Is my math right?

[brewchief]

I have some new used lights for my garage, each has 6 52w T-5 bulbs, 6x52 is 312 watts, do I have to add more wattage for the ballast(s)?

It's looking like I can only put 4 lights on a 15 amp circuit and stay under the 80% rule, is that correct?

 

[Bert_]

Look at the ballast label, it will tell you line amps.

Do not base your calculations on lamp watts. Many times the lamps doesn't actually get powered with the wattage on the label. For example most 32W T8's only use 28W or so, the reverse can be true also.

 

[cybrdyke]

52 watt?
Who makes a 52 watt T5 lamp?
CD

 

[Shiftless]

I hope you have some pretty high ceilings.
Assuming around 100 lumens per watt, each of your fixtures is pumping out 20,000 lumens.
How big is your garage and how high are your ceilings?
Six of those fixtures will light up a big area. Depending on your planned usage, you might be better off with more fixtures with fewer lumens per fixture.

CD:
Maybe brewchief is referring to 54 watt T5s

 

[mrobins297aaa]

for what it's worth, I have 7, T8 6 lamp 32w fixtures on one 20 amp circuit.
the math works out: 192w / 120v = 1.6 amps x 7 = 11.2 amps

the actual total current draw is 12.5 amps

sorry I had to edit I have T8 fixtures

 

[James-W]

I was under the impression most people were getting rid of the ballasts and going with the LED type tubes which use way less power.

 

[brewchief]

54 Watt is correct.
I would prefer led lights but these were free, a friend works at a warehouse that converted from these T-5 lights to leds.

The lights I have were from either the cooler or freezer area and have a clear plastic cover for bulb protection, they are designed to be mounted higher then what I have for ceiling height but we have a bunch of the same lights in a low ceiling area at my friend's shop and they work pretty decent.

My garage is currently lit with a couple of old T-12 shop lights so even though these lights aren't perfect for my use it will be a huge improvement.

I mostly just wanted to make sure that I wasn't making a mistake with the number of lights I put on each circuit.

Sent from my XT1254 using Tapatalk

 

[cybrdyke]

The 4 lamp ballast and 4 lamps uses 240 watts total. The 2 lamp ballast and 2 lamps uses 118 watts total. So, each fixture uses 358 watts. That's 2.98 amps per fixture @ 120v.
Good luck,
CD