White wire arcing to equipment ground with breaker off

[SILVERGUN]

I had an odd experience last night and am just looking for a possible explanation.
I have been working on a fixer upper and needed to move a run of 10/3 NM that is feeding my electric hot water heater.
This feed comes from a small single breaker panel that is next to my main panel and being fed from a second meter. (off peak meter?)

I turned the breaker off and started to disconnect the wires at the water heater.
Black and Red fed the 2 input wires to the unit. But the white wire from the feeder cable was connected to the equipment ground point on the little cover that goes over the wires on the top of the unit. (the bare copper ground wire in the feeder cable was not used)
When I disconnected that wire I got an arc between the wire and the screw. So I did it again to confirm that it wasn't just static.
Same thing, an arc.
I went back to the panel and checked to see if I was getting any leakage through the breaker, but wasn't.
I pulled the breaker and disconnected the white wire from the neutral/ground bus and tried again. Of course, no arc now.

No shock other than my own surprise that I was working on a live circuit that I thought was dead.
I did take notice that there is no proper earth ground coming off of either panel. I will be installing a ground rod (or 2).
Any thoughts?

[PRR]

I assume this is US/Canada. I do not know other places.

You should have dirt-rods, but this is more for safety against external trouble, not inside the building.

I can't see it from here, and do not know your experience. I can't know what you may NOT be seeing/reporting because you don't know.

There must be something odd because the white wire should not spark.

You MUST have solid "ground" bond from the heater shell, though this sub-panel, thru main panel, to utility "Neutral" and dirt-rods. It should be impossible to have any voltage on touchable metal, a fuse would blow.

If this sub-panel once linked to a time-meter, and that is discontinued, who knows what they did in that change? Trace the run, open the boxes.

A conventional water heater does NOT take a Neutral, it is normally run on 240V across the two hot legs. You need two hots and a ground.

With 2-G cable you get a black and a white. You mis-use the white as a HOT. You are strongly encouraged to re-mark the ends of the white so later workers know it is not a Neutral.

With 3-G cable, you use the black and red as Hots, and connect the Bare as ground, both ends. The white should be idle and tucked away from trouble.

Is the breaker for the water heater 2-pole? It normally should be. In some cases a 240V heater may be wired on 120V power (my fixerupper was this way). Heating time is 4X longer, but that may be OK for light use.

Water heaters (on 240V) run 3500-4800 Watts. Nominal demand is up to 20 Amps at 240V. Because the load may be "sustained", the 80% rule applies, we wire for 25A. This is a 25A-30A 2-pole breaker and #10 wire. If a 1-pole breaker, it better be 120V connection and will draw 10 Amps. A very sharp Home Inspector will find the 120V connection and call it out as a shortcoming. (Most won't notice.)

[Ritchie200]

Bonding  of ground and neutral can ONLY occur at the first main disconnect after the meter base. As PRR said, the neutral should not be used or connected. You did say this was a dedicated panel fed from the meter base? Separate from the main home panel?  Not a sub-panel off the main panel? The breaker is a 240V tiebar breaker? Connect back to water heater and disconnect from panel and check wiring for voltage. Is there a plumbing ground on the main home panel? A reverse polarity situation on a circuit in the other panel could be backfeeding through the water lines - even with di-electric water line connections to water heater.  If older home check for the little water line "upgrade" ground strap connections to grounded outlets (not allowed, get rid of them).  Not unusual for those old two wire outlets to be wired backwards or wired wrong when grounded outlets were installed. Also, shame on you for not carrying a $5 buzz stick to check for hot circuits.  Regardless of your unwarranted attacks on the immortal man on the silver mountain, and my hats, I would still like to see you around here for a while longer...

Jim

[SILVERGUN]

Thanks PRR:
I assume this is US/Canada. I do not know other places.
-yes, US
You should have dirt-rods, but this is more for safety against external trouble, not inside the building.

I can't see it from here, and do not know your experience. I can't know what you may NOT be seeing/reporting because you don't know.

There must be something odd because the white wire should not spark.

You MUST have solid "ground" bond from the heater shell, though this sub-panel, thru main panel, to utility "Neutral" and dirt-rods. It should be impossible to have any voltage on touchable metal, a fuse would blow.

If this sub-panel once linked to a time-meter, and that is discontinued, who knows what they did in that change? Trace the run, open the boxes.

A conventional water heater does NOT take a Neutral, it is normally run on 240V across the two hot legs. You need two hots and a ground.

With 2-G cable you get a black and a white. You mis-use the white as a HOT. You are strongly encouraged to re-mark the ends of the white so later workers know it is not a Neutral.

With 3-G cable, you use the black and red as Hots, and connect the Bare as ground, both ends. The white should be idle and tucked away from trouble.
- This 2nd feeder comes in the house as 2- #6awg with a twisted ground right to a small box that only has one 2 pole, 30 amp breaker. On the input side of the box there is a small ground/neutral buss bar where the supply ground is connected.
They had the white and bare copper conductors from the 10-3 water heater feeder attached to that bus, which I get...
But over at the heater they did not use the bare wire and had the white connected to the frame of the heater with a green screw.
With the breaker off - there was a small arc from white wire to frame of unit. 

Is the breaker for the water heater 2-pole? It normally should be. In some cases a 240V heater may be wired on 120V power (my fixerupper was this way). Heating time is 4X longer, but that may be OK for light use.
- Yes, 2 pole breaker
Water heaters (on 240V) run 3500-4800 Watts. Nominal demand is up to 20 Amps at 240V. Because the load may be "sustained", the 80% rule applies, we wire for 25A. This is a 25A-30A 2-pole breaker and #10 wire. If a 1-pole breaker, it better be 120V connection and will draw 10 Amps. A very sharp Home Inspector will find the 120V connection and call it out as a shortcoming. (Most won't notice.)

Jimbo, I hope you see your answers in there also. And yes, there are some ungrounded outlets to be found. I have been going around and upgrading them because luckily they do have ground conductors in the wire. I don't see any water line ground clamps, but I'll look harder.
-
Any chance I might have been seeing a capacitor discharge from inside the water heater power supply?

[Ritchie200]

They look like this:

[PRR]

There is no capacitor in a water heater.

There is something you are not telling us, something you have not found.

For example: power to my house comes on three black wires. There is no way, looking, to know which one is "neutral". It is possible to get this wrong and have the whole house "live".

I'm going to suggest an Electrician, a good one.

[sluckey]

But the white wire from the feeder cable was connected to the equipment ground point on the little cover that goes over the wires on the top of the unit. (the bare copper ground wire in the feeder cable was not used)

Have you fixed this yet? White wire is not used. GREEN WIRE MUST CONNECT TO WATER HEATER GROUND TERMINAL (USUALLY A GREEN SCREW).

[SILVERGUN]

But the white wire from the feeder cable was connected to the equipment ground point on the little cover that goes over the wires on the top of the unit. (the bare copper ground wire in the feeder cable was not used)

Have you fixed this yet? White wire is not used. GREEN WIRE MUST CONNECT TO WATER HEATER GROUND TERMINAL (USUALLY A GREENSCREW).

I have fixed the wiring on the water heater side because I had to move the wire to get the basement bathroom framed up. We did that yesterday so today I can take a look at the meters as it will be almost 50 degrees here in 8southern PA. Ill get you guys some pics because Im sure Ive peaked your curiosity.
Just to clarify:
- It definitely happened. I am waiting for my electrician friend to take a look because it doesnt make sense, but it has to. I dont believe in magic.
To recap:
- with the breaker off I started unwiring the heater by disconnecting the ground screw on the water heater and that's when the white wire arced near the green screw.
- this feeder wire is 10/3 nm with ground. They had the bare conductor and the white wire connected to the neutral/ground bus in the small panel. But on the hot water heater side they had the white wire connected to the ground screw. Bare copper wire was cut back and not used so they were just using the white wire in place of the bare copper wire.
- so I pulled the breaker out of its socket went back and it arced again
- I removed the white and bare conductors from the neutral/ground bus and no more arc
- thats how it currently sits.
- I won't reconnect it until I have an answer, unless to test


Thanks again for your concern and input, I truly value the knowledge and opinions here and I promise to act safely so that I can build another amplifier at my new workbench in my new home.
 
P.S. I have not moved in here yet, so there is time.
I have been working day and night and this is but a minor setback.

[SILVERGUN]

My plumber came over this morning and I started telling him about my experience. He then started telling me about his experience where he almost got shocked by a water heater that was connected to an off-peak timer.
It seems that this might be a common wiring error when people are disconnecting these timers.
I cracked open the box that was connected to this meter and the timer wires are cut so all this thing is now is just an unsafe extension of my main panel.

[shooter]

off-peak timer

I use one of these, saves ~~ $15 a month, BUT, it does need to be the correct one and wired correctly, mine is a 60A 240.  the "dirt" ground, is "star" type, mains>> metal box for timer, AND main ground for HWH.  the timer switches both black and red ONLY.   
aside:
we have many cobbs living in the 1923 cellar, one day I was putzin, heard a "pop" (timer kicking in) at the same time a arc flash, cobbs in the box.  I do preventative maintenance weekly now 

[SILVERGUN]

Thanks shooter...

Here's a couple pics. I can clearly see some insulation breakdown and severe corrosion.

I'm gonna play it safe and eliminate this meter, install a new meter socket box and entry cable to feed my panel.

I plan on dying here, but not from an electrical accident, so it's well worth the time and effort.
I've got a pro electrician/friend all lined up.

[sluckey]

When I disconnected that wire I got an arc between the wire and the screw.

I'm curious about the arc. Was it hot enough to melt the screw or leave a pit or black mark? Or was it just a tiny spark that left no visible signs of an arc?

[SILVERGUN]

When I disconnected that wire I got an arc between the wire and the screw.

I'm curious about the arc. Was it hot enough to melt the screw or leave a pit or black mark? Or was it just a tiny spark that left no visible signs of an arc?

I have already cut back and taped up the white wire. I can go back and check the screw.
The wire was loosely bent around the screw when it happened. I was using an insulated shaft screwdriver and my reaction was to push it back down to making full contact. That's when I went over and pulled the breaker from the panel.
When it arc'd again I was so busy saying "WTF is going on here??" that I headed straight back to the panel to remove the white and bare wire from the buss bar. I needed to get ready for the AM framing job.
It didn't strike me as an exceptionally powerful arc, but then again I work around welding machines all the time so "exceptionally powerful" only applies to 300 amps and up. 

I have already re-attached the wires and cut back the white, but I can go back and look at the screw.

I have confirmed that my dirt rod does not have a path to my panel, unless ivy counts. We will resolve that as well.

[PRR]

I see three black wires. Which is which? Who knows?

I think it is time for a careful rip-out and proper re-wire, with colors or markers.

[SILVERGUN]

This is the area where I can see the insulation is cracked on one of the supply wires that goes inside, out of that meter box

[SILVERGUN]

Electrician showed up...started pointing out what we already saw, so I put him to work.
I said " you got all day?"...he said "well almost all day"...I said "let's do it"
We gutted it from the roof down and right through the main panel.
I upgraded to 4/0 service cable, 200 amp meter box, 200 amp main panel.

He sent me out with a list and I had a good experience at HomeDepot with an electrician running the electrical department.
He knew what I was ordering before I asked him for it and I was back at the house right about the time Craig'o had the 2 meters off the wall. I started on the inside panel and it worked out that we were both ready at the same time to feed the big wire through the house and into the top of the panel to get it mounted. This new panel was almost twice as long as the old one and had to get squeezed into a tight spot above my main waste pipe. We had to raise the inlet hole about 7" up higher on the brick and got lucky that it was only one course.
Bending that big wire was the toughest part of the job and once we got it up and mounted the rest was cake.

I got SUPER lucky and 99% of the old wires reached their new locations. To save money I had him do the outside work and I stayed inside.
He left the meter out and left me there to finish. My 84 year old new neighbor was thrilled to supply me with an extension cord to run lights and after one more trip to the store I finished up around 9.

I am now glad that the wire arced on the hot water heater. It made me re-examine the entire electrical system and forced me to make the necessary upgrade.
$550 parts, $450 labor, 1 pizza, and a beautiful day in the middle of the winter was all well worth the peace of mind to move forward and get closer to getting moved in.

Now, I finally have enough power to run a Major and dry my clothes at the same time....with the AC on and a pizza in the oven.
Life is good.
 

[PRR]

> I got SUPER lucky and 99% of the old wires reached their new locations.

Please pick me some Lotto numbers.

My new box is haloed with junction boxes where I had to splice existing wires.

> $550 parts, $450 labor, 1 pizza, and a beautiful day in the middle of the winter was all well worth the peace of mind....

For all that you got done, that's a real low cost.

200A??  Jealous. If I pull much over 50A on my #2 Al my wall voltage drops below 105V. OTOH, I don't do that (much) and certainly not to justify 600 feet of 0000 cable or a 20KV line and a transformer.

[shooter]

If I pull much over 50A

When we made the offer on our '30s farmhouse it had 1 60A panel with 2 screw-in 30A fuses, I said I don't care about the leaky barn, the leaky garage, BUT I stipulated the mains be brought up to current code, I didn't care about the down-stream romex, or older tube n knob, but the mains had to be upgraded.  each paycheck I'd just run a new branch til the box was full.  I did leave 1 tube n knob branch for posterity 

[SILVERGUN]

Yeah, I couldn't have done it for the REAL cost.

Here's a little follow up. I snagged this out of the trash cause I was still curious.
When I brought it into work for inspection my much older brother said "that's the same exact meter box that caught fire on me"

Upon probing, it is pretty easy to get the insulation to just peel right off of the conductors