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amatantsev 11-05-2008 10:24 PM

Grundfos Circulator with Vaiable Speed Control
Hello, this post is a result of many hours and days of trying to find an answer: is my Grundfos Circulator UP 26-64 F/VS with variable speed control supposed to make the noise that it is making? I am looking for anyone out there that had experience with Grundfos Variable Speed pumps - someone that can tell me if such a pump, normally, makes a humming noise (like a transformer, at 60Hz). The frequency does NOT change with speed at all - it always sounds the same. The only thing that changes with change of speed is the aplitude (level) of noise. Moreover, the noise is completely absent when the dial on the VS control is at 100%. The noise is the loudest at 50%.

The pump was making this noise ever since I installed it last year into an existing system. Yes, I bled the air from the housing. This is a primary loop with NO restrictions besides the boiler - load of the system is not the issue - I 've gone through this with Grundfos support several times. They are now letting me exchange the pump. However - the question still remains: is the VS control supposed to make the transformer noise??!! Will I have the same annoying noise going through the entire system and the house with the replacement pump? Should I just give up on VS and stick to one or three-stage ones?

So - does VS control on Grundfos pump make noise normally at speeds less than 100%? Grundfos tech support claims that the pumps are normally noiseless and I suspect that they would have to be, esp for cases like mine where I have 5 pumps and I plan to replace all of them with VS "miximizers" from Grundfos. That plan depends if I can figure this out first.

Thanking in advance,


ggraeff 01-23-2010 09:19 AM

I have the problem, although don't believe mine is a variable-speed pump (just the 26-64 F). But I definitely get a 60 Hz hum and it can be hard throughout the house. Did you ever get an answer?

amatantsev 01-23-2010 12:33 PM

No I never did get an answer. I ended up replacing the pump but the new one had the same symptom, so I figured that's how they must work... Any contact with Grundfos did not yield any useful info either... It is bizarre how difficult it was to get info on this - unusual for this information age.

yuri 01-23-2010 12:52 PM

Try posting it in our plumbing forum (at top of page) also. ECM motors/variable speed can make some noise as Lifebreath is having issues with them especially in the small sizes. Make take them a year or 2 to perfect them.

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