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the most frequently asked question?

plumb12 Member Posts: 3
The most frequently asked question Circ's or ZV's?
With massachusetts rebates, variable speed pumps equal the cost of ZV's now.
Senario #1) A FHW boiler P/S loop, single delta T circ with a multiple ZV system will have each circuit balanced.
Scenario #2) Same as above, except with multiple delta T circ's.
Which method is more effective and efficient on a multi zoned system?


  • SWEI
    SWEI Member Posts: 7,356
    It depends on the size of the zones. Currently available ECM circulators (Grundfos, B&G, Armstrong, Wilo, and Taco) are sized to pump houses. We need circs sized to pump zones.
  • plumb12
    plumb12 Member Posts: 3
    Yes, this is a residential application. I'm not referring to high head pumps for multi-residential or commercial heating pump systems with VFD controllers. A home with about 3000SF heating area and six zones ranging from 1-4 gpm
  • unclejohn
    unclejohn Member Posts: 1,833
    I prefer zone valves, Thank you.
  • hot_rod
    hot_rod Member Posts: 19,921
    zone valves and delta p circ.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • SWEI
    SWEI Member Posts: 7,356
    edited November 2014
    The ECM circs I listed above are still too big for the vast majority of residential zones. On larger houses, one per floor can sometimes work out well. They work surprisingly well in commercial zone and coil applications. Too bad none of them can be managed by external controls (yet.)
  • Rich_49
    Rich_49 Member Posts: 2,738
    edited November 2014
    ZV's & a Delta T circ large enough for the total maximum GPM
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • Dave H_2
    Dave H_2 Member Posts: 527
    you gotta do the math. in order to pick the right circ, you need to know the flow (Universal Hydronics Formula) and then you need to know the head loss of the project.

    Otherwise, you are just guessing and hoping it will work. Will it work with just choosing one over the other? Probably. But what if it doesn't. Whose to blame?

    With the controls on the circs, you need to make sure the correct control strategy is chosen. When it doesn't work because the math wasn't done, the component gets the blame and its less feature-rich brother gets installed.

    Make sure you know what you have in your hand and why you are using it for your customer. What reasons do you have for zone valves over circs? Go with what works and what you feel comfortable with. All of these pumps can easily do alot of house by themselves.

    Dave H.
    Dave H
  • SWEI
    SWEI Member Posts: 7,356
    edited November 2014
    Good point, Dave.

    Circulators have efficiency curves as well as performance curves. Peak efficiency typically occurs very close to their rated RPM and that when running slower, their hydraulic efficiency is reduced. Running an ECM circ at the bottom of its range gives it no room to modulate.

    Just because your (circulator, boiler, furnace -- pick one) modulates does not mean you can ignore sizing.