Help-@nd question

[sparky723]

What is the general lighting load for a 30,000 sq. ft. bank?

I thought it was figured: 30,000 x 3.5 va (220.12) = 105,000

But my answer key shows 30,000 x 3.5 (220.12) x 1.25 = 131,250

Where does the 1.25 come into the equation?
I can't find that in the NEC anywhere.

 

[Dennis Alwon]

What is the general lighting load for a 30,000 sq. ft. bank?

I thought it was figured: 30,000 x 3.5 va (220.12) = 105,000

But my answer key shows 30,000 x 3.5 (220.12) x 1.25 = 131,250

Where does the 1.25 come into the equation?
I can't find that in the NEC anywhere.

125% is used for continuous loads

 

[JohnJ0906]

Anything that is in use 3 hours or more is considered continuous duty. It is taken at 125%

 

[sparky723]

augh!

augh!

Thats what I was thinking, since it was a Bank and the lights would most likely be in use over 3 hours...DUH!!! Good grief. Oh well, the only stupid questions are the ones not asked.

thanks for ya'lls confirmation on my assumption.

 

[Smart $]

125% is used for continuous loads

Anything that is in use 3 hours or more is considered continuous duty. It is taken at 125%

...but 125% is for AMPACITY... not LOAD.

So if a lighting branch circuit is conducting 16 amperes, are you going to say it has a 20A load?

The author's answer is wrong... period.

 

[Dennis Alwon]

...but 125% is for AMPACITY... not LOAD.

So if a lighting branch circuit is conducting 16 amperes, are you going to say it has a 20A load?

The author's answer is wrong... period.

For load calculation I believe you have to add the 125%.

If your load was 17 amps and the lights were considered continuous would it be okay to use a 20 amp circuit?

 

[SEO]

Per art 210.19 (A) (1) the branch-circuit conductors shall have an allowable ampacity not less than the noncontinuous load plus 125 percent of the continuous load. So on a 20 amp circuit for a continuous load 16 amps is the max amperage on the circuit. 16 X 1.25 = 20.

 

[ray cyr]

Per art 210.19 (A) (1) the branch-circuit conductors shall have an allowable ampacity not less than the noncontinuous load plus 125 percent of the continuous load. So on a 20 amp circuit for a continuous load 16 amps is the max amperage on the circuit. 16 X 1.25 = 20.

or 215.2(A)(1) if you are sizing a feeder

 

[SEO]

Correct I agree.

 

[Dennis Alwon]

Per art 210.19 (A) (1) the branch-circuit conductors shall have an allowable ampacity not less than the noncontinuous load plus 125 percent of the continuous load. So on a 20 amp circuit for a continuous load 16 amps is the max amperage on the circuit. 16 X 1.25 = 20.

Yes I agree -- my point was a counter point to "Smarts" post.

..but 125% is for AMPACITY... not LOAD.

So if a lighting branch circuit is conducting 16 amperes, are you going to say it has a 20A load?

The author's answer is wrong... period.

 

[Smart $]

For load calculation I believe you have to add the 125%.

Got a code reference to back that up?

Can you point to an example calculation in Annex D? ...where the square footage is multiplied by the required VA and 125% to obtain the General Lighting Load.

If your load was 17 amps and the lights were considered continuous would it be okay to use a 20 amp circuit?

To answer the question as put forth, no, provided the circuit is not continuous rated.

However, your question exemplifies ampacity requirements... not load determination.

Scrutinize Example D3 very carefully... In the two "Loads" sections, which of the VA quantities are a result of multiplying by 125%?

 

[ayman33]

125% to size the circuit breaker,the circuit breaker should be load with 80%
so if we have any load current we divide by 80% or muiltipy 125%=(1/80%)
thanks

 

[Smart $]

125% to size the circuit breaker,the circuit breaker should be load with 80%
so if we have any load current we divide by 80% or muiltipy 125%=(1/80%)
thanks

But that assumes all loads are continuous.

Ampacity [in general] = 125% continuous + 100% non-continuous... + 125% largest motor + 100% of other motors... etc.

So the load can technically be anywhere from 0% to 100% of a service or feeder or branch circuit ampacity and still be in compliance.

 

[Smart $]

PS: Welcome to the forum

 

[tryinghard]

What is the general lighting load for a 30,000 sq. ft. bank?

I thought it was figured: 30,000 x 3.5 va (220.12) = 105,000

Your answer is correct to the question asked. Notice 220.12's heading "Table 220.12 General Lighting Loads by Occupancy".

220.12 is for lighting only though not receptacles 220.14(K).

Continuous or non-continuous is not included in the question but lighting is a continuous load. Often non-dwelling applications will distribute lighting from its own panel for correct feeder sizing.

 

[tryinghard]

I think electricians often think of 210.23(A)(1) regarding branch circuitry, even if they don?t know this specifically. They are at least often applying this.

 

[charlie b]

I think this may have been debated before, but I am not certain. So here is my thinking: You do not use the 125% factor, when you obtain lighting load from table 220.12.

You say that lighting is continuous. I say that that is true, but irrelevant. I submit that the fact that lighting is continuous load has already been taken into account, when the numbers were inserted into that table.

Here are some arguments in favor of my point of view:
? Look at the first sentence of 220.12 (not the table, the article). It says that the values taken from the table give you the minimum lighting load. It does not say that the lighting load is 125% of the tabulated values, it says the lighting load is the tabulated value.
? The examples in Annex D do not add 25% to the lighting load.
? For dwelling unit calculations, the value taken from Table 220.12 gets added to other stuff, then we get to use a demand factor. To me, it does not make sense to ?biggie size? a number, and then turn around and ?downsize? the same number a minute later.
? Again for dwelling unit calculations, the value taken from Table 220.12 includes the load associated with a number of receptacle outlets. Those are not continuous loads. So out of the 3 VA/ft2 of lighting load, there is no way to determine how much to call the continuous load of lights, and how much to call the non-continuous load of receptacles.

By counter-example, I often perform a service load calculation late in the design process, by adding the actual watts of the actual light fixtures that I have placed on the plans. I do the math using excel spreadsheets in the format of panel schedules. That is actual lighting load, not a ?take a value from the table? lighting load. I do add 25% to that value, because lighting is continuous.

 

[Smart $]

...The examples in Annex D do not add 25% to the lighting load...

Example D3 mentions 125% when comparing Table 220.12 calculated general lighting load to the actual connected lighting load of a store. To make the comparison, both are multiplied by 125%. Don't ask me why... because comparison can be done without multiplying both by 125% !!!

Later in the example, where determination of service conductor size is performed, 125% of the Continuous Load figured earlier is used. General Lighting Load is part of the Continuous Load. So it does get multiplied by 125% when determining ampacity...