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# Electrical Wiring FAQ (Part 1 of 2)Section - A word on voltages: 110/115/117/120/125/220/240

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```
One thing where things might get a bit confusing is the
different numbers people bandy about for the voltage of
a circuit.  One person might talk about 110V, another 117V
or another 120V.  These are all, in fact, exactly the same
thing...  In North America the utility companies are required
to supply a split-phase 240 volt (+-5%) feed to your house.
This works out as two 120V +- 5% legs.  Additionally, since there
are resistive voltage drops in the house wiring, it's not
unreasonable to find 120V has dropped to 110V or 240V has dropped
to 220V by the time the power reaches a wall outlet.  Especially
at the end of an extension cord or long circuit run.  For a number
of reasons, some historical, some simple personal orneryness,
different people choose to call them by slightly different numbers.
This FAQ has chosen to be consistent with calling them "110V" and
"220V", except when actually saying what the measured voltage will
be.  Confusing?  A bit.  Just ignore it.

One thing that might make this a little more understandable
is that the nameplates on equipment ofen show the lower (ie: 110V
instead of 120V) value.  What this implies is that the device
is designed to operate properly when the voltage drops that
low.

208V is *not* the same as 240V.  208V is the voltage between
phases of a 3-phase "Y" circuit that is 120V from neutral to any
hot.   480V is the voltage between phases of a 3-phase "Y"
circuit that's 277V from hot to neutral.

In keeping with 110V versus 120V strangeness, motors intended
to run on 480V three phase are often labelled as 440V...

```

## User Contributions:

Dev
Dec 21, 2011 @ 12:00 am
In a fire protection circuit, circuts are shown witha no example 6,8,4etc. what it mean?these circuits are connected between smode detector,junction box etc
kevin
Dec 24, 2011 @ 12:12 pm
My daughter dropped a small necklace behind her dresser. The necklace crossed a plug terminal and shorted the receptacle.
I bought a new receptacle and installed the same. I still have no power I suspect there could be a bigger problem,this is aluminum wiring.
I've killed the breaker and call an electrician but am curious as to what happened.P.s. there is a dimmer switch on the same circuit.
dennis
Feb 24, 2012 @ 11:11 am
Regarding new construction wiring and running 12/2 and 14/3 wire in the same box.

I have multiple switches to lights. Ran 12/2 and 14/3 into switch box and inspector wrote correction needed.

What should I have done instead?

thank you
dennis
Robert
Nov 26, 2012 @ 9:21 pm
Does a grounding electrode facilitate the operation of a OCPD, to clear a ground fault ?
@dennis
Mar 18, 2013 @ 10:10 am
Assuming you are installing two switches in a two switch box, you probably should have used 14/2 and 14/3 instead of replacing 14/2 with 12/2. If you are only installing one switch in a one switch box, you should only have one cable in the box.
P k
Jan 26, 2014 @ 10:10 am
I prefer to use nothing smaller than12 awg /the smallest sized wire on a circuit determines the allowable ampacity
Ex: 15 amp-14awg. 12awg-20amp only rule for thumb other factors such as continuous load,heating and others if you do not know the safe NEC rules then please call a qualified journeyman Electrician better be safe

Top Document: Electrical Wiring FAQ (Part 1 of 2)
Previous Document: My house doesn't meet some of these rules and regulations. Do I have to upgrade?
Next Document: What does an electrical service look like?

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Last Update March 27 2014 @ 02:11 PM