Adding a third switch to a two way system


  #1  
Old 06-26-05, 02:09 AM
R
Member
Thread Starter
Join Date: Jan 2005
Location: San Francisco Bay Area
Posts: 530
Received 0 Votes on 0 Posts
Adding a third switch to a two way system

I'd like to say thanks to all who find the time to help out those of us DIYers in here who are ignorant of the tips, tricks, code and otherwise way of doing things when it comes to electrical. I've been in here many hours just reading old posts that I find interesting, and I have learned a great deal by doing that. The one thing I'm impressed about is the patience of the same questions being asked over and over again. I think this is a great forum with great people behind it.

I would like to see a better search function implemented, though. I have a difficult time trying to search for a specific resolution to a problem or question.

Anyway, my question.
I have a light at the top of my stairway, leading to my basement, that can be controlled by a switch at the top of the stairs or by one at the bottom. I would like to add a third switch in another location to control this light. I have access to the switch wiring at the bottom of the stairs but not to the one at the top, nor do I have access to the light wiring.

Can I add my third switch without running any new wires to the light or the top switch? What would be involved?
 
  #2  
Old 06-26-05, 06:09 AM
W
Member
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
Received 0 Votes on 0 Posts
Presuming that this switch circuit is properly installed in the first place, you can add a third switch with access to only one of the available switches.

You would replace the current 'three way' switch with a 'four way' switch, and you would run 3 conductors plus ground between the original switch and the new switch. You would install a 'three way' switch at the new location.

The precise details of this installation will depend upon the wiring method currently used, the gage of the wire currently used, etc. Some of these details will depend upon your location and the versions of the NEC (with amendments) that pertain. Before you start any DIY project you should be sure to do the necessary background reading; there are many details to a proper electrical installation, far more than will be described in posts here. You should get several books on electrical wiring, read them, and then ask here about details that you don't understand.

-Jon
 
  #3  
Old 06-26-05, 06:13 AM
5
Member
Join Date: Nov 2004
Location: CA
Posts: 2,039
Received 0 Votes on 0 Posts
The switches in your system now are three-way switches, meaning they can control a lamp from TWO different locations. ( Someday someone will explain that one to me!). Now, for your new set up, you need another switch called a 4-way. This allows control of the light from THREE different locations. You can find the wiring diagram in any simple electric book or even in the package of the 4-way switch. The 4-way connect "in between" the two 3-ways. Basically, if you can access one of the 3-ways and run 2 two-conductor cables from that location to the location where you want the new switch, you can make this work.
 
  #4  
Old 06-26-05, 09:39 AM
R
Member
Thread Starter
Join Date: Jan 2005
Location: San Francisco Bay Area
Posts: 530
Received 0 Votes on 0 Posts
Thumbs up

Wow, that's great news, I was really expecting the worse. My wife will be so happy with the new switch.

Thanks guys, for the advice, I will definitely pick up one of the books describing the installation.

Randy
 
  #5  
Old 07-10-05, 01:03 AM
R
Member
Thread Starter
Join Date: Jan 2005
Location: San Francisco Bay Area
Posts: 530
Received 0 Votes on 0 Posts
Well, I finally got around to adding this third switch, and it works great, thanks to your comments, and a LOT of reading.

It was a bit complicated at first, but all of a sudden it clicked and I understand it completely now. It was the power wire that was throwing me off. I kept trying to figure out how it got connected to the new 4 way switch. Once I saw that it had to travel over to the new switch location, which is the old three way switch, it all became very clear. Plus, all my existing wiring is in conduit and is black...not like the different colors I saw in all of the illustrations I found.

Oh, and one place I found showed eight different ways to wire a 4 way switch configuration...that really messed me up for a while.

Anyway, thanks again for helping out.

Randy
 
  #6  
Old 07-13-05, 11:46 PM
R
Member
Thread Starter
Join Date: Jan 2005
Location: San Francisco Bay Area
Posts: 530
Received 0 Votes on 0 Posts
I have a new development with this scenario.

As I posted in my last reply I have the 4 way switch connected and all is well. Now, the wife wants me to add another light at the bottom of the stairs that would turn on with the same switch setup and light at the top of the stairs.

Is this possible, given that I do not have access to the switch wiring or the light wiring at the top of the stairs? I do have access to the switch wiring at the bottom of the stairs, and also, this is where the power wires are, if that matters.

I've given it some thought and it seems that it would not be possible without running another cable from the light or the switch at the top of the stairs to the light at the bottom, but I know these 3&4 way circuits can be confusing so maybe there's something I'm not taking into account that would make it possible.

Thanks again...Randy
 
  #7  
Old 07-14-05, 07:15 AM
J
Member
Join Date: Sep 2000
Location: United States
Posts: 18,497
Received 0 Votes on 0 Posts
You can always wire another switch to control the same set of lights if you can run a cable from any of the existing switch boxes to the location of the new switch box. This is true no matter how the existing setup is wired, and no matter how many switches you already have.

Is this what you want to do? Is the switch you want to run the new cable from a 3-way or a 4-way?
 
  #8  
Old 07-14-05, 11:16 AM
R
Member
Thread Starter
Join Date: Jan 2005
Location: San Francisco Bay Area
Posts: 530
Received 0 Votes on 0 Posts
John,

I guess I wasn't clear. Currently I have three switches controlling one light at the top of my stairs. One switch at the top of the stairs, and two at the bottom. Now I want to add another light at the bottom of the stairs to this existing circuit, so that the three switches will control the two lights simultaneously.

I know that I can add another light...the circuit can handle the load. My confusion is whether or not I can add the light without gaining access to the existing light or switch wiring at the top of the stairs.

If I had access to the existing light I know that it would just be a simple process of parallelling off of it to the new light, but unfortunately that would require me to open up some more walls that I didn't want to disturb at this time.

My question is if there is any way of doing this by just using the wires I do have access to at the bottom of the stairs.

I hope I explained it better this time, and thank you for your time.

Randy
 
  #9  
Old 07-14-05, 11:36 AM
J
Member
Join Date: Sep 2000
Location: United States
Posts: 18,497
Received 0 Votes on 0 Posts
You were clear the first time. I just wasn't a very good reader.

If power goes first to the light fixture, then the only place you can connect cable to the new light is at the existing light.

But that doesn't sound like what you have.

So if power goes first to one of the switch boxes, then the only place you can connect the cable to the new light is at the switch box from which runs the cable directly to the existing light.

Unfortunately, I don't think this describes your downstairs switch. But check anyway just in case.

Drywall patching is not that hard.
 
  #10  
Old 07-14-05, 12:04 PM
R
Member
Thread Starter
Join Date: Jan 2005
Location: San Francisco Bay Area
Posts: 530
Received 0 Votes on 0 Posts
The power does go first to the switch at the bottom of the stairs, and I understand that I can tap off of that for the new light, but how would I connect it so that the switch at the top of the stairs controlls it as well as the others at the bottom.

The switch at the top has three black wires. The switch at the bottom, which used to be a three way but is now a four way, has four black wires, two white and one red wire. The other three way has a black, a red and a white wire. The light has one black and one white wire.

Hope this helps.

Thanks...Randy
 
  #11  
Old 07-14-05, 01:34 PM
J
Member
Join Date: Sep 2000
Location: United States
Posts: 18,497
Received 0 Votes on 0 Posts
The power does go first to the switch at the bottom of the stairs, and I understand that I can tap off of that for the new light
Not necessarily. As I said in my prior post, because you want the new light to be controlled by the same switches as the existing light, you can only do this if that is "the switch box from which runs the cable directly to the existing light". Is that or is that not the case? That is the question.

The switch at the bottom, which used to be a three way but is now a four way, has four black wires, two white and one red wire.
How'd you get four black wires and only two white wires? Don't they come in pairs? Are you using something other than Romex cable?

I think you're probably going to need to figure out a way to run a cable between the lights. It's a good time to learn drywalling skills.
 
  #12  
Old 07-14-05, 02:30 PM
R
Member
Thread Starter
Join Date: Jan 2005
Location: San Francisco Bay Area
Posts: 530
Received 0 Votes on 0 Posts
How'd you get four black wires and only two white wires?
This house was built in the low sixties. The upper story, the main living area, is knob & tube. The lower level, or basement was done sometime after the house was built...sometime in the seventies, as far as I can determine, and it was all done in conduit...not to code, either. I have been finding hidden JB's everywhere, and removing them as I go along. I am running in all new circuits using NM.

The original bottom stairs switch, a three way, had three black wires coming into it in conduit, and the conduit went to a JB in the ceiling on the other side of the wall. Inside this JB were many wires for various lights and receptacles for the bathroom and what not in the basement. I was able to eliminate all but the wires from the stairs light as they travel off through the ceiling to somewhere else. I assume they go to the light and the switch at the top. So, left in this JB were three black wires and one white wire...a black and white for power and the two travelers from the other switch at the top. Man, I hope that all makes sense.

Just so you know what I am up against, I have exposed around 15 4" JB's hidden in the walls and ceilings in the basement. Fortunately, almost all of the wiring for the basement was kept separate from the upstairs wiring so removing it has not affected my upstairs devices.

Anyway, I have been experimenting with a test light and have found that you are correct. The wiring to the light comes from the switch at the top, which makes sense, so adding my other light will not work without running a new cable from the existing light to the new light below. Running the new cable would be doable but we have decided that it wouldn't be worth it, so that idea has been tabled for now.

Thanks so much for your help.

Randy

It's a good time to learn drywalling skills.
I know how to do drywall...I just don't like it! lol I can do it but it ends up taking me three times as long as someone skilled at it.
That's one of those areas where I'd just as soon pay somebody to do it.
 

Last edited by rcash54; 07-14-05 at 03:43 PM.
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: