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Does this mean my Grundfos circ pump burned out

Hi everyone,

I think I know what this means but thought I'd check with the experts on this site. See attached two photos. The pump itself is too hot to touch, but the line coming in and out are cool. Also, does the burnt label give you a clue that it got toasty? Thanks all.


  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 6,725
    Doe it still run or has it quit?? Your system could be air bound. The pump if running probably is not moving any water.
  • JohnNYJohnNY Member Posts: 2,424
    Yeah, that doesn't look good. I'd say it's given all it's got. If it isn't moving water, I'd replace it.
    For installations, troubleshooting, and private consulting services, find John "JohnNY" Cataneo here at :
    "72°F Mechanical, LLC"
    Or email John at [email protected]
    John is the Boilers and Hydronic Heating Systems Course Instructor at NYC's Mechanics Institute, a professional Master Plumber, licensed by The Department of Buildings of The City of New York, and works extensively in NYC while consulting for clients in and out of state.
    John also oversees mechanical installations and maintenance for metro-area clients with his family's company, Gateway Plumbing and Heating along with his brother/business partner.
  • Alan (California Radiant) ForbesAlan (California Radiant) Forbes Member Posts: 2,133
    edited October 2018
    When the pump impeller stops spinning for whatever reason, the electrical energy cannot be dissipated by movement of the impeller. Instead, it's dissipated as heat and the motor is often too hot to touch.

    Luckily, these pumps are impedence protected:

    "A method of preventing burning damage when the motor is restricted from rotating; done by setting the motor winding impedance (AC resistance) to a value giving a temperature rise in the windings below the temperature at which burning occurs."
    Often wrong, never in doubt.

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  • hot_rodhot_rod Member Posts: 12,897
    it's been hot. Carefully remove the large screw cap, when the system is cooled down, and obaerve if the shaft you see spins when powered, or a screwdriver slot in the shaft can sometimes get them going. They take a lot of abuse, but that may have crossed the line.

    There is a specific way to pipe a recirculation pump with thermostatic mix valves, I'm not sure yours is correct?.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • ZmanZman Member Posts: 5,601
    That pump is a little aggressive for what you are trying to move.
    You will save some electricity and get more life out of your pipes and circ if you go with something like this.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • HomerJSmithHomerJSmith Member Posts: 843
    edited October 2018
    If you have a lot of mineralization in your water, the rotor may be stuck. These circulators have low starting torque. Take it apart and check the rotor turning. If it is calcified use CLR and soak the rotor to dissolve the mineralization and give it another go.

    I had a pump that wouldn't rotate and when taking it apart a solder ball lodged in the impeller, preventing it from rotating.
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