

[Ticmxman]

Nice. What did you use for the spacers?

 

[cycloxer]

I just used aluminum spacers w/ #6 screws avail from Agent Orange. I wanted ceramic, but good luck finding those.

 

[begreen]

Look for older electronic ceramic spacers. They also were used in some old electric heaters that may show up in a thrift store. Or you can buy them online at:

http://www.sandhillwholesale.com/fi....html?osCsid=5fa4dfae2468a186ea37459bc954164d