Electrical codes and LED lighting

[Rod B]

Hi There,

I live on an acerage, and we keep it lit up at night for some added security. The problem is that I have two banks of lights on switches (15 amp double pole breaker) and a third bank on a photo cell switch (single 15 amp breaker).

When I moved in, I replaced the 75w/90w halogens with 14 watt LED bulbs (there are also a handful of triple bulb fixtures I moved from 3*50w/60w to 3*6w, but you get the picture).

For one reason or another, I usually end up leaving the two manual switches on all day more days that not. I hope by now, you see where I am going... Is it now OK to have the photocell switch control all three banks and remove the 2 manual switches? Or does it have to stay wired up for the maximum fixture ratings?

I figured I'd ask here first, before calling up an electrician (not wanting to assume that he/she would answer my questions over the phone).

Cheers,
Rod

P.S. I'm not asking HOW to wire it, just if it's even possible (and keep everyone in code).

 

[matt_i]

Two issues:

Can the breaker on the new circuit handle the amperage. There's a derating factor for lighting which is basically a continuous draw. (iow you can carry 12A of designed lighting load on a 15A circuit wired with #14 NM-B).

The other is if the photocell can reliably switch on and off the new lighting load which is presumably larger than before. Every switch contact has an amp rating.

 

[Rod B]

Two issues:

Can the breaker on the new circuit handle the amperage. There's a derating factor for lighting which is basically a continuous draw. (iow you can carry 12A of designed lighting load on a 15A circuit wired with #14 NM-B).

The other is if the photocell can reliably switch on and off the new lighting load which is presumably larger than before. Every switch contact has an amp rating.

Thanks for the reply. The current photocell circuit had 7 * 90 watt bulbs = 630 watts (I'm not sure if there are plugs connected to that photocell, but certainly none that I'm using at the moment). My guess is that the fixtures were rated for 120w bulbs (which would be 840watts).

With all the bulbs connected right now, I would have less than 1/2 the watts (e.g. about 298watts), so I assume it could reliably switch the load and that the 15 Amp circuit could handle it...

So, 'theoretically' I'm not worried about the load on the circuit, because I've reduced the wattage so much. I'm not so much worried about if it will 'WORK' more if it's still within code.

Rod

 

[Innovate1]

Since you have less watts than before I don't see any reason you can't run them all on the same circuit and photocell. You need to combine the circuits after the photocell so the main issue I see is running wire to do that.

 

[pmiranda]

You can wire them all to one photocell, but since you asked about code, NEC2020 says
"An outlet supplying luminaire(s) shall be calculated based on the maximum volt-ampere rating of the equipment and lamps for which the luminaire(s) is rated."

Basically, those light fixtures all have (or originally had) a rated wattage on a sticker and code says the breakers and switches have to support that rated wattage, which might not be true after you rewire the circuit.

 

[nadogail]

IMHO. you lights can be controlled by a photocell.

 

[ddawg16]

If you want to be safer....use the photo eye to control a 120Vac relay rated for the full load plus some.

So...photo cell turns on the relay....relay turns on lights.

Personally, I'd mix in some motion sensing lights. Those are more effective at keeping people out. When the lights come on, you know you have motion.

 

[pmiranda]

Motion sensor is a grand idea... if you really want light all night, run half on, and half on motion sensors. Not hard to retrofit right at the light

 

[MrSurly]

The answer to the code question is (as pmiranda cited) effectively NO, you are not allowed to under-protect a device simply because you plan to under-utilize it.

EVERY 100 watt fixture is assumed to demand 100w of protection. Running 5w bulbs doesn’t change the load Calc for code purposes.


Sent from my iPhone using Tapatalk

 

[Rod B]

Thanks for all the responses, I do want it to remain up to code, so will leave that part alone.

I will do a bit more research on my options. I do like the idea of a relay, so will look into that further.

In the meantime, will try to get into the routine of turning them off in the morning... that is the simplest tech wise! Haha

Thanks again!

Rod

 

[acer66]

Personally, I'd mix in some motion sensing lights. Those are more effective at keeping people out. When the lights come on, you know you have motion.

This.

 

[pmiranda]

MAYBE if you find some- good-quality labels that won't fade or fall off, you can relable the fixtures for lower wattage. I don't know if the code allows for that. Ask a real electrician, not just some guy on the internet

 

[CraigStu]

I used a relay a couple years ago to control a 240V line out to the RV parking area. There was a small box out there w/ a 240 and two 120 outlets. We had 4 double flood lights at that end of the property that we used when walking the dog. The relay was referred to as a contactor. The experience we had w/ motion sensing lights that I installed originally was that by the time I turned up the sensitivity enough that we didn't have to walk to within 15 ft of them, then they came on when wind blew tree branches, the neighbors cat walked through, a car or truck drove on the road 60 ft away. etc. The contactor worked great and was controlled by a standard 120V wall switch. We turned it on going out to walk and off when we came back. That way I could leave the sensitivity cranked up and didn't have flood lights coming on and off all night long. I had never heard of a contactor before but when I started looking it turns out the are many, many varieties of them.

 

[manwithtools]

Contactor and relay are the same thing technically. A lighting contactor is made to control lights specifically. There are many other varieties as pointed out.

 

[nateo]

Why not add a timer to the two manually controlled circuits? I bought a couple of these to use on my outside lights.

They fit in a standard decora switch and you can set them to turn on before sunset (calculated using your lat / long) and turn off either at a set time or a set duration. The only problem I've had is after a prolonged power outage you sometimes have to reset the time on them.

 

[Rod B]

Why not add a timer to the two manually controlled circuits? I bought a couple of these to use on my outside lights.

They fit in a standard decora switch and you can set them to turn on before sunset (calculated using your lat / long) and turn off either at a set time or a set duration. The only problem I've had is after a prolonged power outage you sometimes have to reset the time on them.

Yes, that is exactly what I was initially going to do. One of the problems is that I have two light switches on each bank of lights, one at front door, and one at side door. Not a big deal, just means I would have to blank out the side door (or the lights would be turning off on the opposite schedule if someone toggled the switch).

I figured the IDEAL solution was to have it controlled automatically by the photo sensor ( and likely not much more for an electrician to wire up, compared to the cost of the switches).

I may go back to the timer idea now, knowing that I can't just wire them up directly to the photocell. I will look into a relay/contactor first though, as I'd still rather just have it be automatic. Our sunrise/sunset changes drastically over the year, so most efficient would be to run off a photocell.

EDIT: Just noticed that the timers nateo linked have an astronomical clock, that's pretty cool! That would address my concern of having to update the timers throughout the year...

 

[nateo]

EDIT: Just noticed that the timers nateo linked have an astronomical clock, that's pretty cool! That would address my concern of having to update the timers throughout the year...

Yup, you just put in your lat / long and it figures out sunset / sunrise. I have mine set to come on a half hour before sunset and go off at 10 PM. The internal clocks are pretty good too, I have a switch on the house and the garage and they turn off pretty close to the same time every night.

Deals with Daylight Savings, too, despite how much I despise it!

 

[rlitman]

Since you have less watts than before I don't see any reason you can't run them all on the same circuit and photocell...

Not really directly in response to this, and if a contactor/relay is used, this is moot, but look at the ratings on the photocell/timer.

Many will say 600W incandescent, but only 100W LED/fluorescent. Just keep in mind that the derating will be significant for LED. It is not just about watts.

 

[Rod B]

Not really directly in response to this, and if a contactor/relay is used, this is moot, but look at the ratings on the photocell/timer.

Many will say 600W incandescent, but only 100W LED/fluorescent. Just keep in mind that the derating will be significant for LED. It is not just about watts.

OK, gotcha, now I understand what 'matt_i' was referring to when he mentioned the de-rating, didn't catch that.

I was looking more into the option posted by nateo and I am going to order those. It looks like I can get a remote switch as well, and still keep the three-way switch that I already have at the back door.

This way, I don't need to involve an electrician and mess with any of the wiring. I can install the switches myself.

Thanks for all the great info everyone, much appreciated!

Rod