Grundfos vertical CR8 pump screaching noise on shutdown

[Miguel Costa]

Good Afternoon!

I have just came from an installation where there is a Grundfos water pump (CR8)that makes a loud screeching sound when it turns off. Amp draw is OK 5,8 Amps on all 3 phases, pressure increase is normal compared to 2 other exact pumps that are in parallel, voltage across the 3 phases is ok (388 VAC). Seems to work fine, but it always makes that loud screeching sound when it shuts off... Can any one give any insight on this matter? Thanks in advance!

P.S. - I have a video that shows the pump working and turning off with the screeching sound if anyone is interested.

 

[Artisi]

Have you asked Grundfos?

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[Miguel Costa]

Hi Artisi, i have sent the same question to them yesterday. But regardless, I would like to have opinions from the forum because I think that it will yield more valuable information on the causes and mitigation of the problem. There is nothing like getting information "from the horses mouth"! Thanks for the reply!

 

[itsmoked]

From past experience around here I think if you could get us the sound file it will help with the experienced folks around here getting you the answer.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Artisi]

Miguel, my response wasn't a fob-off to your question, but to ask about noise in vertical Grundfos pump in here is a long shot - I would think not many members could give a meaningful answer off the top of their head as the vast majority wouldn't know much if anything about a vertical CR8, I include myself, even though I have some experience with Grundfos pumps, although you might be lucky. The question is probably better of in HVAC forum.
If nothing comes back from Grundfos - raise it again with more detail if possible.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[Miguel Costa]

Artisi, I genuinely didn't take your response as a fob-off! Many times I have overlooked or not even remembered to do the simplest and obvious of things! So you are correct to start off with pointing me in that direction. Kind of like the " is the power on?" diagnostics when troubleshooting home appliances!
I will also post in HVAC forums, sounds like a good idea! thanks Artisi!

 

[Miguel Costa]

Hi Itsmoked, I'm attaching the video with the sound I am asking about. It makes that loud sound when it turns off. Thanks for the feedback!

 

[quark]

Is the entire sound file after pump stopped?

 

[Miguel Costa]

Hi Quark,

pump is running until 0:03, at 0:04 it stops and you can hear the noise I'm questioning about. Thanks!

 

[TugboatEng]

Just speculation but as the pump speed slows after the motor is de-energized it's possible a flow reversal occurs and that may make some interesting sounds until the impellers come to a stop. Think compressor stalll on a turbocharger. An image search shows the impellers to be fabricated sheet metal which may help generate such a noise.

 

[Artisi]

To be honest, I have listened a number of times and haven't any idea that is making the noise.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[LittleInch]

Are you sure you got the right file?

Doesn't sound like a "large screeching" noise to me.
The only odd noise I hear lasts for a fraction of a second - not long enough to identify anything.
I think you need to be there and then try and identify the source - the motor, the pump, something else, some pipework or valve change

It sounded more like a contactor or some sort of bypass fluid noise.
Could just be the non return closing. It's over very fast.

In that environment it could be many things.

Can you post a diagram of the pumps and how they operate?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Miguel Costa]

Hi everybody, sorry for not responding, but i am currently dealing with a death in the family. I appreciate all inputs and promise to respond with more details tommorow. Thank you for your time and interest in helping out

 

[quark]

Agree with Aritsi. There is more screeching noise while running that while it is shut off. Overall, the sound doesn't seem to be too bad. TugboatEng has a point which I thought initially. Anyhow, check motor fan. Usually, when it is misaligned, you don't get much noise during running but can create noise during stoppage.

Sorry to hear about the unfortunate event. Be strong.

 

[Miguel Costa]

Hi everybody,

I have another file with better sound. I think I didn't choose my words right: it's not really a screeching sound, it's more of a "laser gun blast" kind of sound. It's pretty loud. In the new video I eliminated some background noise that's coming from a open water deposit filling. So you can hear the pump starting, works for some seconds and then shuts off with the noise. I will also post a rough schematics of its current installation (I apologise for the artwork in advance!).

Tugboateng - I have also thought of that, I work in refrigeration and with scroll compressors we get that kind of noise on shutdown when a small quantity of gas in the high pressure discharge inverts flow and speeds back to the compressor. The thing is, this pump is in parallel with to other same model pumps, and the other 2 don't make this sound. That's stumping me because if the other 2 pumps made the same sound I would think it would be something related to the rest of the installation (valves, etc). Of course you didn't have any hint to go on because I didn't post a schematics or anything of the sort (sorry).

LittleInch - Yes, the sound it makes is just a fraction of a second when it shuts off. I am following your suggestions, and will post new sound file and schematics and photo of the setup, I should have started that way in the first place...

Quark - I will check the fan alignment, did not look at that while I was there. Thank you very much for the kind words!

Will post the new sound file and schemtics in 30 min.

 

[Miguel Costa]

Video file:

at 0:05 pump starts
at 0:18 you hear a click sound - it's the pressure control shutting off a second pump (that's inactive because I wanted to isolate the sound of the pump in question).
at 0:20 the pump shuts off and you can hear the sound.

 

[quark]

If the other pumps also run simultaneously check whether this pump is starving. Stop other pumps and see if the same noise occurs.

 

[Miguel Costa]

Image file with installation schematics

 

[Miguel Costa]

Quark - the video i posted is showing the pump working alone, I cut out the other 2 pumps while looking into this problem.

 

[Miguel Costa]

Photo of the setup