Heat pump BTUs for dummies
I realize may not be providing enough information to have this answered, but I will ask anyways.
I live in Winston-Salem, NC. Our house is a brick split foyer with ½ the basement finished and the other ½ a garage. Its about 2100 sq ft. Decent attic insulation. We have a 25+ year old AC and a 14 year old 80% propane furnace. The AC is 3 ton. The furnace is 100,000 BTU. I am thinking about replacing everything with a heat pump.
My question concerns the BTUs from heat pumps. If we get a 3 ton heat pump to replace our current system, will the heat output be approximately 36,000 btu? Even if I assume our 100k propane furnace is way oversized, 36k is a whole lot less than 100k. That's a lot of BTUs to lose.
Its entirely possible I am way off base on this, so please forgive my ignorance on this subject.
You need a heat gain/loss calculation done on the home. It's called a "Manual J". I believe there is a calc that you can use on this site for a fee.
A heat pump is typically sized for cooling. Additional btus for heating are supplied by auxillary or supplimental heat, like a furnace or electric resistance strips.
A 3-ton heat pump will put out 36,000 btu at is rated outdoor temp, which is 47F outdoors. As the outdoor temps drop, the btus drop, and so does the temperature of the heated air produced by the heat pump.
I believe that propane furnaces are rated at input btu's, so you have 100,000 x .8 = 80,000 btu output.
have you considered going dual fuel? assuming you don't know what it is, its when you keep the furnace and and a heat pump to the sytem. basically the heat pump does the heating until the outdoor temp. goes below 35 or 40 depending on set balance point where the heat pump is not as effective. this way your not using the propane as often. it kind of acts like the backup electric heat in a heat pump system. just an idea.
100K is simply
Originally Posted by acobra289
unless you are talking about a 90+ year old (no insulation and holes) house.
An ACCA Manual J calc may indicate that the heat loss is only 40,000 BTU.
I might propose a 4-ton 2-stage heat pump.
If you need some help, let me know.
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