Bad connection somewhere.

 

As in ? I had switch off at unit and when it sparked like it did. (Quite big for 6v I thought ). I walked to breaker box and shut it off. So somewhere there is a loose common ? This is at a fed-ex ground distribution center so it could take days checking connections on everything. Is it anything to worry about ? If someone could get hurt I’d like to bring it to attention

 

Wire nut loose.
Bad connection in the panel.

Federal No Blow!

 

Well, if the breaker is off and you got some kind of power and spark, you have an issue. I’d pawn it off to an electrician.

 

Are the ground and neutral separated at the breaker panel???

If not... there is your answer...

Beyond that... would be DIY help... which the forum does not allow.

 

It could also be that that same neutral leg is being used on another hot circuit.
Best to get an electrician involved. These things aren't supposed to happen but they certainly do.
I can't count how many times working in old buildings I had to shut off more than one circuit to finally make all wires going to the equipment I was working on finally be dead....
A couple of months ago one of our new hires asked me why I always ground all the wires to the box before I performed any work......
He found out the hard way lol

 

Building is only 10 yrs old so I would hope the ground and neutral are separate. Guess I can check the box that houses that breaker and check the neutral connections. If nothing is found I’ll let building manager know to get sparky involved. We don’t even change bad residential breakers ,liability issues as we aren’t electricians. Used too but found a cooked buss bar once and figured from then on just refer it out.

 

Ahh the good old cooked buss bar...
See lots of those where the legs aren't balanced properly.

 

Your right “Shouldn't”. Neutrals get twisted together all the time!

 

neutrals yes, hots no, not for dedicated equipment, like exhaust fans

 

I’ve seen crazier $hot!

 

Unbalanced single phase loading can cause it.

 

Was the volt there continuously? Maybe a stored jolt from a capacitor?

 

I have seen a neutral spark before. In my case there was another load on the circuit. Power was running from hot through the load and out to the neutral which I had interrupted by disconnecting it. Normally that neutral would have fed back to the panel. The voltage had dropped across the load so it was minimal, but still enough to give a little spark and tingle.

You could also be seeing ghost voltage with the meter. You need a low z mode or a low impedence volt tester to see if the voltage you are reading is actually significant. Of course if it can generate a spark it probably is significant. Unless that spark was related to a cap discharging somewhere in that circuit.

Also you can have a situation where the wind is spinning a fan motor and generating voltage on an otherwise dead circuit. This probably isn't what is happening in your case but it does happen and can make your multimeter read weird.

On time I was working at an apartment complex and I jumped out my vacuum pump on one hot leg and ground and the pump ran like it was on steroids lol...turns out the apt had no ground rod so the ground was open and it just so happened that inside one of the light switch boxes there was a short to ground making the entire ground circuit 120V so I had 240V at my pump... electricity can really do some weird shit, but it never lies lol.

Sent from my SM-G960U using Tapatalk

 

Probably never had an Electric Panel Inspection, Maintenance, or a Turndown. Seen many Fires from this. Write it in all Caps, on the Ticket. Have your official POC Initial it and Sign the Ticket. Don’t let them sign with a Sharpie or Felt Tip, Ball Point pen only. Got to CYA on this.

 

I believe the NEC requires neutral and grounds be bonded in the main panel but separated in sub-panels. I won't get into why, that's Google's job. There is a YouTube on it I think.
A lot of circuits will share a neutral but have separate breakers. You could try shutting off different breakers to see if there is a neutral sharing situation.. Not code because it can cause the neutral to carry a load larger than the wire should but it happens all the time.
That would be my guess.

 

Only Circumstance where a Shared Neutral was allowed was on a Lighting Circuit, and nothing but Lights could be on it. Not sure if Codes Allow this anymore. Wired many of them up in Iowa, back in the 70’s.

 

and how many “Codes” are not followed in our trade?

 

I believe it's three there abouts.

If sparky has part of the devices meeting at a home run its wrong but common to share a neutral rather than running another wire. It would cost a bit more but could cause a shock to someone that believed the breaker was off. It's a code violation.
We need to remember Code is the legal minimum.

 

Sounds like the neutral isn't grounded. Get an Electrician to look into it.

 

My old boss shared the neutral a couple of times , and he would use a double pole 20 so both lines would always be off

It was strange testing the "neutral" and seeing 4 or 5 amps when the equipment was running

 

Yes if the breakers are interlocked it's to code.

 

If this was a " hot " 120 volt circuit you will get an occasional spark on the neutral based on how you disconnect. Allways start with " hot " , then neutral , then Ground. I've seen guys unhook gnd & neutral 1st and it's sparks cause the hot lead is still connected so it's searching for gnd If it's still hot. Hook up gnd, neutral , then hot last

 

I turned it over to the facility manager to get an electrician involved. I had to move the light switch that controlled the fan. There was power on the neutral at the wire but connection there. There are probably 5 breaker boxes there. Ones only single pole. All double poles in separate box and 3 phase in different boxes.

 

why have a light switch control the fan? should have a switch for the light and a switch for the fan?