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  1. #1

    heat strips for a heat pump?

    Are the heat strips more efficent than the pump or less efficient?

    Also are they a necessity or luxury?

    I am finishing my attic which is 2/3s the size of the downstairs. I will be installing an extra hvac unit. We live in a mild climate, sacramento CA, I am guessing the upstairs will have a very small heat demand since the heat will go up. It would be difficult but not impossible to run an extra wire for the heat strips. So I was kind of hopeing to avoid them.

  2. #2
    Join Date
    Jun 2003
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    Florida
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    9,548
    Less effecient under most circumstances. A necessity usually, but in your case maybe not,with another system in the house.
    If everything was always done "by the book"....the book would never change.

  3. #3
    Join Date
    May 2004
    Location
    Rapid City, SD
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    Even though you could probably get by with out them, it sure wouldn't hurt to throw some small one's in there (like 5kw or so). Just something to help the HP when it goes into defrost or on that unusual night every 5 years that gets really cold.
    "If you call that hard work, a koala’s life would look heroic."

  4. #4
    I would be using a minimum of a 13 seer unit outside temp would rarely be freezing.

    What electrical load does a 10kw strip normally run, 30 amp 220V?

  5. #5
    Join Date
    Dec 2002
    Location
    Houston,Tx.
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    15,843
    Quote Originally Posted by my65ffrcobra View Post
    I would be using a minimum of a 13 seer unit outside temp would rarely be freezing.

    What electrical load does a 10kw strip normally run, 30 amp 220V?
    10 Kw is rough fully around 40 to 42 amps on 220 volts.
    __________________________________________________ _______________________
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  6. #6
    They are great to have if the heat pump fails and in defrost mode when the HP switches over to AC for a predetermined period of time to defrost the outdoor coil. I say get them now and dont regret not having them later. As far as efficiency they arent even on the chart but will get you through in a pinch.

  7. #7
    Join Date
    Mar 2001
    Posts
    1,482
    You'll need the strips to temper the air during defrost and to supplement the pump on those cold foggy nights that happen in Sacramento. Electric heat is 100% efficient, but more costly than running the pump.
    One way to outthink people is to make them think you think. They'll think you're not really thinking what you're trying to get them to think you think...........

  8. #8
    Join Date
    Nov 2004
    Location
    SW FL
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    6,242

    Hmm

    Quote Originally Posted by my65ffrcobra View Post
    Are the heat strips more efficent than the pump or less efficient?

    We live in a mild climate, sacramento CA, I am guessing the upstairs will have a very small heat demand since the heat will go up. It would be difficult but not impossible to run an extra wire for the heat strips.
    Heat strip ( 1.0 ) is much less efficient that heat pump
    (~ 3.4 @ 47'F and perhaps 2.7 @ 30'F)

    Your choice to install heat strips or not.
    However, most regions of the US do not have the option that you do.
    With less than 500 hours < 40'F,
    the heat pump is likely to handle the load > 95% of the time.

    Sacramento CA temperature bin data
    Temperature Hours
    25' F ______ 30
    30' F _____ 116
    35' F _____ 333
    40' F _____ 660
    45' F _____ 924

    Alternate: Use one or two high quality 1.5 kW - 110 V portable heaters for the ~20 nights that temperature is < 35'F.

    Might NOT be a good option where children are living.

    http://www.vornado.com/research/heaters.htm
    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. #9
    Join Date
    Feb 2004
    Posts
    2,597
    Why would it be difficult to run a new wire?

    You have to run a new wire from the panel to the heat pump, right? Well, you also have to run refrigerant lines from the pump to the airhandler.

    Why not run the proper size wire from panel to the ref. lines, then follow them to the air handler?

    Note: Proper wire and breaker sizing should be determined by a qualified electrician.

  10. #10
    Join Date
    Jul 2004
    Location
    Kent, WA
    Posts
    129
    Unless you want freezing air coming out all the ducts during defrost (about 10 minutes of every hour all winter long), install the 10 KW strip. Here in Seattle, my HP frosts very easily when the temps are between 30F and 40F. At 50F, it doesn't seem to need defrost anymore.

    I have my defrost timer set for 60 minutes, but it is often quite frosty by then. Seattle and SFO are pretty similar in climate (high humidity when temps are 32F - 50F), but not terribly cold nor very humid in the summer.

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