Re: Kitchen Wiring Problem


Doug Miller wrote:
In article <1145988778.217667.114960@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>, trader4@xxxxxxxxxxxxx wrote:

Doug Miller wrote:
In article <1145973552.253512.286070@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
trader4@xxxxxxxxxxxxx wrote:
You end up with 240V between the red and black, yes, but so what? It's no
more
dangerous than a 240V circuit for a stove or a dryer.

I'm with Ray on this one. I think it is considerably more dangerous
than a 240V circuit for a stove or dryer. If you're working on a
circuit for a dryer or stove, one would expect there to be 240V between
two hots. But if I happen to be working on a std outlet, most people
would never expect there to be 240V between the two hots.

If a circuit is fed by a double-pole breaker and has two hot wires, one red
and the other black, that would in fact be the normal assumption by someone
who understands residential wiring systems: that it's an Edison circuit, and
the potential between them is 240V. At a minimum, even to the uninformed it
should be a signal to check a little further to find out what's going on
before proceeding.

For example,
I could see someone having things opened up for testing, and allowing
the two hots to touch each other, thinking they would be on the same
phase, which in every case that I have seen, they are.

Allowing the two hots to touch is asking for trouble, regardless of the
type of circuit. Good practice, when opening up live circuits for testing, is
to make sure that *nothing* is touching anything else.

I agree that keeping everything isolated is what should be done. But
for average Joe homeowner, who would never think that there could be
240V between the two hots, I could see it happening.

It's not relevant whether the potential is 240V or not: if you've opened up a
circuit for troubleshooting, that implies there is a fault somewhere. Possibly
that fault is a short somewhere downstream. Allowing the two hot wires to
touch will produce an arc; even 120V arc is plenty dangerous. If "average Joe
homeowner" doesn't have enough brains to keep everything separated while he's
probing voltage on live wires, he doesn't have any business touching the
stuff.


Not saying you can;t do this, but anytime you start to deviate from
what is common or expected, you have to ask, is it worth it, just to
save another neutral run?

So who's suggesting deviating from the norm? This *is* a common situation.
It's "unexpected" only to those who are unfamiliar with Edison circuits.

It's not common in the sense that I've lived in many homes for many
years and I have never seen one.

I've never seen a kangaroo, either, but I understand that they're pretty
common in some parts of the world. :-) -- the point being that it's sometimes
a mistake to generalize from one's own experiences, without recognizing the
limits of those experiences.

And I wouldn't be surprised if some of those homes had Edison circuits that
you weren't aware of. :-)



Geez, you now think I'm so stupid I wouldn't recognize a double breaker
in the panel? The only double breakers I have ever seen in my homes
or other homes I've been involved with were for std 240V loads, ie
dryer, stove, A/C. There were no other double breakers for shared
neutral 120V circuits. If these were common, I would think you;d see
a hell of a lot of people showing up in the newsgroup to ask what
these double breakers were for every day. Yeah, one comes up once in a
while, but if they were all that common, I'd be expecting them all the
time, cause people would wonder what they had. I'd be interested in
hearing from other folks as to how common they think a shared neutral
circuit is.




And if you asked the average
homeowner what an edison circuit or shared neutral is, virtually no one
would have a clue.

The average homeowner doesn't work on his own electrical systems at all.


Again, give me a break. It's very common for a homeowner to replace a
switch or outlet themselves. Not all do, but for a guy claiming edison
circuits are common and well known by everyone, it's pretty bizarre to
be arguing that it's not common for a homeowner to replace a wall
switch.




Yet, it's common for homeowners to replace a wall
outlet or switch. If someone comes in this newgroup and asks how to do
that, I've never seen anyone suggest to be careful, it may be an edison
circuit or to verify that it's not being fed by dual breakers, perhaps
not linked or correctly identified.

You're making the same mistake again: generalizing from limited experiences.
I *have* seen that response here in this group, when someone went to replace
an outlet and found black, white, _and_red_ wires when he was expecting to
find only black and white, and asked what the extra wire was.

And the point is why do this? All that is being saved is one lousy,
cheap neutral wire.

You haven't priced copper wire lately, have you? :-)



I don't think I'm the one who needs to do pricing. You can get 14/2
Romex for .20 a foot. 14/3 is about .30. So for a whopping 50 ft run,
if you do it with 14/3, it's $15.00 for wire. Run two 14/2 cables and
it's $20.00.
Are you arguing that $5.00 is a big deal? Even if it were double or
triple who the hell cares?




Can't a



It saves not only a neutral but a ground as well. A piece of 12/3 has four
wires in it; two pieces of 12/2 have six. A length of 12/3 is a *bunch*
cheaper than twice that length of 12/2.


Oh really, $5 is a bunch cheaper?



Voltage drop is reduced, which may be an issue on long runs.

It's also less labor to run one cable vs. two.

And it uses half as many Romex connectors in junction boxes.

It also reduces the number of conductors in each junction box, allowing the
electrician to meet Code with smaller boxes (and possibly turning a
non-Code-compliant overfilled box into a compliant installation).

Ditto for the number of conductors in conduits.

In other words, you're making hasty generalizations again... just because you
can't imagine any reasons other than saving one neutral conductor, you assume
that there aren't any.


I never said there weren't valid reasons for doing it if you have to.
In fact, I even stated, it could make sense for old work, where there
is no easy alternative. And most of what you cited above, applies to
old work, because in new work, the number or size of boxes ain;t a big
deal. So, thanks for telling me what I already stated. Again, I'd
like to hear from others that have seen shared neutrals commonly used
in new construction.



Not a correct assumption, I'm afraid.

I can see doing this if there is no easy way to do
it otherwise, eg old work, but I would never do it for new work.

Then don't do it. But understand that your reasons for criticizing it are not
valid.

As to the dangers of this practice, here, from the DOE:

http://www.eh.doe.gov/paa/oesummary/oesummary2005/oes2005-15-01.pdf

They discuss that shared neutrals circuits pose unique dangers if not
properly identifed and cite incidents that actually occurred.

Stop the presses! It's just been discovered that electricity can be dangerous!

Seriously, though -- _every_one_ of the incidents cited is traced to improper
installation or documentation. You draw the same erroneous conclusion as the
authors of the report state in the first paragraph: that shared neutrals are
dangerous. This is not correct: the danger comes from improper installation. A
properly installed shared neutral circuit is perfectly safe.


Yeah, I new this was coming. The DOE is wrong too. The point is if
it's easier to make something safer and easier to work on by not
sharing neutrals, and it only costa a few extra bucks, some of us would
prefer to do it that way. This is like arguing that hydrogen
dirrigibles are safe, you just have to keep them away from lightning
and use them properly.





And
this is for industrial settings, where you can expect skilled workers,
not the average home, where Joe homeowner may be changing a switch.

If it's been properly installed (using a two-pole breaker) it doesn't make any
difference whether the guy changing the switch is "Joe Homeowner Who Barely
Knows What He's Doing" or "Joe Licensed Electrician with Forty Years
Experience in the Trade" -- flipping *one* breaker kills the *entire* circuit,
just the same as with a normal 120V circuit.

Now you could say, but that's because they were not properly
identified.

No, it's because they were not properly *installed*, with a *single* means of
disconnecting *all* of the hot conductors. And in at least one of the cases
cited in that report, the energized neutral was apparently due to an incorrect
connection to hot conductors -- improper installation again.


But why not just avoid it where possible all together?

You're certainly free to avoid it if you wish. But to advise others to avoid
it, on the basis of phantom hazards that you perceive largely due to your own
unfamiliarity with it, is not logical.


The hazards are not phantom, but real andl documented and recognized by
the DOE. But then you think they are wrong too.





--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

.

Relevant Pages

  • Re: Kitchen Wiring Problem
    ... than a 240V circuit for a stove or dryer. ... If a circuit is fed by a double-pole breaker and has two hot wires, ... They discuss that shared neutrals circuits pose unique dangers if not ...
    (alt.home.repair)
  • Re: Kitchen Wiring Problem
    ... The only double breakers I have ever seen in my homes ... homeowner what an edison circuit or shared neutral is, ... non-Code-compliant overfilled box into a compliant installation). ... They discuss that shared neutrals circuits pose unique dangers if not ...
    (alt.home.repair)
  • Re: Flickering Lights and Buss Arching
    ... off (the breaker never tripped). ... some arching ocurring in one of the terminals on the neutral buss bar. ... turned off the circuit in question, and the arching and spark ceased. ... Is it OK for neutrals and grounds to share the same terminal on the ...
    (alt.home.repair)
  • Re: Possible causes of "blown" electronics
    ... house neutral or neutral an individual circuit?) ... Loose or lost house neutral would still leave all the ... individual neutrals connected at the neutral bus.......and the return ... The neutral could be loose on your side of the meter base, ...
    (alt.home.repair)
  • Flickering Lights and Buss Arching
    ... some arching ocurring in one of the terminals on the neutral buss bar. ... turned off the circuit in question, and the arching and spark ceased. ... Is it OK for neutrals and grounds to share the same terminal on the ...
    (alt.home.repair)