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Is this main circulator grossly undersized?

Syncro Member Posts: 9
I have a propane converted 6-zone Weil M Gold 5 boiler with a single Taco 010 circ. I think I am calculating the feet of head for longest zone correctly: 140 deg water. 266 ft x 1.4 for fittings = 372 equivalent length. Then multiply by (k=.00295) for 3/4 copper, and times 11.3 for flowrate of 4gpm = 12.4 feet. Add one for the boiler and we're at 13.4. The taco 010 maxes out at about 12 ft of head. 68,000 btuh need for this longest zone. So the best ΔT is about 33 to yield 4 gpm. So the 010 comes up a bit short for this one zone. And what about when more than one zone is calling? Three zones at 4gpm each = 12gpm and the 010 can only handle about 10 ft of head at 12 gpm. So does the water flow follow only the path of least resistance and starve the other zones? Heating is irregular but we've just gotten used to it. I'm thinking I need a different circ but because of the wide swing in GPM with 1 - 6 zones the Taco variable speed ΔT unit is appealing. I know you pros deal with this kind of issue everyday and I'm really interested in what you would suggest and if you think my analysis is on track.


  • Paul48
    Paul48 Member Posts: 4,469
    General Rule

    Is 40000 btus for 3/4" pipe. So, your zone would appear to be grossly over-sized. You might want to rethink zone distribution before circ sizing. When you start daisy-chaining many emitters, you have to allow for the DT, and add emitters accordingly downstream. I'm sure the pros will elaborate on this, I am just a homeowner.
  • Harvey Ramer
    Harvey Ramer Member Posts: 2,239
    edited February 2014
    Install a pressure guage

    on the inlet and outlet side of the pump. Then record the pressures with only the longest zone on. Also measure the supply and return temp while you are running the test.

    With that info we can see where the duty point of the pump is falling and get a good idea of how many Btu's you are delivering to the zone.

    Also, if you have baseboard measure how many feet of pipe with fins on it.

    We can repeat the process for every zone. We can also run simulations with various combinations of zones on. 

  • icesailor
    icesailor Member Posts: 7,265

    In the scheme of things, IMO, it's not as important as getting that turd out of the punchbowl.

    The cost of that oversized circulator (I don't think that it is) is far less to run in its lifetime than you will ever recoup in savings by changing it to something that works "better".

    If it bothers you that much, put in a ECM motor pump and let the pump dial in the load. They work well. So does what you have.

    When bidding jobs, and winning a job or losing it can be over the cost between a 007 pump or a ECM pump, I'm sometimes stunned at the level some will do to find another pump. When the one they have is more than adequate.

    Then, you'll go to PEX Supply or Amazon. Com buy it, and look for the cheapest person to install it for you.

    Who needs it.