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Community and Q&A

What type of water heater and where?

user-2310254 | Posted in Mechanicals on

I was planning to install an electric heat pump water heater in my new house. I really liked what I read about the Airgenerate ati66. But apparently so do a lot of other people. The ati66 is in short supply and not distributed in my region. I can possibly buy one and have it shipped from the West coast.

I could possible substitute an AO Smith Voltrex 80 gallon. It would be easier to source and support than the Airgenerate.

Either one of these units would have to be installed in my basement. Depending where it actually goes, I might have to core out some opening in the basement walls to allow for intake air.

It occurred to me that I could also use an exterior closet for the water heater. Not sure if it would be a good idea to install the heat pump water heater outside (even in Zone 3). But I also have access to natural gas and good put a conventional or tankless gas unit in the closet without any issues. (I don’t want combustion in the living space, however.)

In a way, the closet would be a more central choice for servicing the baths and kitchen areas.

Thoughts? Suggestions?

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  1. GBA Editor
    Martin Holladay | | #1

    See the "water heater decision tree" (below) that I created for my article in Fine Homebuilding.


  2. Expert Member
    Dana Dorsett | | #2

    The lifetime warranty & stainless design give the AirTap series a unique lifecycle economics compared to competing technologies. The net efficiency would be quite GOOD in a ducted configuration in and exterior closet at a US climate zone 3 location. But in a humid zone 3 location there may be more value in putting it in a basement for summertime dehumidification purposes, depending on your heating sources.

    Whether it has a lower lifecycle carbon footprint requires a more nuanced set of accounting of both the combustion efficiency as well as the manufacturing/replacement emissions of a gas-fired beastie, as well as the carbonomics of your local grid power sources: As of 2012 the carbon emissions per kilowatt hour in zone 3 Oklahoma was nearly twice that of zone-3 South Carolina, and enough to make a difference. But these are moving numbers, and with more wind & solar development in lower midwest that could easily flip within the lifecycle of an AirTap.

    Since geographical location and space heating types actually matter, where are you, and how are you heating the place?

  3. GBA Editor
    Martin Holladay | | #3

    You wrote, "It occurred to me that I could also use an exterior closet for the water heater. Not sure if it would be a good idea to install the heat pump water heater outside."

    Manufacturers of heat-pump water heaters specify that the appliances can only be installed in rooms that meet minimum volume requirements. In the case of the A.O. Smith Voltex, the space must measure at least 750 cubic feet.

  4. Expert Member
    Dana Dorsett | | #4

    The exception is the Airgenerate AirTaps, which have ducted air options, and can be installed in vented closets using the duct option. That would clearly be a non-starter for the others.

    On page 11 of the manual ( ):

    "1. Location and space requirements:
    a. Unit installed in a room at least 1,000 cubic feet. If not, room is louvered/ventilated or the unit ducted to
    vent exhaust air."

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