Amp rating of dimmer switch feeding 4 luminaires

[nukem2k5]

I've got a wall switch that I want to replace with a dimmer. The circuit has 4 recessed ceiling can lights on it, which I presume are in the 60-75W range (however, I can't access them from my attic to confirm).

The existing switch is rated for 15A, but all the dimmers that I can find seem to be rated only for up to 600W. Should I select the switch rating based on the total connected load (i.e. presumably about 300W), or based on the upstream protective device (15A breaker in the panel)? I've not found anything definitive in the Code to clarify this.

 

[iwire]

See NEC 400.14 and specifically 400.14(E) it is too long to post here. Now it is odd that 400.14 itself says snap switches but seems to include dimmers as well based on (E).

 

[Dennis Alwon]

Dimmer is based on the lamp wattage that the dimmer controls. 4 - 75 watt bulbs = 300 watt so a standard 600 watt dimmer will work. Change to LED then you need to get a dimmer rated to dim LED bulbs and you need to ensure the LED's are dimmable

 

[nukem2k5]

See NEC 400.14 and specifically 400.14(E) it is too long to post here. Now it is odd that 400.14 itself says snap switches but seems to include dimmers as well based on (E).

I'm using NEC version 2014: 400.14 covers Protection from Damage for flexible cords, and there is no 400.14(E)

 

[nukem2k5]

Dimmer is based on the lamp wattage that the dimmer controls. 4 - 75 watt bulbs = 300 watt so a standard 600 watt dimmer will work. Change to LED then you need to get a dimmer rated to dim LED bulbs and you need to ensure the LED's are dimmable

Thanks. Any code references that come to mind, for my future reference?

 

[mgookin]

I'm using NEC version 2014: 400.14 covers Protection from Damage for flexible cords, and there is no 400.14(E)

Look at 404.14(E)

 

[Dennis Alwon]

I'm using NEC version 2014: 400.14 covers Protection from Damage for flexible cords, and there is no 400.14(E)

Bob meant article 404 not 400

 

[iwire]

Bob meant article 404 not 400

Yes, thank you.

 

[nukem2k5]

So the breaker is sized to protect the wire, but the switch must only be sized to safely carry the expected connected load, even if that means it's a lower continuous rating than the circuit itself is capable of safely carrying?

What if the switch is feeding a general purpose receptacle? Then mustn't the switch be rated for the full circuit rating (15A; since you can't "control" the load that someone plugs into the receptacle - whereas, conversely, luminaries are hard-wired, thus the load is essentially fixed)?

 

[Dennis Alwon]

So the breaker is sized to protect the wire, but the switch must only be sized to safely carry the expected connected load, even if that means it's a lower continuous rating than the circuit itself is capable of safely carrying?

What if the switch is feeding a general purpose receptacle? Then mustn't the switch be rated for the full circuit rating (15A; since you can't "control" the load that someone plugs into the receptacle - whereas, conversely, luminaries are hard-wired, thus the load is essentially fixed)?

Generally switches are rated 15 amp or 20 amp but you cannot just dim a receptacle unless you have a specialized outlet. Lutron makes a receptacle and cord cap for such a situation. Usually one would install it on a lamp.

 

[nukem2k5]

I see. I've seen some switches (not dimmers) that are lower rating (e.g. 960W aka 8A) but intended for use with CFL or LED luminaires. I suppose these are only legally acceptable for use if you ensure the only connected load are CFL/LED fixtures - correct?

 

[Dennis Alwon]

Here is the article

406.15 Dimmer-Controlled Receptacles. A receptacle supplying
lighting loads shall not be connected to a dimmer
unless the plug/receptacle combination is a nonstandard
configuration type that is specifically listed and identified
for each such unique combination.

 

[Dennis Alwon]

I see. I've seen some switches (not dimmers) that are lower rating (e.g. 960W aka 8A) but intended for use with CFL or LED luminaires. I suppose these are only legally acceptable for use if you ensure the only connected load are CFL/LED fixtures - correct?

I have never seen a wall switch that wasn't a dimmer or occupancy/motion switch that was rated under 15 amps. All standard switches are rated for cfl and led. The ones you mention must either dim or turn on auromatically

 

[nukem2k5]

I have never seen a wall switch that wasn't a dimmer or occupancy/motion switch that was rated under 15 amps. All standard switches are rated for cfl and led. The ones you mention must either dim or turn on auromatically

Sorry, yes, the one in particular that I'm thinking of can be remotely controlled via ZigBee controller.

I suppose I was generally curious where it's written in the Code that the rating of a dimmer/switch/etc need not be equal to the continuous rating of the circuit (i.e. of the upstream protective device) so long as the continuous load through the switch/dimmer is ensured to be no greater than the rating of the switch/dimmer.

 

[Dennis Alwon]

Sorry, yes, the one in particular that I'm thinking of can be remotely controlled via ZigBee controller.

I suppose I was generally curious where it's written in the Code that the rating of a dimmer/switch/etc need not be equal to the continuous rating of the circuit (i.e. of the upstream protective device) so long as the continuous load through the switch/dimmer is ensured to be no greater than the rating of the switch/dimmer.

I am curious why you would think the switch would need to rated for the entire circuit since the load side of the switch would generally be a lot less.

I can install a 20 amp circuit and install 15 amp receptacles on it as long as there is more than one receptacle on the circuit. Also look at Table 210.21(B)(3)

210.21 (B) Receptacles.(1) Single Receptacle on an Individual Branch Circuit.
A single receptacle installed on an individual branch circuit
shall have an ampere rating not less than that of the branch
circuit.

 

[curt swartz]

I have never seen a wall switch that wasn't a dimmer or occupancy/motion switch that was rated under 15 amps. All standard switches are rated for cfl and led. The ones you mention must either dim or turn on auromatically

Dennis, you have never installed a Maestro or similar electronic switch? Most electronic switches have a ~6-8 amp rating.

 

[Dennis Alwon]

Dennis, you have never installed a Maestro or similar electronic switch? Most electronic switches have a ~6-8 amp rating.

Yes Curt but those are the dimmable ones not the plain switch--NO????

 

[GoldDigger]

The existing switch is rated for 15A, but all the dimmers that I can find seem to be rated only for up to 600W.

You can also find dimmers rated for 1000W or maybe more, but they usually have external heat sinks and must also be derated when you put more than one into a multi-gang box.

 

[Dennis Alwon]

You can also find dimmers rated for 1000W or maybe more, but they usually have external heat sinks and must also be derated when you put more than one into a multi-gang box.

That's correct. I believe they went up to 2000 watts and could not be ganged with other switches. Lutron have a booster that can take a 600 watt dimmer up to 2000 watts -- I believe. It fits in a 2 gang box separate from the switches, of course.

 

[JFletcher]

Dimmers are sized for the load. I dont know of any that can do more than 600W w/o external heatsinks.*

http://www.electrical101.com/dimmer-switches.html

*Lutron (and presumably others) do make higher wattage dimmers without visible heatsinks. In my experience, dimmers rated over 600W jump in price pretty steeply.

There is no code requirement to size the dimmer based on the OCPD of the circuit.

If this is a commercial job, it may be better to overspec the dimmer for the max wattage bulbs that can be installed rather than what the cans are rated for or what bulbs they put in now. Ive pulled hundred of 100W bulbs out of fixtures rated 60 or 75W max. Seems a lot of people buy those 25,000hr rated bulbs (trading lumens for life expectancy), dont like the light output, then put in higher wattage bulbs to compensate. 10 40W bulbs on a dimmer rated for 600W is okay; 10 75 or 100W bulbs, and the dimmer will melt.