Hotblast Furnace During Power Failure ?

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BIG BEAM
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Post by BIG BEAM » Wed. Nov. 12, 2008 11:27 pm

I have a hotblast furnace and one thing that always bothered me was if I had a power failure and the furnace was cranking along would the furnace be damaged ?I know some air would gravity through the ducts but would that be enough to "cool" the furnace?If I was home no problem,I have a generator but if I wasn't would it over heat and buckle the chamber?
DON

 
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DOUG
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Post by DOUG » Sat. Nov. 15, 2008 4:05 pm

BIG BEAM,
I have a solution for your possible over heating of the stove and your duct work when you lose power.
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Fabricate a hinged door that seals tight with standard weather stripping and attach the door to a ceiling shutter motor. Wire the motor so that it closes when the circulation return blower kicks on and opens when the blower shuts off. This will do two things for you. One, when you lose power your door will open allowing gravity heat flow. Two when the blowers not on, it still allows for smooth low gravity heat flow through the duct when the furnace is at idle. Hope this helps. :idea: DOUG

 
BIG BEAM
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Post by BIG BEAM » Sat. Nov. 15, 2008 8:07 pm

It will "gravity" through the ducts all on it's own.I guess my question is that enough to keep the furnace from over heating?
DON


 
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DOUG
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Post by DOUG » Sat. Nov. 15, 2008 9:12 pm

BIGBEAM, What I forgot to tell you is that I had relocated my blower fan upsream in the duct work. The blower is not behind the hinged door you see in the pictures. So, what that means if you have your blower installed like normal, attached to the furnace like the directions from the HOT BLAST manual, you probably don't have enough cold air return being sucked through the mounted blower to keep the furnace cool without power. The answer to that problem is, still fabricate the door as mentioned in the previous reply, but cut the hole into the bottom of one side ofthe furnace jacket and mount the door there. This should make you at ease, after you see how well it does work. You won't get as much heat as normal, about half from the supply registers and your duct will get much hotter than normal. But if you have the combustion draft kit installed on your hot blast, without power, you won't be stoking the fire anyway. If not, you know that at least a hot firebox will have some relief by sucking in the cooler air from the floor. It does work. No were near the best gravity system, but it should give you peace of mind. DOUG :idea:

 
BIG BEAM
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Posts: 712
Joined: Fri. Jan. 25, 2008 9:34 am
Location: upstate NY

Post by BIG BEAM » Sat. Nov. 15, 2008 9:27 pm

Now that you mention it maybe a combustion fan is the answer.When the electric goes out so does the fire,(mostly) or at least down enough so the furnace doesn't over heat.
thanks DON
Now I have something else to build(I was getting bored anyway).

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