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  1. #14
    Join Date
    Apr 2002
    Posts
    11,808
    can see them installed for 70 to 80 percent in some extreme climates. Could work out to 90 to 95% of the heat you need each heating season comes from the ground 5 to 10% the auxiliary heat working on top of the geo unit

    where i used to live you could size them to meet the entire heating load but it was like diminishing returns. Those sized for the full load were way oversized for cooling.

    Where I used to live was not very humid in the summer so never had a high humidity problem from the over siizing. May be different in your neck of the woods


    You need to talk to someone who knows the 'bin weather data' for your area

  2. #15
    Wow, these are all good comments and I will speak to my contractor about them. Thanks for all of your help - my contractor may not like you in the morning, but you guys are doing a great service for us simple folk!!

    Guelph is not too far away, and would have slightly colder temps in the winter. I'm still not sure I'm comfortable having to use the auxillary heat at only 13 degrees. My contractor had said 99% of heating will be done with geo and 1% auxillary. I'm still not sure how that can be when the btu output is only 70% of the homes heatloss, but I think 1-4% auxilary heat in Canada is too high for a system of this cost (vertical drilling would be required).

  3. #16
    Join Date
    Apr 2002
    Posts
    11,808
    I based my commets on NW Ontario, was not uncommon to see 70 to 80 percent sizing up there

    Back then I would say with electric heat, your were a dollar a square foot for the heating season, that was 8 cents a kWh, and in a colder place then Guelph.

    Heat pump with the auxiliary maybe cut that down to say by a factor of 2.5

  4. #17
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,770
    Don't forget. The heat pump will be running even when the aux is heat is on.
    When its 10* outside, the HP will be providing the majority of your heat, not the aux.

    If your heat pump is providing 70 percent of the heat you need at -2, the aux is only providing 30%.

    So, less then 5KW of aux at design temp.
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  5. #18
    Join Date
    Apr 2002
    Posts
    11,808
    ask him how much more to go to the next size larger and drilling another hole. Also price a dehumidiefier.

    Maybe going the next step up knocks off $75 dollars of the yearly heating cost compared to the one sized for 70%

  6. #19
    Join Date
    Nov 2007
    Posts
    86
    A geothermal system designed to provide 70% of your peak load (the coldest days) is properly sized, as such a system will provide 95% of the heat requirement of your heating season, will also be properly sized for cooling and provide the greatest economy of operating and installation cost resulting in the fastest payback.

    As correctly pointed out in another post, the backup runs in addition to the HP - not instead of the HP. For about 5% of the winter don’t get hung up on the backup – that’s how it’s supposed to be designed and operated!

    SR

  7. #20
    One way we do it in Minnesota to get the maximum efficiency is to use 2 stage equipment. This way you are able to size for 95-100% of the heating load and almost never having ot use and supplemental. You also do nto sacrifice your dehumidification during the summer for the a/c

    Just my 2 cents

    Tj

  8. #21
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,248

    Thumbs up

    Quote Originally Posted by wagnerhvac View Post
    Is Guelph near you? ... geodesigner with your info ... Your balance point would be 13 degrees ... first stage heating 69%

    first stage cooling 100% ... aux heat require 5 KW full emergency 16 KW
    The geo will do about 96% of your heating with 4% back up
    Brampton, Ontario
    Location: Latitude - 43° 42' North
    Longitude - 79° 46' West

    Brampton is West of Toronto

    Guelph
    Location: Latitude - 43° 33' North
    Longitude - 80° 15' West
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  9. #22
    Join Date
    Apr 2002
    Posts
    11,808
    If you plot bin weather temperature vs hours of the year it is at or below the bin temperature, then draw a horizontal line at 65F, the area between the 65F line and the curve will be proportional to your degree days

    You then draw lines at whatever temperature your heat pump is good for and you will see how much heat comes from the earth and how much heat comes from the auxiliary. You can draw a line for whatever temperature the next size larger geo is good for.

    Heat loss calcs, even to CSA F280 are conservative, especially below grade losses, more so when you have good snow cover. As well these calculations do not make allowances for solar heat gains which can be significant in good passive designs, or internal gains from appliances.

    In the mid/late 80s, the old Canadian Earth Energy Association (dominated by Waterfurnace) had a big push to use their "special balance point method" to try to reduce the size of the Geo installed. Smaller geo was less expensive, less trenching/drilling, less pipe, less antifreeze. Lower install cost means more geos wre sold.

    Guelph is mild compared to NW Ontario and the Prairies.
    70 to 80% sizing worked in the more extreme areas and even being grossly oversized in cooling, the ambinet humidity was not severe enough in the summers to create a high humidity problem.

    I would advise getting a staged duct heater. First stage will be your auxiliary per haps 5 kw. Full emergency at 15 kW, would keep you fine until a replacement part showed up from the manufacturer under warranty.

    Guelph would be similar to Cambridge, Kitchener- Waterloo - humid enough that a grossly oversized cooling system would drive up RH, so if you go with the next size up, buy a dehumidifier.
    Last edited by Carnak; 03-23-2008 at 10:57 AM.

  10. #23
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,248

    Smile Brampton ON Temperature Bin Data Approximation and Aux Heat Estimate

    Quote Originally Posted by beenthere View Post
    Don't forget. The heat pump will be running even when the aux is heat is on.
    When its 10* outside, the HP will be providing the majority of your heat, not the aux.

    If your heat pump is providing 70 percent of the heat you need at -2,
    the aux is only providing 30%.

    So, less then 5KW of aux at design temp.
    ~ 500 hours < 15'F / -10'C
    ~ 6,000 hours > 14'F to 60'F/15.6'C

    ~ 3% as auxiliary heat seems rea$onable,
    if your balance point is 18'F / 37,500 BTUh

    ~ 1,357 kwH / $95

    Farenheit Celsius Hamilton London
    90 32.2 …. 12 …. 9 ….
    85 29.4 …. 90 …. 56 ….
    80 26.7 …. 274 …. 379 ….
    75 23.9 …. 491 …. 357 ….
    70 21.1 …. 661 …. 550 ….
    65 18.3 …. 711 …. 687 ….

    60 15.6 …. 704 …. 729 ….
    55 12.8 …. 668 …. 602 ….
    50 10.0 …. 602 …. 634 ….
    45 7.2 …. 574 …. 609 ….
    40 4.4 …. 610 …. 608 ….
    35 1.7 …. 771 …. 730 ….
    30 -1.1 …. 770 …. 790 ….
    25 -3.9 …. 583 …. 631 ….
    20 -6.7 …. 426 …. 479 ….
    15 -9.4 …. 330 6038 354 6166
    10 -12.2 …. 237 483 251 552
    5 -15.0 …. 138 …. 158 ….
    0 -17.8 …. 69 …. 86 ….
    -5 -20.6 …. 30 …. 41 ….
    -10 -23.3 …. 9 …. 16 ….
    -15 -26.1 …. 0 …. 4 ….
    -20 -28.9 …. 0 …. 0 ….


    Approximately (~)
    1,360 kwH for Auxiliary Heat
    with 18'F/ -8'C Balance Point

    Practically, when the outside temperature goes to < 5'F
    one might re-set the thermostat to 62'F. Balance point effectively shifts to 10'F.


    Seems like a lot of effort to save ~ 300 kwh / $21.


    ' F Celsius Heat Load
    70 21.1 0
    69 20.6 722
    68 20.0 1444
    67 19.4 2167
    66 18.9 2889
    65 18.3 3611
    64 17.8 4333
    63 17.2 5056
    62 16.7 5778
    61 16.1 6500
    60 15.6 7222
    59 15.0 7944
    58 14.4 8667
    57 13.9 9389
    56 13.3 10111
    55 12.8 10833
    54 12.2 11556
    53 11.7 12278
    52 11.1 13000
    51 10.6 13722
    50 10.0 14444
    49 9.4 15167
    48 8.9 15889
    47 8.3 16611
    46 7.8 17333
    45 7.2 18056
    44 6.7 18778
    43 6.1 19500
    42 5.6 20222
    41 5.0 20944
    40 4.4 21667
    39 3.9 22389
    38 3.3 23111
    37 2.8 23833
    36 2.2 24555
    35 1.7 25278
    34 1.1 26000
    33 0.6 26722
    32 0.0 27444
    31 -0.6 28167
    30 -1.1 28889
    29 -1.7 29611
    28 -2.2 30333
    27 -2.8 31055
    26 -3.3 31778
    25 -3.9 32500
    24 -4.4 33222
    23 -5.0 33944
    22 -5.6 34667
    21 -6.1 35389
    20 -6.7 36111 Aux Heat Aux Ht Hours kwH
    19 -7.2 36833 BTUh kW 70
    18 -7.8 37555 55 0.02 70 1.14
    17 -8.3 38278 778 0.23 70 15.95
    16 -8.9 39000 1500 0.44 70 30.76
    15 -9.4 39722 2222 0.65 70 45.57 354
    14 -10.0 40444 2944 0.86 50 43.13
    13 -10.6 41167 3667 1.07 50 53.71
    12 -11.1 41889 4389 1.29 50 64.29
    11 -11.7 42611 5111 1.50 50 74.88
    10 -12.2 43333 5833 1.71 50 85.46 251
    9 -12.8 44055 6555 1.92 32 61.46
    8 -13.3 44778 7278 2.13 32 68.23
    7 -13.9 45500 8000 2.34 32 75.01
    6 -14.4 46222 8722 2.56 32 81.78
    5 -15.0 46944 9444 2.77 32 88.55 158
    4 -15.6 47667 10167 2.98 18 53.62
    3 -16.1 48389 10889 3.19 18 57.43
    2 -16.7 49111 11611 3.40 18 61.24
    1 -17.2 49833 12333 3.61 18 65.04
    0 -17.8 50555 13055 3.83 18 68.85 86
    -1 -18.3 51278 13778 4.04 8 32.29
    -2 -18.9 52000 14500 4.25 8 33.99
    -3 -19.4 52722 15222 4.46 8 35.68
    -4 -20.0 53444 15944 4.67 8 37.37
    -5 -20.6 54167 16667 4.88 8 39.07 41
    -6 -21.1 54889 17389 5.09 3 15.28
    -7 -21.7 55611 18111 5.31 3 15.92
    -8 -22.2 56333 18833 5.52 3 16.55
    -9 -22.8 57055 19555 5.73 3 17.19
    -10 -23.3 57778 20278 5.94 3 17.82 16
    -11 -23.9 58500 21000 6.15

    .................................................. .................. 1357 kwh
    .................................................. .................. 0.07 $ / kwh
    .................................................. .................. $95.01
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  11. #24
    Join Date
    Aug 2007
    Location
    MN
    Posts
    2,677
    Quote Originally Posted by cleangreen View Post
    There aren't too many geothermal installers in my area. The one I'm dealing with is recommending the 4 ton Climatemaster, even though it can only produce 37,500 BTU at full load, which is just over 70% of my home's heatloss (52,000 BTU). That sounds small to me. Can anyone help me understand if the system is properly sized?
    get a 2 stage unit that is sized to the heat load at design temp. then you should not be too oversized(if at all) in cooling
    You can't fix stupid

  12. #25
    Join Date
    Apr 2002
    Posts
    11,808
    Quote Originally Posted by dan sw fl View Post
    ~ 500 hours < 15'F / -10'C
    ~ 6,000 hours > 14'F to 60'F/15.6'C

    ~ 3% as auxiliary heat seems rea$onable,
    if your balance point is 18'F / 37,500 BTUh

    ~ 1,357 kwH / $95

    Farenheit Celsius Hamilton London
    90 32.2 …. 12 …. 9 ….
    85 29.4 …. 90 …. 56 ….
    80 26.7 …. 274 …. 379 ….
    75 23.9 …. 491 …. 357 ….
    70 21.1 …. 661 …. 550 ….
    65 18.3 …. 711 …. 687 ….

    60 15.6 …. 704 …. 729 ….
    55 12.8 …. 668 …. 602 ….
    50 10.0 …. 602 …. 634 ….
    45 7.2 …. 574 …. 609 ….
    40 4.4 …. 610 …. 608 ….
    35 1.7 …. 771 …. 730 ….
    30 -1.1 …. 770 …. 790 ….
    25 -3.9 …. 583 …. 631 ….
    20 -6.7 …. 426 …. 479 ….
    15 -9.4 …. 330 6038 354 6166
    10 -12.2 …. 237 483 251 552
    5 -15.0 …. 138 …. 158 ….
    0 -17.8 …. 69 …. 86 ….
    -5 -20.6 …. 30 …. 41 ….
    -10 -23.3 …. 9 …. 16 ….
    -15 -26.1 …. 0 …. 4 ….
    -20 -28.9 …. 0 …. 0 ….


    Approximately (~)
    1,360 kwH for Auxiliary Heat
    with 18'F/ -8'C Balance Point

    Practically, when the outside temperature goes to < 5'F
    one might re-set the thermostat to 62'F. Balance point effectively shifts to 10'F.


    Seems like a lot of effort to save ~ 300 kwh / $21.


    ' F Celsius Heat Load
    70 21.1 0
    69 20.6 722
    68 20.0 1444
    67 19.4 2167
    66 18.9 2889
    65 18.3 3611
    64 17.8 4333
    63 17.2 5056
    62 16.7 5778
    61 16.1 6500
    60 15.6 7222
    59 15.0 7944
    58 14.4 8667
    57 13.9 9389
    56 13.3 10111
    55 12.8 10833
    54 12.2 11556
    53 11.7 12278
    52 11.1 13000
    51 10.6 13722
    50 10.0 14444
    49 9.4 15167
    48 8.9 15889
    47 8.3 16611
    46 7.8 17333
    45 7.2 18056
    44 6.7 18778
    43 6.1 19500
    42 5.6 20222
    41 5.0 20944
    40 4.4 21667
    39 3.9 22389
    38 3.3 23111
    37 2.8 23833
    36 2.2 24555
    35 1.7 25278
    34 1.1 26000
    33 0.6 26722
    32 0.0 27444
    31 -0.6 28167
    30 -1.1 28889
    29 -1.7 29611
    28 -2.2 30333
    27 -2.8 31055
    26 -3.3 31778
    25 -3.9 32500
    24 -4.4 33222
    23 -5.0 33944
    22 -5.6 34667
    21 -6.1 35389
    20 -6.7 36111 Aux Heat Aux Ht Hours kwH
    19 -7.2 36833 BTUh kW 70
    18 -7.8 37555 55 0.02 70 1.14
    17 -8.3 38278 778 0.23 70 15.95
    16 -8.9 39000 1500 0.44 70 30.76
    15 -9.4 39722 2222 0.65 70 45.57 354
    14 -10.0 40444 2944 0.86 50 43.13
    13 -10.6 41167 3667 1.07 50 53.71
    12 -11.1 41889 4389 1.29 50 64.29
    11 -11.7 42611 5111 1.50 50 74.88
    10 -12.2 43333 5833 1.71 50 85.46 251
    9 -12.8 44055 6555 1.92 32 61.46
    8 -13.3 44778 7278 2.13 32 68.23
    7 -13.9 45500 8000 2.34 32 75.01
    6 -14.4 46222 8722 2.56 32 81.78
    5 -15.0 46944 9444 2.77 32 88.55 158
    4 -15.6 47667 10167 2.98 18 53.62
    3 -16.1 48389 10889 3.19 18 57.43
    2 -16.7 49111 11611 3.40 18 61.24
    1 -17.2 49833 12333 3.61 18 65.04
    0 -17.8 50555 13055 3.83 18 68.85 86
    -1 -18.3 51278 13778 4.04 8 32.29
    -2 -18.9 52000 14500 4.25 8 33.99
    -3 -19.4 52722 15222 4.46 8 35.68
    -4 -20.0 53444 15944 4.67 8 37.37
    -5 -20.6 54167 16667 4.88 8 39.07 41
    -6 -21.1 54889 17389 5.09 3 15.28
    -7 -21.7 55611 18111 5.31 3 15.92
    -8 -22.2 56333 18833 5.52 3 16.55
    -9 -22.8 57055 19555 5.73 3 17.19
    -10 -23.3 57778 20278 5.94 3 17.82 16
    -11 -23.9 58500 21000 6.15

    .................................................. .................. 1357 kwh
    .................................................. .................. 0.07 $ / kwh
    .................................................. .................. $95.01
    be closer to London, inland

  13. #26
    Join Date
    Nov 2007
    Posts
    86
    To all those suggesting a larger 2-stage HP to provide 100% heating without back-up and NOT be oversized for cooling. Yes this will work to cover the difference between a GSHP providing 95% of the seasonal heat and that last 5% - but at what cost? A larger, more expensive HP and what else? A larger ground loop (more drilling!), maybe a second circulating pump – there goes your monetary efficiency (longer payback), and for what, a few days a year? It’s your money…

    IMO

    SR

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