Tandem T8 lights.......Will this work?

[robertwhite]

I am about to run my lights in the shop (24x90) and was planning on doing 2 separate banks (left & right). I pulled 2 separate 12/3 stranded sets of wire and the plan was to use one 12/3 hot wire for lights (6 T8 eight footers on each bank) and the other for outlets on the left side. Then repeat for the right side.

So I see that the only tandem 4ft light (96" total) readily available is from Home Depot made by Lithonia. However at $60 each, they are a lot more expensive than buying 4ft lights ($20), hanging cord end to cord end and just plugging them into a ceiling outlet (need the outlet regardless).

Then when I realized that the bulbs were 32 watts, and I multiply 32w x 24 bulbs (12 lights, 2 bulbs each) I get 768 watts. I then divided the 768w by 115v to get 6.7 amps.

Being that a whole bank of lights is less than 7amps, could I then just continue my wires to the other bank and tie them all into a single circuit? Lighting circuit would be 768 x 2 = 1536watts divided by 115v and I come up with 13.35amps which is still less than a normal 15 amp breaker and certainly less than a 20amp breaker.

That would leave me with both leads of the second set of 12/3's to do as I please on the far side of the shop. (receptacles, etc).

Possible or NFW?

ETA: I need the lights to be reflector type, not strip as my ceiling is 15'

 

[Charles (in GA)]

24x90, you don't have a shop, you have a bowling alley!!!

You need to look at the actual amperage listed on the placard/decal on the fixture. The fixture will consume more current than the wattage of the bulbs. Not much on the newer electronic ballast, but some more.

The corded $20 lights most likely have to be hung from the chains and cannot be installed hard up on the ceiling due to heat/fire considerations. The fixtures instructions will tell you if you can mount them directly to the ceiling.

You really do not want to push the wattage draw of a circuit beyond 80% of the circuit/breaker capacity. Anything which is operated normally for over 3 hrs is considered continuous and thus is restricted to 80% of breaker capacity. Thus on a 15 amp circuit, you should not exceed 12 amps, and on a 20 amp circuit you should not exceed 16 amps.

Charles

 

[robertwhite]

Thanks Charles. Sound advice.

I do have a bunch of the same lights in my loft. I will have to check the sticker. As for hanging them, it will be suspended so that is just fine.

In thinking about what you said, it just makes more sense to go with the original 2 bank method.

Thanks for the help.