What size furnace?

debs3November 12, 2012

Hello, A friend of mine just had a new furnace installed. It is an Amana 2-stage, 60,000 BTU furnace. Her house is only 1,000 sf. She lives on the peninsula in the SF Bay Area, so the climate is mild. Isn't it too big? From what I have read on eHow it should only be 25,000 to 30,000 BTU. Am I missing something? Thank you.

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mike_home

The furnace is likely oversized. I believe the smallest furnace Amana makes is 46,000 BTU. It is difficult to find anything smaller.

Do you know the model number? The AMVM96060 has high and low stages of 57,000 and 28,800 BTU respectively. The furnace will probably always operate in the low stage. This assumes your friend has a good 2-stage thermostat.

    Bookmark   November 12, 2012 at 5:34PM
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tigerdunes

Definitely oversized.

There are smaller furnaces available and you can even be ahead of the game with an 80% eff furnace as long as size is correct.

I agree that probably around 30 KBTUs is correct for a location in a mild climate like yours, even a sgl stage but with a high eff blower motor.

IMO

    Bookmark   November 13, 2012 at 6:22AM
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debs3

Thank you "mike home" and "tigerdunes". I have passed the information on. She meets with someone from the company tomorrow. Thank you again.

    Bookmark   November 14, 2012 at 1:11AM
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debs3

Update. My friend and I were thinking a smaller furnace would be less noisy. They told her today it is noisy because her duct work is too small for the number of tonnes (sp?) A furnace with lower tonnes is not made anymore. She thinks they told her this one is 2 tonnes. They are going to replace her duct work at no extra charge. Does this sound reasonable? Thank you again.

    Bookmark   November 14, 2012 at 2:24PM
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mike_home

Furnaces are usually not rated in tons. A ton is equivalent to 24,000 BTUs. A 2 ton furnace would be 48,000 BTU which is in the range for your friend's house.

There is usually little price difference in moving up and down one size when it comes to furnaces. I assume the duct work is noisy because the contractor installed a furnace that is oversized. Now he plans to address the undersized duct work. It would be better and cheaper to have installed the proper sized furnace.

Does your friend have any faith in this contractor? Is he licensed and has he pulled a permit for the work?

    Bookmark   November 14, 2012 at 5:14PM
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tigerdunes

The above post is not correct.

1 ton=12,000 BTUs not 24,000 BTUs.

IMO

    Bookmark   November 14, 2012 at 5:52PM
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tigerdunes

Furnaces are sized to BTUs input, output, and efficiency with the rated size of the blower motor in tons

Don't mean to confuse or get down in the weeds but that in fact is the truth.

Any questions, post back.

IMO

    Bookmark   November 14, 2012 at 5:56PM
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mike_home

My bad, Tiger is correct.

    Bookmark   November 14, 2012 at 8:12PM
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debs3

Thank you everyone. They are going to install the new larger duct work. Will let you know how it turns out.

    Bookmark   November 16, 2012 at 8:54PM
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