Three way switching standard, coast, carter - Electrician Talk - Professional Electrical Contractors Forum

p_logix · 03-06-2008, 08:25 PM

Just out of curiousity I don't do much residential any more only the work in my own home but when i did, of course most commonly i ran into standard 3-way switching. However in some older homes in L.A. I did run in to some Coast threeway systems wich actually uses one less wire (one traveler) then the standard threeway, can throw you off for a second when your not expecting it. And finally the carter 3-way switch, I am no expert to the NEC this is improper and unsafe wiring and it forbids switching of a neutral or grounded leg. The shell will be hot. But some times in old homes we are faced with old wiring such as knob and tube, ancient stuff etc. I've never ran in to the carter 3-way switch just wired it a while back in school for testing purposes only. Just curious if some of you residential guys find Anything other then the standard 3-way switches in some of the areas where you guys are from. Thanks

simmo · 03-06-2008, 09:04 PM

Not familar with your switches in America, but are you talking about a rotary type switch On-Off-On
or a Double throw/Double pole type switch (DTDP) ?

We only switch the active in Australia and run the neutral straight back from the downstream side of the load. For three way switching we would use three switch mechanisms with the middle mech wired in loop with the other two (point to point) wiring. A little hard to explain, but it works for me. lol

InPhase277 · 03-06-2008, 09:05 PM

We just had a discussion about this on Contractor Talk. The "coast" or "California" 3-way is a legal setup, even if confusing. It actually uses the same amount of conductors as a regular setup, it just allows you to take a constant hot out to the remote location.

The "Carter" 3-way was legal until 1923, when the Code specified the screw shell of the lamp socket to be the grounded conductor. I have seen this setup a few times in rural areas I've worked in. It will drive you slap batty trying to figure it out if you aren't expecting it.

InPhase277

simmo · 03-06-2008, 09:43 PM

Is that a socket outlet on the far right side of those diagrams?

Here - that would not meet our codes, no light and power is mixed. Must be seperate light and power circuits.

p_logix · 03-06-2008, 10:07 PM

Actually the coast threeways purpose was because way back only 3 #12 TW wires were a loud in a 1/2 inch conduit. The city of LA a loud 4 #12 TW wires as long as one of the wires was being used as a switch leg. This aloud you to still use a 1/2 conduit. The coast also saves one wire as you only need 4 wires including hot and neutral. The Edison 3 wire three-way requires 5 wires including hot neutral. The Coast is legal but serves no real purpose anymore.

InPhase277 · 03-06-2008, 11:21 PM

Quote:

Originally Posted by simmo

Is that a socket outlet on the far right side of those diagrams?

Here - that would not meet our codes, no light and power is mixed. Must be seperate light and power circuits.

Right, these are non-standard circuits. Here, it is good practice to keep lighting and power separate, but it is not required by code. Good electricians do it anyway.

Notice the "Carter" setup. It is not a code compliant system because it switches the neutral and at times the screw shell of the lamp socket can be energized. This has been outlawed by the National Electrical Code since 1923.

InPhase277

jrclen · 03-06-2008, 11:58 PM

I run into the Carter system from time to time on farms. Mostly wires run between the house and the out buildings. Put in years ago.

frenchelectrican · 03-07-2008, 03:21 AM

the other thing with " Carter system " when you upgrading the service you have to becarefull with them some of them dont use the same circuit for the carter system.

and it did happend to me once long time ago when i was upgrading and heard a light bulb expoled i say " aww Merde " i knew it away took me a while to find the right leg and got that switch and related circuit fix up and brought up to the code anyway.

Merci, Marc

jrclen · 03-07-2008, 11:37 AM

Quote:

Originally Posted by frenchelectrican

the other thing with " Carter system " when you upgrading the service you have to becarefull with them some of them dont use the same circuit for the carter system.

and it did happend to me once long time ago when i was upgrading and heard a light bulb expoled i say " aww Merde " i knew it away took me a while to find the right leg and got that switch and related circuit fix up and brought up to the code anyway.

Merci, Marc

Good point Marc. Those circuits can be hard to figure out until it dawns on us what we are looking at. In the farm buildings I find more wires have been added later but the Carter is still there in the mess. That makes it difficult to spot sometimes. And can surprise us.

frenchelectrican · 03-07-2008, 04:06 PM

there one trick related to this crazy carter system.

instead try to edit my last post but let me add it here with old fuse box where they have double or tripleed even once quadded at fuse connection what i do i take a colour tape so i mark it so i know which leg it was on by time i install new panel box.
it it will be on correct leg so i dont blow it again like what it done to me before.

Merci, Marc

JohnJ0906 · 03-07-2008, 09:25 PM

I like this diagram, as it moves.

Sorry, I can't give proper credit to the person who originally posted this.... as I forgot who it was.

jrclen · 03-07-2008, 10:22 PM

Quote:

Originally Posted by frenchelectrican

there one trick related to this crazy carter system.

instead try to edit my last post but let me add it here with old fuse box where they have double or tripleed even once quadded at fuse connection what i do i take a colour tape so i mark it so i know which leg it was on by time i install new panel box.
it it will be on correct leg so i dont blow it again like what it done to me before.

Merci, Marc

Good idea Marc.

waco · 03-07-2008, 10:50 PM

Best I can recall, the only odd configuration of three-ways I have found are the "derived" neutral at one end. I long ago began using a "standard" method so anybody who comes across my circuits won't have to figure out what I did.

jrclen · 03-08-2008, 12:33 PM

Quote:

Originally Posted by waco

Best I can recall, the only odd configuration of three-ways I have found are the "derived" neutral at one end. I long ago began using a "standard" method so anybody who comes across my circuits won't have to figure out what I did.

What is your standard method? Just so I'll know it if I see it.

waco · 03-08-2008, 04:46 PM

Quote:

Originally Posted by jrclen

What is your standard method? Just so I'll know it if I see it.

Always three wire traveler -- never run through the device. Always red and black travelers and either taped white if used for a feedback or plain white if used for neutral.

However, I never did standardize on which end to feed and which end to loop, but I generally feed and loop opposite ends if I can.

480sparky · 03-08-2008, 08:10 PM

Here's my movies:

waco · 03-08-2008, 08:45 PM

The problem I have with this setup is that there is no neutral (that I can see) to the fixture. Also, all my detached garages have to have a sub-service anyway, so I use 10-3 with ground to the sub-panel and just wire normal lights from there.

My three-ways for exterior lighting at a detached garage use 14-3 on a normal three-way from the house.

JohnJ0906 · 03-09-2008, 09:10 AM

Quote:

Originally Posted by waco

The problem I have with this setup is that there is no neutral (that I can see) to the fixture.

Some times it has a neutral... any time the lamp is on. Sometimes it has 2 neutrals, sometimes 2 hots - anytime the lamp is off.

Definitely a screwy set-up, thats for sure.

I would hope that no one would wire a 3 way like this new. But it is important to understand, just in case you run into one on a service call, or some old work job.

Pierre Belarge · 03-10-2008, 11:32 PM

Quote:

Originally Posted by JohnJ0906

Some times it has a neutral... any time the lamp is on. Sometimes it has 2 neutrals, sometimes 2 hots - anytime the lamp is off.

Definitely a screwy set-up, thats for sure.

I would hope that no one would wire a 3 way like this new. But it is important to understand, just in case you run into one on a service call, or some old work job.

The 3-way to the garage that 480 posted is not a permitted installation and can be dangerous.

As I highlighted, it is only important to understand for troubleshooting purposes.

jrclen · 03-11-2008, 11:10 AM

Quote:

Originally Posted by Pierre Belarge

The 3-way to the garage that 480 posted is not a permitted installation and can be dangerous.

As I highlighted, it is only important to understand for troubleshooting purposes.

Absolutely Pierre. We all agree these are not permitted wiring methods and haven't been since any of us were alive. And they are dangerous. Unfortunately they were still wired up in my area this way in the 50's and maybe even the 60's. On farms mostly.