Strange Humming in Panel

Little Bill

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
Had a guy call me to check out a hum and buzzing noise in the panel. The hum seemed to not be anything I would worry about as I've heard that before. However, when breaker for the air handler for the AC unit was turned off and back on, you could hear the buzzing/arcing sound.
I checked all the lugs and terminals for breakers and all were tight. There is an outside disconnect so I checked the lugs there and all was good.
Also had the POCO come and check their connections and all was good there.

The noise seemed to be coming from the main breaker. The panel is a SqD Homeline 200A main breaker. So I was going to contact them.

They also wanted me to change out some dimmers for regular switches as their LED lights would sometimes flicker badly when on the dimmer. The dimmers had been changed by me just a few weeks ago. But the guy said the lights started to flicker again. I told him the LED lights, which are the wafer recessed type lights, were probably not working right with the dimmers. The dimmers were 3-way and I didn't have any 3-way regular switches with me.
The guy said he would pick some up and change them out.

Here's the odd part.
He called me a while ago and said he got them changed. He says all the flickering, humming and buzzing have stopped. I knew the flickering would stop, but what would changing dimmers out for regular switches have to do with the arcing/buzzing sound coming from the panel?
I told him to keep an eye on it and listen for the arcing sound. I am not convinced that it has stopped!
 
Does the power company use "TWACS" for reading their meters? See the older thread below:

TWACS flickering?

How many have ever heard of TWACS causing flickering lights? Anyone ever ran into a flickering lights problem that can’t be explained any other way other than signal modulation due to the POCO communication system?
forums.mikeholt.com
 
synchro said:
Does the power company use "TWACS" for reading their meters? See the older thread below:

TWACS flickering?

How many have ever heard of TWACS causing flickering lights? Anyone ever ran into a flickering lights problem that can’t be explained any other way other than signal modulation due to the POCO communication system?
forums.mikeholt.com
Click to expand...
If you mean smart meter, then yes.
 
Not just a smart meter, but a smart meter that uses a particular type of power line signalling.

Many smart meters use some sort of radio module for communication.
 
winnie said:
Not just a smart meter, but a smart meter that uses a particular type of power line signalling.

Many smart meters use some sort of radio module for communication.
Click to expand...
I know they read the meters remotely and know if the meter has been pulled. Also, they can shut them off remotely, but that is for those who buy a certain amount of power on a pay as you go method. Kind of like prepaid cell phones, or prepaid debit cards. Don't know if they use the same meters for those or not.
 
Little Bill said:
Had a guy call me to check out a hum and buzzing noise in the panel. The hum seemed to not be anything I would worry about as I've heard that before. However, when breaker for the air handler for the AC unit was turned off and back on, you could hear the buzzing/arcing sound.
I checked all the lugs and terminals for breakers and all were tight. There is an outside disconnect so I checked the lugs there and all was good.
Also had the POCO come and check their connections and all was good there.

The noise seemed to be coming from the main breaker. The panel is a SqD Homeline 200A main breaker. So I was going to contact them.

They also wanted me to change out some dimmers for regular switches as their LED lights would sometimes flicker badly when on the dimmer. The dimmers had been changed by me just a few weeks ago. But the guy said the lights started to flicker again. I told him the LED lights, which are the wafer recessed type lights, were probably not working right with the dimmers. The dimmers were 3-way and I didn't have any 3-way regular switches with me.
The guy said he would pick some up and change them out.

Here's the odd part.
He called me a while ago and said he got them changed. He says all the flickering, humming and buzzing have stopped. I knew the flickering would stop, but what would changing dimmers out for regular switches have to do with the arcing/buzzing sound coming from the panel?
I told him to keep an eye on it and listen for the arcing sound. I am not convinced that it has stopped!
Click to expand...
I have never hear/seen flickering lights and humming from the panel that stopped when changing out switches. What worries me is I have had panels that hum and its not any loose connection but a worn buss bar. In a lot of residential the panels are in the basement. If the basement is on the moist side the buss bars can corrode even thou the rest of the panel is fine. That is my experience and I am not a fan of noisy panels. I am concerned about fire risk.
 
The electrical install is only a few months old, so no corrosion on anything. This is a Church and the AC is the largest load. All heating is gas. I told the guy I expected the flickering of the lights to stop with removing the dimmers, but no way, that I know of, would that stop the buzzing/arcing sound when the AC unit came on. I expect to hear back after the building is used this weekend.
 
Dimmers introduce harmonics to the current flow. Perhaps these harmonics just happened to resonate with some mechanical structure in the breaker.

If you have an acoustic resonance it doesn't take much coupling from the circuit to generate sound.
 
FLIR camera of some kind might help in this situation (well, at least while the buzzing is going on)... but I'll also support the suggestion of it being the dimmer's fault. Down in our cat's lair (aka the basement) we have a light-controlled night light. Any time someone steps in front of it to scoop Miss Kitty's box, you can hear it buzz, and see the LED flicker, as the circuit attempts to modulate some percentage of full brightness.
 
Deltaforce said:
Aluminium or copper bus bars
Click to expand...
OP said Homeline, those are tin plated aluminum. QO would be tin plated copper unless it is one those 6-8 space small panels with horizontal bus, those are typically tin plated aluminum but they do have copper as an option but you won't really find the copper version in a big box store. Some old QO from 70's into 80's did have aluminum bus but everything since they switched to the style main breakers they now have is tin plated copper.
 
I have noticed more such noise coming from equipment like breakers when there is non linear loads being supplied as well as a sometimes even with higher level linear loads, even on very new breakers like OP says he has. I think it usually is some internal component that is capable of minor movement when subject to the 60 Hertz magnetic field so probably in most cases minor defect in molding of the casing that would otherwise more securely hold said component in place? Totally speculation with no proof on my part, but you have to start somewhere if you want to chase it down.
 
kwired said:
I have noticed more such noise coming from equipment like breakers when there is non linear loads being supplied as well as a sometimes even with higher level linear loads, even on very new breakers like OP says he has. I think it usually is some internal component that is capable of minor movement when subject to the 60 Hertz magnetic field so probably in most cases minor defect in molding of the casing that would otherwise more securely hold said component in place? Totally speculation with no proof on my part, but you have to start somewhere if you want to chase it down.
Click to expand...
Minor noise ,no issue ,result of magnetostriction
Larger noise, any incipient fault maybe
Thorough inspection of op panel need
 
winnie said:
Thermo-magnetic circuit breakers definitely have magnetic elements that might vibrate in response to current flow.
Click to expand...
Maybe, but not due to magnetostriction.
The magnetic portion is usually an electromagnet core made of a solid metallic piece with no laminations, in the shape of a U, while the moveable piece is often part of the bimetal used for the thermal portion.
 
1758493603526.png
I love this picture!

It brings back tons of memories for me, of heading to the hardware store to buy those EverReady batteries you are experimenting with.

If I'm not mistaken, you are showing a 1.5 volt dry cell, about 6" tall. Pretty heavy and packed a punch...

1758493013033.png

One thing I know I used to do with them was create electromagnets. My uncle was a ham, and we had tons of shellac / varnished magnet wire to wind choke coils in handmade radios. Wind a bunch around a big nail and hook it up to one (or more in series) of these batteries and it created a great magnet. At least for as long as you could hold it ;)

Sorry to derail this thread.
 
You must log in or register to reply here.
Top