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Grundfos Miximizer

I have a grundofs miximizer UP 15-42 FC/MR on my in radiant floor heating system. It's approximately 18 years old. Four days ago on a cold long weekend in February the miximizer stopped circulating water. All 4 lights are lit up (not blinking). There is nothing in the troubleshooting section of the manual that details this.
When I cycle the power on the furnace and leave the furnace off for more than 4 minutes the pump will circulate with the proper lights blinking for approximately 8 minutes and then all the lights will light up solid and it will stop circulating. It will not correct itself until I cycle the power. I have never had this issue before. I'm trying to determine if its a mechanical issue or electrical in the pump. Does anyone know if there is a thermal overlaod.? is it repairable or am I in search of a new pump.


  • hot_rod
    hot_rod Member Posts: 22,467
    Look for troubleshooting info at the Grundfos site. Or try Grundfos tech support. Also try your local rep, they often have the best hands on troubleshooting advice.

    I believe that circulator is still available
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    EBEBRATT-Ed Member Posts: 15,829
    What @hot_rod said + Have you done any work on the system? Any chance air got in the system?

  • pkehoe_5359
    pkehoe_5359 Member Posts: 2
    I have not done any work to the system and just installed new snifter valves last fall to remove air