# Is my mantle getting too hot?



## ash bucket (Jan 21, 2010)

I have a Fisher wood burning insert in my living room (it was already there when I bought the house). After the stove has been up to temp for a while I can put my hand on the bottom side of the mantle and it is almost to the point of being too hot to touch for very long. This worries me as I like to load up the stove and let it burn overnight while we sleep in the opposite end of the house. The mantle is custom made out of some old lumber. Not sure what kind of wood it is or how old it is. It is unfinished, rough looking, just the way I like it. I haven't measured it yet but the bottom of the mantle sets at least 24" above the top plate of the insert. The insert sets out of the fireplace opening roughly 10". Is there any possibility that it could get too hot and catch fire?


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## gzecc (Jan 21, 2010)

If its too hot to touch, something has to move.  What are the specs for combustibles for that stove?


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## ash bucket (Jan 21, 2010)

Not too hot to touch but much more and it would be. I was kinda hoping somebody could tell me what the specs are on it. I have found absolutely no info on Fisher stoves as I'm sure many people here know. I can't even find any pictures of my stove on the internet much less what the name of it is. All I know is it says Fisher in the bottom right corner of the right door. It has two glass doors.


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## yanksforever (Jan 21, 2010)

How about some pictures!


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## ash bucket (Jan 21, 2010)

Ha! I was waiting for that one. I'll have to take some tonight and post them tomorrow as I am at work now.


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## jharkin (Jan 21, 2010)

I looked it up and the auto ignition temperate for hardwood is approximately 570 F.  Doubt your mantle is that hot if you can touch it 


But as has been mentioned your best bet is to look up the clearances and adjust if necessary with heat shields/etc.  Gives you a margin of safety in case of accidental overfire and covers your rear for insurance and code purposes.


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## ash bucket (Jan 21, 2010)

Thought about a heat shield but I think it would be pretty unsightly. Maybe something I could install during the winter when I'm using the stove and take down during the off season. I wouldn't mind as much what it looked like so long as I could sleep better at night. Anybody have such a thing or know how I could make one?


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## savageactor7 (Jan 21, 2010)

Yes it's too hot...ya have to do something asap. When you play with fire you have to be right all the time...fire only has to be right once.


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## agbagb (Jan 21, 2010)

I've just been looking in to this kind of thing as it was pointed out to me on this thread that storing my logs close to the stove is potentially risky.

Please set me straight if I've got this wrong - If over time (whilst the heat is on) the wood does not char, blacken, then it will be OK.  This can happen at temperatures as low as 80 o Celsius.  If it does blacken it will be giving off combustable vapours that could ignite with a flame or spark. However in practice these small amounts of gasses would be blown away quickly.  I would say, if you can at all times hold your hand on it, it will be OK.

Something else to look, I have a vauge recollection, could be borax as a fire retardent.

Andy


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## ash bucket (Jan 21, 2010)

If I installed a heat shield, how much of a gap would I need between it and the bottom of the mantle. Would an inch suffice, or maybe a couple inches? I'm guessing the more the better.


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## ash bucket (Jan 21, 2010)

I keep an eye on the underside of the mantle often and I see no sign of discoloring. Since this still does not ease my mind, I'm going to have to do something about this especially since savageactor7 put it the way he did. Just not worth the risk.


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## agbagb (Jan 21, 2010)

Before you do, just so you can get an idea of the real risk, try an experiment.  

Hang some paper down from mantle, see how close to the stove top it needs to be before it chars and then ignites. 
Of course don't leave it un-watched and have a bucket of water ready.

Have fun - and let us know how close you can get it.  

If you have a straight up flue pipe the distance from this to inside of the mantle will be more important.  UK regs state 18" for a 6" pipe.


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## begreen (Jan 21, 2010)

jharkin said:
			
		

> I looked it up and the auto ignition temperate for hardwood is approximately 570 F.  Doubt your mantle is that hot if you can touch it
> 
> But as has been mentioned your best bet is to look up the clearances and adjust if necessary with heat shields/etc.  Gives you a margin of safety in case of accidental overfire and covers your rear for insurance and code purposes.



As sustained heat breaks down the molecular bonds in the wood, pyrolysis can reduce the ignition point considerably.



			
				ash bucket said:
			
		

> I keep an eye on the underside of the mantle often and I see no sign of discoloring. Since this still does not ease my mind, I'm going to have to do something about this especially since savageactor7 put it the way he did. Just not worth the risk.



For peace of mind, hang a simple heat shield that is about 8" wider than the stove on the underside of the mantle. Attach using 1" non combustible spacers.


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## ash bucket (Jan 21, 2010)

I'll have to do the experiment sometime when the wife isn't around because I don't even wanna hear what she would say about me playing like that. And the chances of me having a good fire going and her not being around are not good. Nice thought though.

About the flue pipe...is this something to worry about even though my flue pipe is in a masonry chimney?


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## agbagb (Jan 21, 2010)

ash bucket said:
			
		

> About the flue pipe...is this something to worry about even though my flue pipe is in a masonry chimney?



Dont worry about that, the minium distance I quoted is air gap distance

I have the same problem wife problem with experiments as well, be sneaky hang bread up and pretend it's a new way of toasting. :cheese:


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## agbagb (Jan 21, 2010)

Just found this article

Covers the subject of distances to combustable surfaces but nothing specific about mantles


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## Bootlegger (Jan 21, 2010)

When I replaced my old Fisher I installed a heat shield on our cherry mantle.  In the pics below you'll notice that the cherry was charred from years of using the Fisher.  The heat shield actually looks ok, not too obvious.  And yes, you can take it down in the summer.


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## ash bucket (Jan 21, 2010)

Wow, that's crazy how charred your mantle is. Mine doesn't look like that yet. Although over years I'd say it would. I know for a fact that the previous owner of my house did not use my insert as much as I do now.


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## ash bucket (Jan 21, 2010)

So I just found a heat shield for mantels on sale at northern tool for 24.99. Measuring tonight to see if it will fit and will be ordering if so! If not I will be making a custom one out of sheet metal from here at work. Thanks for all your replies. I will still be taking pictures tonight and posting them tomorrow just because I want to and to see what you guys think so check back in. Thanks again! Love this site


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## heffergm (Jan 21, 2010)

You should contact the company to ask about clearances if they're still in business. 

I had to remove my pine mantel. It had been there when I was a kid and my dad was burnig coal in a VC resolute, but when I put the new stove in it didn't meet the spec, which was something like 40". Not worth the risk for me. Code was different back in the 70s when the old stove went in. It didn't even have a liner, just a shorty pipe venting to the clay flue. Burned that thing for 10 years!


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## Battenkiller (Jan 21, 2010)

BeGreen said:
			
		

> As sustained heat breaks down the molecular bonds in the wood, pyrolysis can reduce the ignition point considerably.



Yes, and when it gets to the charcoal stage, it can auto-ignite at about 300ºF.  That's pretty high still, but seeing that cherry mantle charred that bad, I'll certainly make sure that a heat shield is the first thing I install if I go ahead next year with that F 100 Nordic QT I've been eyeballing for my fireplace.

Interestingly, I use a pure charcoal block (made in my stove and cut into a block on my band saw) to silver solder on. I use an oxy-acetylene torch that is at about 5500ºF, and yet the charcoal never starts on fire.  That's because the charcoal needs oxygen as well as heat to burn and the torch uses up all the oxygen.  Pretty weird to see a red-hot block of charcoal sitting there on a fire brick when I know if I toss it into the stove it will disappear in no time.


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## Bootlegger (Jan 21, 2010)

ash bucket said:
			
		

> Wow, that's crazy how charred your mantle is. Mine doesn't look like that yet. Although over years I'd say it would. I know for a fact that the previous owner of my house did not use my insert as much as I do now.



I didn't even know it until I replaced the stove and I took that picture with a flash.


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## Cluttermagnet (Jan 22, 2010)

A mere 1 inch will do ya. That is an oft-quoted separation between various types of heat shields and combustibles such as walls, mantles, etc. Typically wood stove *manufacturers * specify that 1 inch separation. Amazingly, the heat shield usually allows you to decrease to 1/2 or even 1/3 of minimum separation without the shields.

I have a mantle heat shield, it works great! Does a fantastic job keeping it from getting warm. My mantle used to get pretty hot to the touch if the stove was really cranking (not all that often)- but not so hot I couldn't keep my hand on the underside constantly.


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## Cluttermagnet (Jan 22, 2010)

Bootlegger said:
			
		

>


Your mantle shield looks really good! This is the first photo I've seen of it. I did see the charred mantle in an earlier thread.


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## Cluttermagnet (Jan 22, 2010)

ash bucket said:
			
		

> So I just found a heat shield for mantels on sale at northern tool for 24.99. Measuring tonight to see if it will fit and will be ordering if so! If not I will be making a custom one out of sheet metal from here at work. Thanks for all your replies. I will still be taking pictures tonight and posting them tomorrow just because I want to and to see what you guys think so check back in. Thanks again! Love this site


Good deal. That should do ya. Make sure it contacts the wall or bricks that the mantle is hung on- no gap for stove heat to sneak behind. You'll be fine. 25 bucks sounds like a pretty good price for one.


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## hareball (Jan 22, 2010)

When I'm running my Fisher hard and have splits all around it the hottest I've seen on the IR is 110 °F.  The bricks from top of stove up about 6' average 120 °F .


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## ash bucket (Jan 22, 2010)

So I lied in my first post saying the bottom of my mantle is at least 24" from the top of my stove. After measuring, it's 20" to the bottom of the mantle. The heat shield from northern tool will not work on my mantle because it's only 10" deep. My mantle is 13.5" from the brick so I'd have a gap in the back if I got that one. I'm gonna try and make one today at work out of sheet metal. One question...if I run the heat shield through the paint line here at work (ED coat black) it won't give off any harmful stuff if it gets hot will it? The "paint" is baked on in the oven at the end of the paint line anyway. Just wanna make sure it's safe. Hate to create another problem in trying to cure one. Anyway, here's some pictures:


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## heffergm (Jan 22, 2010)

Yikes... Darth Vader would have had that stove if he'd lived long enough to retire to an evil farm somewhere.


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## Bootlegger (Jan 22, 2010)

ash bucket said:
			
		

> So I lied in my first post saying the bottom of my mantle is at least 24" from the top of my stove. After measuring, it's 20" to the bottom of the mantle. The heat shield from northern tool will not work on my mantle because it's only 10" deep. My mantle is 13.5" from the brick so I'd have a gap in the back if I got that one. I'm gonna try and make one today at work out of sheet metal. One question...if I run the heat shield through the paint line here at work (ED coat black) it won't give off any harmful stuff if it gets hot will it? The "paint" is baked on in the oven at the end of the paint line anyway. Just wanna make sure it's safe. Hate to create another problem in trying to cure one. Anyway, here's some pictures:




You definitely need the heat shield with that wood.  As far as the coating goes, you need to check and see what the temperature the product is tested too.  I know if you buy black spray paint at the store it will not work on stove parts, you have to buy the (more expensive) high heat paint.  Check with the product manufacturer.  The gaps on mine are about one inch plastic spacers.  Here's a pic of the gap:


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## Bootlegger (Jan 22, 2010)

Cluttermagnet said:
			
		

> Your mantle shield looks really good! This is the first photo I've seen of it. I did see the charred mantle in an earlier thread.



Thanks, it looks good enough I'll leave it up year round.  It does catch dust and flaky mortar from the brick wall (another project for another day).


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## Cluttermagnet (Jan 24, 2010)

I used stock 14 in wide aluminum flashing purchased at Home Depot. It is thin and comes coiled up in standard lengths. Mine was a 10 ft roll. Nothing special about that paint. 'Regular' enamel paint will hold up fine. You only need stove paint on an actual stove. That heat shield will get nowhere near as hot as the stove.

My mantle has only a little more than half the spacing you are working with. My heat shield totally solved the problem for me. Yours is an easier case. Just cover the entire bottom, back to the bricks, and avoid any way for heated air to sneak up behind the shield. Bend the shield up in front of the mantle with a bit of a front lip, and your problem will be solved.

There's a photo of mine here.  Not real pretty, but very functional.


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## woodhound (Jan 24, 2010)

We just threw a fisher like that in the scrap pile couple weeks ago, thing was in mint shape too.   We had a guy that bought a freedom bay insert and when I went to install it I saw something I will never see for a long time.  He burned his masonry fireplace so hot he boiled the sap out of mantel and it was 30" above the opening.


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## tickbitty (Jan 24, 2010)

You can buy the screws with ceramic spacers ready to go.  These are the same kind that come with the pre-made mantel shield.
http://www.northlineexpress.com/itemdesc.asp?ic=5CO-54230


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## webbie (Jan 24, 2010)

Yeah, I would definitely protect that mantel.......I don't think you will have a problem with any of the paints and coatings at work......the shield is unlikely to hit over 140 or so.

Another option which many use is to install the heat shield so it slips behind the top shield on the insert and then angles outwards and upwards. It would only have to go far enough to cut off the line of sight from the end of the mantle to the stove top....sometimes it even works with a little less since the heat is "thrown" forward.

The Rule of Thumb is pretty good in this case - that if it gets too hot to touch after the stove is in high mode for hours - it is probably too hot.

There are also other concerns with radiant heat inserts...although you don't appear to have that problem. Heat can soak through the masonry right up to mantels or even wood framing in the wall. We recently had such a fire near here caused by an insert. In your case, this is mitigated by the fact that the insert is double wall under the fireplace lintel and also the wall appears to be solid masonry. You would be surprised how many fireplaces have wood in the walls a foot or two above the opening!


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## ash bucket (Jan 25, 2010)

Well look what I installed this weekend. I made this heat shield out of 14 ga. sheet metal. It has about 1-1/4" gap from the mantle. I sprayed it with high temp paint just beacuse. I think it looks ok. Probably will just leave it up all year round. What do ya'll think?


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## gzecc (Jan 25, 2010)

I think it looks good. Can you move it a few inches to the left?


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## ash bucket (Jan 25, 2010)

It's actually centered up on the mantle which is centered to the brick. The stove is what is off-center of the brick and it really annoys me. I was just waiting for someone to notice. Oh well, the stove puts off heat and that's the main thing.


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## savageactor7 (Jan 25, 2010)

Well that was pretty fast ash bucket...good job.


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## Cluttermagnet (Jan 25, 2010)

Good job. Nice, solid steel spacers you found. You're golden now. ;-)

Downright attractive.


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## ash bucket (Jan 25, 2010)

Yes it is poor camera angle. I apologize. I used 6 couplings that measured right at 1-1/4". One on each corner and two in the middle to ensure an even gap. The front lip is clear of the wood. Here's another:


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