Wire Size / Pipe Size Help

Old 04-09-13, 12:41 PM
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Wire Size / Pipe Size Help

I have a garage that is 24' wide by 110 long.

Installing 20 Metal Halide 400W Multi Tap Fixtures.

I can go either the 110vac (4amp) or 208vac (2.4amp) / 220vac (2amp) route (need to throw a meter on it to get correct voltage).

Plan to run a large main run of EMT down the one side of the garage and run the 10 branches off of each one every 10'.

Going to split these into 4 separate breaker circuits. Every other light will come on when energized. See below: East Row Circuits #1 , #2, West Row #3, #4

lMain EMT Tubing running along this wall to supply all 4 circuits l
l l
l #1 #2 #1 #2 #1 #2 #1 #2 #1 #2 l
l l
l #3 #4 #3 #4 #3 #4 #3 #4 #3 #4 l
l l

So, what should the main size tubing be along the East Wall ?

What wire gauge should be used on the main line along the East wall to supply all of the lights ? (total load at 208vac is 12.5amps each circuit) Total length from Breaker to furthest branch is 120'.

What wire gauge for each branch circuit ? (1 fixture on each branch - farthest length is 15')

My guessing would be 1" mainline EMT with 10awg main line wiring.
1/2" EMT with 12awg to each fixture (is this over sized for 15' run ?)

Thanks in advance.....Chucker
Old 04-09-13, 07:53 PM
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I suggest to run them all on 240 volts, to keep the current lower. That will keep each circuit to 10 amps each. Even at 208 volts you would still only have 12 amps. (208v is not normally found in residential) You could use #14 THHN and 15 amp breakers, but if you want to give yourself a little wiggle room, then run #12 and 20 amp breakers.

This will mean you will have 8 wires total, 2 for each group of lights. You could run this fine in 1/2" EMT for the entire run (both #14 and #12), but if you want, you could bump it up to 3/4" for the home run. #10 wire and 1" is way overkill.

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