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  1. #1
    Join Date
    Jul 2008
    Posts
    551

    VisionPRO IAQ and HP winter programming...

    I have read about some people successfully using their heat pumps down to 15-20 degrees. I'm hoping my new system will be as successful. Does the VisionPRO learn when the HP can't keep up and turn it off or does it always run the heat pump and just add the AUX heat? Does it only disable the heat pump when the outside temp goes below the HP shutout temp?

    Also, does the heat pump control defrosting by itself or is there something in the t-stat that controls it?

    Essentially, I want to use my HP as much as possible but I also want my HP disabled if it isn't contributing anything.

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,324
    The HP determines when to defrost.

    Which heat to use when. Is determined by what has been set up in the installers set up menu.
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  3. #3
    Join Date
    Nov 2007
    Location
    Olympia, Wash.
    Posts
    192
    I have found on this site and in my neighborhood, that manufacturers have a default setting of 40 degrees for when the HP switches over to secondary heat source. This is regardless of where you live. I've set mine to switch to secondary/auxilliary heat (gas furnace) when the temp hits 25 degrees. I have a spreadsheet I was given and plugged in all the varaibles of my heat pump and furnace to get a break even point. The gentleman who sent me the program, however, asked me not to share it.

    However, request a copy of the install guide of the IAQ. As I was told, don't screw with stuff you don't know. I just adjusted my set points and temps for aux heat. It saved me money and gives me the lowest enery bills in the neighborhood except the the Ukranian fellow who had radiant floor heat plumbed throughout his house and garage. Beat me by $90 on the coldest months last year and I was beating everybody else between $35 and $150.

  4. #4
    Join Date
    Jul 2008
    Posts
    551
    I don't have a fossil fuel kit. Shouldn't the VisionPRO select when to lockout the heat pump in that case?

    I havent checked to see when the economy break even point occurs between heat pump and my 80% gas furnace. Electricity is so cheap here I'm assuming that temp would be really really low.

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,324
    The IAQ is a dual fuel control.
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  6. #6
    Join Date
    Jul 2008
    Posts
    551
    My economy break even point between my HP and my furnace is -10 F. Is there any danger of not locking out the heat pump down to say 10 degrees F?

  7. #7
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,324
    No.

    If you don't set a lock out temp.
    The stat will switch over to aux when the HP can no longer heat your house. But will use the HP first on every heat call.

    I have a lot of DF's set up like that.

    You can set it like that first.
    Then when you find out what temp the HP has to switch to aux, set up a lock out for that temp, if you don't like the cooler air at those temps.
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  8. #8
    Join Date
    Jul 2008
    Location
    Richmond, Virginia
    Posts
    25

    8303 stat

    Quote Originally Posted by beenthere View Post
    No.

    If you don't set a lock out temp.
    The stat will switch over to aux when the HP can no longer heat your house. But will use the HP first on every heat call.

    I have a lot of DF's set up like that.

    You can set it like that first.
    Then when you find out what temp the HP has to switch to aux, set up a lock out for that temp, if you don't like the cooler air at those temps.
    My installer set up my DF at 40* lockout...with cost of LP gas vs. $0.07 kwh electricity here in Virginia, I plan to reset my call for LP down to at least 30*, maybe lower

    beenthere, does the 8303 stat allow you to not set a lockout temperature like the IAQ? Thanks ......

  9. #9
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,324
    Yes.

    Just set no lock out, and it will use the HP first for every heat call.
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  10. #10
    Join Date
    Apr 2005
    Location
    NE PA
    Posts
    698
    Quote Originally Posted by badtlc View Post
    My economy break even point between my HP and my furnace is -10 F. Is there any danger of not locking out the heat pump down to say 10 degrees F?
    I am not sure what you are trying to say here. Even though the efficiency of your heat pump may look good at -10 deg, the capacity of all heat pumps drops off below 40 deg F. At -10 deg you may be making heat efficiently, but it is likely 10% of the unit's rating or less. That is why another form of heat is required. Not due to efficiency but capacity.

    Usually a properly sized heat pump in a modern well insulated house will handle the load by itself down to 20 deg or so.

    Paul

  11. #11
    Join Date
    Jul 2008
    Posts
    551
    Does the auxiliary heat ever run in conjunction with the heat pump to give it a slight boost? Or, are they always mutually exclusive operations and the aux never runs the same time as the heat pump?

  12. #12
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,324
    Dual fuel. The aux only comes on with the HP during defrost.
    With electric aux, they run at the same time, when the HP can't handle the load by itself.
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  13. #13
    Join Date
    Jul 2008
    Location
    Richmond, Virginia
    Posts
    25

    Kickin' myself

    Quote Originally Posted by beenthere View Post
    Dual fuel. The aux only comes on with the HP during defrost.
    With electric aux, they run at the same time, when the HP can't handle the load by itself.
    And now I wishing that I'd had the LP aux removed when I had my new system installed back in June and instead had the electric strip as aux

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