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What is the best air-to-water heat pump for Zone 3?

minpix | Posted in Energy Efficiency and Durability on

I live in zone 3 in coastal California where temperatures rarely exceed 100 F in summer or drop below freezing in winter. We have a 3200 sq ft home with existing radiant heat. Seeking advice as to latest/greatest air to water heat pump unit to install along with new PV solar system to heat both domestic hot water and floors.

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  1. charlie_sullivan | | #1

    If you haven't already, check out Martin's recent article,

    I would guess the Sanden and Chiltrix are the ones of most interest. Particularly the Sanden because of the CO2 refrigerant for low environmental impact and the high temperature capability for domenstic hot water. Will you want to use the system for cooling as well, with some fan coil units? The Sanden won't do cooling, but the Chiltrix could do all three--heating, cooling, and domestic hot water.

    But the first step is "manual J" load calculation to figure out what heating capacity you need. Then you can see what units fit your actual needs.

  2. GBA Editor
    Martin Holladay | | #2

    Charlie has answered the first part of your question well. Like Charlie, I urge you to read my article, Air-to-Water Heat Pumps.

    The second part of your question concerns PV systems. You wrote that you want to install a "new PV solar system to heat both domestic hot water and floors."

    Once you have finished designing your heating system and chosen equipment to heat your domestic hot water, you can decide whether to install a PV system. The size of your PV system will depend on the size of your lot (if you plan to install a ground-mounted array) or the size of your south-facing roof, as well as limitations established in your local utility's net-metering agreement. (Consult your local utility to determine whether the utility will pay you for any electricity you produce that exceeds your annual electricity usage; most won't.)

    Remember, your PV system is "usage-neutral." The PV array doesn't care how you use your electricity -- whether you use it for seven televisions, three refrigerators, or a water heater. It's just a PV system that makes electricity -- so, strictly speaking, it won't be heating your water for you. What it will do is balance your annual electrical usage, assuming that you have a big enough area on your roof or in your yard, and a big enough checkbook, to install such a system.

  3. minpix | | #3

    Thanks Charlie and Martin for your responses. I've now read Martin's article on air to water heat pumps and realize the many variables I need to address. Just beginning my learning on the subject and may be back to you for more advice downstream. Thanks again.

  4. minpix | | #4

    For anyone interested in the Sanden SanCO2 product, they advise:

    Currently we are preparing to launch the product into the US market, we
    are targeting mid May to have inventory in the US, and will have
    distribution that will serve your zip code (central California)

    As for pricing we expect the product to retail for $3000 to $3500
    depending on the tank size required

  5. Yamayagi1 | | #5

    "ECO-CUTE" R744 refrigerant (CO2) air to water heat pumps have now become rather ubiquitous in Japan and many parts of Europe because of their very high efficiency in making hot water of useful temperatures for domestic hot water and for radiant heating. So far, though, the only one of the many manufacturers that make them in, mostly in Japan, that has entered the US market is SANDEN. They would be a good bet for the use you have described. But the high-pressure refrigeration technology is one that most US refrigeration techs have never encountered, and are unprepared to do repairs on. Best to find out what tech support SANDEN has in the field. Their refrigeration system comes complete and closed-circuited from the factory. I believe the only connections to the unit are water lines and power.

  6. GBA Editor
    Martin Holladay | | #6

    Here is a link to my article on Eco Cute water heaters and the introduction of the Sanden water heater to the North American market: Split-System Heat-Pump Water Heaters.

  7. minpix | | #7

    Thanks for your cautionary comments re servicing Sanden units in the US James.

    And thanks Martin for the link to your Eco Cute article. For newbies like me just trying to come up to speed on this subject, please advise WHY a split-system heat-pump water heater is able to supply both space heating and domestic hot water — whereas it can’t be done with a heat-pump water heater with an indoor compressor.

    Thank you

  8. GBA Editor
    Martin Holladay | | #8

    Briefly, if the compressor is indoors, it pulls heat from your indoor air and uses that heat to raise the temperature of the water in the water tank. The net result is that your indoor air temperature drops. It cools your house. That's a good thing in Florida in July, but it isn't a particularly good thing in Massachusetts in January.

    If the compressor is outdoors, it pulls heat from the outdoor air instead of pulling heat from the indoor air.

  9. minpix | | #9

    Thanks Martin-
    I've got a crawl space under the entire house (high volume) with breezeways all around and good insulation in the overhead flooring. Do you think locating the unit outdoors is still a better idea or do you think putting it in the crawl space would be acceptable? Thanks.

  10. GBA Editor
    Martin Holladay | | #10

    If you are using an air-source heat pump to provide space heat for your house, then the compressor has to be outdoors, not in a crawl space.

  11. minpix | | #11

    Understood. Thanks!

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