I believe the wire is rated at around 600V.

The question is what Voltage should I set the Hi Pot tester to and why. �The
other end of the Hi Pot tester will connect to the conduit.

Thanks

After reading the posts I would like to know the current and voltage
ratings of the contactor coil.

18 guage is small for 800 feet with the usual current requirements for
a contactor. With #18 wire and 24VDC you can sink only 1.33 Amps. And
for practical purposes your contactor current is limited to .13 amps.
More than this the voltage across ther contactor coil will be too low
for reliable operation. Not enough current for the contactor.

If you can't replace the wire with 16 or 14 use a transistor as a
driver/switch at the contactor to make the 18 wire a signal conductor
instead of a switch leg. Use the 24VDC for Vcc on the transistor.
There are also Solid State Switch packages for this.

Most technicians should be able to wire this up with no problems with
the switches, connectors and wire. Your switches do need to be
selected for this. Are your switches rated for DC?

Your momentary "short" in this case may be a result of the component
activity consisting of the L of the coil and the RC of the wire and
the conduit. Possibly caused by spiking from an external source. A
diode across the contactor coil will minimize this. 800 feet is a long
way for #18 wire.

My best philosophy at 12:23 AM!

Bob AZ