WA 01 Admin Question

[Holeshot]

Last week I took the WA 01 admin test and missed 4 out 10 I know i got most of cals rights in the beginning but the last 4 questions i think i got wrong. At first i thought it was an easy because it was asking me many 15 amp circuits on a X By X lighting load.

Square foot x 3
appliance x 2
laundry x1

Do a standard cal for single dwelling and than come up with the total VA lighting

I guess my question is a 15 amp 120v load in va is 1800va however, started thinking after the test and forgot that you can not use a 100% of the breaker load (1800) You can only use 80% (1440)va or 16 amps. Is this the right train of thought or am i off.:-?

Thanks
Holeshot

 

[charlie b]

I am sorry, but I do not understand the question. What was the test question asking you? Was it about calculating load? Was that supposed to include the demand factor for lighting loads? Was it about counting the number of circuits needed? Was it about designing a specific single circuit?

You are right in saying that you cannot load a breaker beyond 80%, if the load is continuous. Lighting loads are considered continuous. But take care with the application of this concept. If you are calculating a service or feeder load, and you start with 3VA per square foot for lighting, you do not add 25% to that calculation, even though lighting is a continuous load. However, if you are designing a circuit, and you will use a 15 amp breaker, and if the load is lighting (or some other continuous load), then your limit for that circuit is 1440 VA, or 12 amps.

 

[Holeshot]

Sorry, about that I took the WA 01 electrical Admin Section 3 Major Cals
Yes it was about calculating loads
The question was how many 15 amp lighting circuits in a Residential that is 60 by 24

2
3
4
5

I guess i am looking for the process to get the right answer. because to me it was not complete question

Thanks
Holeshot

 

[Rockyd]

There's a few missing factors, but let me take a guess based on 1500 square foot . The square footage is based upon the call out in 220.82(B)(1).

Do a standard cal for single dwelling and than come up with the total VA lighting

1500 x 3 (sq ft) = 4500
1500 x 2 (sabc) = 3000
1500 x 1 (sabc) = 1500


For 9000va, perhaps this is trick, but they said lighting only. Sabc and laundry are appliance load. so now you have 4500 only. 4500/1800 = 2.5, so I choose 3 - 15 amp circuits for my lighting minimum (220.14). General use, and receplacles and general illumination. 220.14(A) is about appliances.

You are asking a question that is not about realities of load calc's but rather a revenue generation question. Normally, getting ready for testing, I like to go through Mike Holt's books, and James Stallcup's to wrap my head around all the current though of the day for what the test is going to be testing for.

 

[charlie b]

This is easier than you are making it out to be. The answer is "3."

We need to keep the process of calculating service and feeder loads separate from the process of designing branch circuits. This question is not about load calculations. The existence of SABCs and laundry circuits does not come into play.

As you surmised earlier, a single 15 amp lighting branch circuit can handle 1440 VA. That comes from 15 x 120 x 80%. You have a 60 x 24 foot space, or 1440 square feet. You assign a load of 3 VA per square foot, and that gives you a load of 4320 VA. Divide 4320 by 1440, and you will see that 3 circuits will be enough to supply this load.

 

[Dave Benson]

Wa 01 exam

Wa 01 exam

I thought that on a dwelling unit a 15amp 120volt lighting ckt would be at 100%?

Dave B

 

[Dave Benson]

Wa 01 exam

Wa 01 exam

I tutor for the exams here in Wa and I thought we derated for commercial to 80% and resi was at 100%

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[tallguy]

I thought that on a dwelling unit a 15amp 120volt lighting ckt would be at 100%?

It's not a continuous load, so I'd agree. Either way though, the answer is still 3.

 

[tallguy]

I tutor for the exams here in Wa and I thought we derated for commercial to 80% and resi was at 100%

Not following :-? Are you referring to continuous and non-continuous loads? See 210.19(A)(1) and 210.20(A).