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[email protected] pawlowsk002@gannon.edu is offline
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Default Outlet wiring, does color matter?


wrote:
When wiring up normal 3-prong outlets, does it matter if I switch the
black and white wires on a single outlet in the run?

I've heard the polarity doesn't matter...but want to make sure I'm not
going to short it out or something else horrible.

Also, when wiring up lights, does it matter which color wire I run to
the switch? Most of the how-to articles show cutting the white
wire...does it make any difference?


kj:

The black wire (which can be any color, actually, except white) is the
'hot'.
The white or 'natural gray'-insulated wire is the 'neutral'. Think of
the 'hot'
as a permanently pressurized 'pipe', and the neutral as a 'drainpipe'
which
only carries electricity when the 'faucet' (switch, appliance, etc) is
using
it.

Now, lights and other plug-in appliances are designed so that the 'hot'

is less accessible than the 'neutral'. Ex.: the bulb 'shell' is
connected
to the white 'neutral', and the contact at the socket bottom is 'hot'.

This ensures that if somebody is removing a dead bulb with the light
switch
still on (for instance) and brushes against the shell, they are
unlikely
to get a shock (unless something else is wrong with the wiring). If
the
hot and neutral are reversed, this shell would be connected to the
'supply pipe' and not the 'drain pipe', and the user would be shocked.
(Note that it is still possible to get shocked by a neutral, but it is
less
likely).

Moral of the story: Safety dictates that hot and neutral must be
properly
connected. Follow the manufacturer's directions. If for some reason
it's
easier to do it the wrong way, that's too bad. Do the job right.

Now for switches. Switches must always control the 'hot' side of a
circuit,
cutting off the 'supply pipe'. That way, with the switch off, the only
unbroken
connections (if the light is properly wired) are to the 'drainpipe',
the neutral
side. When a switch is in the neutral it will still stop current from
flowing;
the light will turn on and off with no problems. However, even with
the
switch off, all terminals and wires in the lamp will be 'hot', part of
that
pressurized pipe of electricity, waiting for somebody to provide a path
to
ground. ZAP.

Moral of the story: Switches must be in the 'hot' wire, never the
neutral.
This is a common problem in old houses, where some damfool cut off
and reconnected an old K&T run (where the conductors may be hard
to tell apart) without bothering to check which was which.

There is one situation where you may find a white wire on a switch.
Power may go to a lamp or other switched outlet,then out to a switch
and back to the outlet on the two conductors of one cable. This is
known as a 'switch loop'. If you find a switch with only one
2-conductor cable coming into its box, and something goes on and
off when you flip it, you are definitely dealing with a switch loop.
In
a switch loop, all wires are considered 'hot'. If using cable, code
allows
the white wire to be used as part of a switch loop, but it is not a
neutral, is not connected to any other neutrals, and must be
permanently
reidentified some other color where the wire is exposed inside the
boxes.

Story time. My brother found an (overstuffed) j-box with a
questionable
receptacle in it, in a basement. Removing the receptacle, he proceeded
to wirenut all whites and all blacks together, then turned on the
power.
All well. Then he flipped the basement light switch. ZAP. One of
the
white wires was actually part of a hacked switch loop. He had
created a bolted short. Unfortunately, the circuit was also part of an
absurd multiwire circuit (which split 6' from the service panel) which
was
equally hacked, with overstuffed boxes, insecure connections, and
puny wire nuts, and one leg of this circuit was overfused. Both
breakers
tripped. My brother, being sensible, switched off the offending
light,
and turned the breakers back on. Well, some lights went poof, and
the phone, and some other electronic gadgets, now acted really
funny in a not-working way. Apparently the neutral of the multiwire
circuit had failed somewhere. Rather distressed by this, he shut off
both breakers (I told you he had sense) and we later straightened
everything out. This involved replacing one 4" octagon box with two
4S boxes and eliminating such idiocies as the elusive "switch threep"
- one wire to the switch, one wire from the switch to each of two
boxes,
using two pieces of 12-2 with one wire unused. Ugh.

Moral of the story: learn what you are doing before you do it. There
are
good books out there. Get a permit and get your work inspected.
It costs less than burning the place down. Finally, don't use USENET
as your sole source, and definitely don't use the home center.
House wiring is not as simple as some think.

Cordially yours:
G P