Chris Lewis wrote:

According to Jeff Wisnia :

Ron Hardin wrote:

Toller wrote:


What kind of short was it that didn't trip the breaker?
If you pipes were grounded why would you get a shock off them? Your
resistance has to be thousands of times higher than the water pipes, so if
there was some wierd short that only allowed a couple amps, 99.99% of it
would go through the pipes when you touched them.


This doesn't make any sense to me. Can anyone explain it?


Plastic pipes? The current would then be through the water, not the pipe.


You'd notice a shock when you were grounded yourself, say on a basement floor,
and touched metal in contact with the water.


Generally speaking you're not going to get much current through water with that
small a cross-section. "Feelible" _maybe_.


Continuing current would discharge through the water to grounded devices in
contact with the water, running up the electric bill.


But not by much.


It reduces the heating
requirement in the same amount, though. But it needn't be a breaker-blowing
current.


The real issue is that the copper pipe may well have a full hot short, but the
person is only getting a minor tingle because his shoes/socks are moderately
good insulators, and dry concrete isn't that good a conductor either.

If he sprayed salty water on bare feet, stepped on the concrete and touched the
pipe, it may blow him through the wall.

This is a very hazardous situation. The level of jolt _may_ depend only
on how well the other end of you is connected to ground.

I remember getting a tingle from the frame of a radial arm saw I had just
bought at an auction and plugged in.

Stupid me. I tried to confirm it by touching the saw _and_ the cover attachment
screw of a nearby outlet.

_Whammo_. That hurt!

The ground wire in the RAS plug had come adrift from the third prong and
was contacting the hot wire. The whole case was full live. But it appeared
only a minor tingle because I didn't have good conductivity to the floor.
But when I touched a grounded screw... Whap!

[I learned my lesson. If in doubt, use a voltmeter. Don't use _you_.]

Frankly, guys, if I was in shoes on a concrete floor, and just touching
a pipe gave me a tingle, I'd kill the house power _immediately_ and
get everyone out of the house.

Then, I'd get out the voltmeter, and turn on the power again. Then carefully
(touching as little as possible) start measuring voltages between "supposed"
grounds to figure out what's wrong.

I'd do exactly the same thing...For sure!


And how about those laundry machines? Unless they were both unplugged
from their outlets they should have been grounded too, so something had
to be seriously wrong with the grounding of the electrical system in
that building.


Dryers aren't hooked up to the plumbing. Washers often don't have
electrical conductivity to the plumbing either (the hoses are rubber -
our code requires a bonding strap from case to pipe, but it's often omitted...)

You missed my point there. The OP said he touched *the case* of his new
washer and got bitten. That indicates that the case of the washer wasn't
at ground potential, as it should have been if it was plugged into a
properly grounded outlet, eh?

Water heaters cases don't necessarily have good electrical connectivity to the
plumbing, because the teflon tape or pipe dope _may_ interrupt the electrical
path. Plastic certainly would. Rusty metal unions might too.

Rvery electric water heater I've worked with has had a ground terminal
on it to which an electrical ground lead from the panel should be
connected. If his wasn't then it wasn't to code.


I vote for broken main grounds to both the main electrical panel and the
plumbing, probably at a point where just one conductor was doing both
jobs. That would let all the electric wiring grounds and neutrals and
the entire plumbing system were free to be driven off ground by a faulty
element in the wather heater, or some other device with a slight amount
of internal electrical leakage.


The main thing we know is that the pipe isn't grounded. It _may_ or
may _not_ be connected to the electrical system ground. If it is, the
electrical system ground isn't connected to the dirt (or whatever the
other object the OP was touching when they got the tingle).

Any decent building code requires all metal plumbing supply lines to be
conected to earth ground. That means they'll be grounded anyway even if
there's teflon tape or perhaps dielectric couplings used. (Don't get me
started on dielectric couplings and electric water heaters, I've proved
conclusively they don't do squat to prevent corrosion of the heater tank
when the piping is grounded per code. No less an authority than the
Rheem water heater Company now advises against thier use.)

Could even be that the pipes are well grounded, but the water heater
(he was leaning against it when he touched the pipe, right? ;-) is
ungrounded and is getting a bit of stray voltage because a cracked
insulator, and it was otherwise diminished by the paint coating.

Etc.

Agreed, I think we both know something's AFU with that building's
wiring, and they ought to get a *good* professional out there to put it
right.


If the heater tank was properly grounded, I'm hard pressed to believe
that the electric field strength at the piping ports would be large
enough to put enough voltage on the water in plastic pipes to be felt,
were plastic piping used.


Forget electrical field strength. You won't feel it at these frequencies
and power levels.

Puhleeze! You can have a DC electric field you know. What do you think
causes that tingling you feel when standing outdoors just before an
electrical storm hits? The charge on those clouds sure ain't AC is it?
And you can have a field in any media that isn't a perfect conductor,
such as water.

All I was saying is that the water in the tank isn't a perfect
conductor. So (if the tank was grounded per the "plastic pipe" thesis)
the majority of the leakage current from a rotted through element would
flow to the grounded metal nearest the break, because the shortest path
through the water will have the least resistance. There would be very
little current flowing through the much longer paths to the inlet and
outlet bushings, and I'd expect the voltage there would be negligable.
Of course if the tank shell *weren't grounded* then the whole tank and
the water in it would probably just follow one half of the line voltage.

Just my .02,

Jeff
--

Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"If you can smile when things are going wrong, you've thought of someone
to blame it on."