On Sun, 6 Jul 2008 08:27:03 -0500, "Karl Townsend"
wrote:

OK, everybody, you sold me. I'm going to go ahead and replace both the power
wire and the signal wire in conduit at this time. My ONLY reason is Milady
turns from her normal saintly self into Mrs. Hyde when there's no water in
the house. And, its *SURE* to break either in mid-winter or during harvest
season. Lord willing, I hope to live here another 22 years.

Question 1: The well is 5 horse and 450 feet from the main circuit panel.
What size wire is needed? Both for power and the signal wire. Does the power
ground need to be as large as the two main conductors?

For the power wire you need BIG wire to avoid voltage drop and keep
the pump motor happy for a long time - but there are a few other
questions before I can answer. Is the pump 240V or 480V? 1Ph or 3PH?
FLA? How deep is the pump, and did they oversize that line?

This is one of the few times I will say to go with aluminum wire,
because even though you have to oversize it yet another couple of
gauges the stuff costs a whole lot less. And because they probably
did not oversize the leads from the control box down to the pump, you
want "ridiculous overkill" going from the panel to the wellhead.

And you can go a lot smaller on the ground (two gauges under the
normal conductor size, not counting voltage drop) since it doesn't
carry current under normal conditions - it only has to carry fault
current long enough to trip the breaker. And the well casing is a
huge ground rod, so if everything is bonded together properly there is
another good ground at the far end.

If the signal wires are running at 120/240V from the same supply
panel (but a different breaker!) you can run them in the same conduit
as the power leads, and the #12 THHN/THWN/MTW would be fine for that.
You are only pushing 1/4 amp to pull up the contactor at the far end.

Question 2: Is there any problem with using 100' black plastic coils of
water pipe for the conduit? I have a bunch going to waste.

Yes, there is a problem - mis-identification of services that could
have a FATAL outcome. You decide you need to make a tap to irrigate a
new row of trees, and you (or a farm hand) dig up a promising looking
black poly water line that you think is an irrigation line, Get out
the Sawzall and chop it in two... _


But the grey PVC conduit makes them stop and think "Hey, this isn't
a water pipe - it's the wrong color. Water pipes are white..."

The ONLY time I'd use water pipe for something else is for low
voltage services like security cameras, telephone, data, etc. And
either spray paint it before you bury it or put the "Caution Buried
Telephone Line Below" flagging tape above it in the trench. Or both.

So when they find the orange pipe or the flagging tape, they think.

One other use would be to pull through the 1/2" size Poly pipe as a
"sub-duct" for the control wires, when you pull the 2/0 AL power wires
through the 4" grey PVC power conduit. Then you can replace the #12
wire later if it goes bad or you need more leads, without getting
stuck between the big wires.

If it's inside the grey conduit, external ID is not a problem.

And run pull rope through at the same time, for the same reason -
you can't get a fish tape through later (with wires in the conduit) to
replace bad signal wires without a hell of a fight. Without a rope
you have to pull it all out and all back in.

-- Bruce --