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Grundfos circulator pump problem

dreamweaver74 Member Posts: 4
Is there any repairing my pump. How would I check?

I have a circulating pump (UPS15-58FC, 3-Speed Circulator Pump, 1/25 HP, 115 volt - draws less than an amp that I had running for a month or so off and on a timer. I wired a temperature controller (Inkbird All-Purpose Digital Temperature Controller Fahrenheit &Centigrade Thermostat w Sensor 2 Relays ITC-1000 - relay contact capacity = 10 A) to an outlet into which I plugged the pump. I then plugged the pump in and the controller turned it on and seemed to work fine.. I left it for a day when I had more time to observe and tried it again and the breaker tripped. When I originally connected the pump I had a reverse polarity in my shed. I bypassed the polarity issue by temporarily plugging the shed power (plug end on the romex wire - this is how the shed has been for years before I bought it) into a correctly wired outlet on the outside of the house and running an extension cord to my shed. I plugged the system in and this time the controller popped and hissed. I plugged the pump into the extension cord directly and the breaker tripped. Figuring that I had caused the problem with my original polarity issue. I ordered a new pump and controller. With no polarity issue, I wired controller. Almost the exact same scenario. I installed new pump, pressurized the system bled air. Plugged the pump into an outlet and put it on a timer while waiting to have time to wire the controller. Pump turned on and off on the timer correctly. I wired the new controller to control the same outlet. The controller reached its setpoint and turned the pump on. I was about to claim success when my daughter bumped the extension cord connecting the whole system to the shed. I heard a slight pop but the breaker did not trip. I examined the extension cord it looked like it had one wire burned through. The plug end connecting all of the power to the shed looked like the ground was not connected. I re-wired the end and got a new extension cord. I plugged the pump in, and the breaker tripped.

All of this time I have had another pump grundfos 1/6 hp and a differential controller working on the same circuit. This pump was not running during any of the tests. I have checked that the outlet is supplying ~120 volts thinking there could have been a drop because of the extension cord or controller. I verified that the pump is wired correctly. I checked the (start/run?) capacitor (it has a diode in the circuit) and though I don't see a +/- on the terminals, I get the correct 10uF in one direction and 0L on my meter with the leads reversed.

As i've written this it seems that the issue, besides the wiring in my shed has been the controller. Pump works fine without it, something shorts and then pump doesn't work again. If this is the case. How do I know what went wrong? How do I prevent it from happening again even with a different controller. It seems that it is well oversized even considering a high starting amps.


  • Harold
    Harold Member Posts: 249
    Just reaching here, based on what you have done and not done. tossing out ideas of things to check.

    Is there a required Ground Fault Interrupter on the outside outlet you are using for the extension cord powering the shed? It could be faulty or wired incorrectly. If the GFI sees something it could try to trip and have strange wiring connected somewhere in the shed. Or a controller and GFI don't like each other.

    Perhaps bad wiring in the controller interface. You indicate the controller uses a relay to control the pump. You will then be powering the controller and the pump from the same circuit. I am not sure what you mean about pump runs fine then something shorts and the pump will not run again. Where is the "something"? It is possible that the controller has a solid state switch/microprocessor which might be damaged by a transient from the start of the pump. If the "relay" in the controller is solid state and not an actual mechanical relay, it may not be suitable for your motor, and a starting surge could well be killing that SCR/TRIAC. What do the specs on the controller say about that. Is wiring for pump and controller both on the same legs of the extension cord.

    Just some ideas of possibilities.
  • dreamweaver74
    dreamweaver74 Member Posts: 4
    Thank you so much for your comments. I am reaching for what else to try and you have given me some ideas. I need to check the specs on the controller, it was supposed to work for brewing and mentions running a compressor for the cooling, but maybe my motor has higher transients. I "assumed" that since it was rated for 10A I had plenty of safety factor drawing less than an amp, but I was not considering solid state or mechanical contacts and didn't understand the implications of either.

    The outside outlet is protected by a GFI but it didn't trip. Just the circuit breaker in the panel.

    I'm not sure what the "something" shorting is either. I'm assuming it is "in" the pump motor. I just know that the breaker trips, and then after that the pump won't work again. Now even when i plug the pump in directly, bypassing the controller, the pump trips the breaker as if there is a short. I just don't know how to verify this, or if there is any repair. From my reading on line it doesn't appear so. And I don't see any circuit board that could be replaced. My only thought was the run/start capacitor.

    It seems that the pump motor must be pretty sensitive and not have any internal protection to prevent permanent damage. Is there some external protection I should use for future motors? Like an inline fuse that is more sensitive than the circuit breaker in my panel, but could handle the start up current of the motor?

    I know that my other controller was meant and does control a larger motor, I should try to see if I can use another one of those.

    Thank you again. I appreciate any comments.
  • hot_rod
    hot_rod Member Posts: 19,950
    Then price sounds too good to be true!? You can barely get a cup of coffee at Starbucks for that money :)

    If the pump has run on the cord without the controller, sounds like the controller is the problem? Mis-wired, defective? Should be able to test it without the circulator connected.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Harold
    Harold Member Posts: 249
    I would suggest not using a controller designed to brew beer and run you pump. If you had, and understood, a full schematic of the controller, you might see if it is applicable.

    For example, the connection you are using on the controller may be outputting DC for some special pump associated with the controller. Or a heater. Making beer is a sacred duty; but the beer controller may not be on the same page.

    Just too many variables. And a controller without information. There are more devices to do this without having to understand what the internals of the controller are doing.
  • dreamweaver74
    dreamweaver74 Member Posts: 4
    I tested the controller with a light first and it did run the pump for a short time with no problem.

    I'm assuming the pump has a short in it and will have to be replaced. I'm just wondering if there is some external protection for the pump to protect it from damage in the future.
  • dreamweaver74
    dreamweaver74 Member Posts: 4
    edited December 2018
    I have used this controller for a different pump. I'm assuming I can use this. (Amazon: by thermomart: Differential Temperature Controller T2-T1 Thermostat Water Heater, Pool Solar Panel Pump 2 Sensors Fahrenheit Celsius) Though based on the specs I thought the other one would work, 120V AC and 10 Amps.

    I re-read the submittal sheet and install instructions for the pump and it states that the protection for this pump/motor is "CONTACT" and that the thermal protection is internal. The install instruction state that no external protection is required. But, unless I am reading the start/run capacitance wrong, the motor plugged directly into power trips the breaker and must have a short, I'm just not sure how this happened.