weird one

[fisherelectric]

I went back over this morning and checked everything again. The service cable is fine and voltage between both legs and neutral is good inside and at the meter. The power company is responsible for the meter and service drop and they are coming to check their lines today. I have seen service cable that looks fine completely disintegrated inside the brick and block wall and the neutral braid gone causing all kinds of problems. In those cases the only ground for the house is the water pipe. That doesn't seem to be the case here.

Ok 220/221... just read your post. Now you've got me worried again. I can see how the service neutral going out could energize water pipes but haven't thought about a branch circuit somehow energizing them....without tripping a breaker.
Anything is possible...and, I have found, any combination of things is possible.

 

[charlie b]

Electricity is funny like that. If you lose the service neutral, all the 120 stuff will be going to ground wherever it can including the water piping.

Electricity is indeed funny (i.e., strange), but not funny in that way. Electricity is not going to be going to ground; it has no interest in ground. It is seeking its source, and it doesn?t mind passing through dirt to get there. But dirt (ground) is only a pathway; the mission is to return to the source.

The tricky part of this event is the simultaneous explosion of the light bulbs and the feeling of the shock. I believe a MWBC is involved. When you lose the neutral of a MWBC, the available 240 volts is split between the loads (that happen to be turned on at that moment) on the Phase A side and the loads on the Phase B side. If those two loads are not identical, then one or the other is going to get more than 120 volts across it. A sudden imposition of 200 volts (for example) across a 120 volt bulb would explain the shattering of the bulb.

I suspect that the path for current flow through the woman?s body included the water pipe and the water itself (as it made contact with her shoulder and gave her the burn). Current flowed through her body, down to her feet, into the drain (good chance she was stepping on it at the time), and along the water pipe into dirt, over to the ground rod, and up the GEC back to the N-G bond point, and thus returning to the source.

I further suspect that at some point within the house?s distribution system there is a connection of an ungrounded conductor to the water pipe, or to some point along an equipment grounding conductor). It may be a high resistance connection, such as a section insulation that is wearing thin but not completely gone. Let me call that the ?short circuit point.? This could explain why a person would not feel a shock every time they took a shower. With the loose neutral being, at most times, in reasonably good contact, it would be the primary path for current to take back to the source. Current flowing through the short circuit point would be so small as to be unnoticeable. But when the loose neutral becomes disconnected, the short circuit path would become the only available path, and all current would flow along it. The current would be limited by the high impedance at the short circuit point, but it does not take much current to cause a shock and a burn.

So in essence I am suggesting that there are two problems. Now please understand that the likelihood of two things going bad at the same moment is extremely low. That is not the situation I am describing. Rather, I am suggesting that one problem is there 100% of the time. The short circuit to a water pipe or other grounded point, possibly a high impedance short circuit, is there, somewhere. It is not noticed most of the time, because the loose neutral is not loose most of the time. You would have to be in the shower at the same moment that the neutral becomes loose, in order for the short circuit problem to manifest itself.

 

[charlie b]

I can see how the service neutral going out could energize water pipes . . . .

I can't. Can you (or anyone else) describe how disconnecting one wire can cause another wire to come into contact with a pipe? It has to be simple, but I am missing it anyway.

 

[Dennis Alwon]

I can't. Can you (or anyone else) describe how disconnecting one wire can cause another wire to come into contact with a pipe? It has to be simple, but I am missing it anyway.

Perhaps what he is trying to say is if the grounded conductor from the utility is lost then the 110 circuits will try and follow the path to the grounded water pipes, ie earth.

 

[fisherelectric]

I appreciate everyones' input. There are no MWBCs in this house. I got readings of ~.04v from the shower piping to ground. Amprobe on the water pipe said ~.005a. I think these readings are negligible. Voltage from hot to neutral was ~120.6v on each leg at meter and identical at main lugs. I took these readings at different times with different loads...lights, gas furnace etc.
However, while I was there, since Dominion Va. hadn't responded yet, I called them again and the woman I talked to told me that, unbeknownst to the homeowner, a branch had fallen on her power line and been repaired on the 16th of December.
Anyway...there are 3 splices in her overhead lines between the transformer and the point of attachment at her house, any of which could have a bad connection causing an intermittant neutral. If this woman did feel a shock, which is debatable, I really don't believe it could have caused a rectangular burn blister like she has on her back...it looks to me like it is from flying 100watt bulb glass. This has me scratching my head. Charley b....do you think water coming out of a shower head could cause a burn like that?

 

[charlie b]

If this woman did feel a shock, which is debatable, I really don't believe it could have caused a rectangular burn blister like she has on her back...it looks to me like it is from flying 100watt bulb glass. This has me scratching my head. Charley b....do you think water coming out of a shower head could cause a burn like that?

I have not seen the room, but I would normally expect that there would be a shower door that would prevent a direct hit from flying glass. Sure, there was glass found in the shower, and it might have flown over the door. But a direct hit seems unlikely. Also, I can see flying glass causing cuts on the back, but not burns. The explosion would have added heat to the glass, but the trip across the room should have dissipated some of that heat.

Electrical current can cause burns on the surface of the skin, at the point the current enters the body. I think it could have happened as I described. We know at least that two things did happen (light bulbs explode and shock/burn), and that they are related in time. Perhaps all we can say for certain at this point is that they must have a common cause

 

[jim dungar]

District Attorneys never feel comfortable when their case is made soley on a single eye witness testimony.

Time to play CSI.
When you say "burn blister" was it severe or minor?
Was there any "exit" mark? If electricity caused injury as it entered her body it may have also caused some as it exited.
What was your voltage L1, L2, and N to ground readings at the service?
You got .04V from the shower to ground, did you measure voltage and/or current on any other piping?

 

[fisherelectric]

Jim...
The blister was not severe..but it was a blister..it was rectangular, about
3/4"x 1/2". Nothing on her foot. She said she felt her leg "jerk" like a shock.
I measured voltage to ground from the shower, the sink, and in the basement.
I took the GEC off and measured between that and the piping. Same same. I measured current at the water service..~.005a. I mentioned the voltage at the service above...all normal.
She did tell me she had been drinking fairly heavily...hmmm.
We all know how hot a 100 watt bulb gets. The bathroom is tiny...I would say the glass would have to have travelled at least 4 or 5 feet horizontaly to reach her in the shower.
The 3 TV sets that went bad over the last couple of months: All were old 1 went to static white screen only. 2 she said started looseing its' picture after it had been on a few hours, the 3rd she says she has to let warm up for a while before it gets a picture. I don't know that these symptoms indicate any kind of surge damage.
I never saw any brightening or dimming which she says she has "always" noticed. Power comp has still not showed as far as I know. Thanks.

I can also tell you that it was a 4 lamp vanity light and that the two lamps on the right hand side of the fixture blew, the other 2 lamps remained intact.

 

[LarryFine]

It all still sounds like the piping is becoming energized in short bursts, like there is a fairly good-sized neutral current and an intermittent connection, but the condition has a too-short duration to detect.

Plus, I have seen hot bulbs explode when hit with water spray. Combine a 100w bulb in a fixture probably rated for 60w with a higher-than-normal voltage heating the glass, add a bit of water, and *POP*!

 

[220/221]

There may be no MWBC's in the house but the whole house is a MWBC.

If you lose the neutral service conductor it seems that something somewhere would be tring to get back to it's source in any way possible including the water pipes via the bonding.



I suspect the burn was from glass.
I suspect the glass was broken from water.
Her "shock" may not have been electrical.

I would almost write it off if it weren't for the lights getting bright thing. That is a POSITIVE sign of a compromised neutral connection at the service/feed in this case (no MWBC's)

I would almost write it off if I had not seen it myself TWICE.

Can you (or anyone else) describe how disconnecting one wire can cause another wire to come into contact with a pipe?

The wire is already in contact with the water pipe through several different paths including a diswasher, disposal, washer and bonding conductor. The current flows back thru the neutral service conductor when things are working right. If this path is broken it will take an alternative path and one of those paths may be thru the water pipes.

 

[brian john]

The service cable is fine and voltage between both legs and neutral is good inside and at the meter. The power company is responsible for the meter and service drop and they are coming to check their lines today.

I NEVER, NEVER, NEVER rely on the utility to check anything, at best most of these guys are basic linemen no electrical background basically assemble men.
Not slamming them just stating a fact. If a customer is paying me to resolve an anomaly I resolve it, I am more than willing to work with the utility, if they show up! I have waited days for a utility response.

 

[RayS]

perhars she did get a tingle, then jerked and sprayed water all over, then the lights popped from it.

I had a friend who had an intermittent shower shock for years, lots of people including the POCO looked at it, no solution till they redid the floor. Screw thru a wire, let the juice out when the floor was wet enough/warped just right.

 

[brian john]

They just did not look hard enough.

 

[PetrosA]

Triplex

Triplex

As far as exploding bulbs go, I've had a bulb, in the box, at rest, on the counter at the supply house burst. I've also seen 10 bulbs burst at once in the kitchen when a lightning strike nailed our transformer at home (OK, extreme example since there were probably thousands of volts going through the bulbs at that point). A lost neutral could probably do it as well, depending on how the filament breaks when the surge hits.

One thing I haven't heard you say you did is take amp readings on the two main legs and comparing that to the amp reading of the neutral. That's a good way to identify a neutral problem ahead of the main panel. On a recent kitchen remodel, the lights would get extremely bright when the carpenters ran their table saw. Although it wasn't part of our job, I took amp readings at the panel and found a few amps discrepancy. I checked outside for visible damage, saw none, and noticed that the triplex feeding the house ran for maybe 100' through some woods. No branches were near it, and I couldn't justify spending any more time on it so I called the POCO and reported the problem. Well...

They found that the neutral on the triplex was broken through, with maybe one strand making contact. It turns out that the guy's neighbor was shooting at squirrels on the triplex and damaged it (and we laugh at images of the Palestinians shooting off guns in the air ). They replaced the triplex, and probably saved about 5 new electronically controlled Bosch appliances that the customers had gotten for their new kitchen and laundry.

Good luck,

Peter

 

[hutch75]

Loose neutral

Loose neutral

I had a service call years ago in a 1900's house, where the HO claimed he had lights dimming in the house, and was getting shocks in the shower. Upon investigating, the 100 amp main disc in the basement that had a rigid nipple from the main disc to the fused panelboard was arcing. Further investigation of the service outdoors indicated the neutral connection was damaged, and any neutral current was flowing through a #6 from the main disc to the 1900's galvanized pipe closest to the disc. And yes there were no ground rods either. After informing the HO of the situation, he chose not to pay to have the neutral connection repaired/service upgraded, and said he would call the utility to make the repair. Apparently he did not ever make that call, but he did call back later that month to inform me that every appliance in the house had blown up, and wanted to know why? Upon further investigation(over the phone) he was getting the house re-plumbed, and when the plumber removed the piping in the basement, and neutral connection to the service, not only did the plumber get a shock, but that is when the ho lost everyting in the house.

Apparently, losing a neutral, or having one removed, can really cause damage to electronic equipment. I would make sure that not only is the neutral connection made, but also the ground rods, and water pipe connection made and bonded properly as well. I would also be curious if any of these supplemental paths are carrying any neutral current, and it the bond in the panel is correct.

 

[George Stolz]

And yes there were no ground rods either.

(snip)

I would make sure that not only is the neutral connection made, but also the ground rods, and water pipe connection made and bonded properly as well.

What are ground rods going to do for you in an open neutral scenario?

 

[DBack Elec]

I have heard of this happening with lightning. Was there a storm that night?

 

[PetrosA]

What are ground rods going to do for you in an open neutral scenario?

If you're lucky, the grounding system will disperse the grounded conductor current enough to save appliances and possibly a life. I wouldn't depend on this in an arid climate area, but here in the Northeast, it's entirely possible for the ground rod and water pipe to have sufficient conductivity to ground to carry that load during a fault situation.

Regards,

 

[JohnJ0906]

If you're lucky, the grounding system will disperse the grounded conductor current enough to save appliances and possibly a life. I wouldn't depend on this in an arid climate area, but here in the Northeast, it's entirely possible for the ground rod and water pipe to have sufficient conductivity to ground to carry that load during a fault situation.,

"disperse the grounded conductor current"?

That current is trying to return to source. In hutch75's example, it was probably returning through the neighbors service neutral, via the water main. I doubt that ground rods would help if the water pipe, and hence, the only neutral path was removed. The earth resistance would likely be too high to provide a path back to the transformer ground.

 

[iaov]

Pretty regularly. I think that most of the time I get pronged by a hair of stranded wire. Feels just like a shock.

Pretty regularly for me too. I think old electricians become "shock paranoid" after a while. It helps us to become old electricians!:smile: