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  1. #1
    Join Date
    Sep 2001
    Location
    Vancouver Canada
    Posts
    996
    When sizing up a heatpump do you base your sizing on the heatloss or heatgain?
    "Go big or Go Home"

  2. #2
    Join Date
    Feb 2003
    Location
    S.W. PA
    Posts
    3,298
    i sixe it to the heat gain so the a/c i sized right then add makeup heat to get where i need for the heat loss

  3. #3
    Join Date
    Jun 2004
    Posts
    146
    If you don't have humidity concerns in your area during the summers, then sizing based on heat loss may be more appropriate.

  4. #4
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,271

    Thumbs up Logic

    Originally posted by Black Adder
    When sizing up a heatpump do you base your sizing on the heatloss or heatgain?
    Buy TWO for Winter and One for summer
    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

  5. #5
    Join Date
    Oct 2005
    Location
    Southern Michigan
    Posts
    24

    Re: Logic

    Originally posted by dan sw fl
    Originally posted by Black Adder
    When sizing up a heatpump do you base your sizing on the heatloss or heatgain?
    Buy TWO for Winter and One for summer
    Maybe THAT would work in Michigan! I suspect there would be some redesign to the ducts, though...

    I have seen some folks say that you can oversize the heat pump, either 50% or 100% depending on who was talking. Might be ok here, not much laten heat gain.

    Compromise, compromise...

  6. #6
    Join Date
    Apr 2002
    Posts
    11,808
    Black

    To use a heat pump up there, I would first have to say that the house needs to be well insulated and well sealed.
    I would not use them on some drafty shack.

    I am going to buck the trend here but first I am going to explain why.

    I did a fair bit of ground source in NW Ontario, and the winter design temperatures were a lot colder than Vancouver. I sized this equipment for 70 to 80% of the heat load and for cooling they were easily 50 to 100% oversized.

    Never experienced a summer humidity problem, because the latent load was not there in the ambient air.

    The cooling season was not that long and the summer dewpoints were not overly high. Vancouver has a lot milder winter, but the humidity in the summer does not look much worse than NW Ontario. It looks like 61F is a worst case dewpoint there in Vancouver.

    I would look at the heat output of the units when the outside temp was at about freezing, and size the unit to heat the house at that temperature. Make sure the heat strips can handle the whole heating load when it drops down to your design temp which has to be in say the high teens.

    Probably half the heat strips in auxiliary would supplement the heat pump and keep the place heated during design days, and the second bank could be used in emergency should the compressor fail.

    I did the ground source with duct heaters, never did the air source with the strips. Sometimes the Geo jobs were two hours out of town and when you got a call at 2AM for no heat, it was nice to tell them to put it on emergency and they were warm until you were there the next day to see what was wrong.

    Air Source heat pumps were not viable in NW ontario, but should do pretty good where you are.
    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/

  7. #7
    Join Date
    Sep 2001
    Location
    Vancouver Canada
    Posts
    996
    Thanks for the input guys, especially Carnak, the systems I am currently designing are ground source heatpumps. I will size it to the requirements for heating unless it makes my cooling grossly oversized. Cooling in our area amounts to a couple of weeks a year. For the most part our temps don't drop below freezing during the day. In our area we size to 7 degrees farenheit but most years we never see that cold. average winter temps are well above freezing for weeks at a time. I will add heat strips and stage them so that only on the coldest days should they ever come on full.
    "Go big or Go Home"

  8. #8
    Join Date
    Apr 2002
    Posts
    11,808
    For ground source then I would size for 70 to 80% of that heat load when you are using the 7F.

    If it is closed loop, then look at the heat output when the loop temp is around freezing.

    My brother in law did some bed n breakfast/ game farm on the Island with ground source.

    The place needs to be well insulated, 5 kw as auxiliary heat could probably handle the 7F days, working on top of the heat pump. Nice to have another 10kw then for a total of 15 kW emergency heat.

    [Edited by Carnak on 10-22-2005 at 01:43 AM]
    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. #9
    Join Date
    Sep 2001
    Location
    Vancouver Canada
    Posts
    996
    Thanks for the info Carnak....
    "Go big or Go Home"

  10. #10
    Join Date
    Mar 2005
    Location
    South/West of Quebec in the other part of Canada
    Posts
    2,331
    Black Adler:

    The geothermal you are sizing, does it have a storage tank and hydronic air handlers?

  11. #11
    Join Date
    Sep 2001
    Location
    Vancouver Canada
    Posts
    996
    No storage tank
    "Go big or Go Home"

  12. #12
    Join Date
    Mar 2005
    Location
    South/West of Quebec in the other part of Canada
    Posts
    2,331
    To bad< I had an idea for you

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