Geothermal Ground Source Heat Pump vs Oil Evaluation

Discussion in 'HVAC' started by Johan, Oct 1, 2005.

  1. Johan

    Johan Guest

    Hello,
    I'm about to make a big decision regarding installation of a ground
    source heat pump (closed loop wells) and a traditional hydro air/boiler
    oil-fire system. I'm looking for some advice/comments regarding the
    assumptions/calcs. that I've made regarding cost savings. Here goes:
    1. Southern New England temps.
    2. heat loss calcs from me and others confirms about 85000 Btu/hr
    3. Oil: $2.25/gal, furnace efficiency .85, $19/MBtu
    4. Ground source heat pump: $.096/kWh, COP 4.1, $6.92/MBtu
    5. 175MBtu/year <---is this right? This is roughly based on my previous
    experience with an oil system scaled up for difference in square
    footage between the homes. I realize this is VERY inaccurate. What
    more information do I REASONABLY need for a more accurate number? Is
    there an equation/rule of thumb?
    6. Therefore, for savings calcs, Oil heat costs $3300/year and GSHP
    heat costs $1200/year
    8. $25000 (quoted) additional cost of GSHP over Oil, 11 to 12 years
    payback of investment.

    Any comments/suggestions are greatly appreciated as this is a really
    big decision.
    Thanks
    Johan, Oct 1, 2005
    #1
  2. Johan

    Guest

    Johan <> wrote:

    >I'm about to make a big decision regarding installation of a ground
    >source heat pump (closed loop wells) and a traditional hydro air/boiler
    >oil-fire system. I'm looking for some advice/comments regarding the
    >assumptions/calcs. that I've made regarding cost savings. Here goes:
    >1. Southern New England temps.
    >2. heat loss calcs from me and others confirms about 85000 Btu/hr


    On a very cold day, a 97.5 percentile winter temp?

    >3. Oil: $2.25/gal, furnace efficiency .85, $19/MBtu
    >4. Ground source heat pump: $.096/kWh, COP 4.1, $6.92/MBtu
    >5. 175MBtu/year <---is this right?


    About 1750 gallons of oil? Sounds like a lot.

    >This is roughly based on my previous experience with an oil system scaled up
    >for difference in square footage between the homes. I realize this is VERY
    >inaccurate. What more information do I REASONABLY need for a more accurate
    >number? Is there an equation/rule of thumb?


    Your heat loss calc should lead to a thermal conductance from indoors to
    outdoors, eg 400 Btu/h-F. Multiply that by 24 (hours) and the number of
    heating degree days in your climate, eg 5641 in Boston. So, a 400 Btu/h-F
    house in Boston would need 24x400x5641 = 54 million Btu of heat. Some of
    that may come from indoor electrical usage and sun into windows. Then again,
    you might forget all this heat pumping and solar heat the house, 100%, or
    add a sunspace or some polycarbonate "solar siding" air heaters on the south
    wall. Be sure to make the house extremely airtight, less than 0.2 ACH,
    with a blower door test.

    You might also consider cogeneration, eg a 6 kW water-cooled Honda.

    Nick
    , Oct 1, 2005
    #2
  3. Johan

    Guest

    <pjm@see_my_sig_for_address.com> wrote:

    >Do not cross-post this shit to alt.hvac


    Sez who? :)

    Nick
    , Oct 1, 2005
    #3
  4. <pjm@see_my_sig_for_address.com> wrote:
    >Do not cross-post this shit to alt.hvac



    Sez who? :)

    Nick

    xxxx

    No one of any importance. Lippy is just some flaming forging
    blackmailing spammer who thinks his shit dont stink.
    Power's Mechanical, Oct 1, 2005
    #4
  5. Johan

    Paul Guest

    "Power's Mechanical" <> wrote in message
    news:...
    > <pjm@see_my_sig_for_address.com> wrote:
    >>Do not cross-post this shit to alt.hvac

    >
    >
    > Sez who? :)
    >
    > Nick
    >
    > xxxx
    >
    > No one of any importance. Lippy is just some flaming forging
    > blackmailing spammer who thinks his shit dont stink.
    >

    Maybe alt.hvac does not like solar. Could be why the legislation
    was held up on California solar roofs. With a larger view and a bit
    of training the HVAC people could make lots of money installing
    solar. Just a bit of adjustment that may be good for all of us.
    Paul, Oct 1, 2005
    #5
  6. Johan

    Nog Guest

    "Johan" <> wrote in message
    news:...
    > Hello,
    > I'm about to make a big decision regarding installation of a ground
    > source heat pump (closed loop wells) and a traditional hydro air/boiler
    > oil-fire system. I'm looking for some advice/comments regarding the
    > assumptions/calcs. that I've made regarding cost savings. Here goes:
    > 1. Southern New England temps.
    > 2. heat loss calcs from me and others confirms about 85000 Btu/hr
    > 3. Oil: $2.25/gal, furnace efficiency .85, $19/MBtu
    > 4. Ground source heat pump: $.096/kWh, COP 4.1, $6.92/MBtu
    > 5. 175MBtu/year <---is this right? This is roughly based on my previous
    > experience with an oil system scaled up for difference in square
    > footage between the homes. I realize this is VERY inaccurate. What
    > more information do I REASONABLY need for a more accurate number? Is
    > there an equation/rule of thumb?
    > 6. Therefore, for savings calcs, Oil heat costs $3300/year and GSHP
    > heat costs $1200/year
    > 8. $25000 (quoted) additional cost of GSHP over Oil, 11 to 12 years
    > payback of investment.
    >
    > Any comments/suggestions are greatly appreciated as this is a really
    > big decision.
    > Thanks
    >

    The problem is you need a 1 ton unit for each 250 ft. bore hole which will
    yield 12,000 btu's. so you need 7 bore holes and a 7 ton unit to get 85,000
    btu's. If you need 120,000 btu's you need 10 bore holes and a 10 ton unit.
    Now that will take a great deal of electricity.
    Nog, Oct 1, 2005
    #6
  7. Johan

    Astro Guest

    good thoughts so far.
    As Nick asked, where does the 85000 BTU/hr come from? Is that a peak
    load or a typical one?
    is this a new house or an existing one? If it's existing, what do you
    have now?
    If it's a new one, then you can build the cost into the mortgage and
    make it much less painful. In fact, I've seen analysis that show it to
    reduce your payments because of the savings.
    In my house in PA, I was going through several fill-ups of dual tanks
    (~500 gallons/fill) with oil heat used for water and heat. I installed
    a geothermal last winter and used the oil as backup heat for cold days
    (<~15-20F) and the geothermal the rest of the year. I also got rid of
    my old "high efficiency" 5-ton Carrier A/C system (~10 SEER).
    This summer, my electric usage was down about 25% from last year in
    spite of higher average temperatures. Last winter was very cold and the
    geothermal was running 10-20 hours/day and the oil 1-5 hours/day during
    January to avoid stressing the loop field too much.
    I ended up using about 1 fill of oil 500 gallons, instead of 3 fills
    AND my electric bills were lower! The reason my electric bills were
    lower is because in PA, we get a discount for electric heat, so my kwh
    charge is dramatically lower in the winter. My net savings then is
    about 1000 gallons of oil and ~30% in electric bills. Back of the
    envelope savings then are about $3000/year.
    My system is a 4-ton system.
    In addition, I've also spent the year doing as much as feasible to make
    my house more efficient. lots more insulation in the attic. Low-e
    windows. Air sealing every penetration I can find. I'm getting
    dense-pack cellulose in the walls and cathedral ceilings next week.

    Note - if I were to do it again here in PA, I'd go for a high
    efficiency conventional heat pump. The reason is this - in my area,
    since the balance point for my system is ~15F, a good two stage heat
    pump(i.e. Lennox XP19) with oversized heating could have a balance
    point into the low 20's and work efficiently in the summer, so there's
    not much difference there. And instead of paying $20k for the
    geothermal install, the heat pump might be $7k. That's a lot of saving
    to apply towards the incrementally greater energy costs.

    The efficiency of the conventional HP won't be quite as good for the
    coldest and hottest months, but in your area, you'll probably run 9-10
    months at about the same efficiency as the geothermal system. Keep in
    mind, while the companies will make claims based on your ground
    temperature of ~50F, as soon as your system runs in the winter, the
    ground temp will drop. I installed temperature probes along with my
    loops and monitored ground temp all winter. My loops were operating
    below freezing much of the winter so system output and efficiency was
    far less than rated.

    Just some more food for thought.
    Astro, Oct 1, 2005
    #7
  8. Johan

    geoman jr Guest

    "Astro" <> wrote in message
    news:...
    > good thoughts so far.
    > As Nick asked, where does the 85000 BTU/hr come from? Is that a peak
    > load or a typical one?
    > is this a new house or an existing one? If it's existing, what do you
    > have now?
    > If it's a new one, then you can build the cost into the mortgage and
    > make it much less painful. In fact, I've seen analysis that show it to
    > reduce your payments because of the savings.
    > In my house in PA, I was going through several fill-ups of dual tanks
    > (~500 gallons/fill) with oil heat used for water and heat. I installed
    > a geothermal last winter and used the oil as backup heat for cold days
    > (<~15-20F) and the geothermal the rest of the year. I also got rid of
    > my old "high efficiency" 5-ton Carrier A/C system (~10 SEER).
    > This summer, my electric usage was down about 25% from last year in
    > spite of higher average temperatures. Last winter was very cold and the
    > geothermal was running 10-20 hours/day and the oil 1-5 hours/day during
    > January to avoid stressing the loop field too much.
    > I ended up using about 1 fill of oil 500 gallons, instead of 3 fills
    > AND my electric bills were lower! The reason my electric bills were
    > lower is because in PA, we get a discount for electric heat, so my kwh
    > charge is dramatically lower in the winter. My net savings then is
    > about 1000 gallons of oil and ~30% in electric bills. Back of the
    > envelope savings then are about $3000/year.
    > My system is a 4-ton system.
    > In addition, I've also spent the year doing as much as feasible to make
    > my house more efficient. lots more insulation in the attic. Low-e
    > windows. Air sealing every penetration I can find. I'm getting
    > dense-pack cellulose in the walls and cathedral ceilings next week.
    >
    > Note - if I were to do it again here in PA, I'd go for a high
    > efficiency conventional heat pump. The reason is this - in my area,
    > since the balance point for my system is ~15F, a good two stage heat
    > pump(i.e. Lennox XP19) with oversized heating could have a balance
    > point into the low 20's and work efficiently in the summer, so there's
    > not much difference there. And instead of paying $20k for the
    > geothermal install, the heat pump might be $7k. That's a lot of saving
    > to apply towards the incrementally greater energy costs.
    >
    > The efficiency of the conventional HP won't be quite as good for the
    > coldest and hottest months, but in your area, you'll probably run 9-10
    > months at about the same efficiency as the geothermal system. Keep in
    > mind, while the companies will make claims based on your ground
    > temperature of ~50F, as soon as your system runs in the winter, the
    > ground temp will drop. I installed temperature probes along with my
    > loops and monitored ground temp all winter. My loops were operating
    > below freezing much of the winter so system output and efficiency was
    > far less than rated.
    >

    Astro you paid 20,000 $ for a four ton geothermal system and you need to use
    oil for a backup system?? Sounds like your installer fucked you on the loop
    sizing to save himself some money. Doesn't your geo have electric strips for
    backup?? Also if your system was sized for your house prior to your
    insulating it and you put in a bunch more be prepared to be uncomfortable in
    the next cooling cycle. Optimal loop efficiency is usually not optained
    until the second year of operation so you should see aditional savings then
    if it was properly designed. Oh, because of coil designs, air to air heat
    pumps ( except trane and american standard) lose their efficiency within a
    short period of time and become even less so if not properly cleaned and
    serviced regularly (maintainence). With a geo a home owner basicaly just has
    to make sure he keeps the filter changed regularly. Service is usually just
    a quick check of loop pressures and temps and the electical side components.
    We install high efficiency filters so coil cleaning is usually not a problem
    = additional savings. Your loop if properly designed and sized should see
    below freezing temps only in late winter months and usually those that have
    been colder than normal.

    > Just some more food for thought.
    >
    geoman jr, Oct 2, 2005
    #8
  9. "Nog" <> wrote in message
    news:...
    >
    > "Johan" <> wrote in message
    > news:...
    > > Hello,
    > > I'm about to make a big decision regarding installation of a ground
    > > source heat pump (closed loop wells) and a traditional hydro air/boiler
    > > oil-fire system. I'm looking for some advice/comments regarding the
    > > assumptions/calcs. that I've made regarding cost savings. Here goes:
    > > 1. Southern New England temps.
    > > 2. heat loss calcs from me and others confirms about 85000 Btu/hr
    > > 3. Oil: $2.25/gal, furnace efficiency .85, $19/MBtu
    > > 4. Ground source heat pump: $.096/kWh, COP 4.1, $6.92/MBtu
    > > 5. 175MBtu/year <---is this right? This is roughly based on my previous
    > > experience with an oil system scaled up for difference in square
    > > footage between the homes. I realize this is VERY inaccurate. What
    > > more information do I REASONABLY need for a more accurate number? Is
    > > there an equation/rule of thumb?
    > > 6. Therefore, for savings calcs, Oil heat costs $3300/year and GSHP
    > > heat costs $1200/year
    > > 8. $25000 (quoted) additional cost of GSHP over Oil, 11 to 12 years
    > > payback of investment.
    > >
    > > Any comments/suggestions are greatly appreciated as this is a really
    > > big decision.
    > > Thanks
    > >

    > The problem is you need a 1 ton unit for each 250 ft. bore hole which will
    > yield 12,000 btu's. so you need 7 bore holes and a 7 ton unit to get

    85,000
    > btu's. If you need 120,000 btu's you need 10 bore holes and a 10 ton unit.


    Much depends upon actual bore spacing and the soil thermal transfer
    characteristics ......consider vertical loops set in a sandy aquifer--with a
    water table that's always moving downstream, for instance...

    > Now that will take a great deal of electricity.


    Still, it would cost him one hell of a lot less in electricity than if he
    was to be running straight heat strips.....

    --

    SVL
    PrecisionMachinisT, Oct 2, 2005
    #9
  10. "geoman jr" <> wrote in message
    news:...
    >
    > "Astro" <> wrote in message
    > news:...
    > = additional savings. Your loop if properly designed and sized should see
    > below freezing temps only in late winter months and usually those that

    have
    > been colder than normal.
    >


    I been considering adding an open water loop water coil onto a unit that
    normally operates as "air source" only....source well water flow volume (
    upon heating demand ) being called via a low suction pressure sensor.....

    Hehe--it's a 20 year old Lennox, might just as well I should fucking hack
    it, no ???

    <G>

    --

    SVL
    PrecisionMachinisT, Oct 2, 2005
    #10
  11. Johan

    Guest

    Geoman - you got that right! Remember, I'm the one who bitched last
    winter because my installer was a f*ckwad and installed the vertical
    loops too close together, put in too few loops and generally hacked the
    entire install. They are no longer representing that geothermal
    company...

    OTOH, the system was designed to be somewhat undersized for winter so
    that the Summer dehumidification would be satisfactory. The installer
    wanted to install a 5-ton system which really would have sucked during
    the summer. Oil is the backup because it was already in the house and
    used for a zone that the geo system doesn't reach. I could say more but
    I don't want to hijack the OP's thread any more.

    Your comments are exactly why I asked the OP for more info on their
    home and load calcs. If they put in a single stage system designed for
    heating 85k BTU/hr, they're going to really suffer during the summer.

    I would think the best case for them would be a two stage geo system.
    If they're lucky, they're home is over an active aquifer with plenty of
    water movement.
    , Oct 2, 2005
    #11
  12. Johan

    Nog Guest

    "Duane C. Johnson" <> wrote in message
    news:...
    > Hi Nog;
    >
    > Nog wrote:
    >> "Johan" <> wrote:

    >
    >> The problem is you need a 1 ton unit for each 250 ft. bore
    > > hole which will yield 12,000 btu's.

    >
    > Do you really mean to say that that bore hole can
    > only deliver 12,000 btu's.
    > Heck, my furnace can deliver 10 times that amount
    > every hour. And your bore hole has a lifetime limit
    > of 12,000 btu's.
    >
    > That's not very much?
    >
    >> so you need 7 bore holes and a 7 ton unit to get 85,000 btu's.

    >
    > Are you sure con only get 85,000 btu's?
    >
    > > If you need 120,000 btu's you need 10 bore holes and a
    > > 10 ton unit. Now that will take a great deal of electricity.

    >
    > That's not very much electricity?
    >
    > Oh, I understand.
    > You don't know the difference between energy and power!
    >
    > Never mind!!!!
    >
    > Duane


    ¶ I guess you don't know what a heat pump is! §
    Nor what one ton-hour of refrigeration is!


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    Nog, Oct 2, 2005
    #12
  13. Johan

    Guest

    I spec'd a 4-ton system with a minimum of 600 ft of bores, but
    preferably 800 ft based on my local geologic conditions (solid diabase
    intrusion) and minimal water migration. Based on my winter
    measurements, this would have been an excellent choice. The problem is,
    as you know, if the loop field is too small, the winter ground
    temperature will drop too quickly, unable to recover from the load,
    resulting in a reduced system output
    , Oct 2, 2005
    #13
  14. Johan

    Guest

    as I was saying, with too small a loop field, the ground temperature
    won't be able to recover fast enough to keep up with the load, and
    system output will decrease, as it did.
    The point is, the OP needs to be very cognizant of the installation
    size and ensure that the loop field is adequate.
    Moreover, they need to balance the tendancy to oversize the system with
    a desire to properly dehumidify during the summer. The typical "2x
    heating capacity as cooling" that many endorse will lead to
    uncomfortable summers.
    OTOH, if you use a two-stage or otherwise variable capacity system, you
    get the best of both worlds - enough capacity during the winter and
    long run humidity removal during the summer.

    As the OP indicated, this is a really big decision for them and they
    need information on which to evaluate the systems. I'm showing how it's
    far more complex than simply getting enough BTUs to cover peak demand,
    especially where geo systems are concerned.
    , Oct 2, 2005
    #14
  15. <> wrote in message
    news:...
    > as I was saying, with too small a loop field, the ground temperature
    > won't be able to recover fast enough to keep up with the load, and
    > system output will decrease, as it did.
    > The point is, the OP needs to be very cognizant of the installation
    > size and ensure that the loop field is adequate.
    > Moreover, they need to balance the tendancy to oversize the system with
    > a desire to properly dehumidify during the summer. The typical "2x
    > heating capacity as cooling" that many endorse will lead to
    > uncomfortable summers.
    > OTOH, if you use a two-stage or otherwise variable capacity system, you
    > get the best of both worlds - enough capacity during the winter and
    > long run humidity removal during the summer.
    >


    If you are running a lower capacity cooling stage during summer with a
    marginally sized loop field installed then your yearly net heat loss is
    steadily increased, quite possibly to the point where 'all hell freezes
    over' when an especially cold winter occurs.

    >
    > As the OP indicated, this is a really big decision for them and they
    > need information on which to evaluate the systems. I'm showing how it's
    > far more complex than simply getting enough BTUs to cover peak demand,
    > especially where geo systems are concerned.
    >


    --

    SVL
    PrecisionMachinisT, Oct 2, 2005
    #15
  16. Johan

    Guest

    What's the alternative? In a heating dominated climate, regardless of
    system sizing, you're going to lower the ground temperature. The only
    hope is that the thermal diffusivity and large scale ground thermal
    mass is high enough that during the summer the loop field temperature
    fully restores.
    The problem is the undersized loop field will always draw down too
    quickly and provide unacceptable performance during extended periods of
    cold. And without support of the manufacturer/installer, I have to work
    around those limitations.
    , Oct 2, 2005
    #16
  17. Johan

    Geoman1 Guest

    "Astro" <> wrote in message
    news:...
    > good thoughts so far.
    > As Nick asked, where does the 85000 BTU/hr come from? Is that a peak
    > load or a typical one?
    > is this a new house or an existing one? If it's existing, what do you
    > have now?
    > If it's a new one, then you can build the cost into the mortgage and
    > make it much less painful. In fact, I've seen analysis that show it to
    > reduce your payments because of the savings.
    > In my house in PA, I was going through several fill-ups of dual tanks
    > (~500 gallons/fill) with oil heat used for water and heat. I installed
    > a geothermal last winter and used the oil as backup heat for cold days
    > (<~15-20F) and the geothermal the rest of the year. I also got rid of
    > my old "high efficiency" 5-ton Carrier A/C system (~10 SEER).
    > This summer, my electric usage was down about 25% from last year in
    > spite of higher average temperatures. Last winter was very cold and the
    > geothermal was running 10-20 hours/day and the oil 1-5 hours/day during
    > January to avoid stressing the loop field too much.
    > I ended up using about 1 fill of oil 500 gallons, instead of 3 fills
    > AND my electric bills were lower! The reason my electric bills were
    > lower is because in PA, we get a discount for electric heat, so my kwh
    > charge is dramatically lower in the winter. My net savings then is
    > about 1000 gallons of oil and ~30% in electric bills. Back of the
    > envelope savings then are about $3000/year.
    > My system is a 4-ton system.
    > In addition, I've also spent the year doing as much as feasible to make
    > my house more efficient. lots more insulation in the attic. Low-e
    > windows. Air sealing every penetration I can find. I'm getting
    > dense-pack cellulose in the walls and cathedral ceilings next week.
    >
    > Note - if I were to do it again here in PA, I'd go for a high
    > efficiency conventional heat pump. The reason is this - in my area,
    > since the balance point for my system is ~15F, a good two stage heat
    > pump(i.e. Lennox XP19) with oversized heating could have a balance
    > point into the low 20's and work efficiently in the summer, so there's
    > not much difference there. And instead of paying $20k for the
    > geothermal install, the heat pump might be $7k. That's a lot of saving
    > to apply towards the incrementally greater energy costs.


    I don't know where your going to get a two stage heat pump installed for
    $7K.


    >
    > The efficiency of the conventional HP won't be quite as good for the
    > coldest and hottest months, but in your area, you'll probably run 9-10
    > months at about the same efficiency as the geothermal system. Keep in
    > mind, while the companies will make claims based on your ground
    > temperature of ~50F, as soon as your system runs in the winter, the
    > ground temp will drop. I installed temperature probes along with my
    > loops and monitored ground temp all winter.


    Why install probes along with the loops? Just leave a thermometer in the
    access plugs, the ground isn't going to get any colder than the solution
    going through it.


    My loops were operating
    > below freezing much of the winter so system output and efficiency was
    > far less than rated.


    Then they screwed you on the loop size, the biggest problem I have with the
    competition! My loops seldom go below freezing. Imagine if you hired a
    competant installer.

    >
    > Just some more food for thought.
    >
    Geoman1, Oct 3, 2005
    #17
  18. Johan

    Noon-Air Guest

    "Geoman1" <Geo1> wrote in message
    news:...
    >
    > "Astro" <> wrote in message
    > news:...
    >> good thoughts so far.
    >> As Nick asked, where does the 85000 BTU/hr come from? Is that a peak
    >> load or a typical one?
    >> is this a new house or an existing one? If it's existing, what do you
    >> have now?
    >> If it's a new one, then you can build the cost into the mortgage and
    >> make it much less painful. In fact, I've seen analysis that show it to
    >> reduce your payments because of the savings.
    >> In my house in PA, I was going through several fill-ups of dual tanks
    >> (~500 gallons/fill) with oil heat used for water and heat. I installed
    >> a geothermal last winter and used the oil as backup heat for cold days
    >> (<~15-20F) and the geothermal the rest of the year. I also got rid of
    >> my old "high efficiency" 5-ton Carrier A/C system (~10 SEER).
    >> This summer, my electric usage was down about 25% from last year in
    >> spite of higher average temperatures. Last winter was very cold and the
    >> geothermal was running 10-20 hours/day and the oil 1-5 hours/day during
    >> January to avoid stressing the loop field too much.
    >> I ended up using about 1 fill of oil 500 gallons, instead of 3 fills
    >> AND my electric bills were lower! The reason my electric bills were
    >> lower is because in PA, we get a discount for electric heat, so my kwh
    >> charge is dramatically lower in the winter. My net savings then is
    >> about 1000 gallons of oil and ~30% in electric bills. Back of the
    >> envelope savings then are about $3000/year.
    >> My system is a 4-ton system.
    >> In addition, I've also spent the year doing as much as feasible to make
    >> my house more efficient. lots more insulation in the attic. Low-e
    >> windows. Air sealing every penetration I can find. I'm getting
    >> dense-pack cellulose in the walls and cathedral ceilings next week.
    >>
    >> Note - if I were to do it again here in PA, I'd go for a high
    >> efficiency conventional heat pump. The reason is this - in my area,
    >> since the balance point for my system is ~15F, a good two stage heat
    >> pump(i.e. Lennox XP19) with oversized heating could have a balance
    >> point into the low 20's and work efficiently in the summer, so there's
    >> not much difference there. And instead of paying $20k for the
    >> geothermal install, the heat pump might be $7k. That's a lot of saving
    >> to apply towards the incrementally greater energy costs.

    >
    > I don't know where your going to get a two stage heat pump installed for
    > $7K.
    >
    >
    >>
    >> The efficiency of the conventional HP won't be quite as good for the
    >> coldest and hottest months, but in your area, you'll probably run 9-10
    >> months at about the same efficiency as the geothermal system. Keep in
    >> mind, while the companies will make claims based on your ground
    >> temperature of ~50F, as soon as your system runs in the winter, the
    >> ground temp will drop. I installed temperature probes along with my
    >> loops and monitored ground temp all winter.

    >
    > Why install probes along with the loops? Just leave a thermometer in the
    > access plugs, the ground isn't going to get any colder than the solution
    > going through it.
    >
    >
    > My loops were operating
    >> below freezing much of the winter so system output and efficiency was
    >> far less than rated.

    >
    > Then they screwed you on the loop size, the biggest problem I have with
    > the competition! My loops seldom go below freezing. Imagine if you hired
    > a competant installer.


    Nawww..... he just wants the lowest bidder
    Noon-Air, Oct 3, 2005
    #18
  19. Johan

    Geoman1 Guest

    "PrecisionMachinisT" <> wrote in message
    news:...
    >
    > <> wrote in message
    > news:...
    >> as I was saying, with too small a loop field, the ground temperature
    >> won't be able to recover fast enough to keep up with the load, and
    >> system output will decrease, as it did.
    >> The point is, the OP needs to be very cognizant of the installation
    >> size and ensure that the loop field is adequate.
    >> Moreover, they need to balance the tendancy to oversize the system with
    >> a desire to properly dehumidify during the summer. The typical "2x
    >> heating capacity as cooling" that many endorse will lead to
    >> uncomfortable summers.
    >> OTOH, if you use a two-stage or otherwise variable capacity system, you
    >> get the best of both worlds - enough capacity during the winter and
    >> long run humidity removal during the summer.
    >>

    >
    > If you are running a lower capacity cooling stage during summer with a
    > marginally sized loop field installed then your yearly net heat loss is
    > steadily increased, quite possibly to the point where 'all hell freezes
    > over' when an especially cold winter occurs.


    That would have to be a major undesized loop system for this to happen. On
    a horizontal loop, being no lower than 8 feet, the loop recovers due to
    solar and sensible gains as stated by O.S.U. and others. The Geothermal
    Heat Pump Constortium stated, and I was surprised when I learned this:
    " In winter, the ground soaks up solar energy and provides a barrier to cold
    air. "
    http://www.geoexchange.org/about/how.htm

    Another article I once had, and will look for, gave the percentage of this
    solar gain. I once heard Phil Rawlings teach about problems associated with
    horizontal loops for cooling that are installed under asphalt parking lots
    if the solar gain isn't factored in. Even a yard absorbs solar gains.


    I think we can agree, most loops are not installed to the maximum efficiency
    of the unit but most are grossly undersized. This is where the contractor
    makes his money, by ripping off the customer. The customer swith's from
    propane to Geothermal and saves some money and the customer is all happy,
    not knowing that the 3.27 COP geothermal system he bought is only putting
    out 2.4 or even worse! And in our area resistant heat is now cheaper than
    natural gas, so the customers bill will always show a lower utility bill,
    and they think the other contractor who was going to install an extra 1000
    feet of loop and charge $2000 more was the crook!!


    >>
    >> As the OP indicated, this is a really big decision for them and they
    >> need information on which to evaluate the systems. I'm showing how it's
    >> far more complex than simply getting enough BTUs to cover peak demand,
    >> especially where geo systems are concerned.
    >>

    >
    > --
    >
    > SVL
    >
    >
    Geoman1, Oct 3, 2005
    #19
  20. Johan

    Abby Normal Guest

    GEO

    If memory serves me correct, I think Astro had boreholes in solid
    granite Geoman plus it is a dx system
    Abby Normal, Oct 3, 2005
    #20

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