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  1. #40
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    Apr 2002
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    Quote Originally Posted by RoBoTeq View Post
    You are not paying for the heat in the cooling mode. That heat is waste heat extracted from the air for cooling. The only cost for heating domestic water in the cooling mode is the desuperheater (hot water generator) pump which is also being paid for when the system is in the heating mode.

    When the system is in the heating mode, you have to pay to heat the air or to heat the domestic water; nothing is free. Yes, it is a substantial savings to use the heat pump rather then electric heaters to heat domestic water during the winter, as long as the system has been sized to handle the additional heat load.
    I did a lot of geo in the day going back 20 years ago.

    Some customers wanted a switch to turn the hot water pump off in cold weather. as in it was cold enough that some auxiliary heat was being called for. I looked at it as six of one or half a dozen of another.

    They paid to run the water heater element some more or they paid to run the auxiliary heaters some more.

    Under milder weather when auxilairy was not needed, I figured the desuperheater saved them money even if it stole from the heat that went to the house. Every location is different, these geos in NW Ontario were sold to save on heating bills, the fact that they air conditioned was just a bonus.

    I also prefered two tanks, the geo heated a preheat tank (with no heating elements powered) the preheat tank fed their actual water heater. If the preheat tank was elevated a little with repsect to the desuperheater connections on the geo, even with the pump off it water circulated by gravity, like a thermosyphon.
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

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  2. #41
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    Apr 2008
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    Northwest Arkansas via Chicago Area via Straight Up from There on Lake Superior
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    Quote Originally Posted by Carnak View Post
    ...

    Some customers wanted a switch to turn the hot water pump off in cold weather. as in it was cold enough that some auxiliary heat was being called for. I looked at it as six of one or half a dozen of another.

    They paid to run the water heater element some more or they paid to run the auxiliary heaters some more.

    Under milder weather when auxilairy was not needed, I figured the desuperheater saved them money even if it stole from the heat that went to the house. ...
    Carnak, sounds like you are saying that it doesn't matter if the resistance heat strips in the geo provide the hot water or an auxiliary electric HWH. Sounds reasonable but doesn't it assume that the HO has sufficient "spare" capacity in the geo system to be able to do this even in the coldest weather. I believe RoBo pointed out and I verified that this can be a very expensive choice if the HO buys "extra" geo capacity to do this. An extra half or full ton of geo is a very expensive HWH. I can't speak to the cost or even feasibility of adding enough heat strip capacity to handle this.

  3. #42
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    Apr 2002
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    I am saying when it is cold enough to need auxilairy heat to keep the house warm, it does not make any difference if you stop running the desuperheater or not.

    I can't see anyone over sizing a geo to provide domestic hot water when it works from desuperheating, maybe you get 4000 Btu/hr desuperheating a 5 ton.

    There were products out there that could put full heat output into water (be it potable or hydronic heat) or into air on demand.

    I sold a lot of geos on the North Shore of Superior, sized anywhere from 65% of the heat load to 100%. You use bin weather data to make the decision. Do we put in a 3.5 ton system and 90% of our heat is from the geo and 10% of our heat for the heating season is from auxiliary. Do we buy a 4 ton, that costs more than a 3.5 ton, put more pipe in the ground, use more antifreeze and now 94% of the heat comes from the geo unit and 6% comes from auxiliary or do we put in the 5 ton, even a more expensive unit, more pipe in the ground and we get 97% of our heat economoically from the geo and 3 % of our heat from a duct heater at 8 cents a kWh?

    Most common was size them for 80% or more of the demand heat loss. Probably gave them 95% of the heat they needed. During the extreme weather they either ran the duct heater or wore a sweater
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  4. #43
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    Nov 2000
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    What brought the subject of the domestic water heating up was the assumption made that "free" domestic water heating capability was available during the heating mode.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  5. #44
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    Quote Originally Posted by RoBoTeq View Post
    This is correct, if the system is sized properly and there is adequate well length for the type of ground as well as proper well grouting.

    In the winter operation though, the water heating is not really operating as a desuperheater, but rather as a water heating heat pump. You are getting your heat from the condenser side of the system, not the evaporator side.
    It's always the condenser side

    all that changes is the function of the air coil and water coil-- this is less anal than arguing free hot water
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  6. #45
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    Nov 2000
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    Eastern PA
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    Quote Originally Posted by Carnak View Post
    It's always the condenser side

    all that changes is the function of the air coil and water coil-- this is less anal than arguing free hot water
    I said it was the condensing side. Someone else here mentioned getting free heat from the evaporator in the heating mode.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  7. #46
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    Apr 2008
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    Quote Originally Posted by Carnak View Post
    ...

    I sold a lot of geos on the North Shore of Superior, sized anywhere from 65% of the heat load to 100%. ...l
    Where might that be, Carnak? I know that on the South Shore of Lake Superior in the portion of the UP of Michigan that I am familiar with, I'm not sure that a HO would even know what geo is. Are we talking the same rocky and sandy soil mix? How did geo make inroads into Ontario?

  8. #47
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    Apr 2002
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    Across the Lake from the UP can be sand, clay , rocks or a mixture

    but the typical common thing was 'wet'

    I put them in from Pigeon River to Schreiber going back to the late 80s
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  9. #48
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    Nov 2000
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    Eastern PA
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    Quote Originally Posted by Carnak View Post
    Across the Lake from the UP can be sand, clay , rocks or a mixture

    but the typical common thing was 'wet'

    I put them in from Pigeon River to Schreiber going back to the late 80s
    The wetter, the better. A closed loop system in soil with water moving through it can be just as efficient as an open loop system.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  10. #49
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    Apr 2002
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    liquid sunshine

    144 btu a pound making frost
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  11. #50
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    Jul 2006
    Location
    Virginia
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    238
    Quote Originally Posted by RoBoTeq View Post
    What brought the subject of the domestic water heating up was the assumption made that "free" domestic water heating capability was available during the heating mode.
    I agree it is not free but at a COP of 5 it is a lot cheaper than the electric elements in the WH. But it still produces far more hot water in the winter than the summer. According to my contractor this is normal for the 410 systems. I do have a kick ass loop burried in the ground with springs all over the place(almost a swamp).

  12. #51
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    Nov 2000
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    Quote Originally Posted by drsmith012 View Post
    I agree it is not free but at a COP of 5 it is a lot cheaper than the electric elements in the WH. But it still produces far more hot water in the winter than the summer. According to my contractor this is normal for the 410 systems. I do have a kick ass loop burried in the ground with springs all over the place(almost a swamp).
    I get that the wet loop system is a big benefit, but I see no reason why R410a would make any difference then a R22 system of the same capacity.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  13. #52
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    Apr 2008
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    Quote Originally Posted by drsmith012 View Post
    I agree it is not free but at a COP of 5 it is a lot cheaper than the electric elements in the WH. ...
    DRS, I think that several are making the point that a COP of 5 is useless for HW unless you either have enough surplus geo capacity to heat your house and make HW too or if you don't you revert to electric stripes that are at about COP = 1 just like an electric HWH. If you do have this "surplus" you most likely paid a very high cost for your new "HWH". That said, I assume that you could shut down the geo HW generation when the an undersized (but cheaper) system gets strained but then again how long would somebody keep that up.

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