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Circulator Pump still runs a while after Zone Valve closes

rickhow
rickhow Member Posts: 14
in Radiant Heating
Grundfos Alpha Auto Adapt pump with LED display. 2 Honeywell zone valve system.
While heating the pump shows gallons per minute and watts being used which varies depending on if 1 or 2 zones open. For this example, lets say just 1 valve is calling for heat. Pump running. Thermostat is satisfied, the valve closes, but the pump "runs" for another 15 to 30 seconds (never timed it to be precise, but its at least 15), showing same number of gallons and watts usage, then declines say from 2 gpm, to 1, then to 0, the display goes blank, as I say taking at least 15 seconds or bit more to do so.
Shouldn't the pump just stop at same time as when last zone valve closes?? How can it be circulating when both zones are closed? Where is the water going?

Comments

  • Ironman
    Ironman Member Posts: 7,508
    It’s a “smart pump”, but it doesn’t instantly respond to changes in the system.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    HomerJSmith

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