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X ` Man

On 10/4/11 6:11 PM, wrote:
On Tue, 04 Oct 2011 15:59:50 -0400, X `
wrote:

I'm thinking of upgrading to a larger standby generator, probably a 17KW
model.

The generator will be approximately 50 to 60 feet away from the house
circuit breakers. The wire will run under the main level floor and above
the lower level ceiling.

I want as little current drop as possible. The generator provides
100 amps.

One of the contractors under consideration wants to use aluminum wire,
but I am more than willing to pay the premium between aluminum and
copper. I don't have an electrical "handibook" available.

What I am wondering:

1. Is 4/0 copper wire heavy enough?

2. Anyone know a supplier for about 70 feet of the stuff?

Our local electrical suppliers don't seem to want to provide a length
that short.

Thanks.

P.S. I'm really only interested in replies from those with an
educational or professional electrical background.

1/0 should be plenty, That will drop about 1.5v or about a 0.6%. I
would even consider going with #1, dropping 1.8v, still under 1%.

You also have to remember you are not really going to be using a
constant 100a (or you really need a bigger generator) so those V/D
numbers are conservative.

What you are looking for is THWN, usually dual listed as THHN/THWN.
Any electrical supply house will have it and you can usually get it at
Home Depot, depending on how many pros shop at yours.
That will go easily in 2" Rigid Nonmetalic Conduit (the gray stuff).
You can get it in smaller pipe but the pull is harder. The ungrounded
conductors (2) and the neutral (1) will be full sized but the green
wire ground can be smaller. It will be sized based on which wire you
selected for the ungrounded conductors.
If you went with the minimum size (#3 if you can find it or #2) the
ground can be #8.
As you adjust for voltage drop, the ground has to get bigger too.
Anything up to 2/0 copper will be a #6 and the 4/0 you are talking
about needs a #4

Whether you bond the neutral in the generator will depend on what kind
of transfer switch you buy. If you switch the neutral, you bond the
neutral in the generator (AKA a separately derived system).
If the neutral is not switched in the transfer equipment, you do not
bond it at the generator .... but that union master electrician you
hire should know this ;-)

Thanks. Of the three contractors I've "interviewed," one is a union
shop. Very few union shops do homeowner electrical or plumbing work in
"these here parts." All the shops claim to use licensed master
electricians.

Fortunately, we have a 500 gallon LP gas tank buried in the back yard.
The gas supplier's master plumber will do the connect to the genny for
$200.

--
I'll believe corporations are people when Texas executes one.