Wiring Fluorescents Question

[mmhouse]

I have three single bulb incandescent fixtures in my 3-car garage. I'd like to replace them with 4' fluorescent fixtures and would like more than three...maybe eight.

How many fluorescent fixtures can I safely wire into the existing boxes?

 

[Iron-Iceberg]

Ck the watts on the bulbs. Fluorescents use watts just like a incandescent bulb. Just a lot less. IE my fluorescents are 4' and use 35 watts per bulb. 2 bulbs per fixture is 70 watts. Less than a 100 watt flood lite bulb.

 

[Charles (in GA)]

You need to use the amp draw of each fixture as indicated on the data plate or placard of the fixture. Fluorescent lights are induction lights, and actually draw more current than the total of the bulb wattage, not much, but some.

Lighting is a continuous load and as such, you should not exceed 80% of breaker capacity. If the circuit only supplies these lights, and nothing else, and is a 20 amp Circuit Breaker, then the 80% load would be 16 amps. for a 15 amp CB, that would be 12 amps.

Charles

 

[mmhouse]

Thanks Charles...great info!

Another question....how does the light output of fluorescents compare to incandescents? I have three 200w incandescents in the garage now and would like to double the amount of light. How many 2-tube 4' fluorescent fixtures would I need to accomplish that?

 

[pattenp]

To compare light output you need to look at lumens not watts. Watts is a mesurement of power consumption. Example: A 100 watt incandescent light bulb emits 1500–1700 lumens, where as a 100 watt high-pressure sodium vapor lamp emits around 15,000 lumens.

 

[pattenp]

I found info that says that one T5 54 watt, 48 inch long, high output fluorescent bulb produces 5000 lumens. Your three 200w incandescents should produce around 9000 - 10200 lumens, so four 4' T5 high output fluorescent bulbs should give you double the light at 20,000 lumens.

 

[Sicbird]

The most cost effective way would probably be to get several cheap fluorescent shop lights from Wal-Mart, Home Depot, etc. Something with two 32watt T8 lamps in it, that is the most common setup. If you want/need the lights to turn on below freezing you'll likely have to spend more money and get an industrial type fixture with a higher quality ballast. The label on the ballast will show the temperature rating. The F32T8 lamps should use about 0.1-0.3 amp each (by lamp, I mean "bulb"). The more you install, the better your light distribution & lack of shadows. Just don't put too many on a switch and exceed it's current rating.

You can go with T5's, but they'll cost more money. The HO's especially run hotter. The smaller the lamp diameter, the hotter the glass is.

In case you're not aware, the size designation (T5, T8, T12, etc.) is the diameter of the lamp in 1/8's of an inch. Example: T5 indicates 5/8" diameter.

Hope that helps a little...

 

[mmhouse]

Thanks Sicbird...yes that help a lot.

My garage rarely if ever falls below 50 degrees so that's not an issue.

Why does the amp draw vary so much for the same bulb? Is it a difference in the ballast?

I was looking at going with T8's. What's the advantage/disadvantage of going with T5's instead? Does smaller diameter = lower power consumption?

 

[kbs2244]

Man, are we over engineering this or what?
Just hang them and plug them in.
They will draw less and give better light.
I would even leave the old lights in place to give some “instant on” while the tubes warm up.

 

[mmhouse]

Sorry, I don't mean to beat it to death...but I'd rather do a little research up front rather than wishing I'd done something different after the fact. I'm fairly experienced at carpentry and other tasks but I'm definitely not an electrician.

I'm planning to attach them to the ceiling and run conduit rather than having cords hanging. I did want to make sure I don't draw too many amps on the circuit that's readily available.