safety question

[safetybobnj]

I am working an OSHA question and cannot find the answer or formula in the NEC or OSHA Subpart S, or across the internet...

Question is:

How many 300 watt incandescent lamps may be on a 20 ampere 120 v branch circuit?

If you know the number, plz explain how you derived that # and where I can find the formula so I can calculate in future situations.

Bob

 

[ryan_618]

Re: safety question

Lighting is considered a continuos load, and therefore the 125% rule applies.

120V*20A=2400VA/80%=1920VA/60W=32

EDIT: I started typing so fast I figured 60W bulbs!!! 1920VA/300W=6 bulbs

[ March 02, 2004, 01:29 PM: Message edited by: ryan_618 ]

 

[wanderer20001us]

Re: safety question

120V * 20A = 2400VA * 80% = 1920VA / 300W = 6 300W bulbs.

 

[bennie]

Re: safety question

Is lighting considered a continuous load even when it is not a continuous load?

I calculate;

120 X 20 = 2400 divided by 3 = 8 lamps

 

[wanderer20001us]

Re: safety question

It depends on the situation. In this case, I would err on the side of continuous. 300W sounds like highbay and highbay are typically continuous. I'm not saying this is the case, but without more info, better safe than sorry.

 

[bennie]

Re: safety question

I agree. Considering the question is apparently in a test, only the known facts should apply. A variable, not specified, is only speculation.

 

[roger]

Re: safety question

Bennie, I agree. Many test are failed by the test taker reading more into the question than is there, or answering with their experiences or even common sense.


I also agree that 300 watt incandescent lamps would probably be in a continuous installation, but that would be part of the question if it were pertinent.

Now, how does this question relate to OSHA?

Any circuit overloading or misuse would be an issue for other electrical codes, which would only be referenced by OSHA I would think.

Roger

 

[safetybobnj]

Re: safety question

All who posted replies: Thx for your insight and help, especially the formula. 6 it is!

Bob

 

[pierre]

Re: safety question

Am I mistaken, but is not all lighting considered as continuous regardless?

Pierre

 

[charlie b]

Re: safety question

I don?t think the NEC explicitly states that lighting MUST be treated as ?continuous.? I strongly suspect that I would lose any disagreement with an Inspector, if he said it should be continuous, and if I wanted to say it was not. The only thing I found was in Example D3. That example used the 125% factor for both general lighting and for the show window lights.

 

[ryan_618]

Re: safety question

Originally posted by charlie b:
I don?t think the NEC explicitly states that lighting MUST be treated as ?continuous.? I strongly suspect that I would lose any disagreement with an Inspector, if he said it should be continuous, and if I wanted to say it was not.

I got a nice little chuckle out of this.