Ground wire arcing in breaker box

Question

While inspecting the breaker box in my shop area I noticed inside the breaker box was a ground wire that was loose inside the box.

The other circuits had grounds connected to the neutral bar.

Upon further inspection I noticed the loose ground wire had touched the inside edge of the breaker box and at some point had arced against the breaker box itself.

Upon even further inspection it appears the ground wire itself was presently hot.. although nothing was plugged into the single outlet for this circuit (30 amp 125v travel trailer hookup)

I turned off the circuit breaker and traced the circuit to an outdoor outlet that looks very old.

My question:

was the problem likely with the outlet? (many dead bugs and webs inside the outlet)

Can I just order a new outlet and hook it up ? Should I go ahead and reconnect the ground to the neutral bar?

The shop was built long ago by the person I bought the house from.. the breaker box doesn't appear to have a grounding bar at all which makes sense because there is no grounding electrode outside. The shop has independent electricity with it's own drop not connected to the house main box.

I'm a certified home inspector (took a class for my own benefit not for a profession) but I was trained to simply notice when it isn't correct and tell them to get an electrician to inspect it further.

What do you think about a new outlet and hooking the ground back up to the box?

Answer 1

The starting point here is that your building does not have a Grounding Electrode System.

1. Every outbuilding is required to have one.

2. Your wiring has been done in the style of a separate service, even though it's more of a split service with the house. Not only does a service need a GES, it also needs a Neutral-Ground equipotential bond to peg neutral to earth potential. Yours has none of that.

So you need to drive 2 ground rods 8' long, at least 6' apart and preferably on opposite corners of the building. Then run some, let's say #6 bare copper wire from the ground rods to the panel. Must be continuous, no splicing. At that point I would obtain an accessory ground bar for your panel and land them on that accessory bar, then also add a #6 strap from the accessory ground bar to the neutral bar. This assures you have a neutral-ground equipotential bond. There's no harm in having more than one as long as it's in the main panel, however, having only one allows a neat diagnostic trick.

That will bring your "main panel" up to Code.

I would also move all my grounds to the new ground bar (or to a ground bar tied to chassis). This is not a Code requirement for a main panel (it is for a subpanel), but it allows a neat diagnostic trick. Now that all grounds are on the ground bar, look for any neutral-ground screws (green) or straps that are on the neutral bar. You want to isolate neutral from chassis/ground (except for that #6 strap you installed). Now, you can put a clamp ammeter around that strap. It better say 0 amps. If it does not, you have a ground fault. Chase that by shutting off breakers until it goes away, then divide the faulty circuit until you find the particular problem.

Answer 2

The shop has it's own power and own meter? That's really neat- probably cost him a penny too!

The neutrals and grounds don't have to be separated then. Still surprised there's not two bars on either side though.

OK on to your question: When you said the wire was 'hot' I'm assuming you mean 120V on it. That's troubling, obviously. Worse is nothing blew. So the first thing I would do, assuming you're comfortable doing so, is disconnecting the power that feeds that wire (breaker to outlet), confirming the ground is 'dead' now, then powering off the whole box (to be safe). I'd then go remove that external outlet and inspect both the wires and pigtails in the box for corrosion, arcing, etc. Arcing and/or fire discoloration on the wire tips may present as discolored copper and micro-balls of copper- sometimes splattered on the surrounding components.

Bring the outlet back inside (seal up the external box) and inspect it for burn marks as well. Please consider testing the continuity between ground, neutral, and hot to see if there are any shorts.

Now comes the tricky part- re-energizing the circuit. If you've left the ground wire floating still you'll need to turn the breakers back and and measure from ground to.. ground bar, I guess, and see what voltage its floating at. It should be zero or possibly some small amount of parasitic voltage.

Assuming it's clean and not hot, you should be OK to hook it back up to the ground bar (AFTER DISCONNECTING THE POWER AGAIN). And when you throw the breaker back on, it shouldn't blow.

The concern is the wiring out to the outlet might be damaged as well, possibly through over-drawn. You'll want to check the gauge on the wire- it wouldn't be the first time someone ran 14 gauge and had it hooked up to a 20A breaker. Most outdoor tools draw loads of current, and (assuming in conduit) it may have overheated.

Just go through this methodically and you'll be OK.

Now if the breaker immediately trips I would, again, turn off the power, disconnect the hot from the breaker, cap it/nut it, cap and nut the neutral and ground as well.

You'll need to do some more investigation at that point and, if you're not comfortable, should probably want to get an electrician involved.

If you want to put up any photos too that could help my mental view of the box and outlets.

Take care- J

Answer 3

Just an update.. before I installed the new outlet.. I tested voltage without any outlet.. voltage from black to white was 120 according to my multimeter.

Voltage from black to ground is 0.0 and white to ground just to check is 0.0.

Nonetheless my tester still beeps when held close to the bare copper wire.. technically I've been able to get it to beep when touching a bare wire that isn't connected to anything at all.. the plastic casing is cracked and metal on the end of the electric detector is exposed..

I literally had it start beeping when I held it next to a wire clothes hanger...

I touched the bare ground wire to the side of the box and no arcing.. the multimeter says it has 0.0 volts..still bothers me that the beeper goes off on it but not on the neutral sheathed wire..

For now I'm leaving the circuit turned off