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How do you determine the load on a particular switch?

post #1 of 10
3/11/07 at 9:17pm
Thread Starter 
OK guys yet another newbie question. Now that I understand the issue with subtracting 200W from adjacent dimmers such as the Insteon KPL V2 or the SL V2 dimmers, now I'm wondering how one goes about determining actual load on a particular switch. How do I go about determining whether I need a 600w or 1000w switch? Do I literally count the number of lights that that one switch controls and then multiply that by ??? Should I assume a 100W bulb in each light socket, or should I go so far as to unscrew the light and find out what the max load in the canned light (for example) is? I'm thinking that the latter may be the real answer.

I'll keep searching for an answer, but thought I'd also ask in the meantime.
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post #2 of 10
3/12/07 at 12:26am
Multiply the maximum bulb that can be put in the can by the number of cans.
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post #3 of 10
3/12/07 at 9:26am
I second QQQ on this. That way, if someone comes through and just throws in the max rated lamp, you'll still be covered.
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post #4 of 10
3/12/07 at 9:33am
My ignorant question for the hour: Are there any inefficiencies of a relevant scale introduced along the chain? That is, does it take >100w to provide a 100W lightbulb with power, and enough so to warrant a fudge factor?
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post #5 of 10
3/12/07 at 9:59am
Actually, you'll also want to consider determining the load with at least 10% headroom. Some dimmers heat up pretty quickly at their full rated load. Also, subtract for ganged dimmers.
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post #6 of 10
3/12/07 at 1:08pm
Quote:
Originally Posted by Rondo1 View Post

Now that I understand the issue with subtracting 200W from adjacent dimmers such as the Insteon KPL V2 or the SL V2 dimmers,

One note of interest as it relates to Insteon, there is a thread over in the Smarthome forums that a 1000W dimmer is nothing more than a 600W with more cooling fins on the sides. And if you break them off to fit side-by-side in a box, then you are back to a 600W dimmer.

Edit: Added link: http://www.techmall.com/topic.asp?TO...erms=1000,Watt
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post #7 of 10
3/12/07 at 11:47pm
Thread Starter 
I just replied to that discussion too. What baffles me is that the discussion seemed to just end last November. Yet SH hasn't answered the question. So now I'm pretty nervous about going forward because I dont know what the real load for a 1000w dimmer is if it sits in the middle of a 3 gang box of 3 dimmers. Is it now 600w due to the fins being removed or is it now a mere 200w because its ALSO in between two other dimmers. Good grief.
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post #8 of 10
3/13/07 at 5:55am
Quote:
Originally Posted by Rondo1 View Post

Is it now 600w due to the fins being removed or is it now a mere 200w because its ALSO in between two other dimmers.

My guess is that you are left with a 200W dimmer. But remember, if you are using dimmers as part of a virtual 3-way circuit, if you don't have a load on it, then no derating is required.

One trick you can use with Insteon if you have virtual 3-ways is to use the unsued traveler wire to send the load to another switch in the circuit.

And yes, SH should have provided a direct answer, but they didn't.
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post #9 of 10
3/15/07 at 1:51am
Thread Starter 
Unfortunately all 3 switches are SINGLE switches and are not a part of a 3-way setup. In the end, my friend has agreed to bring his electrician back in to move one of the switches to another gang box, so the issue is moot.
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post #10 of 10
3/15/07 at 8:05am
There is one other option and I'm sorry I didn't think of it earlier. If you have access to the wiring to the lights say in an attic, you can either use an Inlinelinc or a regular dimmer and locate it in the attic. Then just use a dimmer as a controller and no derating would be required.
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