sub-panel in 60ft garage

[pjb153]

My question is really two parts.

My neighbor is getting ready to wire his 60ft x 40ft garge/shop. He will need a bunch of 240 power for the welders and lift, but for the normal lighting.. do you think he should run 12 g wiring or save the extra money and wire the lighting with 14 g? The spans are long, especially running from the panel to the other side of the garage. but..

I mentioned to him it might be cheaper to wire a 100 amp service, then run a sub-panel to the other side rather than span the length with a bunch of wire.

 

[Charles (in GA)]

I have a 60x60 steel building. Everything is run from one 200 amp/40 circuit panelboard, except for a sub panel put in at the compressor that, at present, only runs the compressor.

There is not much difference in the price of 12 vs 14 gauge wiring and using 12 gave some flexibility in what the circuit is used for in the future. Some locales do not allow 14 gauge at all.

Charles

 

[trainer]

It depends on now much your particular fixtures draw, but generally 15 amp circuits with 14 ga. wire are sufficient for lights.

You'd need to do the math on pricing to see which option for the panels are cheaper. If all else was equal, or at least close, I'd go with one panel to keep things simple.

 

[pjb153]

Thanks.. I think using 14 g is best, considering the cost difference is not that great between the two.

A second smaller sub-panel might be the way to go to save on wire. If you figure at least three circuits for overhead, workbench, side wall lights. thats 60ft + 20ft up each wall x 3. it could add up fast.

 

[logical]

I doubt the wire savings (if there even really would be any) could possibly offset the cost of establishing a sub-panel. You still have to get from the new panel up and over to the lights. The cost of 60 feet of #6 wire, a 100 amp breaker and a panel would buy a lot of 14-2 Romex and you wouldn't have to guess which panel to walk to when a breaker goes.

The 14 vs 12 wire for lights is strictly about how may lights of what size are on each circuit. Often, it's cheaper to limit it to 15 amp circuits to allow buying cheap 15 amp rated wire, switches, breakers.

 

[sparky1562]

I would just go with 15 amp lighting circuits. You would have to have more than 36 40W flourescent lamps (for example) to max out the circuit and #14 romex is so much easier to mess with and terminate. I would save the #12 for power circuits. I too would just run them out of the one panel. No need for a sub panel.

 

[logical]

For loading on a 15 amp circuit I figure as follows. Lighting is a continuous load, so the circuit can only be loaded to 80% or 12 amps. 40W fluorescent lamps, well that is the rating of the lamp, you need to use the load of the ballast, which is about 50W for a 40W lamp. So the maximum number of 40W fluorescent lamps on a 14 amp circuit would be 24 or 12 2-bulb fixtures.

Which would likely be at least half his shop.

 

[sparky1562]

40W fluorescent lamps, well that is the rating of the lamp, you need to use the load of the ballast, which is about 50W for a 40W lamp.

Actually, assuming electronic ballasts which is the standard these days, 2 40 watt lamps on an electronic ballast only pulls about 71 watts, depending on the specific ballast. For 2 32 watt T8 lamps, it can be as low as 63 watts.

50 watts is safe, but you might be leaving some capacity on the table!

 

[Mr_fixit]

That's a big building. I'd use a sub panel and definately 12 gauge for lights.

I have a 42' building with a main & sub, the sub is at one corner of the building, the other panel almost at the other end.

For me , I'm still adding receptacles, lights & welder plugs, & other stuff 10 years later.
Maybe you're a better planner.....

 

[sparky1562]

For me , I'm still adding receptacles, lights & welder plugs, & other stuff 10 years later.
Maybe you're a better planner.....

Not me! I seem to rip circuits out and re-route them as soon as I get them installled! I put a little 4 ciruit 60 amp panel in the barn, ripped it out 4 months latter and put in a 12 circuit. Put a 200 amp in the garage 2 years ago and just reworked my welder outlet, my compressor outlet and all the light switch circuits. Seems I ran those wires across the 5 standard trusses that I just cut out and replaced with sissor trusses! Go figure...