Circuit breaker box hisses

[Texas Kingsnake]

Hi there. Back again with a new problem.

My wife was doing the laundry and I was working near the circuit breaker panel. When she turned the machine on I heard a loud buzz from inside the box. Less than a second long. I had her turn the machine off, took off the panel cover and watched as she turned the machine back on. I saw arcing at the left-handed side of the panel at the point where the heavy black cable from the street enters the box. I had her turn the machine on and off and it happened again. Then I pushed the black wire right where it enters the clamp and it hasn't happened again, despite having all the same lights and appliances on.

I am thinking the clamp has loosened over time. I am going to get a well-insulated screwdriver, put on very heavy rubber gloves and am going to try to tighten the clamp which may have not been tightened in 40 years.

Does the power *really* need to be killed at the meterhead? I've changed out breakers without killing main power (so much frikkin' stuff needs to be reset after a power shutdown that I hate doing it)?

Anything else I should consider? Is the washine machine motor about to fail and is drawing a huge amount of current at startup? How do you even measure the inrush(?) current in such a case. Would pressing on the wire near the clamp cure it temporarily or is some other process in play?

What would account for it happening twice and then not happening again. The only real intervening act was to push on the wire jacket at the point it enters the clamp on the circuit panel. Very strange.

TKS

[philo]

Yes, the power has to be OFF

...however... DO NOT FOOL with it . call a licensed electrician ASAP

Just tightening the connection is not going to be a fix as since there was arcing, some burned wires and connectors will need to be replaced

[dpb]

Sounds quite plausible and yes, simply pushing on the wire could easily have broken the point at which the arcing was happening.

It's certainly possible to just tighten the connection w/o cutting power; I'd be much more comfortable going on if I had seen the actual condition of the wire and connection before I just went on, however. If it was actually arcing to that point, good chance there's some built up corrosion and/or arc damage that should be taken care of.

Particularly if the external feed is Al instead of Cu, I'd not even think of not doing the above, cleaning it all up well and replacing the antioxidant.

[trader_4]

Not unusual for a loose connection to behave differently after you push it or fiddle with it. It may just be temporarily making better contact now. You can tighten it live, as long as you're 100% sure you know what you're doing.

[philo]

If he was 100% sure of what he was doing he would not tighten it live.

also see my other replies

[Terry Coombs]

Really ? Without seeing the situation you are going to tell this guy stuff needs to be replaced ? I go along with have a licensed electrician check it , since the OP doesn't seem to understand how serious this *COULD* be , but it could also be as simple as tightening the screw and walking away .

[philo]

I worked on high power circuitry for 38 years and cleaning a bad connection is not the answer.

Believe me I've tried. Once a connection has been burned and tarnished no amount of cleaning can ever again provide a satisfactory connection. All connectors and wires must be replaced...or if the wire/cable is long enough...cut back to good , fresh copper.

For low power circuitry, cleaning is probably OK though.

[philo]

Yes, He said it arced. That means there is 100% chance burning of some type has taken place. I go along with have a licensed electrician check it

That's how houses burn down...

I think all here agree that a qualified electrician should handle this.

>

[trader_4]

Yeah, I agree with those of you that pointed out that if it's been arcing, then it should be checked to see if it's damaged. I wasn't thinking about what arcing that's been going on could have done.

[philo]

For those who may have missed my posts over the past year or so, my background is industrial batteries and I have repaired literally thousands of chargers whose output is anywhere from 80 to 350 amps.

When I was still new on the job , if there was a burned or tarnished connection, I'd typically wire brush it down then sand it until everything was smooth and shiny.

It did not take me more than a year to realize that was only a temporary fix as the connection would always go bad again.

Once copper is heated it actually goes through a chemical change and becomes copper oxide. If the burned portion is cleaned, the copper still has a tarnished look to it.

If you cut a new copper wire and compare it to a cut, tarnished wire you will see the difference.

That's why I said all must be replaced.

If some hardware was replaced that ended up actually being OK, no harm done.

I think all see the corollary.

[dpb]

On 10/16/2015 5:21 PM, philo wrote: ...

I don't know your scope of "high power circuitry" but I'm guessing it's far more than a house feed. I've had very good success over the years in doing so as long as the connector/wire haven't been severely damaged.

The key is first gotta look at what the situation really is, though, not just assume tightening alone will be enough.

[philo]

I worked with circuits 80 amps and above...which would come into the range of a house power feed.

I do believe your statement however and assume it was just a very small arc on a relatively low current circuit.

BTW: I found the picture of my socket wrench.

It was the day I decided that it would be OK to work on a live circuit as long as I had my wrench all taped up.

I was 100% sure of what I was doing until it slipped and the insulation was cut

[Seymore4Head]

BTW it is free for the power company to come out and pull the meter. No reason not to. No reason to call an electrician either.

When I tightened my mains, the power company guy was leaning on the wall watching me and even loaned me his 1/2 inch Allen wrench for the neutral connection.

[RealPerson]

It probably did loosen over time or was never tightened well, and just shifted a small bit. What you propose makes sense. Just be safe. If the floor is concrete, stand on a piece of plywood too. Otherwise call an electrician. Do this soon or you could end up with a fire or at least damaged wires or the box. A shot of PB Blaster on that screw head wont hurt to make it move easier.

[dpb]

What voltage(s)? I've worked on/used HV instrumentation where it's definitely true that any imperfection is the death of the connectors, and on high amperage busses (kAmp power-plant kinda' things) where it's also true, but really never had any difficulties with the 100A 240V or less unless it was truly awful.

The farmstead wiring here dates to as early as the first REA days in places (1948) so I've quite a lot of experience over the house, barn, grain elevator, hog farrowing facility plus a half-dozen or so other outbuildings. There are loads from fractional to 15 hp scatter all over so have a pretty wide range of power/current draws.

"The road to hell..." We're all comfortable until something unexpected goes wrong.

[Ralph Mowery]

I agree. I worked with lots of industrial electrical equipment, lots of 480 volt 3 phase from a few amps to around 500 amps.

There were hundreds if not thousands of breakers and switch gear that was inspected with an IR camera every year or two. If a connection shows evidence of overheating, sometimes cleaning and tightning would solve the problem, but often it would show back up on the next scan , usually about a year later.

Cutting back and changing seemed to be the long term solution.

[Unquestionably Confused]

[snip]

If it's copper, I'll check to you as the authority. If it's AL as is the bulk of underground feeds over the past 45 years or so, is it the same deal with arcing.

The only thing I'm going with is DON'T mess with that service drop while it's live. Period!

If it's AL on the drop, you're definitely going to have to clean it up, recoat with the anti-oxidant paste and really crank it down. IIRC correctly those lugs are fitted with an Allen socket. Just way too much that can go wrong screwing around there even if you didn't have to pull the wire out to clean and re-coat.

He can, in the end, do whatever he wants. His widow can report back where he went wrong. ;)

[Unquestionably Confused]

[snip[

LOL! Was it a Craftsman? What'd they say about their lifetime guarantee?

[clare]

Your main power lug is loose - and quite possibly burned. You may or may not be able to tighten it. Trying to tighten it with the circuit live COULD get nasty if the lug is damaged and comes off the buss when you try to tighten it.

I have had a burned lug on a service panel and was lucky enough to be able to find a used replacement lug - and even luckier to be able to replace it and the cable connecting to it which had also been damaged by the arcing.

And yes, just pushing on it would possibly temporarily correct it.

[RealPerson]

I guess 12VDC would qualify as low power, but some still draws a lot of amps. I've had to clean corroded wires many times on vehicles, and reconnect them. Just recently, there was a melted plug under my dash, powering the blower motor (for heater). I removed the plug and found the wires overheated, so I cut off a half inch on each end. That was all I could spare. Then I soldered them and taped. That plug is a common problem on my vehicle, and there have been some fires because of it. The plug was under rated for the current draw.There was a recall for it, but that expired years ago. The vehicle is a 1995 model. According to what a mechanic told me, the recall had them remove the plug and crimp the wires together. I think soldering is a far better splice than crimp connectors.