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Thread: Hot water

  1. #1
    Join Date
    Aug 2008
    Location
    Seattle, WA
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    42

    Hot water

    First post, hello all

    I am trying to find out what my options might be for using some sort of heat pump for house hold hot water.

    I've seen a few models of heat pump that install on the water heater, but they are all more "self contained" than I would like, and none of them produce as much heat as a standard 5500 watt electric water heater (~18000 BTU). I would like to take advantage of all that free heat in my attic during the summer, but I'm not sure it makes sense to put the entire unit up there. What keeps coming to mind is a water source heat pump that uses an air/water heat exchanger and fan in the attic as its heat source.

    Am I limited to the small, self contained units? Thanks for any ideas.

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,601
    Standard water heater element is 4500 watts. 15,385 BTUs.

    I don't believe they have anything like you want at this time.
    Sounds like an expensive way to save money on domestic hot water, only in the summer.
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  3. #3
    Join Date
    Jul 2008
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    Poestenkill, NY
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    Look into evacuated tube solar - excellent way to preheat domestic hot water with the power of the sun. There are also heat pumps that have "de-superheaters" which pre heat domestic hot water - but the heat pump is not there to heat the water alone - it's an accessory of sorts.

    Google those terms and educate yourself.

  4. #4
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    Aug 2008
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    Seattle, WA
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    Quote Originally Posted by beenthere View Post
    I don't believe they have anything like you want at this time.
    Sounds like an expensive way to save money on domestic hot water, only in the summer.
    Well, it would work in cooler temperatures as well, just not at an astronomical energy coefficient. Actually, I also considered the possibility of using air from the conditioned space when outside temperature is low, essentially piggy backing on the warm air provided by the main heat pump, but that's yet more complexity, making your point about cost even more relevant.

  5. #5
    Join Date
    Jan 2004
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    Lancaster PA
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    The self containted ones you mentioned, come with an electric element for back up when the temp is too low for the heatpump.

    In the average basement, they should work fine.
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  6. #6
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    Aug 2008
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    Quote Originally Posted by larobj63 View Post
    Look into evacuated tube solar - excellent way to preheat domestic hot water with the power of the sun. There are also heat pumps that have "de-superheaters" which pre heat domestic hot water - but the heat pump is not there to heat the water alone - it's an accessory of sorts.

    Google those terms and educate yourself.
    OK, let's talk about desuperheaters Googling has turned up precious little, and the guys who installed my heat pump didn't know mich about them, and told me they weren't available (or that Lennox doesn't make one) for my HP, so I gave up. My HP is a Lennox XP19. Do you know of any desuperheaters available for that system?

    Anyway, I was under the impression that a desuperheater won't provide enough BTU to perform under any real hot water load. Besides, they only work when the heating system is running, which means I get almost no benefit at all when the temp outside is between, say, 60 and 80, which it is a lot in this area.

  7. #7
    Join Date
    Jun 2001
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    DFW
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    684
    Quote Originally Posted by gp_wa View Post
    OK, let's talk about desuperheaters Googling has turned up precious little, and the guys who installed my heat pump didn't know mich about them, and told me they weren't available (or that Lennox doesn't make one) for my HP, so I gave up. My HP is a Lennox XP19. Do you know of any desuperheaters available for that system?

    Anyway, I was under the impression that a desuperheater won't provide enough BTU to perform under any real hot water load. Besides, they only work when the heating system is running, which means I get almost no benefit at all when the temp outside is between, say, 60 and 80, which it is a lot in this area.
    The problem with modern HVAC heat pumps is not the BTU's, it is the temperature. You can use a desuperheater to preheat the water going into a water heater and save some money, but it starts to get complicated, especially when you start looking at freeze protection, etc...

    I use a heat pump water heater for my house. It is located in my 'basement' and works quite well. It does not have fast recovery, so I use an 85 gallon Marathon electric water heater as the storage tank and as a back up to the heat pump.

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