Tempered fireplace glass explodes

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All,
A few nights ago I had a good fire going with the tempered glass doors closed on my pre-fabricated fireplace. Well, I guess it got too hot, after an hour or two, because one of the glass pieces shattered into small cubes. No biggie, I had a replacement, but now I have questions.
Questions:
1. The fireplace has tempered glass (it is a "Majestic BR42") whose glass doors are able to withstand a documented gradual rise to 550F. Did my fire get that hot? I admit I loaded it with 4 or 5 small logs but it was not roaring by any means (I had good embers at the bottom tho that were burning quite hot).
2. I'd like to not worry about the glass doors anymore. My choices are a) get rid of them, b) never close them, c) rebuild a *real* fireplace or woodstove, or d) get better doors. I'd like to do d) for now. If I were to replace the glass, should I simply get thicker tempered glass? Or is there some other product that is the same thickness (3/16" or 1/4" I don't know for sure) that has extra heat protection?
3) Assuming a correct installation (the home builder installed it so you never know, but assume for the moment). Using standard wood for fuel, could I cause the fire to get so hot that it catches something on fire inside the wall, like some studs or drywall or insulation? Is it really that easy for a residential fireplace to get so hot with traditional fuel that it is a hazard to surrounding material used that is "to code" in all respects?
Thanks for any insight!
cj
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Chris Jarshant wrote:

No fan to draw the hot air into the room? All my FPs are direct vent gas ones with thermostat controlled fans. No glass front ever cracked or shattered in their use for more than 10 years.
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Chris Jarshant wrote:

Instead of temperature, it could have taken a sharp hit from an exploding ember. It's not unusual to find nails in wood. Also it could have been in a strain from a slightly warped frame.
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Not sure if you're fire got too hot or not but I would think the glass would trap a lot of the heat with little escaping to the outside. If you have a choice, you might consider replacing them with a screen.....it'll allow more heat to pass as well. I can get my fire going pretty hot (never measured it but I would think it's above 550 degrees easily). On the install, it's hard to say what you've got. Fireplace clearances and dimensions are pretty specific but for the pre-built units, I'm not sure what they are. I do know that for a built fireplace, you need 8-8.5" behind the firebox of nothing but masonry or air (I see different opinions on whether it's 8 or 8.5" and whether or not to leave an air space), the mantle should be 12" in. minimum above the opening, and wood members shouldn't come within I think 2" of the fireplace masonry but you really should check that. I'm building a fireplace now outdoors and have no combustibles near it at all so I really haven't paid much attention to the clearances required. If you do decide to build your own, I believe a footing of 12" thick that extends 6" beyond the footprint of the fireplace is necessary. It may not make sense for you if you're in a slab floored house as you may have to cut out an opening in your floor to pour a footing that thick. Cheers, cc
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Screened opening makes sense if you're trying to heat the county, at the expense of cooling your house, or if you want ventilation in spring or fall; else you gotta be nuts. A fire at 550F is a smoker; over 1000F you're cooking.
Forget the screen. Go for a properly-designed woodstove or insert and hook it in, and get some useful heat out of it without having to wear a flack-jacket and full-visor.
J
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Chris Jarshant wrote:

I wouldn't worry about it.
Tempered glass can blow up for absolutely NO reason at all. You will probably never have this problem again if you simply do nothing.
This may sound like a half-ass answer but it's the truth. I've been holding a piece of tempered glass in my hand and had it blow up for NO reason.
Ever heard of a doorglass blowing up in a car before for no reason? Same thing.
Call any glass shop and they will tell you this.
BTW, I'm sure there is a scientific reason for it but a glassman isn't a scientist : )
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no reason at all.
I think you are mistaken.
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Had that happen to me once, scary as anything. Just buckling my son in his carseat in the back after church one Sunday, my wife is standing next to the car talking to some people, and BOOM, the entire back window shatters into a million tiny pieces. We puzzled over this for hours. No cars were going by (to throw a stone), not under any trees (something to drop), very few people around on sunday morning (to throw or shoot something), no one was touching the window at the time or for at least an hour prior, not a very cold or hot day (for temp stress), not windy at all (?). It was a pretty old window -- probably 22 years or so.
The glass repair company wasn't surprised at all. "Happens all the time" they said, explaining that it is just a terrible coincidence of stresses and wear and whatever, combined with old glass, possibly a tiny defect from the manufacturing, a hairline crack spreading slowly over time, or whatever. But the effect is that it seems fine one minute (we even scrapered ice off it that morning), and next thing you know it is just bits and pieces.
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kevin wrote:

For all you doubters just read this post.
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Toller wrote:

Well, I've been in the glass business for going on 26 yrs, so I believe YOU are the one who is mistaken.
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I'm sure there is a reason, you just don't know what it is. [g]
I had the pane of a sliding glass door spontaneously self-destruct "for no reason." We were sitting right there when it started. My wife first though the PITA neighbor kid shot it with a bb gun but it was the inside pane of a double-pane glass. It actually took a minute or so for the crazing to propagate over the whole surface.
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clipped

The windshield on my car broke a while back. For a few days there was a small "y" shaped crack, then it went all the way up. I suspect it happened because heat was uneven. Car has been sitting in Florida sun for 8 years. Even morning sun is surprisingly hot, and I think the sunny side got hot before the shady side did. Slider could have had just a scratch, and enough stress from heat to expand it. After all, glass cutting is just extending a scratch.
Had the glass on a gas grill explode once, but that was because it was hot and it began to rain.
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Wes Stewart wrote:

Why snip my post when I wrote the following?
"BTW, I'm sure there is a scientific reason for it but a glassman isn't a scientist : )"
Tempered glass explodes all the time. If there is a reason, I've never heard of what it is in the 26 yrs that I've been in the glass business.
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This happened to my fireplace years ago, replaced the glass with a new piece and it has been good for over ten years now. Any defect in the glass will be exposed under the extremes presented in a fireplace installation. Tempered glass is only designed not to shatter into dangerous, sharp shards. Many people think it is the same as bulletproof glass. No. The only thing you want to be sure of is that the glass is loose in the frame. You need to account for thermal expansion. If the glass is tight to the frame when it is cold it will be stressed when it gets hot. And you have to clean the crud out of the frames regularly too.
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Chris Jarshant wrote:

This doesn't answer your question, but about three years ago I bought a glass and screen doored one for out firplace from Home Cheepo. While installing it I was suprised to see the instruction sheet warned against closing the glass doors while a fire was burning inside.
I thought this was strange, since the box it had just come out of had a nice color picture on it showing a fire merrily burning behind the closed glass doors.
I went to the manufacturer's web site and found similar photos, so I hooked an email to them asking why the instructions said not to do that.
I got a wishy washy answer from them saying that it was ok to close the doors on a fire "most of the time", but that an extra hot fire could possibly cause the glass to shatter.
WTF? We've gone ahead and closed the doors on plenty of fires in that fireplace since then and the glass is still OK.
Jeff
--
Jeffry Wisnia

(W1BSV + Brass Rat \'57 EE)
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clipped

the middle is hotter than the perimeter of the glass, it would logically be stressed. Any tiny scratch is the beginning of a crack, just like when you use a glass cutter.
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wrote:

I'd contact the company and complain. If it made for heat, it should not explode. Besides someome could get hurt and they would have a legal case. Even if they dont do anything they at least know, but likely they will give you a free door. Who knows, there may even be a recall. All it takes is a phone call, email or letter.
The old wood stoves used mica, that never broke.
I should note that you could have had the wood too close to the doors, The fire should be to the rear.
I agree with the guy that said you are losing heat with glass in front, a screen is better. No sense wasting the heat with fuel prices what they are.
Of course there is one other possibility..... Did you notice a guy wearing a turbin near your house? Could be terrorists <lol>
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On 5-Feb-2006, snipped-for-privacy@UNLISTED.com wrote:

How does the glass reduce the heat?
Replace the glass with a screen and the air flow will increase the rate of combustion and carry the heat up the flue. Using glass doors, properly sealed, increases the efficiency of a fireplace by a lot. They reduce the air flow and allow you to choke down the fire. That's why glass doors have been used on fireplaces for the last few decades.
Since glass doors are quite common and they are there to increase efficiency,, it is not reasonable to assume that they shouldn't be used. I think the most reasonable explanations are either that the glass had a scratch or crack in it and differential heating caused the crack to propagate or that some liquid (was the wood really dry?) hit the glass and caused a significant temperature gradient locally.
Mike
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wrote:

It has always amazed me how few people know that glass doors are supposed to be closed when you are burning a fire. I always try to appeal to the pure logic of it. If they are not supposed to be closed while the fire is burning then what is their purpose? The fireplace already has a flu to close when you are not burning a fire so logically there is no purpose served by glass doors at all unless they are closed while the fire is burning.
I mean do these people think they are there to keep the cat out?
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