A whole lotta three-way light switches.....


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Old 02-25-12, 05:47 PM
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A whole lotta three-way light switches.....

I have successfully wired a single electrical outlet to a pair of three-way switches at opposite ends of a hallway. Now I have a bigger project and I don't even know if this is possible.

My basement (aka "The Forever Project") is essentially divided into five areas. I intend on mounting multiple light buckets in each area:

Gym Area: 4 buckets
TV Area: 4 buckets
Play Area: 8 buckets
Storage Area: 4 buckets
Office Area: 10 buckets

I want two banks of five three-way switches, one bank at the top of the stairs and the second bank behind the stairs at the bottom, so that any area of lights can be turned on or off from either bank of switches. The staircase is in the mdidle of the basement; the gym, TV and play areas are on one side, storage and office areas on the other. The basement area is roughly 1,200 square feet; about 950 square feet are on the gym/TV/play area side leaving about 250 square feet on the storage/office side. The circuit break panel is in the corner in the TV area, diagnally opposite from the office.

I have a 15 amp circuit that will be dedicated to lighting. By my calculations this should be more than sufficient for all 30 buckets. Assuming I put no greater than 15 watt CF bulbs (75 watt equivalent) in each bucket, that's 450 watts in total. On a 120v circuit I would need less than four amps to drive all 30 buckets at once.

What I don't know is how to wire all of this together. If this were a breadboard electrical project I would run a lead from the power source to a four point power block. On three of the points I would power the gym/TV/play lights, then I'd run a lead from the fourth point to the other side of the basement where it would connect to another two point power block which would power the office/storage lights. Each lead off the power blocks would be wired as if they were distinct three-way circuits.

Is this the same way to approach household current? Are there power blocks designed for household current? Or is there another way to go about this? And if there's anything else I'm missing please let me know. Thanks!
 
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Old 02-26-12, 05:57 AM
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I hope you are referring to "can" lighting. Never heard it called "buckets", but interesting, anyway. A single 15 amp circuit won't handle that many lights. I know you "promised" not to put but small CFL's in it, but promises can be broken, and a future owner may decide to put a big 75 watt bulb in each one.....see? Break the rooms down and run a separate 15 amp circuit to each room for lighting.
Since you are in the framing stage, wiring would be easy. I would, however, get a book, similar to Wiring Simplified. It will tell you the different configurations of 3 way lighting available and you can choose which one suits you best. Power blocks are fine for DC projects, but not practical for AC.
 
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Old 02-26-12, 06:44 AM
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I have never heard them called buckets either.

Chandler is correct. The load of the circuit needs to be designed to handle the load of the max wattage per light. So your calculations need to be using 75 watts per light. You can then only load a circuit up to 80% of max current (15 amps) which is 12 amps. A separate circuit is not needed per room, but a 15 amp circuits will run 19 cans each so two circuits are needed for your lighting.

One other thing I'd like to point out is you may have a hard time finding a 5 gang box and plate. You might be limited to 4 gang unless you special order them.

Lastly, per 2011 code, a neutral is required in each switch box. Therefore, there is really only one way to wire the 3 ways:
run the 14/2, hot and neutral, to the first box.
14/3, travelers and neutral, to the second box.
14/2, switch leg and neutral, to the light.
 
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Old 02-26-12, 07:59 AM
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You could probably make a five gang box using "gangable" metal boxes and some BigBox stores sell configurable plates made up of individual pieces that snap together. You need to probably place a board (2X4 flat) at the back of the stud bay to fasten the box to.
 
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Old 02-26-12, 08:12 AM
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If the areas are divided by walls, why not have the separate rooms switched individually? Having a set of switches at the top of the stairs and at the bottom of the stairs, seems counterproductive, IMO. I would have a stair light controlled by 3 way switching, but have my big gang box at the base of the stairs. You could, then 3 way from the big gang box to each area to be lit. If no walls, no need for 3 way lighting.
 
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Old 02-26-12, 02:38 PM
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Math

Chandler: I am confused. Is my math incorrect? Lowes will sell me a 15 watt CFL bulb that's the equivalent lighting of a 75 watt bulb. I am looking at a total of thirty (30) bulbs in the basement. 30 bulbs by 15 watts apiece is 450 watts in total. Going by Ohm's Law (watts = amps x volts) on a 15 amp 120 volt circuit I could run 1800 watts of light. I need 450 watts - 25% of the maximum load on that circuit. Why do I need five 15 amp circuits - enough to power 9,000 watts of light - to run 450 watts?

The odds of a future owner putting 75 watt incandescent bulbs into every single fixture (bucket, can, whatever) is fairly small. Incandescent bulbs are already starting to get a little more difficult to find and will only get more difficult as time goes by, plus there's the fact that I just recently moved into this house so any new owner is likely many years down the line which would make incandescent bulbs that much more difficult to find.

As far as ganging the switches, I was thinking more along the lines of a three and a two switch box.

Although I don't know why it's relevant to how to wire this up: I simplified my explanation in my original post, and since y'all seem concerned about my apparent need to have switches at both ends of the staircase I will clarify. One set of switches will be at the top of the stairs. This is because my house is a ranch style house and the basement entrance is more or less in the center of the house. Having a bank of switches at the top of the stairs will save a lot of leg work if lights are left on in the basement.

The second bank of switches would be positioned thusly: Go down the stairs (12 of them), turn 90 degrees right, walk two paces, turn 45 degrees right, walk nine paces to the wall at the center of the room. The second bank would be at that location in the wall. Given the nature and purpose of these rooms, this arrangement of switches is the most convenient for us.

A friend of a friend is an electrician and he's coming over on Wednesday evening to help me sketch out this project. Thanks for your insight.
 
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Old 02-26-12, 03:07 PM
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Why do I need five 15 amp circuits - enough to power 9,000 watts of light - to run 450 watts?
You don't. You really only need two. 30 lights x 75 watts (max wattage can is rated for) = 2250 watts. 2250/1440 (80% of 15 amps) = 1.56 15amp circuits. Even though you plan to use CFL's, unless the lights only accept CFL's (two or four pin) you have to size the circuits worse case scenario. You size circuits according to the nameplate of the fixture.
 
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Old 02-26-12, 03:55 PM
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I wasn't suggesting you needed all the rooms circuited. I didn't explain myself well. Breaking up the rooms into smaller circuit groupings would have been better. As Scott said, two circuits would be sufficient. But, as he also said, you have to go with the rating on the fixture, not what you plan on putting in there, no matter how remote it is that a future occupant will load them up. I don't believe anyone suggested putting the switches both in the staircase. You want them 3 way for convenience sake, and that's fine. I was suggesting not having them both in the stairwell (and your OP does state it would be on a different wall). I was suggesting another method, but did not know what your motives were. That's cool.
I remodeled a 1970's house once and they had TWO banks of 4 switches over each other controlling who knows what, and another two banks of 4 switches on adjoining wall less than 10 feet away. A true wiring nightmare.
 
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Old 02-26-12, 08:59 PM
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Am I wrong in thinking that each can or pot light is considered a 'load', and the max loads per circuit is 12 under code. Am I wrong on this understanding.
 
 

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