Singing noise related to water pump


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Since our central heating system was upgraded in October we have noticed a singing noise in the house when the water circulating pump switches on. It is a new Grundfos UPS2 15-50/60 pump with 3 speeds. Reducing the speed reduces the noise but it doesn't go away, and we need to use the maximum speed to heat the house effectively.

The noise sounds like a musical tuning fork. It comes from any part of the house where there are pipes or radiators, as well as from the pump, but is not easy to pinpoint. It is not loud, just annoying. How loud it is depends on where you are in the room and what direction your head is turned. It is as though the noise from the pump transmits to the water everywhere in the system.

The system works well otherwise, there are no other clues, although there is a slight unrelated whistling from the boiler flue which is being investigated.

A Magnaclean filter was fitted and has removed about a cupful of black rust already.
 
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ben...could be vibratory, try holding onto various pipes/fixtures to see if that makes a difference. Also, an air leak...brother had a radiator that would 'sing'....or a constricted water line. And, I have heard the couplers between the motor and pump 'whine'.(if you have one)
 
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Don't think it's an air leak, an air leak tone would "waver", and I tried holding on to the pump pipes, no change. When I get time I will try shutting off different radiators at a time, as has been suggested elsewhere.
It must be something to do with the pump, and the noise being conveyed by the water in the system, as when you turn the pump down to speed 2, the singing note drops proportionately.
 
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Air leak would not necessarily waver...have heard it both ways...depends on whats driving the air, which is obviously the pump.
I can recall (long ago) the bleeders on radiators that would whistle so loud that we had to leave the room...fortunately there have been a lot of improvements since then ;o]
 
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and another passing thought....if they are using PWM tech to vary the speed of the motor, some motors will react to that with a loud shrill..(pulse width modulation speed control)
 
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You say a loud shrill, my pump noise is quiet so can I assume that is not the problem I have?
 
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ben, motors hum, pipes/water can amplify that. electronic speed controls can make a motor squeal or just hum loudly...they seldom mate up perfectly. And perhaps you don't have that. It's along shot, but if your boiler people had a spare motor/pump they could stick on there just to experiment.....
 
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OK, next time he comes he said he would try fitting a Wylie pump. Long waits after Christmas though!
 
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Problem solved. Singing noise completely gone. Plumber replaced the Grundfos with a DAB 40-70/130. Whether the Grundfos was faulty or there was an incompatibility with my system we will never know. Thanks for all support.
 
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