Another electrical question...

[aka Larry]

From all the questions from me lately you might have guessed I'm getting close to pulling wire in my new shop. All the EMT is now in place and I'm getting down to the brass tacks so to speak.

My plan is to have my lighting on one circuit, but one three separate swithes. One switch will control half of the overhead lights, another the other half, and yet another the two over the workbench.

My question is I had 'heard' that there is a limit on the circuit size of residential lighting...limited to 15A. Is that true? Can I have a 20A lighting circuit?

FWIW, the above lighting circuit will work on a 15A breaker, but I'll have to go buy an additional breaker, which is no big deal, but I already have an unused 20A breaker.

 

[Norcal]

20A is fine.

 

[Charles (in GA)]

What you probably "heard" is that lighting circuits are considered a continuous load by the NEC. As such, continuous loads (Lighting, heating, anything that exceeds three hours continuous operation) are limited to 80% of the circuit rating. ie. you install a 20 amp circuit with lots of lights. The total amp load of all lights on the circuits exceeds 16 amps (which is 80% of 20 amps). In this case, you need to split the load onto two circuits.

Charles

 

[theoldwizard1]

Your 20A breaker had better be connected to 12 gauge wire.

 

[pattenp]

Something to consider is if you're using florescent fixtures it's best not to have them on when changing out bad tubes. So if your lights are all on one circuit you may be changing a tube in the dark. I like having my lights on more than one circuit.

 

[Falcon67]

I have two 20A light circuits, one with 8 fixtures and one with 6 fixtures. I have 8 each 8' fixtures in the main car area. There are three switches by the door. 1 turns on one fixture right at the door. The other two switches turn on two fixtures in the first "bay" and 2 between the bays. The last three work off a switch on the far wall. Those cover a third "bay" where there is space for misc work. The idea is that I can come in the door, turn on a single light, cross the 28' parking area and enter the work/tool room, which is on a different light circuit. When I leave out, I can shut down the work room and still see to the door to get out. And I only have lights burning where I am working, except for one.

 

[Steevo]

I put my overhead fixtures (15 of them) on three switches, one for each outer row, and one the center row (5 fixtures per row).
I used a 20a breaker with 12ga to the light switch box, then pigtailed the three switches off of that, and used 14ga from the switches to the fixtures.
The inspector ok'd it, so I guess it's to code.

 

[aka Larry]

What you probably "heard" is that lighting circuits are considered a continuous load by the NEC. As such, continuous loads (Lighting, heating, anything that exceeds three hours continuous operation) are limited to 80% of the circuit rating. ie. you install a 20 amp circuit with lots of lights. The total amp load of all lights on the circuits exceeds 16 amps (which is 80% of 20 amps). In this case, you need to split the load onto two circuits.

Charles

I designed all the circuits at 80% load so I'm good there.

Something to consider is if you're using florescent fixtures it's best not to have them on when changing out bad tubes. So if your lights are all on one circuit you may be changing a tube in the dark. I like having my lights on more than one circuit.

Since I'll have three switches I can have fixtures on/off as needed to change out bad tubes.

Your 20A breaker had better be connected to 12 gauge wire.

I'm running 12GA THHN wire on every 120V 20A circuit. I'm using 10GA THHN on the two 240V 30A circuits.

 

[eljefino]

Check the ratings on your switches; the cheap ones IIRC are only good to 500 watts. "HP rated" ones do better and they just feel better; more of a "click".

 

[pattenp]

I think it's a no no to use #14 as part of a 20A circuit. I would say that the entire circuit has to be #12. Your inspector may have overlooked that.

Edit: I guess if the fixtures are hardwired then it was okay. I just wouldn't feel warm and fuzzy about having #14 in a 20A circuit.

I put my overhead fixtures (15 of them) on three switches, one for each outer row, and one the center row (5 fixtures per row).
I used a 20a breaker with 12ga to the light switch box, then pigtailed the three switches off of that, and used 14ga from the switches to the fixtures.
The inspector ok'd it, so I guess it's to code.

 

[Charles (in GA)]

Stop and think about what size wire is attached to the fixture by the manufacturer, 14, 16, 18. Not any different using a short pigtail of a smaller size to supply a single fixture. Now running the wire any distance, and supplying several fixtures, no, I would not do that.

Charles

 

[pattenp]

I got a feeling that the run of #14 from the switches to the fixtures isn't a short pigtail.

 

['04 Cummins]

Stop and think about what size wire is attached to the fixture by the manufacturer, 14, 16, 18. Not any different using a short pigtail of a smaller size to supply a single fixture. Now running the wire any distance, and supplying several fixtures, no, I would not do that.

Charles

UL listed equipment (pre-wired light fixture, for example) doesn't have to meet the code requirements for wire size. They meet UL requirements.

14 gauge wire in Steevo's case does not meet the NEC minimum standards. The inspector must have missed it, or his local jurisdiction is/was recognizing a much older version of the code.

 

[ishiboo]

UL listed equipment (pre-wired light fixture, for example) doesn't have to meet the code requirements for wire size. They meet UL requirements.

14 gauge wire in Steevo's case does not meet the NEC minimum standards. The inspector must have missed it, or his local jurisdiction is/was recognizing a much older version of the code.

+1.

Though I'd say in this case, I would NOT pull it and redo... it'll be fine.

 

[PRH44]

Please be advised the branch circuit wiring methods are NOT permitted to be smaller than the over current protective device rating (breaker or fuse).
Fixture wires fall under code section 402. This sections covers wire integral to fixtures and similar equipment. 402 also covers fixture tap conductors.
A fixture tap is the portion of the wiring that taps the branch circuit and connects to the luminaire.
Conductors permitted to be used as fixture wires and fixture taps are called out in 402.3
They have specific insulation, ampacities and certain limitations.
Fixture wires are NOT permitted to be used as branch circuits.
A fixture tap can be an approved cord or whip, field or factory installed.
The fixture tap is permitted to be smaller than the branch circuit if an approved fixture wire type recognized in 402.3 is used, and the over current protection requirements of 240.5(B) are met.

If one installs a tap that is the same size or larger than the branch circuit, it can be any approved branch circuit wiring method. The conductors would not be required to be a fixture wire type recognized in 402.3.