# humming afci



## A.W.Davis (Oct 17, 2006)

I got a past client calling about an AFCI breaker humming in the sub-panel. 

Has anybody ever heard of this happening? I dont want a diagnostic, advice or how to......I just want to know if this is a common occurance. The breaker is a 20 amp Murray AFCI breaker. All the wiring is new and everything works just fine....it just hums. 

I will probably just replace the breaker, but just wanted to know if anybody else has experienced this?


----------



## MSSI (Mar 25, 2006)

They Hum when they dont know the words...:laughing:


----------



## wiremeup (Mar 5, 2008)

Had this happen just once so far. I believe it was a Murray AFCI as well. Replaced the breaker and it took care of the problem.


----------



## neolitic (Apr 20, 2006)

MSSI said:


> They Hum when they dont know the words...:laughing:


Knew it was coming,
didn't expect it so soon.


----------



## mdshunk (Mar 13, 2005)

I think this instructional video pretty much sums up the main reasons why AFCI's might hum.


----------



## cmec (Nov 3, 2007)

Murray breakers use to be fully magnetic and would hum when the load came close to capacity, have had lots of service calls about noise in the panel over the years, What about the afci ?


----------



## Stickman (Mar 7, 2008)

Ran in to this a few times on a regular breakers brand new and used. Turned out to be home owners installed compact fluorescent bulbs (non dimmible) on dimmers. Breakers was humming like no tomorrow. Took the cf bulb out breaker shut right up.


----------



## Bkessler (Oct 8, 2005)

I think a batch of murray afci breaker was recalled recently.


----------



## MALCO.New.York (Feb 27, 2008)

mdshunk said:


> I think this instructional video pretty much sums up the main reasons why AFCI's might hum.


Great song Shunk!

And YES! CHEAP (N:Vision) Non dimmable compact fluros will hum a nasty tune or even flash. They may even cause a system-wide hum.

Sylvanias do not cause this symptom.


----------



## A.W.Davis (Oct 17, 2006)

mdshunk said:


> I think this instructional video pretty much sums up the main reasons why AFCI's might hum.


:laughing:
Thats great......that's why love this forum. You guys always seem to get a chuckle out of me when I need it the most.


----------



## A.W.Davis (Oct 17, 2006)

cmec said:


> Murray breakers use to be fully magnetic and would hum when the load came close to capacity, have had lots of service calls about noise in the panel over the years, What about the afci ?


 
Its the AFCI breaker that is humming. 

When you touch it the humming goes away completely. The circuit is far from being overloaded.


----------



## MALCO.New.York (Feb 27, 2008)

Remove it, drop it from two feet up flat on its side and plug it back in to the box. Sounds screwy but try it!


----------



## A.W.Davis (Oct 17, 2006)

MALCO.New.York said:


> Remove it, drop it from two feet up flat on its side and plug it back in to the box. Sounds screwy but try it!


 
I will do that and see what happens. I forgot about that trick. :w00t: :whistling :no:

edited to add smilies


----------



## SonoranShocker (Oct 28, 2008)

MALCO.New.York said:


> Remove it, drop it from two feet up flat on its side and plug it back in to the box. Sounds screwy but try it!


Ive done that too....Why does that work?!


----------



## rbsremodeling (Nov 12, 2007)

SonoranShocker said:


> Ive done that too....Why does that work?!



Just like women you need to knock em upside the head every once in awhile for them to work right:whistling


----------



## thom (Nov 3, 2006)

MALCO.New.York said:


> Remove it, drop it from two feet up flat on its side and plug it back in to the box. Sounds screwy but try it!



I usually just soak the inside of the panel down with the garden hose. It's quicker.


----------



## knothole (Feb 24, 2006)

A.W.Davis said:


> Its the AFCI breaker that is humming.
> 
> When you touch it the humming goes away completely. The circuit is far from being overloaded.


I had a Siemens AFCI breaker that did the same way. Changed the breaker and everything was OK.


----------



## HallisseyDesign (Jul 6, 2007)

thom said:


> I usually just soak the inside of the panel down with the garden hose. It's quicker.


Can I watch when you do this?!:clap:


----------



## Electric_Light (Nov 25, 2007)

A.W.Davis said:


> I got a past client calling about an AFCI breaker humming in the sub-panel.
> 
> Has anybody ever heard of this happening? I dont want a diagnostic, advice or how to......I just want to know if this is a common occurance. The breaker is a 20 amp Murray AFCI breaker. All the wiring is new and everything works just fine....it just hums.
> 
> I will probably just replace the breaker, but just wanted to know if anybody else has experienced this?


What is the type of load? Standard front end rectified SMPS has a very high crest factor and the high dI/dt causes stronger and faster change in magnetic field in wires and cause humming. 

The coil is likely to hum more if it's feeding a lot of residential grade fluorescent ballasts, CFLs, dimmer switches and IT equipment as these are all rectified front end loads. 

CF 3 is typical for IT equipment. Note the sudden rise in current. 
http://www.kikusui.co.jp/common/product/image/full/pcz-fig1.png

If you were to go to an outside transformer, one bearing a lot of sinusoidal loads, like motors and heaters clearly sound different from one heavily loaded with office equipment due to highly harmonic loads.


----------



## A.W.Davis (Oct 17, 2006)

knothole said:


> I had a Siemens AFCI breaker that did the same way. Changed the breaker and everything was OK.


 

Thats exactly what we did. 

My electrician was too busy to make it over so I swapped out the breaker myself and everything is fine.


----------

