In that case the ground wire did NOT go back to the panel, but to a
clamp on a cold water pipe.
Until the 70s that was legal.
But stupid. And that's why they outlawed the practice. The wire went off
to parts unknown (in my case) and some small amount of current leakage
apparently caused galvanic corrosion to occur where it lamped to the
waterpipe. It caused a pinhole leaked to develop. All tucked away
behind a stapled ceiling and hard to find without making a mess.
In my mind, those are two good reasons why they changed the code and
why such connections should be removed and done according to modern
rules whenever they are discovered even if they are still grandfathered..
As for the OP, what was legal in the 70's is moot.
*Actually the 2014 code does still permit the connection to the waterpipe.
Article 250.130(C)(1) states that is is permitted "At any accessible point
on the grounding electrode system as described in 250.50". The waterpipe is
part of the grounding electrode system. The water meter and water heater
bonding jumpers would have to be in place and the clamp would need to be
approved for the type of metal piping.
I really don't want to dive into this can of worms again so I'll just note
all the potential failure points of using a clamping method from the code
fragment you cited and I'll bet many more live in 250.50:
The waterpipe is part of the grounding electrode system
IF and only if
1) The water meter is jumpered
2) the water heater is jumpered
3) any section of the pipe that's been replaced by pex or plastic is
jumpered
4) the right kind of clamp is used that won't cause galvanic corrosion
I would add that the wire from the outlet box is labeled as to where it's
going off to. When I checked the outlet and it failed, opening the box was
no help. When I tried to trace the cable back to the panel with a fox and
hound I couldn't tell where the ground wire was going because it was stapled
high inside the joist (badly stapled, I might add).
I removed one stapled ceiling tile (what a mess that was - so much so it
helped lead to taking the whole damn ceiling down) and saw the wire going
off at 90 degrees from the main cable. Tracing that proved to be impossible
with the fox and hound so that aided in the decision to pull more tiles
(this was a critical outlet for power tools in the workshop). The readings
on the tester were flakey. Sometimes it would be grounded, other times the
test lamp would flicker or extinguish completely, especially if there was a
load on the second outlet of the receptable in question.
It's just my opinion, obviously, but a wire that's used primarily as a
life-saving measure going off to parts unknown should have a "good"
provenance. It was obviously NOT done by an electrician because of how
poorly the wiring was connected - it was nicked and barely under the screw
and not stapled near the box. Another clue was that it was 10 feet FROM the
damn panel and done when the ceiling wasn't in place so a real sparky would
have just run a new wire and breaker (and they did for the window air
conditioner outlet that was clearly added on at some point).
Tote all the potential failure points up and it's clear using a pipe as a
ground has lots of potential risk - at least compared to pulling new wire..
I understand why it was grandfathered: I am sure the NEC weenies feel that
any form of grounding is better than no grounding at all.
Many of the outlets in the house were three-pronged but NOT grounded, FWIW,
another sign of a rank amateur. Still with the basement open it would have
been simple to do it right and after pulling the ceiling that's what I did.
Replaced all the old outlets that I found that had three prongs but no
actuall ground connection with new two pronged ones and ran all new circuits
to areas that were critical - along with GFCI's.
This was 1940's cloth covered wiring and I am sure oxidation of the
conductor along has slightly degraded its ampacity.
That is what I think happened in your case. The disimilar metals of the
ground clamp (Brass) attached to a steel pipe acted as a battery.
FWIW, it was a plated steel clamp on a copper pipe - same thing really.
Just like a water heater. The clamp should not have been buried in a
finished ceiling. The ground wire should have been run over to the water
meter location where it would have been accessible and could have been
clamped to the water pipe or the grounding electrode conductor.
I think you're 100% correct about how that happened. Obviously none of this
work was ever inspected - properly at least - and the only good thing about
all this jack-legging was I got to knock a few thousand off my offer after
doing a walkthrough of the house with my outlet tester. I recall the
comment "We had a lot of appliances that had three prongs so my son replaced
the old two prong outlets so we didn't have to use those adapters anymore.."
The sounded proud that he could do it! I really don't think they understood
the ramifications of using 3 prong outlets on ungrounded circuits. Someone
did, eventually, which is why the green wire to the basement outlet
eventually appeared. I believe he had installed new shop lights that needed
a ground to operate properly.
The wiring in this house ran up to the attic and then down again like
octopus tentacles inside hard plaster walls so running a ground wire along
the original cables (or pulling new wire) just wouldn't be feasible. And
that's why I can understand the NEC rules about waterpipe clamps.
So I ran new 12/2 w/ground and GFCI's to the window AC's, the outside of the
house, the kitchen and the office and used dual skinny breakers to wire them
to the panel. For the most part, only very light loads are now running off
the old wiring. Much of it is CFL lighting, further reducing the risk of
overloading the old wires and in most cases, not needing a ground wire
anyway.
At first I was concerned that I had too many dual breakers, but the electric
consumption has dropped slightly each year as I retired plasma TV's for LED
TVs, 30 year old refrigerators for new high eff. ones, CFLs for tungsten
lighting, etc. So it's clear that even though I have more circuits than
before, the total load on the panel is actually lower than it's been
historically.
I'll save it for another thread but my neighbor's electrician son solved a
very interesting puzzle in which some of the lights in his mom's house went
off for several hours early in the AM and then came back on by themselves
without resetting any breakers or GFCI's. I couldn't diagnose it, and
neither could he until I told him that a single UPS's started chirping at
3AM, which I thought was low voltage but seemed to be battery failure., so I
got up and shut it off. No other UPSs beeped so I assumed it was a local
event until my neighbor told me about her basement tenant's lights going
out, too. When I restored power to the UPS and turned it back on the next
day, everything was fine and the battery tested out as good - I was about to
replace it just in case but it was less than a year old.
You've got good analytical skills, John. What do you think it was? (-:
*I don't have a simple answer for this. Things that I have found when troubleshooting that particular problem a
Loose connection on the circuit breaker.
Loose neutral connection on the neutral terminal bar in the circuit breaker panel.
A bad circuit breaker.
Loose connections on one or more electrical outlets on the circuit.
A loose splice under a wire connector (This is common with DIYers who don't twist wires together before twisting the connector on).
Loose connection on the main circuit breaker or the main feed lugs.
A corroded neutral wire that had a few strands broken as a result of long term water damage. (Water getting into the SE cable and traveling down into the meter socket and eventually the main panel).
Loose connections in the meter socket.
Loose connections at the weatherhead.
Loose connections at the power company transformer.
A damaged overhead service wire that has been rubbing against the house or trees whenever the wind blows.
A damaged underground sevice feeder between the meter and transformer.
This past week I got a call from a couple living in a condo who have been having problems with their cable box going out briefly and then coming back on. I was there a year ago for the same problem on one of their cable boxes. This time it was all three boxes. They had the cable compnay come out so many times to rewire and replace that they will no longer come out for this problem which they believe is with the electrical wiring. Last year I pigtailed and replaced 2 outlets and never heard back from the couple until this week. Last year they reported that nothing else was occurring such as flickering lights. This year it was the same, no flickering lights, but they also admitted that they did not use the lights on these circuits too often. I found the three cable boxes to be on two circuits. I checked the voltage at the main panel and it was consistent on both phases and to ground as well as to neutral. I replaced the two breakers and opened up every switch and outlet on these circuits. The outlets were a builders cheapo model with no screw terminals, only the back stab holes. Every outlet that I removed from the wall had the wires come out of the back stab with little effort. On one particular wall receptacle with six wires attached, one of the neutral wires had only about a quarter inch of copper showing which made me think that it was not making good contact when it was inserted into the back of the original outlet. I pigtailed and replaced every outlet on the two circuits. I tightened every connection in the main panel. The only thing that I could not do was check the main breaker because it was in a 6 gang meter stack that the power company had locked up. I told the couple to call me if the problem persisted and I would get the power company to unlock the meters.
A tool that I have found to be very helpful is the Amprobe Inspector:
http://www.amazon.com/gp/product/B00...7Y2DQQOIYSDVF7
On the above job it told me that I was on the right track by pigtailing when I compared the before and after readings.
Another tool to use is an ammeter to measure the current on the grounding electrode conductor at the water pipe and the ground rod. If there is current flowing on the grounding electrode conductor, that tells you that there is a problem with the neutral conductor.
I should add that I was quite familar with the condo complex above as I have been doing work for the association for several years. In that time I have found many problems that go back to the original installer. One that stands out is a woman who had a new furnace installed in her condo. She kept having problems with it and the service technician and her own electrician told her it was an electrical service problem which was the responsibility of the association. I measured 30 volts between ground and neutral at her main panel. I go outside to have a look at the meter stack and noticed a house panel for the outside lights. I took the cover off of the house panel and saw a black wire on one main lug, a white wire on the other main lug and a bare wire on the neutral bar. The house panel only had one circuit breaker in it. I removed the stack cover and saw the black and white on the main breaker and the bare on the ground terminal. I took the white wire off the breaker and put it on the neutral bar. In the house panel I took the white wire off the main lug and put it on the neutral bar. I installed a separate ground bar and attached the bare wire to that as well as the grounding conductor for the one circuit. The woman's furnace is now working properly.
John Grabowski
http://www.MrElectrician.TV