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Best ecm circulation pump advice

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dough041
dough041 Member Posts: 34
in Gas Heating

i have a rinnai ru199in heat only boiler. Theres 3 seperate hot water baseboard zones with 3 grundfos ups15-58 3 speed pumps installed on the supply side set to low speed. Then on the return at the boiler there is also a grundfos ups15-58 set to medium speed. Its been running great for a couple years and for preventative maintenance I have several parts in case ( eg: ignitor/ flame rod etc) I was planning on ordering an extra circ pump to have on hand . I was thinking of getting grundfos alpha 15-58f ecm pump and install that at the return and save the return ups15-58 as a spare? Any thoughts or suggestions?

Comments

  • hot_rod
    hot_rod Member Posts: 27,116

    with multiple circs it sounds like you have some sort of primary secondary piping, a pic or sketch would show that.

    If so the pumps are hydraulically separated.

    An ECM as the boiler pump would save some electrical energy. I don't know it would add much more value in a fixed speed. Some boilers can vary the boiler pump speed for an efficiency boost. Those circs are controlled by the boiler and have a specific control algorithm.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • dough041
    dough041 Member Posts: 34

    Thanks Bob - yes its primary secondary. I assumed the flow control with the mentioned pump would automatically adjust the flow when set to auto adapt? I currently have the 3 speed pump at the return set to medium due to all zones calling for heat because of the extreme cold temps in the northeast now. My furthest zone seems to have a “flow noise” ( not air ) maybe because the ups15-58 has too high of a flow rate even at low speed? ( off the subject sorry),

  • hot_rod
    hot_rod Member Posts: 27,116

    Unless there was something causing the flow through the boiler to change, the pump is always seeing the same "head" flow resistance through the boiler HX.

    Auto adapt is used when zone valves are opening and closing changing the pressure drop in the system. The pump "learns" to slow down as zones close off, speed up as zone valves open..

    Velocity, over pumping, is more like a gently hissing sound. A sound you hear when an outside silcock is left open :)

    Gurgling an air sound. Pop, tick or creaking a tube expansion noise, perhaps.

    If it is a 3/4 fin tube zone or radiator I don't think speed 1 would be flowing too fast? Maybe if it is a super short loop?

    Screenshot 2026-01-29 at 4.23.54 PM.png

    If the pump has an isolation valve on the outlet, discharge side, try throttling it down slowly to see if the noise stops. Basically using that iso valve as a balancing valve to slow flow.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream

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