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circulation pump differences

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jeff3176
jeff3176 Member Posts: 9
in Radiant Heating
Hello all! Looking for any help regarding circulation pumps on my system. My upstairs zone has a Taco pump rated at 23gpm max. My basement zone has a grundfos pump, looks like its rated at 15 gpm max. My Taco pump is getting noisy, so I want to have a replacement on hand. I can get a Grundfos 3 speed with check valve locally, but I have to order the Taco. Can the Taco be changed to a Grundfos, or does the gpm matter? Thanks!

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  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,006
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    You should be able to change the Taco to a 3-speed Grundfos 15-58. I doubt that your upstairs zone needs a lot of gpm, but the pressure drop will determine what speed you need. What kind of heating do you have? Radiant in the floor? baseboard? fan coils?


    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • Dave H_2
    Dave H_2 Member Posts: 556
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    For one, I doubt you would need 23 gpm for the upstairs zone of your home nor could you get that much anyway. Flow is determined by the amount of radiation in the zone and then the pipe size.

    3/4" pipe can safely handle 4 gpm, 1" = 9gpm, 1-1/4" = 14 gpm..... Having a circ that can do 15 gpm in a zone that needs only 4 doesn't get the heat there any faster or better.
    Its just oversized and that's it. Oversized circs are detrimental to the system performance.
    Now there are circs available today that are variable speed and can be setup (there is no magic in them) to the application and needs of the system.

    The flange to flange distance is the same and they are interchangeable.
    Dave H

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