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True variable speed pump

Does anyone know of a true variable speed pump. One that can drop down to 1 or 2 GPM?
I have an HEC-2 and it doesn't slow down that much. The basic application is hot water baseboard circulator configuration, but not exactly.
thank you

Comments

  • Dave H_2
    Dave H_2 Member Posts: 585
    Joe,
    The HEC-2 does have a minimum speed (see here http://www.taco-hvac.com/uploads/FileLibrary/100-101.pdf) for the performance curve. You can get to the low speed and achieve that 1-2 gpm you are looking for. 1 to 2 gallons or minute is 20,0000 BTU's on a design day. If your system is about that size, you are right, it will be hard to vary below that speed.

    How much baseboard is connected to your system?
    Also, are you looking for a variable speed circulator or a high efficient ECM circulator?

    Dave H

    Dave Holdorf

    Technical Training Manager - East

    Taco Comfort Solutions

    Mad Dog_2
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 9,317

    Can you provide the total feet of element in your baseboard system. That is the part of your radiators with the aluminum fins. and how many fins per inch?

    And I believe @Dave H_2 may have a typo. The rule of thumb for 2 GPM is 20,000 BTU. (that is based on a 20° temperature drop between the supply temperature and the return temperature.)

    And you can get a Pump with temperature probe to be placed on the supply and return pipes and set the ∆T in order to get that 20° difference, or you can get a generic ECM that will just find a nice pressure differential without using the sensors.

    And Yes, you will get lower operating cost either way. So the question is do you only need lower cost operation, or do you want something else also?

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • Dave H_2
    Dave H_2 Member Posts: 585

    @t4chi

    When this post was written in 2015, Taco had the option of AC variable speed circs and we also had a Delta T ecm at the time.

    These circs have a minimum speed and I was curious what we were connecting it to

    Dave Holdorf

    Technical Training Manager - East

    Taco Comfort Solutions

  • hot_rod
    hot_rod Member Posts: 23,280

    When you say "true variable speed" something needs to tell the circ what speed to run. Either sensors or the delta P operation, controlled by the algorithms in the software.

    If you want a manually adjustable ECM variable speed, the B&G Vario has a dial to dial in required speeds.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • jumper
    jumper Member Posts: 2,385

    Varying the speed of any dynamic machine like a centrifugal pump cannot produce every flow one may want. You'd think that a positive displacement pump can……