Is Genral Lighting Load taken at continuous 125%?

[Finite10]

Al my exam prep calculations say to take lighting at 125% when it's continuous, as in a commercial building, but I can't find it anywhere in article 220 Load Calculations.

I thought Table 220.12 load minus Table 220.42 Demand Factor was THE minimum lighting load.

The exam prep questions do not ask for:
1) feeder conductor size discussed in 215.2(A)
2) OCPD
3) Servicer
Where loads are taken at 125% when continuous.

What is the code citation I am missing?

 

[Dennis Alwon]

Look in definitions for continuous load.

 

[Finite10]

Thanks Dennis

Thanks Dennis

I am familiar with that, yes. 3 hours+. Still confused on its application though...

Do I calculate dwelling unit general lighting load as continuous too? Is there a reference or approved source that tells me which occupancy types in 220.12 are continuous use, and which are not?

I don't get it, it seems to me that the tables take everything into account. Where they don't there's a citation I can find. I've searched posts from 2008 on this and there's no confirmation I can find.

 

[iwire]

As the definition states ..... if the load is expected to be on for more than 3 hours it is continuous.

So for a home I would not call a typical lighting circuit continuous as I would not expect that all the fixtures on that entire circuit would all be on at the same time for more than 3 hours. The fact that one light one or two lights on the circuit might stay on 24/7 would not make the entire circuit a 'continuous load'

On the other hand if I was figuring the circuits for an open office space I would call that circuit a continuous load.

 

[Finite10]

Thanks for the reply iwire

Thanks for the reply iwire

That does make sense. But in Alaska and northern states I'd expect dwellings to have lights on more than 3 hours for over 6 months a year, but not Florida etc.

I know my lights are on 3+ hours in the evening for over 6 months a year, as well as everyone I know around here too. I was kind of figuring that the table took an averaging of all that into account to avoid subjective calculation. Does the code allow for that -aside from the AHJ?

 

[jumper]

Nothing in 220 says you have to multiply continuous loads by 1.25.

It when you size the wire and OCPD that you makes you do it.

You may have an actual load of X amps, but that does not mean you can install conductors for that size.

So you do the math then, because you will have to later when you select the conductor.

 

[charlie b]

I don't know if this will clarify the question, or whether it is related to the question at all. But if I am calculating a service or feeder load, and if I use a value of watts per square foot from table 220.12 for the type of building, I do not use the 125% factor. Is that what you are asking?

 

[Finite10]

I don't know if this will clarify the question, or whether it is related to the question at all. But if I am calculating a service or feeder load, and if I use a value of watts per square foot from table 220.12 for the type of building, I do not use the 125% factor. Is that what you are asking?

Yep, that's what I'm asking -for load calcs in VA not conductor, service, or OCPD. I find all practice exams calculate commercial light load at 125% but I can't find where that's required by code except for conductor, service, or OCPD. Only in example D3 Store Building in Annex-D does it do that. But is that 'required' by an article? Annex D is informational only.

 

[jumper]

Okay, lets try this:

You have a non continuous load of 100 amps and a continuous load of 100 amps, how many amps does the conductor for this load need to be sized at?

 

[Finite10]

Okay, lets try this:

You have a non continuous load of 100 amps and a continuous load of 100 amps, how many amps does the conductor for this load need to be sized at?

125% of continuous + 100% of noncontinuous for conductor, service, branch, or OCPD.

Maybe I'm wrong in separating 230 and 215 sizing from 220 load calcs. I dunno...

 

[jumper]

125% of continuous + 100% of noncontinuous for conductor, service, branch, or OCPD.

Maybe I'm wrong in separating 230 and 215 sizing from 220 load calcs. I dunno...

You have to deal with 215 or 230 at some point.

 

[Finite10]

True. Is that why Annex-D example derates cont. at 125%?
Sure would be nice to have a code citation requiring it, if so. IMHO

 

[jumper]

True. Is that why Annex-D example derates cont. at 125%?
Sure would be nice to have a code citation requiring it, if so. IMHO

It is all about selecting the conductor and OCPD.

Look at the example, it says "Minimum Size Feeder (or Service) Overcurrent Protection" and"Minimum Size Feeders (or Service Conductors) Required" not actual connected load.

 

[Dennis Alwon]

If you are looking for the load to determine the branch circuit and the load is continuous then you would use 125%. Thus, a lighting load of 1600 watts @ 125%= 2000 watts. So a 120V cir. @ 20 amps is good for 2400 Watts. So that works on a 20 amp cir.

Another way to look at it is to take 80% of 2400watts for continuous load. This leaves me with a maximum of 1920 watts allowed on the cir. 1600 watts is good to go again. Hope this helps.

 

[charlie b]

OK everyone, we are dancing around the question, and not seeing what is actually being asked. So for now, please forget everything posted so far, and look at Example D.3. I think that example has an inconsistency within itself, in addition to an inconsistency with the words in article 220.

When it calculates continuous loads, it mentions “general lighting,” and there is an asterisk next to those words. A footnote explains to us that we need to compare 125% of the actual connected load to 125% of the value calculated from table 220.12. Using the numbers in Example D.3, it is saying we need to compare 125% of 8500 VA (i.e., 10625 VA) to 125% of (3 x 3000), which would be 125% of 9000, which would be 11,250 VA. But the lighting load included in the calculation performed in Example D.3 is only the 9000, not the 11,250. That is what I mean when I say it is inconsistent with itself.

That said, the text of article 220.12 says that the minimum lighting load shall be as given by table 220.12. It does not say that the minimum lighting load shall be 125% of what is given in the table. So the example is inconsistent with the words in the code.

I think I see a code revision proposal in my future.

 

[Dennis Alwon]

The OP said not service, OCP or conductor size-- I assume he meant branch circuit-- perhaps I misunderstood.

 

[sgunsel]

My understanding is that Table 220.12 is the minimum general lighting load for the occupancy - it doesn't get altered by continuous/non-continuous, that's already factored in. You then calculate the actual load with 125% for continuous lighting as in store fronts an office areas and 100% for any non-continuous lighting (stock rooms, storage areas, and likewise). The load you actually use will be the greater of the two values.

I usually find the VA/gross sq. ft. values in the table exceed actual calculated loads, someimes by quite a bit. Probably because most lighting installed today is fluorescent or other with higher efficiency than incandescents. The table seems to assume incandescent lighting fixtures.

 

[Finite10]

OK everyone, we are dancing around the question, and not seeing what is actually being asked. So for now, please forget everything posted so far, and look at Example D.3. I think that example has an inconsistency within itself, in addition to an inconsistency with the words in article 220.

When it calculates continuous loads, it mentions ?general lighting,? and there is an asterisk next to those words. A footnote explains to us that we need to compare 125% of the actual connected load to 125% of the value calculated from table 220.12. Using the numbers in Example D.3, it is saying we need to compare 125% of 8500 VA (i.e., 10625 VA) to 125% of (3 x 3000), which would be 125% of 9000, which would be 11,250 VA. But the lighting load included in the calculation performed in Example D.3 is only the 9000, not the 11,250. That is what I mean when I say it is inconsistent with itself.

That said, the text of article 220.12 says that the minimum lighting load shall be as given by table 220.12. It does not say that the minimum lighting load shall be 125% of what is given in the table. So the example is inconsistent with the words in the code.

I think I see a code revision proposal in my future.

Exactly! Thanks for your valuable time charlie and everybody really. Imagine the collective wisdom and compounded knowledge on this board.

Anyhow, I feel just a bit less crazy now. Which leaves me a long ways down the road still. I can't wait for Saturday's Master Exam to be over-with.

 

[jumper]

Exactly! Thanks for your valuable time charlie and everybody really. Imagine the collective wisdom and compounded knowledge on this board.

Anyhow, I feel just a bit less crazy now. Which leaves me a long ways down the road still. I can't wait for Saturday's Master Exam to be over-with.

My 2 cents. Every test I personally took had me factor in the 125% for a commercial light load. Good luck on your exam.

 

[Finite10]

My 2 cents. Every test I personally took had me factor in the 125% for a commercial light load. Good luck on your exam.

That looks like advice I should apply, at least until charlie is finished with them. Do I want to be right and fail?... or answer right and pass this thing.

"You may have noticed that the less I know about a subject the more confidence I have, and the more new light I throw on it."
-Twain