> >
>

# 3 way wiring - Power>Light>Switch1>Switch2>Light

## 3 way wiring - Power>Light>Switch1>Switch2>Light

#1
01-21-14, 07:52 AM
Member
Join Date: Sep 2012
Location: USA
Posts: 29
3 way wiring - Power>Light>Switch1>Switch2>Light

I'm working on finishing my basement and almost half way through. I think I'm figuring out most of the electrical but I'm not entirely sure about this one. I've been looking through other posts but haven't found the answer. I liked the diagrams on this site also but they don't have the exact scenario I'm asking about (Installing A 3-way Switch With Wiring Diagrams - The Home Improvement Web Directory). Basically I want to run the power through the light, then to a switch (at the bottom of the stairs), then onto the second switch (top of the stairs) and then to the last light at the top of the stairs. Is that possible and if yes, how do I do it? I tried to sketch this out in the diagram this morning using my daughters markers. Hopefully it makes sense. I'm also running two other 2 way switches to a light off of the power source so that's why the extra lines.

Thoughts?

Attached Images
#2
01-21-14, 07:59 AM
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 13,987
It is much easier to wire with power into and out of the switches instead of the lights.

#3
01-21-14, 08:09 AM
Member
Join Date: Sep 2012
Location: USA
Posts: 29
So could/should I then run the power to Switch1 then to the light (at the bottom of the stairs), then up to switch 2, then onto the second light (at the top of the stairs)? My primary confusion is wether I can run the second light after the second swtich. Does my question make sense?

#4
01-21-14, 08:12 AM
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 13,987
The simplest is power to Sw1 xx-3 cable to Sw2 and then xx-2 cable to the light.

#5
01-21-14, 08:21 AM
Member
Join Date: Sep 2012
Location: USA
Posts: 29
I can't think of a good way to do that without running lots of extra wire which I don't really have space for (never mind cost). Remember, switch 1 is at the bottom of some stairs and switch 2 is at the top of the stairs... and there are TWO lights (one at the top and one at the bottom).

I've seen plenty of diagrams with people wiring power through the light, etc... my primary question is running a light at the end of the run AFTER the 3 way switches.

#6
01-21-14, 08:28 AM
Member
Join Date: Sep 2012
Location: USA
Posts: 29
Would this work better?
(I'm also assuming I can find a way to use the Light1 as a junction box to run extra power out to other switches and lights without being impacted by the 3way switch setup).

Attached Images
#7
01-21-14, 08:37 AM
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 13,987
You are going to need something like xx-4 cable to do this.

Also the newer code is now requiring a neutral at the switches.

#8
01-21-14, 08:55 AM
Member
Join Date: Sep 2012
Location: USA
Posts: 29
The "orange" color on my diagram is intended to represent a neutral. Is that what you are referring to?

Or is the problem if I turn a neutral into a hot wire between the switches? That's interesting as there are so many resources on the web that seem to imply that is an acceptable standard. If that's the case then I guess the options truly are limited. I kind of find that hard to believe as it will require me to run so much wire back and forth through the walls and studs, etc.

#9
01-21-14, 09:15 AM
Member
Join Date: Sep 2012
Location: USA
Posts: 29
I think I can come up with a way to run it like this...

Power > Switch1 > Switch2 and then from there run power to each light (off of switch2). I'm thinking that wouldn't be too bad and seems to meet what you're suggesting. (easiest way and maintains neutrals at each switch)

#10
01-21-14, 09:18 AM
Member
Join Date: Jan 2010
Location: United States
Posts: 9,880
Or is the problem if I turn a neutral into a hot wire between the switches? That's interesting as there are so many resources on the web that seem to imply that is an acceptable standard.
ALL switches are required to have a neutral by the 2011 NEC regardless of what WAS an acceptable standard. Like PCboss said, you can use either 12-4 or 14-4 NM-B cable (aka romex) to achieve this. What code has your local AHJ adopted?

Power > Switch1 > Switch2 and then from there run power to each light (off of switch2). I'm thinking that wouldn't be too bad and seems to meet what you're suggesting. (easiest way and maintains neutrals at each switch)
That should work.

#11
01-21-14, 09:21 AM
Member
Join Date: Mar 2006
Location: USA
Posts: 29,711
The "orange" color on my diagram is intended to represent a neutral.
XX-4 wire has Black, Red, White, Blue, plus bare ground. Many instructions on the web were written based on code cycles older than 2011. A white can be repurposed as an ungrounded conductor but due to 2011 code changes it is usually needed as a neutral.

#12
01-21-14, 09:26 AM
Member
Join Date: Sep 2012
Location: USA
Posts: 29
Thanks for everyone's input so far. What about something like this then (see pic below)?

Also, I'm assuming that I can splice out of the box where switch 1 is to run power to other traditional switch/lights?

Attached Images
#13
01-21-14, 09:33 AM
Member
Join Date: Mar 2006
Location: USA
Posts: 29,711
That is what PCBoss sugested:
The simplest is power to Sw1 xx-3 cable to Sw2 and then xx-2 cable to the light.
But as drawn there needs to be a junction box between the two lights.

#14
01-21-14, 09:38 AM
Member
Join Date: Sep 2012
Location: USA
Posts: 29
Actually, this diagram would be accurate to what I'm now thinking.

Attached Images
#15
01-21-14, 09:41 AM
Member
Join Date: Mar 2006
Location: USA
Posts: 29,711
That would work but number of conductors in the left switch box may require a deep box.

#16
01-21-14, 09:41 AM
Member
Join Date: Sep 2012
Location: USA
Posts: 29
See my most recen reply (adjusted image). Can I basically use the second switch as the junction box (i.e. run wires out of that switch to each light).

#17
01-21-14, 09:46 AM
Member
Join Date: Mar 2006
Location: USA
Posts: 29,711
You do not have switched power for the lights in the right hand box. Switched power for the lights comes from the neutral and common terminal of the switch in the left hand box.

#18
01-21-14, 10:27 AM
Member
Join Date: Sep 2012
Location: USA
Posts: 29
One more somewhat related question.

To get the extra space I need in the switch box would I be able to install a double gang switch box but just install 1 switch and use the extra space for all the wires (splices)? I could then just drywall over the extra space that doesn't actually have a switch in it. Would that pass typical inspections?

#19
01-21-14, 10:36 AM
Member
Join Date: Sep 2012
Location: USA
Posts: 29
Similar question from someone else:
http://www.doityourself.com/forum/li...ng-3-gang.html
Looks like I'll either need to find a way to cover that piece behind the drywall (i.e.metal plate) or just put a normal plate cover with a blank.

#20
01-21-14, 11:28 AM
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 13,987
You could use a deep 4" square box with a single gang plaster ring.

#21
01-21-14, 11:31 AM
Member
Join Date: Mar 2006
Location: USA
Posts: 29,711
To get the extra space I need in the switch box would I be able to install a double gang switch box but just install 1 switch and use the extra space for all the wires (splices)?
Yes, you would then install a standard switch and a two gang plate with one blank and one switch opening or a Decor switch and a double gang Decor plate with a blank in one opening.
I could then just drywall over the extra space that doesn't actually have a switch in it.
No you can not. The whole box must remain accessible.

#22
01-21-14, 11:38 AM
Member
Join Date: Sep 2012
Location: USA
Posts: 29
Thanks, I just remembered this box has two other unrelated switches in it so it's already going to be a 3 gang box. I might need to get a 4 gang box and just have a 3 gang plate and one blank. Not the best aesthetically but probably my best option. I don't know if there is anything like a 3 gange plaster ring to place on a 4 gang box (not even sure how that would really work so I'm assuming no).

#23
01-21-14, 11:49 AM
Member
Join Date: Oct 2013
Location: United States
Posts: 189
Power-light-switch-switch-light

Basically I want to run the power through the light, then to a switch (at the bottom of the stairs), then onto the second switch (top of the stairs) and then to the last light at the top of the stairs. Is that possible and if yes, how do I do it?
Wiring your 3-ways Tip to Tip will allow you to have lights and or receptacles along the circuit path. 2-conductor to first light, 3-conductor to first switch, 4-conductor between switches and 2-conductor to last light.

#24
01-21-14, 05:10 PM
Member
Join Date: Mar 2012
Location: USA
Posts: 7,458
Any 3-gang box should have sufficient space in it for one 3-way switch and two on/off switches, plus the conductors. To make sure, you can gang 2 deep old-work boxes onto a stud-mount gangable deep device box. Are the other two switches in the box on/off switches?

If you already said this I missed it: Is this a 20A circuit with 12AWG conductors or a 15A circuit with 14AWG conductors?

#25
01-22-14, 07:45 AM
Member
Join Date: Sep 2012
Location: USA
Posts: 29
Thanks, I will probably try a 3-gang box first and see if I can make it all fit. It will actually need to hold three 3-way switches. It will also need to run two more lines out of it to another set of lights/switches. I plan to use 12AWG on a 20A Circuit.

#26
01-22-14, 08:12 AM
Member
Join Date: Mar 2006
Location: USA
Posts: 29,711
nd see if I can make it all fit.
Code wise that isn't the question. To be code compliant box fill (wires and devices) can not exceed the cubic capacity of the box.

Box Fill

More Wires Need Bigger Boxes - Fine Homebuilding Article

#27
01-22-14, 08:28 AM
Member
Join Date: Sep 2012
Location: USA
Posts: 29
Good point. Thank you for pointing that out. If I count correctly I guess I need 45 cubic inches. So a big 3 gang box might do the trick. I'll make sure I validate before I put it together.

#28
01-22-14, 09:41 AM
Member
Join Date: Mar 2012
Location: USA
Posts: 7,458
If I count correctly I guess I need 45 cubic inches.
Plastic boxes should have their volume molded inside. Three 2" x 3" x 2-1/2" gangable boxes should have 45 in.[SUP]3[/SUP] of volume, but it doesn't always work out that way. Three 2" x 3" x 3" gangable metal boxes would be large enough.

I plan to use 12AWG on a 20A Circuit.
Why are you planning to install a 20A circuit for lighting? Those are usually 15A circuits, and using 14AWG conductors will save you a significant amount on box fill.

#29
01-28-14, 08:32 AM
Member
Join Date: Sep 2012
Location: USA
Posts: 29
If I'm going to be running 8 LED recessed lights with dimmer switches (4 lights per dimmer switch) and 2 standard lights with one switch should I use 12AWG and 20A or can I use 14AWG and 15A?

Also, when I first started wiring the system I didn't realize I could run 2-way wire and then connect to 3 way wire after the switch. Now I've learned that's the standard way so I think I need to pull the long 3-way wire I had run to the panel and replace it with 2 -way wire. I'll only use the 3-way wire between the switches where it is needed.