New Furnace Too Small


Old 02-01-04, 02:10 PM
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New Furnace Too Small

I just moved into a new house in Pittsburgh, PA. It was a new construction / spec home. The house came with a Trane XR90 gas furnace, model TUX120C960D0.

Twice in the week that we have been in this new house the furnace has shut off over night due to frost clogging the intake pipe outside the house. It is easily cleared and the furnace comes right on, but this can't be right. The furnace guy says he is going to come over and maybe reroute some of the pipes to prevent this or something? The first night it happened was moving-in day and he said we probably let a lot of moisture into the house with doors open. But it happened again last night and we weren't moving anything!

The outside dimensions of the house are 31' X 59' (by my calculations that is 1,829 sq. ft. per floor). It has 2 living floors and the 3rd lower level is a garage and basement (about half each). So, the total square footage is minimumally 3,658. At most, add in another 900 sq. ft for the basement and it is 4,700.

Trane's web site says this furnace is capable of 113,000 BTUH.

A web site I found ( says that this many BTU's is appropriate for a house only 2,825 sq. ft. A house that is 3,658 sq. ft. requires 146K BTU's.

What am I missing? Is this furnace WAY undersized or what? Is the frost accumulation a symptom of an undersized furnace?
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Old 02-01-04, 03:55 PM
Ed Imeduc's Avatar
Join Date: Aug 2002
Location: Mountain Williams Missouri
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New, just moved in. Get the furnace guy back and fix it for sure dont let up. Does the furnace heat the home to 70o now if so its ok Id say. You cant go by sq ft of a home for what the BTU heat loss is . You have to do a heat loss on the home. ED
Old 02-02-04, 08:13 AM
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the size of your furnace is not the problem. the problem is what is making the intake pipe freeze up?
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