Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Grundfos Pump Housing Temperatuire

J Van Lund
J Van Lund Member Posts: 19
The outside housing temperature on a 12-year old Grundfos UP15-42has a temperature increase of 10 to15F over the circulating water temperature inside the circuits. Water temp 110F; outside pump temp 125F. Is this a cause for concern or replacement?


  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    I believe they rate their motors for a given temperature above ambient, not the circulating water temperature. Its usually listed on the motor.

    Only way to know for sure if you are in trouble is to check the motor amperage. And even that isn't much help, because some of these little motors draw the same amperage with a locked rotor as they do under normal full load.


    There was an error rendering this rich post.

  • Tinman
    Tinman Member Posts: 2,808
    What Mark said - check the amp draw. The pump is rated for water temps in excess of 200*F.
    Steve Minnich
  • hot_rod
    hot_rod Member Posts: 22,262
    Are you sure it is circulating, not air locked. if the temperature continues to increase it may be air locked

    The motor will add some heat it is a 42W motor, some is pumping energy, some heat.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • SWEI
    SWEI Member Posts: 7,356
    The efficiency of small PSC motors is abysmal. The other 75% of that energy has to go someplace.