Draining attic furnaces?


Awl --
On the utterly useless ng alt.hvac, reference was made to a lennox 90% furnace not working in a very cold attic, that some drain was freezing up, causing the furnace to malfunction.
What needs to be drained in an attic furnace? In ANY furnace? I have a furnace with a dehumidifier whatsits, and no drain.
The only drain on my furnace is for the A/C condensate.
And also, what exactly is malfunctioning and why?
--
EA




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wrote:

Is it your furnace, or someone being abused at alt.hvachackforabeer, the drain on a condensing furnace cant freeze.
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wrote:

Is it your furnace, or someone being abused at alt.hvachackforabeer, the drain on a condensing furnace cant freeze. =========================================
I guess Google is my friend: http://en.wikipedia.org/wiki/Furnace is a good article, explains condensing furnaces.
Actually, it was a mechanic posting. They don't abuse other ""tradesmen"", just home-moaners. When a tradesmen posts, they figger they have another participant for their circle-jerk.
Here's the thread:
---------------------------------------

Yes it is a little hacky, I thought it might have been freezing in the trap too, that's why as I mentioned we insulated and put heat tape on the trap and drain line thinking that woud solve the problem, but it didn't. I think something is freezing in the furnace itself.
---------------------------------------------------------------
So, they seem to agree that some water is freezing, just not as to where. Since I don't think the system would really care if condensate is freezing or not, mebbe it could be a lockout sensor for flue gas temp, sort of like flame detection?
I'm a little hardpressed to figger out what a furnace is doing in an attic, as well, but that's another story.
--
EA




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Existential Angst wrote:

exhaust vapors so much that water condenses and must be drained. Much depends on the furnace design on where it might be freezing. I know on my unit, it could happen in several places, however, it won't as it is in the somewhat warm basement (60 degrees or higher). I have a condensate pump on my system, and if it gets over full, it will shut down the furnace. The output hose did have a little dip in the line, and when it froze, the heat shut down. So, you have to check the entire run from where it come out of the heat exchanger/fan unit, all the way to the place where it finally drains. I could be anywhere. I doubt if it is inside the furnace, as it makes its own warm environment (when it's running properly) and probably won't freeze, unless you are in a really cold environment. So, it's probably somewhere after the water exits the box.
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Art Todesco wrote:

Hi, Now there you go, EA, over to you.
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Well, Tony, doesn't it boggle your mind as well, that one can have a dialogue amongst a bunch of struggling home-moaners that is 20-30x more intelligent, informative, and productive than ANY thread in the HISTORY of alt.hvac?
It had to have been all that freon, affecting their already assaholic brains....
--
EA



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wrote:

Forced air furnaces in an attic are not unusual. In many larger two story homes they have one in the basement for the lower portion of the house and one in the attic for the upstairs. Much easier to run the ducting and better temp control.
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Existential Angst wrote:

In addition to what Art said, a condensing furnace should never be put in a non conditioned (attic) area. The risk of damage due to freezing is too high. The entire heat exchanger can be damaged if it freezes during a power outage or even between cycles if it's off long enough.
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That's news to us here in NJ where they are going in loads of new construction. A similar argument could be made against putting AC units in attics or bathtubs upstairs. There is always some small risk of potential damage. But properly installed they do just fine.
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On Fri, 15 Jan 2010 07:54:37 -0500, Existential Angst wrote:

The 90% efficiency furnaces create condensation in the exhaust and it needs to have a drain line on them. If it freezes this condensation backs up and blocks the exhaust, creating backpressure and the temp rises, causing the furnace to shut down.
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Existential Angst wrote:

You'd think no one has ever heard of heat tape. When I install a walk in freezer, I install electric heat tape on the drain pipe. The same stuff will work on the drain line of a condensing furnace located in an attic or a utility room that is unheated. It's a simple problem to cure with off the shelf products.
TDD
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