Studying Residential Lighting Wiring Practices

[janagyjr]

I'm studying residential lighting wiring practices at the moment (it's chapter 8 in Electrical Wiring Residential, 16th Edition, Ray C. Mullins) and the author is speaking of some Rules of Thumb (caps and emphasis his, not mine) and I'm wondering if he's just pulling words out of his backside.

Some of the methods he's speaking of he titles "Outlets per Circuit Method" and the "per square foot method" (basically using load calculations as per the NEC). Are there really any such Rules of Thumb methods, or is it just the NEC "per square foot method"?

Asking on another forum to get widest possible aggregate of responses.

 

[jumper]

I size the service to the connected load or the 3 VA per sq. ft. rule, whichever is greater.

I size the branch circuit to the connected load.

 

[janagyjr]

For general-purpose lighting and receptacle outlets, how do you compute the connected load, though? Just by what the plans or ho specifies?

 

[jumper]

In residential, general purpose receptacles have no connected load, certain areas like SABC/kitchen and laundry require that you account for a load.

 

[janagyjr]

So just use the 3VA/sq-ft formula? Seems like it'd be easier to just use the Code book to calculate the basics and then over-compensate a bit. Takes all the guess work out of that.

 

[iMuse97]

So just use the 3VA/sq-ft formula? Seems like it'd be easier to just use the Code book to calculate the basics and then over-compensate a bit. Takes all the guess work out of that.

That's the start. Also, all NEC 220. Section IV. Also see NEC Annex D for examples.

 

[cadpoint]

The NEC states what it states!

Because a structure and the service size are numerical numbers and a protentional math sum can be an extraction can be made, as you referenced.

" FOR ME " a SQ FT measurements, or to call out for such, for me has always been odd as to addressing the exact total service requirements in general.

I've never understanded that one aspect!

The NEC clearly states and address's - What is required of a Circuit or Service(period).

 

[gndrod]

3W per sf

3W per sf

I'm studying residential lighting wiring practices at the moment (it's chapter 8 in Electrical Wiring Residential, 16th Edition, Ray C. Mullins) and the author is speaking of some Rules of Thumb (caps and emphasis his, not mine) and I'm wondering if he's just pulling words out of his backside.

Some of the methods he's speaking of he titles "Outlets per Circuit Method" and the "per square foot method" (basically using load calculations as per the NEC). Are there really any such Rules of Thumb methods, or is it just the NEC "per square foot method"?

Asking on another forum to get widest possible aggregate of responses.

Maybe using luminosity photometrics for both point and zonal lighting methods would be more appropriate instead of the branch circuit 3W per sf value given in the NEC. When lamping out a kitchen, the lighting strategy will not be consistent within the room sf outlet requirements of Art.220 due to the counter two small BC appliance receptacle outlet rule from [210.52(C)(1)] and energy efficiency rules that may be imposed by the local AHJ. (I.e. CA Title 24) The rule of thumb for lighting does not exist for both reasons.

Surface illuminance levels are dictated by concentrated and reflected performance of output efficacies of the lamp source (CFL, LED, Incandescent) and the reflective efficiency (Coefficient of Utilization) of the luminaire housing needed at specific locations. Each luminaire must be positioned to meet standard illuminance levels specified for both mood and task visibility requirements set by the architectural design of a project.

Lighting is not defined by outlet, but by footcandle levels at the locations specified. Recessed over-sink lamping can vary anywhere from 15W - 75W depending on the type of lamp and the distance above the work plane. Wiring to the outlet will be either 14 AWG or 12 AWG, depending on the contracted BC sizing and the local code requirements.

 

[janagyjr]

Maybe using luminosity photometrics for both point and zonal lighting methods would be more appropriate instead of the branch circuit 3W per sf value given in the NEC. When lamping out a kitchen, the lighting strategy will not be consistent within the room sf outlet requirements of Art.220 due to the counter two small BC appliance receptacle outlet rule from [210.52(C)(1)] and energy efficiency rules that may be imposed by the local AHJ. (I.e. CA Title 24) The rule of thumb for lighting does not exist for both reasons.

Alright, so no real rule of thumb for lighting.

Surface illuminance levels are dictated by concentrated and reflected performance of output efficacies of the lamp source (CFL, LED, Incandescent) and the reflective efficiency (Coefficient of Utilization) of the luminaire housing needed at specific locations. Each luminaire must be positioned to meet standard illuminance levels specified for both mood and task visibility requirements set by the architectural design of a project.

*Greek*

Lighting levels are dictated by required tasks in certain rooms, architect/contractor figure those numbers out, I install by the plans. Roger that. (at least, that's what I'm reading into that).

Lighting is not defined by outlet, but by footcandle levels at the locations specified. Recessed over-sink lamping can vary anywhere from 15W - 75W depending on the type of lamp and the distance above the work plane. Wiring to the outlet will be either 14 AWG or 12 AWG, depending on the contracted BC sizing and the local code requirements.

This is quite the complex task, more so than I imagined. Will require further reading on my own. Thanks for the response!

 

[jumper]

So just use the 3VA/sq-ft formula? Seems like it'd be easier to just use the Code book to calculate the basics and then over-compensate a bit. Takes all the guess work out of that.

You are over thinking this, I will put it simple terms:

If you are taking a test: Use the NEC.

If you are designing it: Use the specs, NEC, and common sense.

If you are working as an employee: Do what the boss says, it's his license and insurance.

If you have stamped EE drawings: Follow the prints, it's the EE's stamp and O and E insurance.

If it is a bid: Ask someone else, I am clueless, never bid anything in my life.