Correct ground and wire sizes for 100A subpanel

[-G.]

How did you get #1 wire into a 100 amp breaker?

You should run 3- #4 insulated wires for your 2 hots, and neutral.
Outside of the conduit, run a #4 solid copper ground wire. In the sub
panel, ground and neutral must be separate. There should be no bonding
of the ground and neutral in the sub panel.

You say: " I looked it up, and it looks OK,"
If I were you, I'd throw that book away.

qje...@nospam.noedencity.com wrote:

> I've got a subpanel fed by #1 gauge wire from a 100 amp
> breaker through 10 feet of plastic 2" conduit. It has a #8
> gauge wire insulated ground connected back to the main
> panel. I'd like to doublecheck the sizes of the wires and
> particularly the ground. Can anyone confirm that this meets
> code? I looked it up, and it looks OK, but I'd like a
> doublecheck.

--
Just _Don't_Say_ Just!

[zxcvbob]

qje...@nospam.noedencity.com wrote:
>
> I've got a subpanel fed by #1 gauge wire from a 100 amp
> breaker through 10 feet of plastic 2" conduit. It has a #8
> gauge wire insulated ground connected back to the main
> panel. I'd like to doublecheck the sizes of the wires and
> particularly the ground. Can anyone confirm that this meets
> code? I looked it up, and it looks OK, but I'd like a
> doublecheck.

I assume we are talking copper wire here.

The ground needs to be #4 or larger. It could also be argued that you
need #1 wire for the ground because that's the size of your largest
ungrounded conductor. But since you have 100A overcurrent protection
you should be OK with #4.

The #1 wire for the hot conductors is OK but a big overkill. Contrary to
what someone else has told you, use stranded wire for the ground. It is
a lot easier to run through a conduit. I *think* the NEC prohibits
solid conductors larger than #8 in a conduit. But I reused the old
service entrance conductors to supply a feeder circuit to a subpanel in
another building when I rewired my electric service and the inspector
didn't mind that the grounded conductor of the old wiring was #6 solid
wire in a conduit.

Why did you use such a large conduit? 1" would have been plenty big.

HTH :-)

Bob

"Now just in case I'm incapacitated for some reason, do you know how to
start a man's heart with a downed power line? Well, there's really no
*wrong* way to do it." -- Hank Hill

[Speedy Jim]

Art. 250-95 says the Equipment Ground (what he has)
need only be #8 Cu for 100 Amp OC protection.
Jim

[zxcvbob]

Thanks for looking it up, I was going from memory. Shame on me!

It sounds like whoever wired it up originally did it right, and they
used #1 for the hot conductors because it was handy, or they had some
short pieces to use up.

Best regards,
Bob

[Gene S]

Why not run the ground with solid copper - "outside"
the 2" pipe?

--
E-mail: ge...@thegateway.net

"zxcvbob" <b...@a51web.net> wrote in message
news:3BD828B7...@a51web.net...

[zxcvbob]

I think Jim just confirmed it.

Best regards,
Bob

qje...@nospam.noedencity.com wrote:

>
> zxcvbob <b...@a51web.net> wrote:
>
> >It sounds like whoever wired it up originally did it right, and they
> >used #1 for the hot conductors because it was handy, or they had some
> >short pieces to use up.
>

> Can anyone confirm that the use of stranded #8 Cu for the
> ground in the same conduit was OK?

>
> >
> >Best regards,
> >Bob
> >
> >
> >Speedy Jim wrote:
> >>
> >> Art. 250-95 says the Equipment Ground (what he has)
> >> need only be #8 Cu for 100 Amp OC protection.
> >> Jim
> >>

[snip]

[Speedy Jim]

Art. 250-91(b): (slight editing)
The equipment grounding conductor run with {} the circuit conductors
shall be {}:
(1) a copper or other corrosion-resistant conductor.
This conductor shall be solid *or* stranded; insulated, covered, or
bare...

Jim

qje...@nospam.noedencity.com wrote:
>
> zxcvbob <b...@a51web.net> wrote:
>

> >It sounds like whoever wired it up originally did it right, and they
> >used #1 for the hot conductors because it was handy, or they had some
> >short pieces to use up.
>

> Can anyone confirm that the use of stranded #8 Cu for the
> ground in the same conduit was OK?
>
> >

[Tom Horne]

> Why not run the ground with solid copper - "outside" the 2" pipe?
>

Because the National Electric Code requires that the ground be run with
the conductors vis.

"Types of Equipment Grounding Conductors. The equipment grounding
conductor run with or enclosing the circuit conductors shall be one or
more or a combination of the following: (1) a copper or other
corrosion-resistant conductor. This conductor shall be solid or
stranded; insulated, covered, or bare; and in the form of a wire or a
busbar of any shape;" ... (C) NFPA

There are some exceptions for short lengths of flexible raceways were it
is not practicable to run the equipment grounding conductor inside the
raceway but they do not apply to the installation as described.
--
Tom

[Calvin Henry-Cotnam]

Speedy Jim (vo...@nls.net) said...

>
>Art. 250-95 says the Equipment Ground (what he has)
>need only be #8 Cu for 100 Amp OC protection.

I was going to say #6 Cu, as the CEC says that size is needed for
bonding a 100 A service. If the NEC has a specific article covering
this situation, then I would use it (though, you couldn't go wrong
with the #6 unless it puts your conduit fill too high!)

--
Calvin Henry-Cotnam | "Nothing quite livens up a suburban
DAXaCK associates | neighbourhood like a driveway boasting
Richmond Hill, Ontario, Canada | plastic milk crates loaded with crap."
http://home.ica.net/~calvinhc | -- John Oakley, radio talk-show host
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[Calvin Henry-Cotnam]

-G. (anim...@yahoo.com) said...

>
>How did you get #1 wire into a 100 amp breaker?

Square D QO 100 A breakers, according to their technical spec sheets,
have terminal lugs that can accept #14 to #1 Cu.

I can't comment on other breakers, but I suspect similar ratings.