lighting circuits...one or two?

[rvcoaster]

i have decided to redo my lighting circuits. i have redone every electrical run and box in the garage except for the lighting, and i am not happy with the lighting. originally i had just changed boxes and lefty the original layout but i think i have a couple issues with the existing setup.

1. i have an overfilled box; i dont know if its technically overfilled but it has too much stuff in it for my comfort.

2. i think i may be on the edge of running too much current on the lighting circuit.

garage is approx 24x30x9 and i have added ceiling insulation and OSB, am installing a furnace and plan on insulating and covering the walls soon. the way it is setup now i have one interior lighting circuit that also lights 2 of 3 exterior lights. the interior lighting is 7 duplex outlets in the ceiling feeding (for now) 6 2xt12 cheepy shop lites that will eventually be replaced with permanent T8 fixtures.

so for now i am not approaching current issues, but i plan on running 28 4' T8 bulbs in there when i am done. i'm thinking 32 watt T8 bulbs (not sure)? 2 or 4 per fixture.

should i have two 20A circuits for lighting? is my future plan too much for 1 20A circuit?

thanks.

 

[pattenp]

You need to determine the total number of fluorescent fixtures and style you are going to install. You then need to use the amp draw of the ballast in the fixture to figure the load. Do not use the watt of the tube to figure the load. Once you have your load, size your capacity at 125%. So as an example if you have 6 fixtures that draw a total of 12A you could get by with one 15A circuit. Your total load will determine the number of circuits and size needed.

 

[kbs2244]

You don’t say where you are located.
But if winter cold is an issue I would have a separate switch for some old fashioned incandescent bulbs for fast light.
(I don’t care what they advertise. Fluorescents take longer to get bright.)
It also give you quick light when you just want to run in and grab something.
You do not have to light up the whole place.

They also seem to cancel out the fluorescent “strobe light” effect that can make some power tools look like they are not running when they are.

I was glad to see the post that said the ban on them was not going to be 100%
They have a place.

 

[ForceFed70]

My experience (in Canada) is that good T8's light up damn fast even when it's really cold in the shop. I wouldn't bother with incandescent for this reason.

I wanted to point out that residential code says 15A max for lighting circuits. Not sure why.

If you think 15A isn't enough, you'll have to use more than 1 circuit.

 

[kippieland]

I have T8's and it gets damn cold here....they light a little bit slower when its cold but they are working fine. They are all rated for 0 degrees fahernheit. As someone who has rewired his shop (same size as yours roughtly) I would suggest running Home Depot(or where ever) and getting a book on electrical and general codes. They helped me a ton. Good luck.

 

[Falcon67]

I use T8s and they work fine in cold weather. My 24x40 will use either 21 4 foot units or 12 8' (going back and forth on this) plus bench lighting. I plan on two 20A circuits with the lights split more or less even across the circuits. I had 14 4 foot and one 8' in the last shop and those T8s pulled a total just under 11A when all lit up.

 

[D KRAGER]

I just happen to have a 4 bulb T-8 ballast here in my hand. It says for 4 x 32 t-8's it will draw just under 1amp. (.90) This is per fixture (4 bulbs)

So on a 15 amp circuit, I think lighting load you are allowed 80% of the circuit. So 12 amps. So roughly you could go with 12 fixtures (total of 48 bulbs) if that's the only thing on that circuit.

A side note: this is where people get confused, do not go by bulb wattage to figure amp draw. This is because the ballast changes the voltage to the bulb, so the voltage at the bulb is not 120v. Always look on the ballast. It will give you amp draws for different bulbs.

 

[rvcoaster]

thanks for all the help so far. the shop lites i have now say "multiply bulb wattage by 2.5 for volt/line/amps" which i am not real sure what that means...

two 40 watt bulbs (80 watts x 2.5) = 200 watts seems like a lot of draw. i guess its not too important as these are temporary anyway.

i drew up some new lighting plans yesterday, the simplest being left/right half of garage layout. another idea would be every other fixture, this is where i dont know. i cant imagine wanting half the garage lit up so maybe every other fixture is the way to go?

in my new plans i drew i plan to move all three outside lights to the same circuit (instead of one outside lite) and this circuit shares the garage door openers. the lights are rated 339MA so i assume all three are roughly 1 amp. any idea why they did it this way (two outside lites on inside lite circuit, one on garage door circuit)?

this has been a big help for me.

 

[sberry]

Most garages get wired cheap initially, they are not workshops. As for lighting I would want a couple circuits for a couple reasons, large fixtures for temp lights could be added, usually this kind of thing runs one at a time,adding something may not be a problem, you can work on one circuit and not disable all the lighting. Some more wire may be in order, some method as was stated for service lights and some lights dedicated to work spots, no point lighting the roof of your car if you are working diligently at a bench. No need to turn every light on in the place for a simple task or to retrieve a tool.
Remember you can rewire for convenience, the stuff is not a lot of good if it isn't where it needs to be.

 

[VHF]

thanks for all the help so far. the shop lites i have now say "multiply bulb wattage by 2.5 for volt/line/amps" which i am not real sure what that means...

two 40 watt bulbs (80 watts x 2.5) = 200 watts seems like a lot of draw. i guess its not too important as these are temporary anyway.

Does it mean multiply the wattage of one bulb by 2.5 to get the total draw? 40 watts x 2.5 = 100 seems a little more reasonable for a fixture with two tubes.

 

[Falcon67]

Standard T8s are "32W" bulbs but typically run at 28W from what I read. HO lamps pull more watts. When I figure watts/sq ft for my T8 light layout, I used 28w per lamp.

 

[olytdi]

I wired two main banks of lights in my shop: east bay and west bay. In addition to that, I have a dedicated fixture over each of the two main bench areas. Lastly, KBS2244 has it right -- a couple of incandescents wired to the first switch inside the entry door are great for going out to the shop to grab a whatever. With a variety of lighting configurations, I can light over benches, light one side or the other, or turn on the whole shiterie and bask in the photons.

 

[Racecarl]

I have twelve T8 2 bulb fixtures in my 24X30. According to the spec sheet they draw .9A, and I am running them all on one 15A breaker. So far, they work great. I only turn these on if I know I am going to be in the shop for a while.

If I am just popping in to grab something quick, I have an outdoor style fixture with two halogen bulbs. The light is mounted above the walk-in door, with one bulb aimed to the far corner and the other aimed to the future location of the workbench. The switch I used for the halogen lights has a 'night light' inside, which makes it easy to see in the dark. These lights are on the same 15A circuit as the 500W outdoor halogen driveway light.