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# Maximum wattage for a circuit or switch

#1
10-24-11, 05:54 PM
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Join Date: Oct 2005
Location: Florida
Posts: 1,466
Maximum wattage for a circuit or switch

I understand in the case where I have a single circuit supporting multiple sets of lights, the threshold is more on the individual switch's wattage rating and not the circuit itself?

For example, let's say I have a single 20A circuit split into three separate switches, and each controls a group of six to eight recessed lights, I need to make sure the total lights for one group is less than the maximum wattage for that switch right?

So if I have one group of eight lights at 60W each, the total wattage is 480W and I should have a switch for say 600W to be safe, right?

Or do I add up all the wattages for all the switches and the total needs to be less than a certain amount for the circuit?

What I found is that there seem to be no MAX WATTAGE labels on most switches. Today I looked at some of them on the box, and the instruction sheets inside, and on the actual switch carefully, I did not see ANY sort of MAX WATT specifications.

For example, this one by Trademaster

Here is the specification PDF:

http://www.smarthome.com/manuals/4232.pdf

No info is listed. I checked a few Leviton switches at Home Depot, same problem. I must be missing something?

#2
10-24-11, 06:08 PM
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Join Date: Jan 2010
Location: USA
Posts: 9,397
Single pole and three way switches are rated in amps, dimming control switches are rated as to the maximum wattage they can be used for.

#3
10-24-11, 06:58 PM
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Join Date: Oct 2005
Location: Florida
Posts: 1,466
Thanks, how would I figure out if I am overloading my circuit or switches?

For example, if my 20A circuit is supporting three sets of lights:

7 lights at 40W each
2 lights of 100W each
2 lights of 40W each

Three switches, but two of them are in a combo switch. The switches are just standard 15AMP single pole switches.

#4
10-25-11, 04:52 AM
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Join Date: Jul 2002
Location: Maryland
Posts: 14,594
Your 15 amp rated switches are fine. Even the 2x100 switch is switching less than 2 amps.

#5
10-25-11, 06:18 AM
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Join Date: Oct 2004
Location: WI/MN
Posts: 18,759
Volts x amps = watts, therefore amps = watts/volts. Thus, in your case, the first switch controls:
(7 x 40 w)/120v = 2.33 amps

The other two are less than this.

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