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  1. #1
    Join Date
    Nov 2006
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    I have a Westinghouse 93% efficient gas furnace with an outdoor air conditioning compressor. The A coil is above the furnace. I would like to change the outdoor compressor to a heat pump and use the gas furnace only as a back up heat source if the heat pump can't keep up. I live in San Jose, CA.

    I have a 7,500 watt photovoltaic system on my roof so all my electricity is free. I am trying to convert all of my gas appliances to electricity.

    Can I change the AC compressor to a heat pump? Can I use the same A coil? Will I need a special thermostat or other controls to make it work properly?

    Thanks in advanced.


  2. #2
    Join Date
    Oct 2004
    Tyler, TX
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    Yes, you can have a gas furnace with a heat pump.
    Whether or not you can use the indoor coil would depend on the particular model coil you have.

    Heat pumps must have a matched indoor & outdoor unit. Just offhand, I would say, don't reuse the indoor coil.

    A local contractor could give more guidance.

    Mention "dual fuel" when you call.

    [Edited by Wild Leg on 11-02-2006 at 03:57 PM]
    RSES Certificate Member Specialist

    Southwest Regional Association of RSES Secretary, 2017

  3. #3
    Join Date
    Jun 2003
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    You cannot change your a/c compressor to a heatpump without extensive work. You can change your entire outdoor unit(condenser) to a heatpump, and have a matched indoor coil installed,as long a s the airflow's correct. A local contractor is better suited to show you your options.Different controls are used,unless you have a h/p stat(universal). Free electric, I don't blame you.
    If everything was always done "by the book"....the book would never change.

  4. #4
    Join Date
    Sep 2006
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    So what does it cost to get 7,500 watts for free? Is this the new thin rubberized sheets that glue to the roof?

  5. #5
    Join Date
    Nov 2004
    SW FL
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    Originally posted by mchild
    So what does it cost to get 7,500 watts for free? Is this the new thin rubberized sheets that glue to the roof?
    FREE is a rather loose term
    ALWAYS !
    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

  6. #6
    Join Date
    Sep 2002
    I don't know
    Post Likes
    So what's your surplus power per day as it is?

    On cold days, heatpumps can suck a hell of a lot of juice; less than electric resistance heat, but a hell of a lot nevertheless.

    Photovolaic systems do not produce as much in the winter as you probably know; on the other hand, 7.5kw is huge. (I don't even want to think about how much that cost you - even a 1kw system is upwards of $10,000)

    Direct solar hot water is the preferred renewable heating source.

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