Buzzing Panels

[TWsystems]

Hi Pros

A little help please ... I'm out of ideas.

I have a remodel project with an existing 600 Amp Service with 5 subpanels (3 of which are new).
The 3 new Panels make a noticeable buzzing noise. The 3 new panels are Murray - the 2 existing are Square D

Nothing is even close to being overloaded and we're not talking about the buzzing from the arc fault breakers.

There is a 3 Phase converter in the system for a couple 3 Phase Laundry Machines and there are several UPS battery backup units throughout on different panels for some sensitive AV and Network Electronics. None of which seem to affect the buzzing noise whether on or off.

There is a backup generator and transfer switch - which does not affect the buzzing noise whether on or off.

If we shut down all the breakers the buzzing goes away - if we start to turn loads back on - any loads - the buzzing will start again as soon as there is about a 5 amp draw on it.

We have tried isolating which circuits might be the culprit - but it makes no difference which loads are on or off - the buzzing will start after a small amount of current starts to pass through any circuit on any of the 3 panels - we have changed guts and breakers - to no avail

I'm totally baffled - we can't seem to figure this one out - after 30 years in the trade I thought I'd seen about everything - but this is bizarre

Has anyone encountered this before and what was the solution?

 

[GoldDigger]

SWAGs:

1. Conductors coming in through separate holes in ferrous metal enclosure.
2. Loose fasteners on the panel bus bars in the new panels.

Is there non-linear load which cases high current pulses with steep edges?

Tapatalk!

 

[TWsystems]

SWAGs:

1. Conductors coming in through separate holes in ferrous metal enclosure.
2. Loose fasteners on the panel bus bars in the new panels.

Is there non-linear load which cases high current pulses with steep edges?

Tapatalk!

No to 1 & 2 above - not sure about non-linear load - possibly some of the UPS units protecting the Electronics racks - but shutting them down has no affect. The obvious would be loose connection or branch circuit near its tripping point - none of which are true

 

[mbrooke]

Any specific breaker or circuit that causes this when energized. Is the noise coming from the main by chance.

 

[TWsystems]

Any specific breaker or circuit that causes this when energized. Is the noise coming from the main by chance.

No particular circuit or combination of circuits either on or off make any difference (except all circuits off). Only shutting off the entire sub panel at the main makes it stop, or shutting off all breakers in a sub panel. Introducing any load (turn on any circuit) makes it start again. Only the new Murray panels make noise - existing Square D do not

 

[GoldDigger]

This is tough.

If I were unfortunate enough to be in this situation, I would consider getting a stethoscope or better one of those surface contact wand type noise locators used by auto mechanics, to try to isolate where it is coming from.
Also, if really desperate and if the panel is protected by an upstream feeder breaker, I would consider jumpering around the main just to rule that out.

 

[MichaelGP3]

I would change out one of the Murray panels with a different brand. If the new one doesn't buzz, I will leave you to draw your own conclusion.

 

[MichaelGP3]

That wasn't mean't as a slap at Murray panels. It's possible that their resonant frequencies in the audible band (due to dimensions and properties of the component materials) are being excited by higher frequency energy nearby. If you are going to swap out a panel, select one that is as different from the Murray as you can find.

 

[ptonsparky]

That wasn't mean't as a slap at Murray panels. It's possible that their resonant frequencies in the audible band (due to dimensions and properties of the component materials) are being excited by higher frequency energy nearby. If you are going to swap out a panel, select one that is as different from the Murray as you can find.

:thumbsup:That is a much better job of saying what you hadn't meant to say.

 

[cowboyjwc]

Are you sure it's the panels and not the conductors? No transformer nearby?

 

[sparkyrick]

I would change out one of the Murray panels with a different brand. If the new one doesn't buzz, I will leave you to draw your own conclusion.

You get what you pay for! :thumbsup:

 

[mbrooke]

If this is a commercial setting or industrial Murray isnt something that should be there for beginners. Yes, I know nothing in the code requires it, but a pinch stab junk panel running under commercial or industrial loads is a bad idea. This is why so many panels are bolt ins in such environments.


My advice: Change to square D NQOD:thumbsup:

 

[TWsystems]

Yes it is the conductors that buzz not the panel

 

[sbfwtx]

sbtytx

sbtytx

Hi Pros

A little help please ... I'm out of ideas.

I have a remodel project with an existing 600 Amp Service with 5 subpanels (3 of which are new).
The 3 new Panels make a noticeable buzzing noise. The 3 new panels are Murray - the 2 existing are Square D

Nothing is even close to being overloaded and we're not talking about the buzzing from the arc fault breakers.

There is a 3 Phase converter in the system for a couple 3 Phase Laundry Machines and there are several UPS battery backup units throughout on different panels for some sensitive AV and Network Electronics. None of which seem to affect the buzzing noise whether on or off.

There is a backup generator and transfer switch - which does not affect the buzzing noise whether on or off.

If we shut down all the breakers the buzzing goes away - if we start to turn loads back on - any loads - the buzzing will start again as soon as there is about a 5 amp draw on it.

We have tried isolating which circuits might be the culprit - but it makes no difference which loads are on or off - the buzzing will start after a small amount of current starts to pass through any circuit on any of the 3 panels - we have changed guts and breakers - to no avail

I'm totally baffled - we can't seem to figure this one out - after 30 years in the trade I thought I'd seen about everything - but this is bizarre

Has anyone encountered this before and what was the solution?

Buzzing of panels is almost always the result of harmonics in the system somewhere. Caused by something ...on any of the panels ...fluor. lights, ups system, and especially VFD drives. Look and see if you have anything like that hooked up on any of the panels ... may have to go breaker by breaker on the existing panels ...

 

[TWsystems]

Thanks to all who helped

Thanks to all who helped

Thank you to those who helped brainstorm... it ended up being the 100+ Lutron Dimmers causing the noise. I thought I had ruled that out early on, but certain combinations of those and other loads were the culprit. To Lutrons credit, they stepped up and replaced everything ... problem solved ... great company. The idea about the stethoscope was genius, by the way. Sometimes it's easy to overlook the obvious.

 

[Sierrasparky]

Thank you to those who helped brainstorm... it ended up being the 100+ Lutron Dimmers causing the noise. I thought I had ruled that out early on, but certain combinations of those and other loads were the culprit. To Lutrons credit, they stepped up and replaced everything ... problem solved ... great company. The idea about the stethoscope was genius, by the way. Sometimes it's easy to overlook the obvious.

Very interesting.
What dimmers were they?
What did Lutron replace them with?

 

[Ponchik]

How exactly did you guys figure out it was the 100+ dimmers?

You also mentioned that ANY LOAD would make the buzzing start, so what does that have to do with the dimmers? Or you meant any lighting load???

Why would three panels BUZZ and not the other two? Assuming these are lighting panels ONLY, then again ANY LOAD & ANY DIMMER that has 5 amps makes it buzz??

 

[Petewales]

Buzzing Panels.

Buzzing Panels.

Bad information reporting.

You have to be careful reporting measurements in the field of problems when asking for trouble-shooting help. Inaccurate detail reporting can send everyone down the garden path.

Remember, "GAGO" = Garbage In - Garbage Out.