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Community and Q&A

Air to water heat pump with water to air heat pump air handler

user-7820720 | Posted in Mechanicals on

I am in the process of designing a smaller house (1456 SQ ft) in zone 5a and I am looking into air to water heat pumps, a geo system and a mini split system with a central air handler. I want to have one HVAC system capable of doing heating and cooling and was leaning towards a central air handler to avoid having to put electric baseboards though the house as a backup and multiple condensate drains. When looking into air to water I really didn’t like the options of either fan coils all over the house or an air handler because of the higher water temperature required for heating. With a geo system the cost of the vertical wells needed on my property was eye popping. Then I started to think what if I used an air to water heat pump to supply the water for the geo air handler instead of wells. To me it seemed to make sense because the air to water heat pump would be supplying a pretty low water temp and the water to air heat pump would have a stable temp just as if it was coming from the ground. Both units should typically be running at their maximum cop. Having a set up like this would cost about $1500 more than a mini split with a central air handler. Besides costing more, potentially using more energy than geo and potentially complications of having two separate heat pumps I was wondering what people thought about this and if it would work the way I imagine? I saw a commercial application almost like this but they used a boiler and a cooling tower to condition the water to about 60-70 degrees instead of a heat pump. Thanks in advance!

Brendan

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Replies

  1. paul_wiedefeld | | #1

    Hi Brendan,

    While it would work, just install an centrally ducted air-to-air system, "minisplit" or otherwise. At the end of the day, you're using outdoor heat to raise the temperature of refrigerant, which then will transfer that heat to air in the blower. What you’re proposing is using two compressors, multiple heat exchangers, and a circulator or two to achieve the same results as using one compressor and no pump - inherently less efficient than air-to-air. And it’ll cost much more than $1500 more - the buffer tank alone probably exceeds that.

  2. DC_Contrarian | | #2

    For a 1500 square foot house this sounds way too complicated.

    In a small, tight house sometimes you will run into the problem that the heating and cooling loads are too small for even the smallest minisplit to operate comfortably and efficiently. Unless that is a problem some sort of air-to-air solution, probably a minisplit, is most appropriate.

    You won't need to have electric baseboard backups, modern heat pumps have improved cold weather performance. If resistive heat is needed it can be integrated into the air handler.

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