Long lighting runs

[rotortuner]

Here’s the deal my shop is a good sized building and I am starting to run some lighting. Will have about 11 amps on each circuit. From the panel to the switch is about 65ft. Then from the switch to the last light is about an additional 100ft. 165ft total. Planning on using 12/2. I have looked up tables and seams like I’m close to max length. My only other option would be to run a 50a sub panel over next to the switches. Thoughts?

 

[Shiftless]

Relax...you’ll be fine.
Realize that all of the current won’t have to flow the whole 100 feet. Your fixtures are spearhead out along that length, right?
Even if you had all 11 amps at the very end of the 165 feet, your voltage drop would be minimal.

 

[rotortuner]

Spaced every 12’ starting at 110’.

 

[Shiftless]

Spaced every 12’ starting at 110’.

What is the amp draw of each fixture and how many of them are you putting up?

Six fixtures at about 2 amps each?


I would yield to an electrical engineer on this, but from what I can figure, your voltage drop should be tolerable...maybe 5% at the one furthest away.

If you really want to know the exact numbers you have to calculate the voltage drop at the fixture that’s first in line and then use the remaining voltage for the calculation for the run to the next fixture and so on until you get to the last fixture.
If somebody wants to do this after the OP gives the specs, go right ahead. I’m gonna stand on my approximation.

I don’t know what effect that would have on your lights but if you’d rather have 2-3% voltage drop, go with 10ga. Personally, I wouldn’t do that. Even if you use 6 ga. you’ll still have more than 1% voltage drop.

 

[rotortuner]

I’m probably just going to go for it.

5 lights each at 2.2a 12ft apart. Last one at 160, then 148, 136, 124, 112. They are LED indoor fixtures.

 

[nh_yota]

I wouldn't lose sleep over it. Lights are not as sensitive to voltage drop as motors.

 

[u2slow]

Probably overkill for LED, unless you need 2 circuits.... but I like doing a MWBC alternating which hot leg the fixtures are on. Then you have a balanced load, and figure your voltage-drop on 240V math.

 

[ard]

could homerun the 110ft using #10. running a sub panel for lights seems nuts.

If you run the VD on 110@12A; 120@10; 130@8 etc, there is a surprising stack up.. could be 5%+

 

[Bert_]

Probably overkill for LED, unless you need 2 circuits.... but I like doing a MWBC alternating which hot leg the fixtures are on. Then you have a balanced load, and figure your voltage-drop on 240V math.

Multiwire is great for stuff like this.

 

[ard]

Multiwire is great for stuff like this.

FWIW- I ran 12/3 to all my lights in the shop, with two switches, one for each 'leg'. They were 'banked' with each switch controlling half of the room.

But when I wired up directwire LEDs to my fluorescent housings, I was able to run one bulb in each housing on a leg- so one switch lights the whole shop at 50%, the other at 100%