Intelliflo "tone"

[sbcpool]

I've had my Intelliflo for a few weeks now and it has been very quiet ... up until last night. Last night it started making what I can only describe as a "tone" that resonates through the entire house. It's like a musical note that you can hum to in musical harmony. It woke me up at 2 o'clock on the morning and I couldn't figure out what was making the noise for like 15 minutes. I was going from room to room looking for the kids running a fan or something. When I opened the door to see if it was coming from a neighbor I noticed it coming from the area of the pump. The pump was only running at about 700 rpm and filter pressure is less than 2 psi at that rate. I checked the skimmer basket and pump basket, but both were clear.

I researched a little and saw a couple of posts reporting similar sounds, but they were either unresolved or caused by some major damage to the pump that I'm fairly certain I don't have.

Any ideas before I call Pentair would be appreciated.

 

[JamesW]

Possibly the seal. When the carbon face rubs on the ceramic face, it can generate a squeak or squeal. Try changing the speed to see if the sound changes.

Sometimes the faces wear a certain way and begin to squeal. Sometimes the sound will go away as the faces polish themselves against each other.

It might be bearings. See if the seal is leaking, which would get water on the bearings and cause corrosion.

 

[sbcpool]

I did try adjusting the speed down and the pitch didn't seem to change, but the intensity did. I could be wrong, but the pitch seems too low to be mechanical rubbing. It sounds very much like a pure ~175 Hz sine wave tone (like this). I'll try and record it at night when the ambient noise level is low enough.

 

[Rancho Cost-a-Lotta]

Could it be the base of the pump vibrating against the equipment pad? Did you try moving the pump around a bit?

 

[sbcpool]

I thought about that. I will see if I can wedge some wood shims under it to see if that has any effect. I will be super happy if that's the issue because I can just put some kind of foam rubber under it and it will quiet right up.

 

[scottts]

Almost anything having to do with the VF electronic drive or rotating parts of the motor and pump would change frequency with speed. Unless its something in the electronics, before the VF part, humming at the third harmonic of 60 Hz (180Hz). That might not change. Like some magnetic component - transformer or inductor in a line filter maybe.

 

[sbcpool]

Today I discovered something interesting: The tone is much louder at the skimmer than the pump itself. It sounds almost exactly like blowing across the top of an empty bottle to generate a tone. I made a short recording. This is the sound at the skimmer box, not at the pump. The pump is 30 some feet away behind the house and running at about 1,850 RPM. Any noise you hear is ambient, or from the skimmer box itself.

https://sndup.net/96db/skimmertone.mp3

This is the tone I hear throughout the house and it's making me crazy.

This is what the pump sounds like at the pad:

https://sndup.net/4p32/padsound.mp3

 

[sbcpool]

I thought this frequency analysis was also interesting. There's a very clear tone right at 190 Hz that is 23 dB louder than what's recorded at 188 Hz and 192 Hz. There's also a smaller peak at 38 Hz, which is the 5th harmonic to 190 Hz.

 

[JamesW]

Is there anything in the bottom of the skimmer below the basket?

Maybe something clogging the line vibrating from the water flow?

 

[sbcpool]

Nothing is visible. I don't suspect that's it. The pump makes the same tone, but it's drowned out by the other mechanical noise. I think it's more noticeable inside and at the skimmer because the mechanical pump noise is not there to hide it.

You can see the same 190 Hz spike from the recording at the pad, it's just surrounded by more noise.

 

[JamesW]

I don't know what is making the noise.

Does the sound change frequency at different pump speeds?

 

[sbcpool]

I intend to explore any possible relationship between pump tone and speed tonight when the ambient noise is more quiet to allow better recording. I will take a few sample recordings at different speeds to explore any mathematical relationship that might exist. Right now I can't see an obvious connection since ~1850 RPM is 30.8 revolutions per second, and that doesn't fit into 190 Hz very well unless the pump happens to have 6 impeller blades and the true RPM is 1900. That would fit perfectly.

 

[lakeboater]

I am very interested in this thread. I reported the same issue (inside the home tone) a few months back related to my VSF pump. I thought it might be related to the ground drying out under the equipment pad. When I returned this week, (after rainy season) I hear no difference. While I am no musician, I thought the tone sounded similar to "middle C" That's not far from 190 Hz.

I do not hear the sound in my skimmer though. I hear and feel the vibration at the pump inlet and outlet piping. I can't damp it by holding onto the pipes. Since the frequency is low, I don't think a thin piece of rubber will change anything, it will have to be something very soft.

Kudos to sbcpool for getting some frequency analysis.

 

[Oly]

This is unique. Cool frequency analysis.

 

[sbcpool]

So here's what I measured tonight:

1744 RPM 174 Hz -29 dB
1900 RPM 190 Hz -23 dB
2140 RPM 214 Hz -30 dB
2380 RPM 238 Hz -45 dB (barely audible)

I'm forced to conclude that the sound is caused by a 6-blade impeller based on the fact that it's precisely 1/10th the RPMs. 1744 RPM is 29.067 revolutions per second, times 6 blades is 174.4 Hz.

For whatever reason I'm assuming my plumbing resonates strongly between 160 - 220 Hz, with a peak around 190 Hz, which causes the loud "tone" you can hear in the house and around the pool deck. Anyone who has built a bass speaker box knows that resonant frequency depends on port diameter and length, so I imagine that's exactly what's happening here with water instead of air.

If I'm right, it's rather unfortunate because the sound is going to make me burn this pump in pile of thermite sooner or later.

 

[JamesW]

Maybe check the impeller for debris that might be causing it to be unbalanced.

Maybe design a noise cancelling device that can create an mirror image sound that will cancel the vibration?

Probably need a sensor and some sort of contact microphone.

https://www.molex.com/molex/products/family/road_noise_cancellation_sensors

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Maybe use a video motion magnification app to visualize the motion to help analyze the issue.

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[JamesW]

Since the pump is new, just file a warranty claim if you can't resolve the problem.

Maybe the shaft is bent or the rotating parts are not perfectly balanced.

Maybe create a vibration isolation base for the pump.

 

[sbcpool]

I'll try my luck with Pentair, but I can't see it going well.

Me: Good morning. I'd like some assistance with my pump.
Pentair: Sure, what seems to be the problem?
Me: It makes noise when it's running.
Pentair: Yes, sir. Um, mechanical things make noise when they're running.
Me: Yes, but this particular noise is like a tone that resonates throughout my house. It sounds like a single musical note that goes on for 8 hours. It's not just a typical motor noise.
Pentair: We'll send someone out.
Pool guy: Yeah, pumps make noise. It's fine.

 

[sbcpool]

I tried making a recording inside the house, but unfortunately my limited equipment has too much noise to record it well. However, it is very apparent on a spectrum plot even from a recording inside.



You can see that huge spike around 155 Hz (pump's at 1550 RPM currently) that's 20+ dB louder than the ambient sound levels at that frequency. If you notice is actually the loudest sound recorded in the house. It's very apparent to the ears, just not consumer-level recording equipment.

 

[ajw22]

I would send your frequency and RPM analysis in a email to Pentair Support. @MyAZPool has figured out how to navigate the support group and may have some tips or contacts for you.