I finaly found a contractor that seems to know whats going on. He agree'd and said that that return air vent needs to be MUCH larger. It should be more than the CFM of all the air going out. I helped him run new duct work I was so happy to get it in. We boxed in the trusses over about 6 feet and then ran new duct work, large rectangle back to the wall. From the wall, we used 2, 8" runs about 3 feet down to the cold air return. We used these because it saved having to make a new plenum and would work for that short of a run with 2 of them.
It has not been very cold, so its hard to tell how well things are.
It was a good experince, enjoyed learning from him. Have many cuts on my hands from the sheet metal
He suggested changing the other duct work as well. That the plenum should fit into the duct work, not the duct work into the plenum. Right now the heat is coming out the both sides, and restricting the air flow.
I'm thinking its somthing I can tackle alone, but maybe I'm being over confident? Or will leaving the current 8" work fine?
Anyone know how much changing over to larger duct going out will help on a gas bill?
To the people worried about the cheapest bid or the details,
I did not pay for any of the installation, the furnace or even the filter. When I negociated the terms of the sale the owner said he could include that. I'm assuming that he had a "hookup" or friend in the business, and could get it done really cheap.
So yes, it probably was a very cheap bid. I do have the contact information of the installer though from the warantee information I requested after the install.
I called him, he said it was the insulation. I could have taken it to court and waited the months for him to come up from Detroit and get it settled. All the while I'll be paying a in ecess of $300+ heat bill all winter.
Or I can try to find a contractor to repair it, its a small town I live in with 2-3 local contractors. I only found one I liked and he's from a different county, older guy but was extreamly informative.
To make it short and simple.. That was the right size furnace. If the temp reaches no higher than 68. I agree with the contractor. You have another problem. I use a 75,000 for my 1200 house plus basement. Acually, I am running it at about 40,000 output. and still keeps up.
The biggest mistake the amature furnace installer make is putting them on to big.
I dont even have the time to tell you what things you have to consider when deciding what size furnace to install.
Duct type and size
IWC filter, A coil, windows, traffic