Need advice for cabin heat pump

ellbakerJuly 24, 2011

I have been self building a small cabin in Alabama. It is 20x34 with a full basement (walk out). The basement is a Superior Walls system on three sides and a 2x6 framed wall. The main floor is all 2x6 with blown in cellulose. The Main floor is one big room with the exception of a small bathroom (8x6). It has a cathedral ceiling with a loft at one end (14x20). I ran a J calculation with HVAC-Calc. Total heat gain is 10K BTU and heat loss is 21K BTU.

I was planning on using 2-3 mini split heat pumps upstairs. Either 2 12K or 3 9K with one in the loft. Problem is there are limited to no installers of the mini pump system nearby. Second problem is the wife hates the look of the indoor units!!

I am now reconsidering and thinking about having a traditional heat pump installed. The air handler would take up my laundry room in the center of the basement. I can move the laundry to another room. I have 8'9" floor to ceiling. My question is there sufficient room to install a duct system in a chase and maintain an 8' ceiling? If not, how much height will I need to give up?

It may be impossible to get ducting up to the loft so I may still need at least 1 mini split system for the loft or it will be unbearable in the summer.

I have a HVAC guy coming out some time next week to give me a quote. It is a rural area and the choices are limited for installers. This guy took my square footage over the phone and said I need 3.5 tons. I think that is overkill and he may not be taking the low load of the basement on the cooling system into account.

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mike_home

It sounds like you are doing your homework. Hopefully you will find a competent HVAC contractor.

You may have to give up some ceiling height for the duct work. It is possbile to create a box on the ceiling next a wall?

How can the HVAC contractor say you need 3.5 tons of cooling when your calculated heat gain is 10K BTU? Are you going to review the data with the contractor?

    Bookmark   July 25, 2011 at 10:17AM
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ionized_gw

It is too bad that you can not find minisplit installers near you. Though things are improving; knowledge is spreading. There are minisplit solutions that do not involve hanging units on the walls.

    Bookmark   July 25, 2011 at 6:48PM
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ellbaker

I met with him and discussed the differences in load calculations. He said he confirmed his assessment that the house required 3.5 tons of cooling after looking at it. He said he needed 1600 CFM and that would require a 3.5 ton air handler. The 1600 CFM was the driving factor. He did agree that a 3 ton condenser would do the job. I asked about Manual J and he said it was all in his head :-) The guy is 72 and has a good reputation in the area.

    Bookmark   July 26, 2011 at 7:59AM
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mike_home

You can get a copy of HVAC Calc for $50 and do the calulation yourself. I have not used it myself, but I have read is does correlate well with the software which professionals use. Ths software is good for a 2 or 3 month period.

    Bookmark   July 27, 2011 at 4:42PM
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