I want to mount a light and receptical on a 2X6 Pressure treated post
at the end of my property. The distance is about 150 feet. I want to
mount a 500 watt three way Halogen light that can be switched on at
the light post itself or up at the house. I also want a receptical
that will be mounted on the same pole as the light that will be always
hot regardless of the switch state on the light. Power will be coming
from the house. I will be running the wire in 3/4 conduit that is
already in place. My questions are as follows:
How many wires need to be run through the conduit?
What gauge should I use considering the length of the run and the
Since I will probably need to use the colored stranded wire (as
opposed to Romex) what is the proper colors to run in this situation.
1 Always Hot. (goes to hot on plug, plus common terminal on switch)
I'd go with 12 gauge myself. Your best friend here is a voltage drop
table. (do a google search on it)
Since the wiring is in underground conduit it will have to be rated for
wet locations. All underground raceway systems eventually get water in
White for neutral. Black, red or blue for the hot and switched wires.
Green for ground.
Personally, I'd use black for the always hot conductor, and red or blue
for the two switched hot conductors. You could also run all black for your
hots and just use colored tape (red or blue) at the ends to mark what is
Not to be talking to myself, but I shouldn't have said the always hot
goes to the common terminal on the switch. It shouldn't. The common
terminal of the switch on the pole should go to the light.
Essentially you're running an extra conductor (The always hot one) just
for the sole use of the plug.
firstname.lastname@example.org (David Jensen) wrote in
5 wires minimum - 1 ground, 1 neutral, 2 3-way switch travellers and 1
constant hot. Power would be run to the inside switch before heading
Be careful not to overfill the conduit or run these wires with low
voltage wires in the same conduit.
You didn't specify what will be powered off of the receptacle. There's
information at this site about voltage drop calculations:
In particular, this page:
If I were doing it, I'd probably use 12 gauge for a 15 amp circuit and 10
gauge for a 20 amp circuit. I doubt upsizing is strictly necessary,
however. The distance isn't that great.
Green, white, black, red and blue would be one good combination but
green, white and 3 blacks would also be OK if you keep the blacks
straight by marking them with tape or something.
If the conduit is PVC, 5 wires will do it. (1) equipment grounding
conductor (must to be green), (1) "neutral" (must to be white or gray), (1)
"hot" (any color except green, white, or gray), and (2) travelers (any color
except green, white, or gray).
A 15 amp load on a #10 wire would put about 114 volts at the receptacle.
I just did a similar install at my lake house, only I included a light over the
garage, 2 post lights along the driveway, then the 3rd post light near the
street. Each (except the light on the house) has an always-hot outlet, and the
the street side post light has the 3-way. You need 5 wires in PVC.
Used a neutral, ground, a hot traveller, switchleg traveller and the common
Black - Always hot for the recepticle
White - Neutral
Bare - Ground (could be green if you prefer)
Red - "Traveler" for the 3-way switch
Black - "Traveler" for the 3-way switch (I don't know if it would be a code
violation to use a different color, blue maybe, to distiguish
between the always hot black wire?)
14 gauge is adequate for 500 watts, but I'd probably use 12 gauge
considering the distance you have to run.
Be sure to use a weather proof switch and recepticle out at the post.
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