Buzzing breakers

[Sparkdizzle]

Hello all!
Big fan of the forum, but first post.

I received a service call last week at a Starbucks from an HVAC tech concerning a breaker that was apparently “sparking really bad” when he was attempting to verify voltage in the panel for an Ice machine. I figured it was simply a loose connection. When I got there I found out the store is essentially BRAND NEW, having just been renovated and only re-opened for five days.

Now, I locate the panel of the breaker in question and hear a cacophony of erratic buzzing from this panel when I opened it. It sounded load based, coming and going quite randomly, but seemed to be coming mostly from the 2p breakers, but it was very hard to tell. I tried putting my(gloved)hand on whichever breakers I thought the buzzing was coming from, thinking maybe loose connection, but nothing. It was unnerving.

Based on the horrendous noise coming from this panel, and the fact that this store had JUST been renovated and is under warranty, I didn't even bother to troubleshoot the breaker I was called there for(which I think was non related) and promptly showed myself out. But i'd never heard such noise before.

3Ph Eaton panel w/GHB style bolt ons. I TOOK VIDEO OF IT,

 

[Sparkdizzle]

whoops.....as I was saying, this isn't my service call, but I'd Like to know what you guys think.

 

[Sparkdizzle]

Another video maybe 5 minutes later. Its still there, just not as prevalent. In both videos you might not be able to hear, but the buzzes are coming from various parts and seem to "jump around", making it hard to pinpoint a specific location.

 

[ptonsparky]

Backup. Show the whole panel. 1 or 3 phase? MWBCs? Parallel feeder? How were they arranged? How many VFDs? Current at the time on each leg and neutral?

 

[Dennis Alwon]

I have occasionally heard buzzing when a heavy load on startup occurred but not continuously. Not sure what to advise other than try changing out the breaker. You will need to isolate which breaker is the cause of the buzzing.

 

[Knuckle Dragger]

C

First thing I would do is check loads, voltages, cycles on all circuits, make sure they corrispond with what they are supposed to feed, if all good, identify which breaker or breakers are making the noise. Turn off CB and disconnect leads and see if noise continues with with the CB on and no load. Inspect the connections on the appliance. If good find a replacement breaker and see if the noise continues.
I'm not qualified to give much more advice from here without actually being there.. sorry.

 

[Sparkdizzle]

I have occasionally heard buzzing when a heavy load on startup occurred but not continuously. Not sure what to advise other than try changing out the breaker. You will need to isolate which breaker is the cause of the buzzing.

The problem is that it’s multiple breakers. Listen to the 1st video if you haven’t already, it sounds like the whole panel of breakers were intermittently buzzing.

 

[Sparkdizzle]

Backup. Show the whole panel. 1 or 3 phase? MWBCs? Parallel feeder? How were they arranged? How many VFDs? Current at the time on each leg and neutral?

These are all good questions, most of which I didn’t take readings on. Panel is 3phase, no VFDs onsite. Yes there were MWBCs, Voltage line to line and line to N was fine on the feeders(I didn’t check branch V), No parallel feeders. I did take a few current readings real quick on a few 2p 20 breakers, because it sounds like they were going to explode, but nothing was overloaded.

 

[480sparky]

I'd start turning breakers off one at a time to narrow it down to a specific breaker. I'd then check the connections to the bus bars.

 

[ptonsparky]

The problem is that it’s multiple breakers. Listen to the 1st video if you haven’t already, it sounds like the whole panel of breakers were intermittently buzzing.

The high frequency was about 720 when I looked at it early this morning, FWIW, but that was this morning before adequate coffee.

 

[MrJLH]

I sure hope you are wearing some PPE being that close!

 

[cowboyjwc]

Is there a lighting contactor in that panel?

 

[FionaZuppa]

They are just singing, leave them alone.

btw, if you can hear it like that then 100% you can feel it. touch each one, which one(s) are vibrating?

 

[ptonsparky]

The high frequency was about 720 when I looked at it early this morning, FWIW, but that was this morning before adequate coffee.

...not right at all.

 

[kwired]

Backup. Show the whole panel. 1 or 3 phase? MWBCs? Parallel feeder? How were they arranged? How many VFDs? Current at the time on each leg and neutral?

He said it was at a Starbucks, not really sure what is typical for them for equipment. VFD's (larger ones anyway) would most likely be on HVAC, but I could see cooking or other heating equipment possibly being solid state controlled and have some similar non linear characteristics and non linear lighting loads.

What I hear for noise in video clip sure sounds like noise you hear from VFD/VFD driven motors though.

 

[Dennis Alwon]

It almost sounds like there is a fan in the panel.... I also would start a slow shutdown and see what happens-- they can't all be making that noise

 

[FionaZuppa]

It almost sounds like there is a fan in the panel.... I also would start a slow shutdown and see what happens-- they can't all be making that noise

toss in some Starbucks metal straws, see when the buzzing stops hmy:
maybe some gremlins have a nest behind the panel in the wall?
but, not sure what the point of post is if the OP is not engaged in the project. some buzzing OCPD's........................ and?

I didn't even bother to troubleshoot the breaker I was called there for(which I think was non related) and promptly showed myself out. But i'd never heard such noise before.

 

[ptonsparky]

He said it was at a Starbucks, not really sure what is typical for them for equipment. VFD's (larger ones anyway) would most likely be on HVAC, but I could see cooking or other heating equipment possibly being solid state controlled and have some similar non linear characteristics and non linear lighting loads.

What I hear for noise in video clip sure sounds like noise you hear from VFD/VFD driven motors though.

Peak was 4593 HZ according to my app.

 

[Sparkdizzle]

I sure hope you are wearing some PPE being that close!

You bet your bottom dollar I was.


Sent from my iPad using Tapatalk

 

[Sparkdizzle]

Is there a lighting contactor in that panel?

No, they have a separate cabinet for their LCP.