After 30 years use, I replaced my water heater pump Grundfos model UP 15-18
with a new unit 3 years ago. I just noticed it no longer seems to be
working: it just hums very quietly, no vibration whatsoever. The capacitor
measures 10 uf as rated. I have 46 ohms resistance between the plug, zero
to ground. Before I replace [fairly pricey], any other tests or ideas?
Thee is a screw on the back of the motor. Remove it and inside you can see
the shaft. With a small screwdriver, you can turn the shaft a bit. This can
be done with power on or off. If the power is on, it may start to turn
slightly and then pick up speed. When mine were getting old, I had to do
that at the start for heating season, they they were good for the year.
When one of the pumps finally did go I replaced it with a Taco. It was just
not as quiet, but it did pump water just fine at half the price.
I wish as these cost @ $200.
You'd think there might even be kits available. But I tried replacing the
bearing with the last one and I'd say Grundfos really didn't make these
bearings "user serviceable."
As to your original post, check the amp draw. That's totally valuable
Hope you can dissemble the pump, clean it up, and make it last for a
few more years. Some electric water pumps (Bell and Gossett comes to
mind) have oil holes to drip in some ND20 oil.
I've search but not found Grundfos parts and assumed I'd have to buy a new
I was pleasantly surprised that the local Grundfos dealer encouraged me to
bring the pump in for a free disassembly. Pump had overheated [showing
brown build up in interanls] but bearing was good. Dealer installed a new
rotor/impeller assembly and unit seems good as new. $25. I was shocked by
the high level of service.
The water here in Hawaii is soft - rain water filtered through lava dikes.
My pipes are 30 year old copper but I never see crud in any of the faucets.
The brown residue was very thin, just enough to upset the tolerances of the
low hp motor.
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