Metal Mantel Shelf for Wood Burning Insert

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hariot

New Member
Hearth Supporter
Sep 27, 2009
3
Northern Ct
Hi,

This is my first posting. I apologize in advance for it’s length. We will soon be having a flush mounted, wood burning fireplace insert installed. Our house is a 1950's contemporary and we want a simple look. After the insert is installed we will put up a mantel shelf (no surround, just a shelf). Our ceilings are not incredibly high, and at some point in the future we want to put a big screen TV above the fireplace. To conserve space (height) we'd like to be able to mount the mantel shelf lower than the limits dictated for flammable materials. So, as we see it, we have two shelf choices, stone or metal. We have toyed with the idea of a manufactured stone shelf, perhaps fabricated as a floating shelf, with no supports visible. But that could get expensive (like, more than the cost of a TV). Another option is a metal (aluminum) shelf. They can be had at the right length (about 5 feet) for less than $150 and are an easy DIY install. The aluminum shelf has a slight upward lip at the front edge so decorative items like stones/fossils or pottery can be displayed with no fear of them falling off.

So, to my question. I'm aware of the NFPA Minimum Mantel Vertical Clearance data. But these apply only to flammable mantels and do not consider the most efficient movement of heat away from the upper fireplace wall. What I'd like to know is; is there data available for the best depth of shelf and height of placement (relative to insert and TV) for a stone or metal shelf. Clearly the deeper the shelf, the more air it will deflect. But at the same time I'd like my shelf to be as shallow as possible. The fireplace will be “flush”, the future TV will be "flat". The last thing I want is a two foot deep shelf! Also, my assumption would be that the lower I mount the shelf, the more heat it will deflect from a TV. But perhaps it’s the exact opposite! Doubtless the aerodynamics of convection and the physics of radiation are far more complicated than I have considered.

If anyone knows of some proven rules of thumb or actual researched data it would be very helpful. Any informed opinion about the use of a metal shelf (I know metal is a good conductor) would be much appreciated. I will of course be doing temperature checks on the upper fireplace wall, once the new insert is installed. The metal shelf I prefer is 4 inches deep, though there is another I could use which is 5.5 inches deep. And nobody needs to lecture me on either the aesthetics of a TV-over-fireplace installation or on the potential body mechanic consequences. Our current TV is mounted high on a shelf next to the fireplace and it all works very nicely. I am also keenly aware of the potential harm heat and smoke can cause to delicate electronics. But thats why I’m asking this question. I’ve read lots of good information on this forum and am hoping there’s a smart member out there who can help me get this right.

I thank you most kindly for your time. And in advance for your assistance.[/size]
 
Welcome to the forum. I am not the smart member you're looking for, but I did stay at a holiday inn a few weeks ago. Sorry I don't have any specific data, but in regard to your question - I would think the further out the mantle protrudes, the better, the higher up the mantle is, the better and the closer the TV is to the top of the mantle, the better. If the mantle is low to the fireplace, doesn't stick out very far and far below the TV, I could pretty easily see the heat just wafting right around the mantle and continuing to climb right back up the wall. Also, most (if not all) flat screen TV's have some sort of active cooling (fans) so they are automatically pulling in surrounding air. You would just have to look at this image - rotate it 90 degrees counterclockwise and imagine the red arrows are warm air coming off your fireplace.

(broken image removed)

You seem to have the warnings covered and you're right - the mantle space above a wood burning fireplace is not real happy home for expensive electronics. So give it a shot, but if the TV dies, don't say we didn't warn ya.
 
Two things to think about. First, aluminum will conduct heat very well, so you want to make sure you don't put anything flammable on it.

Second, the ideal height for a TV is to have the bottom third of the screen at eye level. This puts the bottom of my 60 inch tv slightly above the handle on the door of my insert. That's why my TV is next to the insert.
 
Thanks for the replies so far.

The insert we are hoping to get is a Scan DSA 4. I'm hoping that it's design will throw as much heat forward (not up) as possible. The airflow diagram Pyro Extraordinaire posted is interesting. I guess I won't know the full effect until I take temp readings with the new insert and then again with my "mantel" in place. Don't worry Mater of Fire. I won't put anything flammable on my metal mantel. And please don't worry about the mounting height issue. As I said, for years we have had a TV next to the fireplace, at the same height as "above the fireplace" would be and it's not only acceptable, it's a great height. We will be sitting over 16 feet from any new TV and have never found this height to be an issue in any way. A new TV WILL go over the fireplace. That's not in question. My issue is trying to figure out the best way to make my little aluminum shelf plan work.

Thanks again to both of you. Hope there are more of you out there with other helpful comments.
 
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