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dellhop
November 9th, 2007, 11:36 AM
Hello all,

Is it possible to run two sets of three way switches off one power feed? I have a basement with 6 cans on one side and 5 on the other. I wanted to drive each set of its own set of 3-way switches. Assuming they can all run off of one 15amp breaker, is there a way to do this?

The simplest way I can think is to add a box before the recepticles to split the power feed into two with pigtails. Although that just feels wrong somehow. If necessary I can bite the bullet and use two breakers, one for each set of lights/3-ways, but I wanted to try and save some space on the panel. Thank you.

joed
November 9th, 2007, 12:58 PM
Sure you can use the same power feed for two or more sets of 3way switches.
The actual routing of the cable depends on the room layout. If you happen to have one switch from each set in the same boxes it becomes easy.

Roger
November 9th, 2007, 01:04 PM
Sure, this diagram shown is for one set.

To take onward power to your other set of three ways just bring another 14/2 G into the switch box that is getting the incoming power as shown below and connect it to the incoming power along with the first set of 3 ways. Then run it to the second set of 3 ways wire the second set just like it shows here then daisy chain the lights to the switched power.

Or as Joe said if both sets start at the same box then just use pigtails to the incoming power for both switches in that box then run 2 14/3's to your other switches. You can either run the cable carrying the switched power to the lights from your 2nd 3-way switches or from the 1st whatever is easiest or best.

The menu bar on the right of the home page shows several wiring methods for three ways if this one doesnt work for your set up. a 15 amp circuit provides 1800 watts so 11 cans at 100 watts max each is 1100 watts to give you an idea.


http://www.selfhelpandmore.com/switchoutlet/3way/3wayboth/3wayboth.jpg

dellhop
November 9th, 2007, 01:11 PM
Great. Thanks guys.

joed, that exactly what I would have. So based on that and Roger's response I think I take the incoming wire, use a pigtail to create two of each wire and connect those to the switches. I then follow the diagram Roger provided for each switch.

Sound good?

AllanJ
November 9th, 2007, 01:19 PM
There should be no problem running two sets of 3-way controlled lights from one feed. You do have to watch the "box fill", or how many wires are coming into each box depending on the box size.

Start by running a 14-3 cable directly from one 3-way switch to the other 3-way switch in that set.

Supposing the power comes to one 3-way switch. To minimize box fill problems, run the 14-2 to the lights themselves from the other 3-way switch in that set (diagram Roger provided above). With this arrangement the white of the 14-3 is the neutral and not screwed on to any switch.

Then suppose you feed the second set by running a cable from the power feed location (switch box in the first set) to a switch box in the second set:

Two 14-2's and one 14-3 enter a box for a total of 7 conductors valued at one point each. The switch counts two points, all the grounds count one point, and if there are screw down cable clamps at the back of the box, count one more point. Pigtails (wires totally within the box) count zero points each. With clamps the point count is 11. For 14 gauge wires count 2 cubic inches per point for a required box size of 22 ci.

You will probably not have box fill problems if one 3-way switch of each set share a double gang box and the power enters there.

The idea of a junction box first where the power feed connects to two intermediate 14-2's to feed the two light sets (subcircuits) could arise if single boxes were installed and you had to run the 14-2 from the lights to the same box as the power.

You don't need two circuit breakers and two complete circuits back to the panel unless those cans are for heat lamps, such as in a health club.

dellhop
November 9th, 2007, 01:21 PM
Or as Joe said if both sets start at the same box then just use pigtails to the incoming power for both switches in that box then run 2 14/3's to your other switches. You can either run the cable carrying the switched power to the lights from your 2nd 3-way switches or from the 1st whatever is easiest or best.

The menu bar on the right of the home page shows several wiring methods for three ways if this one doesnt work for your set up. a 15 amp circuit provides 1800 watts so 11 cans at 100 watts max each is 1100 watts to give you an idea.


http://www.selfhelpandmore.com/switchoutlet/3way/3wayboth/3wayboth.jpg

Roger just saw your edit. That confirms what I though. And thanks for the Watt totals. I think I will be using 11 x 60W so looks good to me. Thanks again guys.

dellhop
November 9th, 2007, 01:31 PM
There should be no problem running two sets of 3-way controlled lights from one feed. You do have to watch the "box fill", or how many wires are coming into each box depending on the box size.

Start by running a 14-3 cable directly from one 3-way switch to the other 3-way switch in that set.

Supposing the power comes to one 3-way switch. Run the 14-2 to the lights themselves from the other 3-way switch in that set.

Then suppose you feed the second set by running a cable from the power feed location (switch box in the first set) to a switch box in the second set.

Two 14-2's and one 14-3 enter a box for a total of 7 conductors valued at one point each. The switch counts two points, all the grounds count one point, and if there are screw down cable clamps at the back of the box, count one more point. Pigtails (wires totally within the box) count zero points each. With clamps the point count is 11. For 14 gauge wires count 2 cubic inches per point for a required box size of 22 ci.

The idea of a junction box first where the power feed connects to two intermediate 14-2's to feed the two light sets (subcircuits) could arise if boxes that are too small were installed.

You don't need two circuit breakers unless those cans are for heat lamps, such as in a health club.

Wow Thanks Allan. I was just starting to investigate the number of wires in each box. I was hoping to go the easy route and use the simplest of configurations (3-way -> 3-way -> lights), but if I read that correctly then I might run into that problem. The 3-ways will be in the same box (hopefully....2 in one box and 2 in another). So power into one box (14/2), 2 14/3s to connect each set of 3-ways, and then two 14/2s on the other end going to the lights.

Box 1 would have 1 x 14/2 and 2 x 14/3. [8 (conductors) + 4 (switches) + 1 (grnd) = 13 (best case with no clamps) x 2 = 26 cu inch]

Box 2 would have 2 x 14/2 and 2 x 14/3. [10 (conductors) + 4 (switches) + 1 (grnd) = 15 (best case with no clamps) x 2 = 30 cu inch]

Do screw down cable clamps exist in the blue plastic boxes. I am not familiar with the clamps as I though the holes in the boxes were designed to secure the wires coming in.

Thanks again for the info.

dellhop
November 9th, 2007, 01:34 PM
You will probably not have box fill problems if one 3-way switch of each set share a double gang box and the power enters there.

Got me again with editing :) This is exactly what I was planning on doing.

AllanJ
November 9th, 2007, 01:41 PM
The molded blue fingers at the back of plastic boxes to hold the cables in place don't count any points.

Even if you are within the box fill limit, it can still be hard to stuff everything in the box. If you pushed the wires into spring loaded holes in the switch (or receptacle) with no screw-down tightening, then the act of stuffing things into the box can sometimes compromise the contact.

dellhop
November 9th, 2007, 01:43 PM
The molded blue fingers at the back of plastic boxes to hold the cables in place don't count any points.

Okay cool. SO when do clamps come into play? New Work style?

dellhop
November 9th, 2007, 01:49 PM
Even if you are within the box fill limit, it can still be hard to stuff everything in the box. If you pushed the wires into spring loaded holes in the switch (or receptacle) with no screw-down tightening, then the act of stuffing things into the box can sometimes compromise the contact.

Believe me I won't use the holes. Screws all the way for me baby :) Thanks.

Roger
November 9th, 2007, 02:19 PM
Only when they are internal and part of the box in most cases......some plastic boxes have them but it isn't that common.


http://www.electrical-supply.net/images/products/CB8-R.jpg

dellhop
November 12th, 2007, 01:30 PM
Thank you Roger and Allan for your help.

dellhop
November 26th, 2007, 12:06 PM
Okay the planning has come a little further. Is this adivisable?

A double gang box containing 2 dimmer three-ways (powering 2 sets of recessed lights totaling of 11---6 and 5), has 14-2 feed from the panel, and 2 14-3 to the other three-ways. Can I add another 14-2 to the pigtails and drop that about 10 inches to another double gang box below that contains one three-way (a signle recessed at the bottom of stairs) and one 2-way switch (switch outlet). I am pretty sure I would be okay with fill and code, but not sure about whether its the "right way" to do it.

So instead of using a four gang box with 3 3-ways and a 2-way I use two double gangs, where the second is powered by a feed from the first.

Hope that makes sense.

My last question pertaining to this is: A regular switch recepticle is worth 2 points when figuring out the fill of the box...what about dimmers are they also 2? The dimmers I have purchased have the slider up and down and a toggles below the slider.

As usual thank you very much for your expertise.

AllanJ
November 27th, 2007, 12:59 PM
Currently the box fill formulas are somewhat watered down where the "device" whether it is an ordinary switch or a dimmer counts as two points.

No problem (other than possible box fill issues) putting additional switches in a separate switch box down below.

dellhop
November 28th, 2007, 06:23 AM
Thanks Allan, Yeah I think I'll be okay with box fill. I just wanted to make sure I was okay with doing it that way.