20 recessed lights in one circuit

[Gaston]

a 15 amp . 120V . circuit supplied by a 14/2 conductor that is rated at 80 % , load , will allow me 12 amp . before I over load the circuirt . so , my question is based on an imaginary scenario.
I have , 20, 65 W. bulbs for my lighting circuit (obviously this is a dedicated circuit ) ,which will requiere 1,300 watts to operate . My circuit is allowing me 1,400 watts total for distribution. since I have 1,300 watts demand this will leave me with an additional 100 watts . But since I want to know the resistance of of my bulb I go to R = E square / P wich in return I get = 221.61 . by rounding the number I get = 222 ohms per fixture . Now , I'm curious about the amps that each will be consuming so I go to I= P/R and my result is = 0.541 amps. or by rounding it I get 0.5 amps. per bulb .
If I use I= P/E P =1,300 divided by E = 120 V. = 10.83 Amps

if I multiply the 222 ohms X 20 fixtures I get 4,400 total .

but I again am curious about my current flow and ther fore I go to

I = E square / R and find the result is = 10.28 wich is not exactly
the 10.83 that I got from my first attemp.

perhaps you guys have some input on the subject .

Backin the 1996 we were not allowed to connect more than 10 recessed cans in one given circuit . But back then circuits where tighter to work with , not like today that the rules have opened up but if any of you know where I can find this changes I will appreciate it or if any explanation possible .

Thank you .;)

[LarryFine]

Thisw is simple enough. The NEC requires that the maximum wattage permitted by the fixture and trim combination (which means a trim swap could cause issues) must be used.

In other words, if these fixtures can accept 75-watt bulbs, that's the figure you should use. 20 x 75 = 1500 watts. Since 12 x 120 = 1440 watts, you would be over the limit.

[iwire]

First as these are recessed lights the NEC requires you figure the circuit using the rating of the fixture, not the rating of the lamp.

20 - 150 watt rated fixtures with 65 watt lamps would be 3000 watts, not 1,300 watts.

Also a 15 amp circuit can provide 15 amps 1800 watts non-continuous. In my opinion few dwelling unit circuits are continuous loads.

[LarryFine]

In my opinion few dwelling unit circuits are continuous loads.In my opinion, lighting can easily be continuous, unless the fixtures are over-lamped, causing the thermal cutout to cycle.

[iwire]

In my opinion, lighting can easily be continuous.

Larry take a look at the actual definition.

Continuous Load. A load where the maximum current is expected to continue for 3 hours or more.

It's not that one or two lights on the circuit must remain on for more than 3 hours.

All the lights on the circuit would have to be on for more than three hours before it would meet the definition of continuous and this assumes only lighting on the circuit.

Once the circuit is mixed with receptacles I am not even sure if it could ever be considered continuous.

I am not saying you can't lightly load the circuit (I usually shoot for 10 to 12 amps on a 20 amp circuit) I am just saying we are not required to.:)

[LarryFine]

All the lights on the circuit would have to be on for more than three hours before it would meet the definition of continuous and this assumes only lighting on the circuit. It didn't occur to me, from the OP, that the lights would be broken into more than one switched circuit.

But, they still could easily be all on simultaneously if these are the only lights in use in the room(s) in question.

[iwire]

But, they still could easily be all on simultaneously if these are the only lights in use in the room(s) in question.

Yes Larry they could, a lot of things can happen.

We can plug more load into a circuit then it is capable of.

My point is, and has been, that it is not required to call it a continuous load.

That call is up to the installer and the inspector.

If the NEC required it how would you distinguish yourself as an above average EC? :)

[radiopet]

Most of the Recess Lights I install are labeled for 75W maximum bulb, we happen to use 65W because we buy them in bulk but I agree the factor needs to be 75W ( or what ever the fixture is rated for in regards to the bulb )

20 Recess lights with lets say a 75W rating would be = 1,500 Watts

1500 Watts translates into 12.5 Amps for a maximum of (20) 75W bulb

I happen to agree in that I would not consider this a continuous load per se'. could it become one ( yeah I know my son and his "LEAVE" the light on habits ) but chances are the OCPD, the Thermals in the Cans would snap in before the conductor was the issue.

[Greg Swartz]

I had this situation last week.

The owner wanted 38 can lights in the basement, 3 keyless, 2 sconce, and 1 vanity light. (and a partridge in a pear tree... :roll: )

The problem bacame that he wanted over 20 of them on 1 circuit, in fact, he wants 12 and 14 respectively on 2 sets of switches. I could not allow that of course. (Our cans are rated at 75w) That would be 26 on 1 circuit... not to mention receptacles...

Anyway, I told the homeowner that we need to be careful. I also am working with them to make them use fluorescent tubes. I go there tomorrow to see what happened over the weekend...

Greg :cool:

[bikeindy]

I had this situation last week.

The owner wanted 38 can lights in the basement, 3 keyless, 2 sconce, and 1 vanity light. (and a partridge in a pear tree... :roll: )

The problem bacame that he wanted over 20 of them on 1 circuit, in fact, he wants 12 and 14 respectively on 2 sets of switches. I could not allow that of course. (Our cans are rated at 75w) That would be 26 on 1 circuit... not to mention receptacles...

Anyway, I told the homeowner that we need to be careful. I also am working with them to make them use fluorescent tubes. I go there tomorrow to see what happened over the weekend...

Greg :cool:


Why would you have to put them on one circuit? Even if a home owner wanted 25 Cans on one switch they make two pole switches.

[danickstr]

hope they never want a dimmer to be installed or they will be cursing.

[radiopet]

Why would you have to put them on one circuit? Even if a home owner wanted 25 Cans on one switch they make two pole switches.

Still would not remove the fact that (25) 75W Recess Lights would be 15.625 ( 16 A ) on a single circuit so would be a NO-NO anyway unless of course they ran a 20A circuit just for those lights.

Good call Greg...sounds like they need a consultation from ya on what they can or can't do.

[LarryFine]

The problem bacame that he wanted over 20 of them on 1 circuit, in fact, he wants 12 and 14 respectively on 2 sets of switches. I could not allow that of course. (Our cans are rated at 75w) That would be 26 on 1 circuit... not to mention receptacles...Now, this shouldn't be an issue. With two switched groups like that, two circuits would work fine, with a third one for the remaining lights (and receptacles, unless a fourth (and fifth?) circuit is run for those).

[Dennis Alwon]

Now, this shouldn't be an issue. With two switched groups like that, two circuits would work fine, with a third one for the remaining lights (and receptacles, unless a fourth (and fifth?) circuit is run for those).


It is possible that the OP cannot easily add more circuits.

[LarryFine]

It is possible that the OP cannot easily add more circuits.Absolutely, but, as with many things in our business, the requirement doesn't change to suit the convenience.

Besides, if that is the case, the 15a- vs. 20a-circuit choice Paul mentioned would also be moot.

[bikeindy]

Still would not remove the fact that (25) 75W Recess Lights would be 15.625 ( 16 A ) on a single circuit so would be a NO-NO anyway unless of course they ran a 20A circuit just for those lights.

Good call Greg...sounds like they need a consultation from ya on what they can or can't do.


UH I was suggesting in my post that he would use two circuits.

sure adding circuits might be difficult but isin't that what we get paid to do. On a basement with a panel in the garage we usually run a sub to the basement. depends on how many circuits are needed.

[Dennis Alwon]

sure adding circuits might be difficult but isin't that what we get paid to do.

Only if the HO pays us to do what needs to be done. I have walked on many a job because the ho wanted to cheap out.

[Greg Swartz]

Why would you have to put them on one circuit? Even if a home owner wanted 25 Cans on one switch they make two pole switches.

Point taken... they DO make 2 pole switches...

Greg :cool:

[Greg Swartz]

hope they never want a dimmer to be installed or they will be cursing.

Well, I went back today to install switches (before drywall mind you)
and the home owner had blanked off all my receptacle boxes (smart guy)

He didn't want the switches I had bid, and had bought 600W slide dimmers....
ROFL....

I have 12 cans on 1 set of switches and 14 cans on another set of switches (3 ways)

umm... 65w bulbs x 12 does not equal 600W!!!

So, I took out bulbs and wrote a letter to the homeowner reminding him that this will either melt the dimmer OR cause a fire... (or anywhere inbetween!)

So, we'll see where I stand soon. I have already installed the switches... removing and replacing them is an extra...

Greg :cool:

[Greg Swartz]

So, I took out bulbs and wrote a letter to the homeowner reminding him that this will either melt the dimmer OR cause a fire... (or anywhere inbetween!)
Greg :cool:

This has already happened to me. I got a call from a HO from a job I did 6 months ago asking why his 600W dimmer melted. Told him I didn't know.

Turns out he added 8 track heads to my track lights I had installed... went from 8 - 50W MR16 to 16...

...um I don't know why it melted Mr. Homeowner, sir!

Greg :cool:

[Greg Swartz]

We were talking about 2 pole switches...

... anyone know if they make 2 pole dimmers? I think I remember somewhere in a distant past using them in a commercial application...

Greg :cool:

[danickstr]

1000 w dimmers are rated by how many fixtures are in the box, as you probably know, but it may help, at 45 bucks a pop retail.

[e57]

Once put roughly 8000 watts of lighting on a single pole 600w dimmer and it worked just fine. (Most of a small showroom) Via two Lutron HP panels.... five 20a circuits. You can dimm most anything with them.

[Gaston]

First as these are recessed lights the NEC requires you figure the circuit using the rating of the fixture, not the rating of the lamp.

20 - 150 watt rated fixtures with 65 watt lamps would be 3000 watts, not 1,300 watts.

Also a 15 amp circuit can provide 15 amps 1800 watts non-continuous. In my opinion few dwelling unit circuits are continuous loads.

my recessed cans are rated at 90 w. max so if I have 20 @ 90 W I'll be @
1800 w. but I'm using 65 w. and the fixture is rated from 60 w. up to 90 w. max , then it's possible to sqeeze the max of the juice .:roll:

[tallgirl]

my recessed cans are rated at 90 w. max so if I have 20 @ 90 W I'll be @
1800 w. but I'm using 65 w. and the fixture is rated from 60 w. up to 90 w. max , then it's possible to sqeeze the max of the juice .:roll:

You have to use the maximum rating.

Makes me wonder if there's a market out there for stickers that say "65 watt maximum" for situations like this ...

[stickboy1375]

With recess cans, can't you use the can & trim to determine the max. bulb selection? May not be the best design.. but definitely an option.

[celtic]

Makes me wonder if there's a market out there for stickers that say "65 watt maximum" for situations like this ...

....and who will read that?
Only the original installer :D

[Gaston]

You have to use the maximum rating.

Makes me wonder if there's a market out there for stickers that say "65 watt maximum" for situations like this ...


ok , My true question her is , that if in the unlikely scenario of this occurrence ,( of course this a curiosity of mine on paper )is it feaceble by the fact that at 90 W. x 20 = 1800 W ?. again this is me stretching the circuit to the max ,not that I would do it or even try . :roll:

[Greg Swartz]

The cans we are using are the standard HD halo cans. I believe the max wattage is 75W, however the homeowner is using 65W bulbs.

I know, I know... you have to use the max rating of the fixture!

But regarding my situation, the homeowner has not called me back... I don't know what they'll do.

Regarding the lutron panel... ha ha very funny! :grin:
I've installed those too... but for an el-cheapo homeowner, the panel will cost more than his entire electrical bid! :smile:

Greg :cool:

[e57]

Regarding the lutron panel... ha ha very funny! :grin:
I've installed those too... but for an el-cheapo homeowner, the panel will cost more than his entire electrical bid! :smile:

Greg :cool:

You're doing this and whatever else there is for <$650?!?!?!? :rolleyes:

(At least thats what I get a HP-4 for, HP-2 for ~$300) :grin: Then the T&M for where you remote it to...

He's cheap enought to max out the switching at his own whim, then he should ba able to pay the consiquences via your change order.

You also realize that he's low balling you, but spending top dollar for everything else. (Speculating if your situations are anything like mine...) Whine about an extra circuit for a couple hundred, then spend $50K for the tile alone in the guest bath... And import an Itailian to install it!