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  1. #1
    Join Date
    Feb 2007
    Posts
    999

    A basic heat pump question

    If one used a heat pump for heating, with gas heat for backup, is there any way to program the furnace to recover from a night time setback, while still retaining its backup function?

    Could this possibly be done using 2 thermostats (some wires connected in parallel)? Is it ever done?

    AM

  2. #2
    Join Date
    Jul 2006
    Location
    St.Paul, MN
    Posts
    125
    This is done all the time on modern systems by simply using a 2 stage thermostat. The fossil fuel kit needs to support this though or modifications can be made because the heat pump needs to shut off when the furnace is running.
    Remember, some poor fool has to work on what you install someday, and it might even be you.

  3. #3
    Join Date
    Dec 2006
    Location
    Middle Tennessee
    Posts
    11,347

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    Quote Originally Posted by ampulman View Post
    If one used a heat pump for heating, with gas heat for backup, is there any way to program the furnace to recover from a night time setback, while still retaining its backup function?

    Could this possibly be done using 2 thermostats (some wires connected in parallel)? Is it ever done?

    AM

    a honeywell 8000, or IAQ stat will do that for you

    they also have (fossil fuel kits) built into the electronics

    caution, stat needs to be configured properly



    .

  4. #4
    Join Date
    Feb 2007
    Posts
    999
    Quote Originally Posted by yorkguy View Post
    This is done all the time on modern systems by simply using a 2 stage thermostat. The fossil fuel kit needs to support this though or modifications can be made because the heat pump needs to shut off when the furnace is running.
    Thanks, Yorkguy. I've never considered a heat pump before, so trying to learn more about them.

    I believe I'm correct, in reading here that in certain conditions, strip heat can run along with the HP. Is there ever a situation where gas back up would do so, also?

    AM

  5. #5
    Join Date
    Mar 2008
    Location
    northern Indiana
    Posts
    114
    I believe I'm correct, in reading here that in certain conditions, strip heat can run along with the HP. Is there ever a situation where gas back up would do so, also?



    Gas furnace and heat pump should not run at the same time.
    Causes high pressure faults.

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,876
    The 8000 series, and teh IAQ stat can do what you want. But, why do you want to increase the cost of heating your house in the warmer part of the heating season?

    Enable the adaptive recovery of the stat, and the HP will start sooner to get the temp up, and cost les then bring on the gas furnace for quick recovery.
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  7. #7
    Join Date
    Feb 2007
    Posts
    999
    Quote Originally Posted by teeball57 View Post


    Gas furnace and heat pump should not run at the same time.
    Causes high pressure faults.
    I kind of thought that the evaporator might get too hot (pressure) running both.

    Quote Originally Posted by beenthere View Post
    The 8000 series, and teh IAQ stat can do what you want. But, why do you want to increase the cost of heating your house in the warmer part of the heating season?

    Enable the adaptive recovery of the stat, and the HP will start sooner to get the temp up, and cost les then bring on the gas furnace for quick recovery.
    Your point is well taken. Actually, just gathering information.

    AM

  8. #8
    Join Date
    Sep 2006
    Posts
    136
    Quote Originally Posted by Airmechanical View Post
    a honeywell 8000, or IAQ stat will do that for you

    they also have (fossil fuel kits) built into the electronics

    caution, stat needs to be configured properly.
    I would love to know how to do this with an IAQ. I have an IAQ with adaptive recovery set and I have not figured out a way to use the gas during setback recovery.
    Thanks,

    Mark

  9. #9
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,876
    The IAQ qill attemp not to use the gas furnace if adaptive recovery is enabled.
    Also, if the gas furnace is locked out above x degrees, it won't use the furnace either when it is above that OD temp..
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  10. #10
    Join Date
    Mar 2008
    Location
    dalton ga
    Posts
    39

    heat pump & gas backup

    the others are right. heatpump and gas can not run together. high head pr. you are talking about a* fossil fuel sys. when a heatpump sys. comes on if the stat set point is 3 deg.? above temp. -its brings on backup heat,ie--electric or gas.{fossil fuel.) yes- in heat pumps you have times when hp & strip heat are on at the same time. in fossil fuel --never should. there are tstats and fossil fuel kits for fossil fuel sys.--bill porter kits,(which are great) 1f95-377 w/r stat* 1f95-377 works on time. call for heat- heat pump comes on. if cant bring set temp to set point in x amount of time, it turns off heat pump then brings on emg. htg. gas.1f97-377 w/r stats are in short supply. they have a replacement. you can have a outdoor stat that will not let the hp come on below 30deg?? or whatever.then only use gas. 2 stats? i see a prob. never seen it. most fussel fuel stats have to be pro. to know what they are doing.-- int. rec. stats learn when to bring on backup. they ?? panic when you set them to be 72 at 6pm and its 5.30--68- bring on backup ,have to be 72 at 6pm.a furnace can not be programed. its in the stat or kit. i have been told i dont know everything.--i dont. there may be more. i hope this helps.

  11. #11
    Join Date
    Apr 2008
    Location
    Bemidji MN
    Posts
    64
    In my neck of the woods (northern Minnesota) we use heat pumps in conjunction with a modulating electric plenum heater hooked to off peak electric along with a gas furnace for backup. The only brand I sell is Electromate plenum heaters....I fell the best in the industry. By the way...the plenum heater is installed above the a-coil so the "added" heat is after the a-coil......thus not affecting the head pressure. The plenum heater takes care of all and any fossil fuel kit. It requires a standard (not H.P.) t-stat and an outdoor sensor hooked to the plenum heater to control balance the point. On a call for heat the h.p. starts and if necessary (based on a predetermined set point) modulates the electric strip heat on and off to maintain a certain plenum temp (there is a supply duct sensor downstream from the plenum heater and a-coil). Something like 104 degrees. This way we can run our h.p.'s down to 0 degrees outside and still maintain a steady room temp. After 0 degrees it turns off the h.p.and the strip heat takes over from there.....until the electric is rippled (by the power company) them the gas or oil furnace takes over. Do any electric companies offer an off peak program besides Minnesota's?

  12. #12
    Join Date
    Dec 2006
    Location
    Middle Tennessee
    Posts
    11,347

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    Quote Originally Posted by NGHTYRTE View Post
    . heatpump and gas can not run together.

    this is not a correct statement!

    when a heat pump/dual fuel system goes into defrost, the heat pump and furnace will operate at the same time!



    .

  13. #13
    Join Date
    Mar 2008
    Location
    Baltimore MD and Ridgebury PA
    Posts
    542
    The Honeywell 8000 works very nicely for this. I do have a question for you though... you ask about the gas furnace coming on after a setback... do you intentionally want this for some reason? The heatpump should be able to recover more efficiently and the 8000 will do so if using intelligent recovery and OD temp is above the lockout temp.

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