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Modern circulators vs modern zone valves for small flow rates

I know this one has been discussed before, but there have been advances in pumps since the last I saw. I’m also looking for advice on my specific design, which has a relatively small flow load. I’m finalizing my radiant ceiling design, but know that my floor load is less than 4gpm, and I expect the total including ceilings, to be not much over 7….if they all run simultaneously. 4 circulators seems like overkill, especially since my basement zone will be less than 1.5 gpm. I like Taco’s Viridian 1816, and that solves some of the energy waste, but one of these circulators could easily power all 4 zones in my home, at half capacity. My Navien NCB 240e has an outdoor reset sensor, so this system should be running most of the day in the cooler months, all those watts add up. Are there design considerations that might be worth noting?

Multiple circulators create redundancy. Zone valves might save a little money. Zone valves save energy. What else am I missing?


  • Leon82
    Leon82 Member Posts: 684
    You would run the 1816 in pressure mode so it will adjust for the load as valves open and close.

  • hot_rod
    hot_rod Member Posts: 19,281
    I agree dedicated circs for such small gpm loads seems overkill.
    You could plot the system curve on the circ curve to get an idea where they will actually be running.
    A delta P circ and zone valves would be my choice.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Dave H_2
    Dave H_2 Member Posts: 526
    How about the 0018e? The difference between this and the VR1816 is the bluetooth connection to the circ. You can dial it in to exactly what you need and use even less energy. You can also get a real time shot of the wattage when running.

    Dave H.
    Dave H
  • hullabaloo
    hullabaloo Member Posts: 9
    Thanks Dave. I hadn’t seen that pump and wish I had, since I probably would have gone with it. If I could have found it in stock anywhere. It looks popular. I would be running it in constant pressure mode either way since I’m running zone valves, though it offers 9 curves instead of the 3 I bought. I don’t have a thorough understanding of head loss and it’s effect on other zones/manifolds, but I believe that the pump meets the demand of the zone with the highest head loss, then other lower head loss zones just increase the flow? In this case the 1816 that I have on order on “low” meets a 5 ft head, which would give me a 15° delta T. The 008e brochure is a bit blurry, but looks like I could get a 3’ head. Which I guess would allow me to hit a 20° delta T without restricting flow through the balancing valves and save a little money on pumping costs. Probably it won’t make a great deal of difference in the end, but the additional control and additional data appeals to the geek in me.
  • hullabaloo
    hullabaloo Member Posts: 9
    Thanks Hot Rod. I was slow to see your response (I need to somehow set myself up to be emailed when there is a reply) but came to the same conclusion in the end. As I told Dave, if I understand it correctly, running a variable speed pump in constant pressure mode on the lowest setting for a TACO 1816 should be perfect for my system. The last of the needed components arrives Monday, so I should find out soon!