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Community and Q&A

Heat pump water heater + AC + refrigerator combo, someone?

Jin Kazama | Posted in Energy Efficiency and Durability on

Only wishful thinking ,

has any commercial products come up with a combo of any of the floowing items ??

– heat pump water heater ( tanked )
– heat pump AC
– heat pump heat
– refridgerator/freezer ??

I don’t know why, but i think i recall looking at a product a few years ago that
comboed AC and water heater ??? can’t find it anymore

what about water heater and refridgerator ?

I’d say, if use the heat generated by refridgerator/freezer pump,
would it make enough to hold up water temp in a tanked WH ??
i don’t know the math implied ( because i don’t have a clue to the HP effic ratios :p )

neway, seems like we are cooling and heating stuff at the same time,
why not joint both ??? passivehause style !!!

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Replies

  1. Jin Kazama | | #1

    http://eec.ucdavis.edu/ACEEE/1994-96/1994/VOL03/019.PDF

    just found the following :

    In a typical single family home, the total annual heat
    discharge from the refrigerator condenser is approximately
    half the annual domestic water heating “recovery load”
    which includes end uses and pipe losses, based on new
    refrigerators with 750 kWh/year consumption and
    60 gallons (227 liters) per day water use with 70°F
    (39°C) temperature rise. For apartments and mobile
    homes, where the number of occupants per dwelling are
    typically lower, average annual refrigerator condenser
    output more nearly equals average recovery load. The
    conventional refrigerator heat output increases building
    cooling loads, and decreases heating loads.

    I understand that during heating seasons, WH standby losses and refrigerator heat
    is not an expense anymore, but still ...

  2. GBA Editor
    Martin Holladay | | #2

    Jin,
    Q. "I think i recall looking at a product a few years ago that comboed AC and water heater ?"

    A. It's called a desuperheater. Because of the cost of the equipment, it makes much more sense in Florida than in Canada. Here are some links:

    http://www.trevormartin.com/hru.asp

    http://heatexchangers.doucetteindustries.com/category/desuperheaters

  3. GBA Editor
    Martin Holladay | | #3

    Jin,
    Concerning the idea of a refrigerator / water heater combo appliance: the concept has been discussed many times on GBA, most recently here: Seasonal Changes in Electrical Loads. On that page, see Marc Rosenbaum's musings, as well as the comments below.

    Marc Rosenbaum wrote, "I find myself wishing for a fridge/freezer that rejects heat to a domestic hot water preheat tank, just as it's done in commercial refrigeration. But energy will need to get more costly before that device appears on the market."

    Dana Dorsett commented, "The volume of hot water from combi's like that might (barely) be enough to serve kitchen needs. If a pretty-efficient American style refrigerator uses 350kwh/year that's about 1.2 MMBTU (at most) delivered to the water, or about 3270BTU/day. Assuming an 80F delta on incoming water that's about 5 gallons/day as an upper bound, which may be enough to serve a modest water-use home kitchen, but would be less than adequate for many/most. In a heating dominated climate you'd have to discount for the amount of space heating that would be otherwise lost too. Yes there's still a net benefit, but whether it's a sufficient benefit to product-ize and sell with reasonable ROI for both the homeowner & manufacturer isn't so clear."

  4. Jin Kazama | | #4

    Ok well this calculus gives a very different scale of things from the study on my link

    what about using something u linked :

    http://heatexchangers.doucetteindustries.com/viewitems/desuperheaters/aquefier-series-heat-recovery-units-1-5-to-5-tons-?

    seems unexpensive at ~450$

    using it with AC...again as you said would probably makes more sense in a cooling climate.not here up north

    Then this from Trevor-Martin :

    The more efficient, high SEER models run with lower hot refrigerant temperatures so they don't heat water as fast as the lower SEER models

    breaks the purpose of using it with recent mini splits
    and i woudln't consider any other current type of AC in any efficient building ...

    ok maybe trying to save pennies is not a very good idea to invest on :p

    ( maybe it is even less here with the first batch of electricity @ 0.06$ )

  5. D.W. Crosby | | #5

    Hi, you might want to consider a look at greenstep.com. The have a suite of products that produce the energy from solar to take care of heating and cooling, and that can also convert heat to electriciy. Their air conditioner is efficient enough to run on solar as well. We are tearing down our home and rebuilding with their technology. Regards, DWC

  6. Jin Kazama | | #6

    mr Crosby: i don't even see anything of interest on their site other than the regular "super green efficiency" marketing pages ...

    are you working for this company ? :p

    what is the link with the topic please?? link to direct product or solution pages if possible

  7. Tim O'Brien | | #7

    I designed residential and commercial heat pump water heaters years ago. My company marketed a residential heat pump water heater incorporating ventilation, space heating, and space cooling options. We did not incorporate the refrigerator/freezer combo.

    The challenge for these applications is finding a high temperature demand coincident with a low temperature demand. The demand coincidence is key. If there is no coincidence of demand you will be driving one (hot or cold) end of the heat pump from the other and possibly causing problems. Heat pump water heaters in cooling climates make good sense as they offset cooling load when making hot water - most of the time they can respond to hot water demand and provide needed cooling simultaneously. Heat pump water heaters in heating climates make less sense.

    Commercial heat pump water heaters in laundromats and sit-down restaurants offered a rapid payback. the need for hot water and air cooling is coincident in these applications. I used to recommend that the remote evaporators in restaurant kitchens supply air onto the spot where the employees (should) spend most of their time because once the heat pump water heater is installed and operating, the kitchen employees will spend as much time in the cool supply air as possible.

  8. Steven Gaynair | | #8

    Would it help to put the HPWH in a louvered closet next to the fridge. The HPWH would be raised on a drawer base to raise the air intake up to take advantage of heat from the fridge and cooking. The cool exhaust would be ductted to the back o the fridge to cool the coils. Would that safe a few dollars?

  9. GBA Editor
    Martin Holladay | | #9

    Steven,
    Your idea won't save much energy, because these loads aren't usually simultaneous. The issue of simultaneity is what usually scuttles these schemes -- and the hardware needed to solve the simultaneity problem is too expensive to justify the investment.

    One more point: never install a heat-pump water heater in a closet unless the size of the closet meets the minimum volume of the heat-pump water heater manufacturer. Usually, the room has to be fairly big -- so I would call this a "mechanical room," not a "closet."

  10. Steven Gaynair | | #10

    Are these realistic in multi-family applications? Mechanical rooms are too small compared to manufacturer's recommendations. If I put it in the kitchen, it would need some sort of surround otherwise buyers/renters would turn up their noses. Should I stick with an efficient standard tanked water heater in these applications?

  11. GBA Editor
    Martin Holladay | | #11

    Steven,
    Obviously, I'm not going to recommend that you violate the manufacturer's installation instructions. If the mechanical room is too small, it can't go there.

    I think that putting a heat-pump water heater in the kitchen isn't a good idea. As you guessed, it's too noisy.

  12. Steve Knapp CZ 3A Georgia | | #12

    @Steven. You might be interested in this video by Matt Risinger: https://www.youtube.com/watch?v=5EzfmLFCYy4. This doesn't address your issue directly, but does show that some HPWH can be installed in fairly small spaces.

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