Hi. I'm laying out my basement lighting. I expect to have 25 recessed lights, each is 75watt max rating (even though I will use LED, I know I must still assume max rating of fixture). 25x75=1875watts/120V = 15.6amps. So, I cannot use one 15amp breaker and 14awg wire. Can I wire all the lights with 12awg and a 20amp breaker? All comments appreciated.
Thanks Theodore
Are these in *one* room? Does this one (proposed) lighting circuit represent the entire basement? Are they all controlled from a single switch? Are they arranged in one long (electrical) "line" (i.e., the 25th lamp being the farthesst electrical distance from the supply)? What's the longest "electrical length" encountered? Have you guesstimated what the voltage drop will be at each fixture? Have you considered what you will rely on for lighting if/when that circuit is "off"?
Typically, a (lighting) branch circuit is sized at 80% of its load.
No. You are limited to the number of "devices" on the circuit Generally accepted as 8 on 15 amp and 12 on 20 IIRC.. I'd wire it on 2 circuits, with either 2 rings, or rows, or every second lamp on opposite circuits. I'd use an edison circuit,or at least a double (120/240) breaker powering a 2 pole contactor controlled by a single switch if you want all lights on at once all the time. I have an application where 3 circuits are controlled by a 3 pole (3 phase) contactor controlling 3 circuits of lighting on one switch - 12 potlights per circuit, 20 amp breakers. Originally 75 watt incandescents, currently running 9 watt LEDs.
Sorry, I should have described more. These lights are in 4 separate areas/rooms of the basement, on 4 separate switches. Approx 6 lights per room/switch.
Safety considerations aside, I'd put the lights on several circuits, you would not want your basement to go completely dark if a breaker tripped.
You are not supposed to use #14 at all if you have a 20A breaker.
So, when the circuit trips, you're completely in the dark (?)
Usually, you try to arrange to have an alternate source of light/power adjacent or nearby -- so you're not left in the dark. I like to have an adjacent room on a different branch circuit so I can let light stream in through an open doorway, etc.
Also, have you considered using LED *fixtures*? Using an incandescent fixture with an LED replacement bulb ties you to the VA rating of the fixture, not the bulb within. Using an LED *fixture* lets you get away with less.
I haven't looked at the transient characteristics of LED lighting to know what sort of "surge" they impart to the line. Presumably, they have been designed with the characteristics of incandescent counterparts in mind? (i.e., I wouldn't want to end up welding the switch contacts together from some start-up surge owing to capacitors in the lamps)
Lighting tends to be considered a continuous load so the branch circuit must be sized at 125% of that load (said another way, you can only "use" 80% of the rated circuit ampacity -- 16A for a 20A branch circuit).
If you put an outlet on the same circuit, then the rules change.
You also have to look at *where* the load is located. Putting a 16A load on the end of 100 ft of wire will result in a voltage drop of ~6.5V at that 100 ft point. The maximum *recommended* allowed voltage drop on a branch circuit is 5% (6V for 120VAC). The maximum recommended drop AT THE FAR END OF A BRANCH CIRCUIT is 3%.
[#12 AWG is considerably more annoying to work with than #14 AWG. You might want to keep that in mind]And, of course, *local* code requirements trump the NEC all the time. (I lived in a place that required EMT for all runs!)
Have you cornered anyone at your local electrical supply house to see what sort of "free advice" they offer? (which you will take with a grain of salt...)
That applies to *outlets* (180VA per single/dual), not circuits that are used exclusively for hardwired lighting devices.
That applies to *outlets* (180VA per single/dual), not circuits that are
Understood. This would be a dedicated lighting circuit, or circuits. Absolutely no outlets on it. Outlets will have separate circuit(s) and breaker(s).
The code says you will be fine, general lighting circuits in the US are based on square footage, not the number of outlets. YMMV in the great white north.
If you think you would ever have all 75w lamps and all of them will be on at once, by all means go with the 20a circuit but that is a design decision not a code decision.
That is not legal on a 20a circuit, even if it works.
... and only applies in commercial in the US
Not to be pedantic but any termination of a circuit where energy is used is an "outlet". not to be confused with a "receptacle" where you plug things in or a "lamp holder" or "luminaire" where you install a "lamp" (AKA light bulb). Those are just types of outlets. A "device" is a piece of equipment that does not consume energy, like a switch, breaker or any of those other little pieces of hardware in an electrical installation like the wire nuts, connectors etc. The lamp holder itself is a device but the location is an outlet.
If we are going to talk code, lets speak the language so nobody gets misinformation. ;-) The reason why you get away with having all of those lighting outlets on one circuit is 210.23(A)(2) specifically exempts "luminaires" (AKA light fixtures) from the fixed in place equipment. You also have the protection of 240.4(D) (AKA idiot protection) that artificially derates 14,12 and 10 gauge wire so the breaker is only
80% of the actual conductor ampacity. Your 80% protection is built into the 14a breaker on 14 gauge wire, which is actually 20a wire in 310.16.They know nobody actually reads those labels and you may use LEDs, CFLs or you might screw in 150w PAR-38s. The breaker will trip before the wire overheats. Being in the dark is another "design issue" not a code issue. Personally I would split them up but I couldn't make someone do it with a red tag. The same is true of loading too many outlets on a circuit. The code just says you have to allow 3VA per square foot in residential but it is not specific about how you wire it other than the ambiguous "Load Evenly Proportioned Among Branch Circuits" in 210.11(B). That is hard to determine until you see how the homeowner arranges their furnishings and equipment so it is pretty much meaningless.
That is the idiot clause. (240.4(D)) that says unless otherwise permitted in the code 14 ga wire shall be protected by a 15a breaker. (12=20, 10=30) It forces the 80% rule on "small conductors"
I could tell you where it is otherwise permitted but your head might explode (like a legal 40a breaker on 14ga wire)
When you start talking about "fixture wire" (your 18 ga example) that has to be part of a "listed" assembly, typically U/L listing. Typically 18 ga wire has a design ampacity of 7a but in a listed assembly where the load is controlled it can be protected by a 20a breaker. You are dealing with 2 issues, "overload" and "short circuit" protection. An overload is simply having too much load on the wire. Short circuit protection is a bolted fault where there is essentially no limit to the current but the resistance of the wire and the breaker, An 18 ga wire, less than 50 feet long will operate a 20 a breaker in a bolted fault.
At least that is the thinking.
You can still get in plenty of trouble with extension cords but we were talking about lamps.
Correct. This is a good location for an "edison" or multiwire circuit. He needs AT LEAST 2 circuits, whether 15 or 20 amp.
As long as he doesn't tack on "one" convenience outlet he might get away with it. Local interpretations vary.
This is the problem ^^^^^^^^^^^^^^^^^^^^^ In most areas, there is no way to appeal an inspector's ruling. So, if inspector misinterprets the Code (or, is "having a bad day"), you're stuck with his ruling.
It's not short-circuits that one worries about, but rather the heating caused by the higher resistance of the smaller diameter conductors over the longer term.
Feel free to keep making things up. Show us the code sections that say at least two circuits are required.
Point taken and agreed. To summarize and rephrase: the subject is a lighti ng circuit(s) on which there will be 4 groups of luminaires (one group in e ach "room" of the basement, and each group having 4-6 luminaires), and each group is activated via separate switches; and NO receptacles will be insta lled on this/these dedicated circuits.
And it seems that even though it is NOT prohibited by the NEC, the concensu s is that I should split this into two 15amp lighting circuits for two reas ons: easier to work with 14awg, and better design such that a tripped break er wont plunge the entire basement into darkness.
Did I get all that right? :) All comments appreciated.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.