What size breaker for these lights?

[badams14]

I have a bunch of these fixtures that I got from a demo, and 2'x2' fixtures as well. How many of these can I string together on a 15A circuit, or am I better going with a 20A?

It's a 30'x32' with 12' ceilings. I am thinking 10 of the 2x2' fixtures and a row of the 4x2's in the middle.


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[Speedy Petey]

How are you going to install them in a garage?? (I assume it's a garage or shot, no?)
Those are meant to lay into a grid ceiling.

 

[badams14]

Yes, I'll hang them from the trusses.


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[CJ7VFR]

Well, amps equals watts divided by volts. So if each light fixture uses four (4) 34 watt bulbs, then each fixture would be using 136 watts with all four bulbs installed. That works out to 1.13 amps for each light fixture, or 1.13=136/120.

If you go with a 15 amp breaker and 14 gauge wire, then you could have about 13 light fixtures. If you go with a 20 amp breaker and 12 gauge wire, then you could have about 17 light fixtures.

This would put you at the absolute max power usage for each breaker, and you never want to actually do that.

I think the rule of thumb is to go no more than 80 percent of the breakers capacity for safety.

So you could have 10 light fixtures on the 15 amp breaker and 13 light fixtures on the 20 amp breaker.

I personally would go with the 20 amp breaker even if you are going to install 10 light fixtures. It is always better to be safe than sorry.

Jim

 

[Slowgsr]

Well, amps equals watts divided by volts. So if each light fixture uses four (4) 34 watt bulbs, then each fixture would be using 136 watts with all four bulbs installed. That works out to 1.13 amps for each light fixture, or 1.13=136/120.

If you go with a 15 amp breaker and 14 gauge wire, then you could have about 13 light fixtures. If you go with a 20 amp breaker and 12 gauge wire, then you could have about 17 light fixtures.

This would put you at the absolute max power usage for each breaker, and you never want to actually do that.

I think the rule of thumb is to go no more than 80 percent of the breakers capacity for safety.



Jim

Your math is great but your forgetting the ballast draw.
To the OP the ballast will have amperage draw listed, good luck I hate hanging/surface mounting drop in fixtures, just ain't right. Even if they were free

 

[CJ7VFR]

Your math is great but your forgetting the ballast draw.
To the OP the ballast will have amperage draw listed, good luck I hate hanging/surface mounting drop in fixtures, just ain't right. Even if they were free

I figured I would forget something! That is why I said not to max out the breakers. It's never a good idea.

My math was just for quick figuring.

Also, to the OP, if you are indeed going with 10 of these 4 light fixtures, it is highly recommended that you put them on a few switches instead of just one.

This way you don't have to turn all the lights on to just go into the garage for something quickly, like to put the garbage out, or to just get tool and then go back into the house.

With multiple light switches, you can have the right amount of light for the task you are doing, and not waste a lot of electricity for no reason!!!

Also, if you have more than one "people" door in your garage, think about having a few lights on a 3 way switch. This will let you turn on a few lights from either door entrance, and give you enough light to get in and out of the garage without banging your shins into stuff!

Jim

 

[badams14]

Thanks for the help


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[wyliesdiesels]

Lights are considered a continous load, so the circuit cant be loaded more than 80%.

15a = 12a continous load

20a = 16a " "

 

[Rkbuell]

Ballistic draw is what should concern you not ballistic output. Rear the ballistic spec are post a picture of it.

 

[badams14]

Do I base the Amps off the ballast alone or do I add up the bulbs and ballast?


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[Speedy Petey]

Lights are considered a continous load, so the circuit cant be loaded more than 80%.

Where is that written???