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Delta-P situation specific

Hello all, first post but I have lurked for a while. 2 years ago we installed a geothermal system with an 80 gal buffer tank and a backup navien 55,000 btu boiler. Navien is wired to start up if the second stage of the geo unit (2 2.5ton pumps in one box) doesn’t bring the tank up to temp in 10 min of run time.

We have in floor radiant in the kitchen bathroom and living room and Purmo panel radiators with thermostatic control valves in the bedrooms and as additional heat in the living room (12 ft ceilings dropped to 10 ft but still a bear to heat when cold like this last week).

We have thermostats in the kitchen and living room running 15-58 zone pumps for the floor heat and a 15-58 hooked to the 3 downstairs radiators set to run whenever the primary loop pump runs.

Now that you have the system picture the question is this: we are remodeling our bathroom and I want to put in a hydronic towel rack which will have a TRV, also saw at my in laws a TRV 4” oF the floor for their bathroom in floor, was intriguing. If I plumb all 5 TRV loops/radiators to a manifold should I use a delta p, delta t, or normal pump.

Done a lot of reading and the answer is clear as mud


  • hot_rod
    hot_rod Member Posts: 22,157
    Delta P function is ideal for zoned systems either TRVs or zone valved systems. The ECM pumps are nice for replacing those 15-58 zone pumps at some point also, about 50% electrical consumption reduction withECM powered circulators.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Steve Thompson (Taco)
  • Zman
    Zman Member Posts: 7,569
    You want the pump to respond to changes in pressure (valves opening). I say Delta P
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    Steve Thompson (Taco)
  • pmartens07
    pmartens07 Member Posts: 2
    How should a delta p pump in this situation be switched? I’m guessing something that powers it as soon as outdoor temp reaches a certain point? I’m really not that good on the controls side of this. Everything is controlled through an Argo relay box, any suggestions?
  • Ironman
    Ironman Member Posts: 7,376
    If you use a Grundfos Alpha, simply plug it in and set it to "Auto".
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.