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Air to water heat pump with back up boiler

I want to use an air to water heat pump that can only handle return water of 120F with a supply of 130. I need to have the back up boiler operate at 135 on extremely cold days. Would a hydraulic separator allow me to use my heat pump at 120 return and pump into the separator while allowing the boiler to put out 135F when needed. I would want to do this as the heat pump is more efficient than the condensing boiler. Thanks for any input, Jim

Comments

  • NRT_Rob
    NRT_Rob Member Posts: 1,013
    it's hard

    to run both together.



    depending on how often you need backup, might want to keep it simple and infinitely modulating with an electric boiler called with a stager of some kind when needed to "boost" the temp up.



    otherwise this is likely to be "either or" unless you segregate the emitters into a high and low temp system, presuming you have some that do not need to get to 135.
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
  • zacmobile
    zacmobile Member Posts: 211
    edited September 2010
    tank

    You could use a large stratified buffer tank to utilize multiple heat sources with differing temperature requirements with common emitters.



    http://www.buderus.us/products/storagetanks/tankssolarsystems/logaluxpl750-2s.html



    http://www.tisun.com/eng/content/download/2433/36024/version/30/file/EN_TK_2010_K4_Speicher_rz.pdf
  • NRT_Rob
    NRT_Rob Member Posts: 1,013
    only

    if you can ensure the return water will always be below your minimum for the heat pump. That would seem tricky on most systems.



    and for the cost of that tank, you could run electric backup for about a hundred years. Snarky, but the point is that's an amazingly expensive tank last time I checked. Has the price come down at all recently?
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
This discussion has been closed.