I saw a short piece on the news about a homeowner that was electrocuted just days after moving into his new house. It happened near me in Clermont, Florida. They didn't give much information on the news, but they did show part of a video taken by the HO's wife's lawyer. Apparently the guy was killed when he was connecting the clothes dryer vent hose onto the metal duct. The duct had voltage on it. The video showed an electrician reading 120vac on the metal part of the bathroom medicine cabinet. He checked the cabinet and used the ground on the nearby receptacle. The investigation found a drywall screw through a metal wall stud and into an unsupported piece of nm inside the wall. They said it was only into the ungrounded conductor in the romex. Supposedly the metal studs were energized, and I'm guessing that the dryer duct was secured to the studs. You would think the breaker would have tripped, unless they had poorly installed grounding, also.

Edited for spelling

[This message has been edited by XtheEdgeX (edited 02-22-2006).]

If he had an "Bank" Earth Leakage Breaker it would have tripped when the leakage exceeds 30 mA and he would be still alive.

Tragic incident.

Edge, this is not unusual. There is no metal in the wiring method, box or even the plumbing. I am not sure where the path would be to trip the O/C device until the dryer does get hooked up.
These houses are built on a slab with an isolation membrane under the steel framing. The panel will be on a block wall in the garage. Everything is in Romex with plastic boxes. If they don't get caught with a luminaire having to go directly over a stud, requiring a pancake box I am not sure there is any way the steel gets bonded.
In commercial with EMT and steel boxes this is not a problem. It gets bonded all over the place.
I bet we start seeing metal framing coming under 250.104(C)
The contractors probably could have made this issue go away if they just used steel boxes for the dryer and the range. That would give them some fat EGCs bonded to the steel with a few pennies added to their cost. If we get required bonding under 250.104(C) they will be stringing #4 or larger all over.

When is the rest of the world going to use steel pipe and boxes like us?

Tom

We had similar problem in the housing industry a few years back. One of the home builders was using a sheeting on the outside of the house that had a thin layer of material that looked like aluminum foil. Some type of thermo barrier. Then the vinyl siding was nailed on top. The siding guys were using 1 1/2" and sometimes 2" nails and the nail would penetrate the romex and electrify the skin of the sheeting, the down spouts and I had 88 volts to ground on one of the brick fronts of a house. The guy doing the pressure washing kept complaining that he was getting shocked and was smart enough or lucky enough to get away from the house. As a result I haven't seen any of this type of sheeting being used since.

Has anyone else noticied the tendency of people to use the biggest nail they can find, regardless of the job? If they're attaching to 3/4 plywood, what do they really think that extra 1.25" of nail is actually doing? I recently had a nail-through-the-Romex repair because the H/O was using 10d finish nails to attach quarter-round molding to his baseboard. That must've been load-bearing baseboard-trim...

-John

I had one where the cabinets were hung with 4" drywall screws and they got the romex right in the middle. Never told the homeowner about the sparks. I found it by opening the cabinets and seeing the burn marks. Rod

OK, add this to the stupidity factors....
200 amp SEU cable, straps about 24-30" apart.....nice.

OH, all the guys had was 2-1/2" screws.....guess who actually screwed his own NMC/SER!!!!!!

John

Here is the news story http://www.local6.com/money/7302637/detail.html

A little bit off topic, but I never leave a kitchen rough in without using nail plates over every cable filled hole in the walls that will be behind either the upper or lower cabinets, regardless of how well centered my holes were in the studs. I have seen those 4" long screws in the finish carpenter's parachute bags one too many times.

I don't see many metal studs up here but aren't they structural steel and thereby have to bonded?? Why would you use plastic boxes on steel studs, do they use a nail on like box with tech screws??

The argument against bonding goes that they are not "exposed" steel members.
It is clear anything attached to them like the dryer vent can or the medicine cabinet is exposed.
They use plastic boxes because they are a few cents cheaper and faster to install.
Yup they just screw the mounting flange to the steel framing with drill screws.
If they used a steel box for the dryer, the stove and the bathroom vanity outlets they would have most of the steel bonded.

WALRUS:
Here in NJ there is some metal stud in resi, mostly remodel, or basement finishing. These are lightweight studs, 2x3 & 2x4 are common.

I have seen pieces of wood 2x4 inserted in the metal stud, screwed, and a nail-on plastic box into the wood. There are plastic boxes with a front flange to tec screw to the metal, and some have a bond screw and 'clip' to 'bond' the studs.

Now, IMHO, metal studs, metal boxes. As an EC, we do comm, metal studs MC cable, or EMT. Yes, in some instances, I could use NMC, but I choose not to.

As an AHJ, if it's NEC compliant, I have to accept it, personal opinions, or preferences don't count.

John

I had a job some time ago in a prefab unit, one of the "Arcon" units erected here just after WWII as temporary housing intended to last 10 years (and still with us 60 years later).

The roofing on those was asbestos sheets fitted over a steel truss system of small girders and tubes. Apparently the plumber had been crawling around up there doing some work, got shocked when he reached across a strut, and had no intention of going back up there until it had been checked it out (a wise decision!).

It turned out to be a T&E (Romex-type) cable which had been slung loosely across the base girders and then had a ton of junk stacked on top so that the sheath had been damaged.

After taking care of the obvious repair and rerouting of the cable, I also installed bonding on the metalwork.

Years ago, I had a simular situation... (Rather than tell the story all over again, I'll see if I can find the last time I told it here...)

Oh I cant find it... Anyway, troubleshooting at a resturaunt, that the dish washers had been getting shocked at for years, a screw that held the sheet metal to the wall, that the sinks were mounted to went through cable and conduit behind. Seperate ones, seperate phases, so if you touched one sink you got 120, if both 240. On top of that the manager did not want to fix it, so I shut off the service....

Funny part, metal walls, metal pipes to metal sinks, nothing tripped - nothing grounded.