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Old 11-08-2010, 10:42 AM   #1
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Furnace too big?

About 6 years ago, I bought a new house. As part of the renovating process, I had a Home Depot contractor put in a new furnace in which also allowed central air conditioning to flow through the same vents. For a little over 5 years both A/C and heat seemed to work just fine but then at the end of last winter, the furnace started blowing nothing but cold air. At the time it was not a major concern as winter was pretty much over. When Fall came around, we had another heating contractor examine the furnace. This guy immediately pointed out that the furnace was too big our house. He went ahead and replaced the filter and did whatever he needed to do to get the furnace generating heat to the house again. 2 weeks later, the problem was back. The guy comes back and now says in order to fix the problem, they'll need to redo all the duct work because basically they can't handle the oversized furnace. Obviously, that route will not be cheap but I'm puzzled at frustrated at what to do. It just doesn't make sense to me that something that worked for 5 years would be the result of it being the wrong one for my house. Any input or advice would be greatly appreciated


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Old 11-08-2010, 11:49 AM   #2
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It just doesn't make sense to me that something that worked for 5 years would be the result of it being the wrong one for my house.
Ayuh,... I agree,... I'd call a different contractor for a 2nd opinion...
Or rather, a contractor that can Fix the furnace, instead of just replacing it...


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Old 11-08-2010, 01:59 PM   #3
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Why not call back the original contractor? Shouldn't this be under warranty?
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Old 11-08-2010, 02:34 PM   #4
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First, have someone do a "manual J" calculation to see if your furnace is truly oversized.

Replacing all the duct isn't going to solve the problem of the furnace being oversized. I would find a tech who can get the furnace repaired and then check the temperature rise when the unit is running again to make sure you don't need to modify the duct to keep from cracking the heat exchanger, having the furnace shut off on high limit or to reduce excessive air noise from having duct that's too small.

I wouldn't replace all the duct if it isn't necessary because then when you do install the correctly sized furnace in 15 years your duct will be the wrong size.
"The physician can bury his mistakes, but the architect can only advise his clients to plant vines." -- Frank Lloyd Wright
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