On Mon, 13 Aug 2007 17:19:43 GMT, (Doug Miller)
wrote:

In article , "no spam" wrote:

Personally, when it comes to wiring bigger IS better.

Nonsense. Except on very long runs, bigger wire provides no advantages at all,
and does provide significant disadvantages:
a) higher cost
b) greater difficulty in installation
c) difficulty in finding compatible receptacles (for example, try finding a
15A rated receptacle that will accept AWG8 wire)
d) the larger the wire, the fewer of them the Code allows you to put in a box.

Even more so when it
comes to a workshop. I'm looking at building a new home in a few years and
if I can afford it I will 'over wire' the entire house for a couple of
reasons. First, look around your house now and think about how it looked 10
years ago. How many more electrical items do you have now? How many more
might we have in 10 more years?

This purpose is achieved much more easily, and at considerably lower cost, by
keeping the wire size the same and increasing the number of circuits.

Second, its much more difficult to have an electrical fire if you wire a 20
amp breaker with wire that will carry 40 amps or so.

Nonsense again. The risk of electrical fire is not significantly greater using
AWG12 wire on a 20A breaker, compared to using AWG8 -- and in fact, you'd
probably be creating a substantial risk of fire by attempting to connect a
standard receptacle to conductors that are too large to fit under the screw
terminals. Sure, you can pigtail the connections -- let me know when you're
getting ready to wire up those receptacles. I want to come watch you stuff
the wires back in the box; I could use a few laughs.

And then I'll phone the local electrical inspector. "Wire that will carry 40
amps or so" is AWG8 or larger. You might want to consult Table 314.16(A) in
the NEC to see how many AWG8 conductors the Code allows you to put in a
standard device box. (Hint: except with the largest device box available, it's
not enough to supply a receptacle -- and forget about feeding through to
another receptacle, or using anything larger than AWG8.)

Third, if you need to 'upsize' later its a lot easier to just put in a
larger breaker than putting in new or more wire.

Nonsense yet again. What, exactly, do you plan to "upsize" to, anyway? It's a
Code violation to put a 20A receptacle on a circuit protected by anything but
a 20A breaker. The larger wire serves no purpose at all.


#12 thhn cu wire is actually rated for about 35 amps. The
restriction to 20 amps is mainly based on the rating of the terminal
on the CB. You may use the higher ampacity ratings before taking your
derating but still can't have over a 20 amp breaker.

Mike M

In article , Mike M wrote:

#12 thhn cu wire is actually rated for about 35 amps.

30A, actually.

The
restriction to 20 amps is mainly based on the rating of the terminal
on the CB.

That's part of it, but not the only reason. 10, 12, and 14 gauge wires are the
sizes most commonly used in residential circuits. The allowable overcurrent
protection is set by the Code at a value significantly under the actual
ampacity of the wires to reduce the risk of fire from overloading a circuit.

You may use the higher ampacity ratings before taking your
derating but still can't have over a 20 amp breaker.

Which means that the higher ampacity ratings are, for all practical purposes,
irrelevant. :-)

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

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

On Sat, 18 Aug 2007 13:36:19 GMT, (Doug Miller)
wrote:

In article , Mike M wrote:

#12 thhn cu wire is actually rated for about 35 amps.

30A, actually.

Shows how bad my memory is getting.

The
restriction to 20 amps is mainly based on the rating of the terminal
on the CB.

That's part of it, but not the only reason. 10, 12, and 14 gauge wires are the
sizes most commonly used in residential circuits. The allowable overcurrent
protection is set by the Code at a value significantly under the actual
ampacity of the wires to reduce the risk of fire from overloading a circuit.

You may use the higher ampacity ratings before taking your
derating but still can't have over a 20 amp breaker.

Which means that the higher ampacity ratings are, for all practical purposes,
irrelevant. :-)

This is true for residential work generally, but in commercial work
where you might be derating for continuous load, number of conductors
in pipe, as well as ambient temperature it can make a difference.

Mike M

since my first posting a few weeks ago I have contacted an electrician
who than decided not to show up. I than decided to do the wiring
myself and am happy to say that it is complete and inspection passed.

I would like to thank all posters who threw their 2 cents in.

Jim



On Fri, 10 Aug 2007 14:19:22 -0700, wrote:

In recent posts I have heard mention of 12/2 and 10/2 wire, as well as
12/3 and 10/3 wire. What is the difference and what would you wire a
new shop with?

I assume the 12/2 and 10/2 mean with ground.? What is the extra wire
in the 12/3 and 10/3 for? Is that for wiring 220V?

Jim

Just a quick note about the progress of my garage. Since the first
post I have contacted an electrician, who decided not to show up. I
thus decided to do the wiring myselft. With the advice from this post
the wiring is finished and passed inspection. I want to thank all who
have thrown their 2 cents in helped me accomplish this part of my
project.

Thank you.

Jim

On Fri, 10 Aug 2007 14:19:22 -0700, wrote:

In recent posts I have heard mention of 12/2 and 10/2 wire, as well as
12/3 and 10/3 wire. What is the difference and what would you wire a
new shop with?

I assume the 12/2 and 10/2 mean with ground.? What is the extra wire
in the 12/3 and 10/3 for? Is that for wiring 220V?

Jim