Hello, I am new to breaktime, though I’ve been subscribing to Fine Homebuilding for the last three years.
I have an electrical question. What are the causes of humming noise coming from an older fuse style electrical panel? I just installed 12 recessed lights with 75 watt bulbs and ran them with 12-2 and 12-3 wire to an open 20 amp fuse. This box is older and therefore does not have a designated ground bar, so I tied both the neutral and the ground to the same bar.
Any suggestions?
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Replies
pull the Mains and check every connection for tightness, including the fuses.feel each fuse for warmth aloose connection will cause things to get warmer than a normal load
if it still hums then a connection is going bad internally.
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when you say "going bad internally" does that mean somewhere in the wiring or somewhere in the panel?
I meant the panel guts, it could be the screw that the fuseholder is attached with, or poor field connection
but the problem is likely a loose fuse which is highly probable, some folks think they're good when the lights come on after screwing one in sight, smell, touch ? is it barely audible or can you hear it with the panel covers in placemight be a circuit that has a good load on it too !.
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Is that panel the main panel? Are those loads the only neutral and ground you have tied together? Are there any other grounding conductors (ground wires) coming into the panel?
You have bonded your neutral and ground wires together. The problem is, being that you apparently don't have any more loads grounded, you have created an unbalanced load. Now the unbalanced current is traveling on your neutral and ground wire. You need to get a ground wire to each circuit, and bond both the ground bar to the panel as well as the neutral bar to the ground bar.
This is an older fuse panel, in fact, I have suggested that my friend should go ahead and upgrade the box, but he does not want to. There are no ground buss bars only three screw-in type neutral bars. All the wiring coming into this subpanel are cloth braided with no ground wires. The main panel is the same.
To answer your first two questions, my new wiring is the only ground to come into the panel. None of the older existing wiring has a ground. There are all two wire braided cloth. From what I've read though, when tying into an older system like this, your only option is to tie your ground unto the neutral bar.
OOPS.
Never underestimate the value of a sharp pencil or good light.
Edited 5/11/2009 7:10 pm ET by JTC1
You never do it on the sub-panel. Although your system is not properly bonded and grounded, you have attempted to bond the grounding and grounded conductors in the sub panel. That is your problem. If you have a ground fault, where does your fault current go, the feeder neutral?
I would designate one of your neutral bars a ground bar, and use a bonding screw to bond it to the panel. Keep your neutrals and grounds seperate in that sub-panel.
Edited 5/11/2009 7:20 pm ET by excaliber32
1)>>You have bonded your neutral and ground wires together.<<
Yes he has.
>> You need to get a ground wire to each circuit,...<<
Most probably, totally impractical short of rewiring the entire house.
2)>> and bond both the ground bar to the panel as well as the neutral bar to the ground bar.<<
Please explain the difference between this action and the action taken in #1 above, i.e., bare ground and neutral from the new circuits are still bonded to each other just by a different path.
Confused.....
Edit: Still confused by statements, but if this is a sub-panel, the box should be grounded and the neutrals "float", i.e., ground bar bonded to box enclosure, neutrals not bonded to enclosure.
Jim
Never underestimate the value of a sharp pencil or good light.
Edited 5/11/2009 7:28 pm ET by JTC1
2)>> and bond both the ground bar to the panel as well as the neutral bar to the ground bar.<<
In the first means of disconnect........the main panel. You never bond a neutral and ground in a sub panel.
This post got me to do something I never do on my off-time......crack open the NEC.
Basically, if your main panel is grounded and bonded, you need to carry the grounds for your lighting circuit all the way back to the main panel and ground them there. This will keep the neutrals at the sub panel and the grounds at the main. It doesn't seem like it makes a difference, but it does. The main has the Grounding electrode system (or it should) and there by a more effective ground path if there ever is a dead short. If you have a ground rod at the main panel, you are probably good to go.
As a last resort, you can supply the lighting circuit on the load side of a GFCI plug. The code is very vague on this and from what I gather, they say it is OK as a last resort. Make sure you use the "No equipment ground" sticker that comes with the GFCI.
Fill out your profile, please.
So you use the NEC at work, do you?
You're giving advice that suggests to me that you are uninformed. For instance, when you say,
"you need to carry the grounds for your lighting circuit all the way back to the main panel and ground them there"
it's an indication to me that you don't work in the trade and therefore don't know a few important things:
1. what you've recommened is not compliant with the NEC. The grounding conductor for a branch circuit or feeded must be in the run with (i.e., in cable) with the current-carrying conductors. See Sections 250.118 and 250.134(B) of the 2008 Code. So, how can the OP run the EGCs back to the main panel, short of running new branch circuit wiring?
2. if that's your actual intent, then why not run a new feeder to a new subpanel and bring the installation up to Code, with a floating neutral bus in the sub?
From a practical standpoint, the key to a safe installation in this situation is to make sure the feeder neutral is intact and the terminations at either end are good. I've seen many many subpanels installed before a floating neutral bus was required and some installed subsequent to the requirement.
More later--
Cliff
Cliff, Minor hijack of the thread, but I have to toss this out:Several years ago you wrote a FHB article on wiring a subpanel. A few years ago I had an in-ground pool installed. Although I wired my house from street-to-outlet, I didn't want to touch the pool wiring, so I hired an electrician.Long story short, even though the subpanel installation was in the contract, he claimed it wasn't and tried gouging me with a change order to install the subpanel. Gouge means a quote of "$1000-$1500, maybe a little higher". So I ran out to the supply house the next town over, bought a 100A box and about 60' of cable, and with the magazine opened to your article I had the thing installed and wired up well before he was ready to tie the pool circuits into the subpanel. I owe you one! Thanks!
>> 2)>> and bond both the ground bar to the panel as well as the neutral bar to the ground bar.<<
In the first means of disconnect........the main panel. You never bond a neutral and ground in a sub panel.<<
Agreed, see my edit in ####.10 @ 7:28pm
JimNever underestimate the value of a sharp pencil or good light.
BTW....
welcome to BT....
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
Uhhh - everbody's missing the real reason it's humming.
It doesn't know the words!
Forrest - just trying to help the new guy
ps - I have some new breakers that hum a bit under load - I thought they just did that
I was reading through these replies hoping that no one had said it yet so that I could.At least I can give you this:Ba-dum-bum!
> It doesn't know the words!That was my first take. But then I thought, "Nah, it's probably the doorbell transformer attached to the side of the panel."
The modern conservative is engaged in one of man's oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness. -John Kenneth Galbraith
To all who replied: I am very grateful for this information. Everyone of you has conveyed not only thoughtful information and expertise wrought from experience but also a wonderful breadth of personality.
I will read more of my home electrical books and give word tomorrow evening how everything went.
Are the lights on a dimmer? And, if so, does the panel humm when they are on and dim?
I have a laptop with a flaky power supply that buzzes. It also makes the breaker panel buzz too, took me a while to figure out the noise source... Tried swapping breakers/ positions, no difference.
Where is the doorbell transformer?????
The modern conservative is engaged in one of man's oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness. -John Kenneth Galbraith
have a laptop with a flaky power supply that buzzes. It also makes the breaker panel buzz too, took me a while to figure out the noise source... Tried swapping breakers/ positions, no difference.
With electronics there is a possiblity of neutral harmonic loading. Not a likely cause with only a single laptop computer plugged in, could become a factor with multiple pc's connected to a single circuite. The buzz in the panel is more likely a loose neutral as CAP and maddog pointed out. Your flacky power sup[ply is just contributing to an existing problem IMO.