Current carrying conductors?

[kwired]

Now what happens when the load is LED lights?

Lighting and retrofits demand the same load calculation for industrial, construction, maintenance, and service industries,

If retrofitting you end up with less load on conductors than you had before.

If designing new, you can light up more area to same light level per circuit than with other light sources.

We are talking about conductor ampacity and overcurrent protection here not load efficiency.

Such load calculation is for general lighting and art 220 calculations. It usually will still be divided into multiple branch circuits that may be 15, 20, 30 or even 50 amp circuits in some cases, which you will apply the conductor ampacity and overcurrent protection rules to each circuit used.

 

[ramsy]

Correctly applying all requirements of NFPA-70 Chap. 3 field tables for derating, ampacity and environmental adjustments, are complex enough for reasonable people to expect they must be done, after getting thru Chap. 3.

A reasonable person does not expect 240.4(D) to drop a bomb on field tables and the derating processes, much less require another (x 1.25)
factor on loads considered inductive, per some other chapter. This circular NFPA code arrangement must be memorized, at the risk of obsolescence with each 3yr-code cycle of new public inputs.

In the case of figuring LED lighting loads per 220.18(B): even though florescent-ballast nameplates standardized on Amp conversion from lamp Watts; to account for power factors and energy losses, some of the LED industry is stuck on Watts, and won't put their drivers on the same page. Lots of LED specs are listed without load Amps, and don't comply with 220.18(B).

I'm sure there's an engineering solution for ampacity with LED's listed in Watts, but NFPA tables and circular references are not informing us.

 

[kwired]

Correctly applying all requirements of NFPA-70 Chap. 3 field tables for derating, ampacity and environmental adjustments, are complex enough for reasonable people to expect they must be done, after getting thru Chap. 3.

A reasonable person does not expect 240.4(D) to drop a bomb on field tables and the derating processes, much less require another (x 1.25)
factor on loads considered inductive, per some other chapter. This circular NFPA code arrangement must be memorized, at the risk of obsolescence with each 3yr-code cycle of new public inputs.

In the case of figuring LED lighting loads per 220.18(B): even though florescent-ballast nameplates standardized on Amp conversion from lamp Watts; to account for power factors and energy losses, some of the LED industry is stuck on Watts, and won't put their drivers on the same page. Lots of LED specs are listed without load Amps, and don't comply with 220.18(B).

I'm sure there's an engineering solution for ampacity with LED's listed in Watts, but NFPA tables and circular references are not informing us.

I see the issue you are presenting now. All I can say with respect to the thread topic it is an issue with determining exactly what the load is and not a direct issue with determining conductor ampacity or overcurrent protection selection.

 

[charlie b]

There's no limit per se, but the 9 is a rule-of-thumb limit before you have to up-size.

Please note that that rule-of-thumb applies only to 20 amp circuits using #12 wire rated for 90C. If you are dealing with 30 amp circuits using #10 wire rated for 90C, the rule-of-thumb is 6 conductors. Do the math described in post #3, and you will see what I mean.

 

[infinity]

Please note that that rule-of-thumb applies only to 20 amp circuits using #12 wire rated for 90C. If you are dealing with 30 amp circuits using #10 wire rated for 90C, the rule-of-thumb is 6 conductors. Do the math described in post #3, and you will see what I mean.

Wouldn't it also apply to #14 conductors?

 

[charlie b]

Wouldn't it also apply to #14 conductors?

Good point. The rule-of-thumb for 15 amp circuits using #14 wire rated for 90C is also 9.

 

[kwired]

Please note that that rule-of-thumb applies only to 20 amp circuits using #12 wire rated for 90C. If you are dealing with 30 amp circuits using #10 wire rated for 90C, the rule-of-thumb is 6 conductors. Do the math described in post #3, and you will see what I mean.

If you need all of 30 amps. If you have a 21 - 28 amp load, it still works with 10 AWG and 9 CCC's in a raceway.