Miswired 3 way switch

[EasyE]

I have a commercial building wired with MC. One switch box has the line in and the line out to the light. Is there a way to make this work? In the past the black is line in on one switch and the black on the other switch goes to the light.

Can I steal a ground wire to turn into a hot and run back to the other switch to make it work? There are other grounds in the box and the box is metal if that matters? Or is there an easier way?

 

[Milton Shaw]

You need at least three wires (14/3) between the switches. Normally you would use the white and red as the travelers between the switches and use the black off the remote switch and hook that black up to the black to the light in the first switch. That's what it should take, never use a bare copper as a hot wire if that is what you are asking.

 

[acer66]

You can not use a ground wire bare or green for anything but for grounding.

Why not pull more wires when you have mc or are they full?

 

[EasyE]

You need at least three wires (14/3) between the switches. Normally you would use the white and red as the travelers between the switches and use the black off the remote switch and hook that black up to the black to the light in the first switch. That's what it should take, never use a bare copper as a hot wire if that is what you are asking.

The traveler leg is 12/3 with ground so I have an insulated green wire that’s really not doing anything.

 

[EasyE]

You can not use a ground wire bare or green for anything but for grounding.

Why not pull more wires when you have mc or are they full?

Yeah I can’t access the boxes easily without destroying the walls.

 

[Wrench97]

12/ 3 with ground would be 4 wires no?

 

[EasyE]

12/ 3 with ground would be 4 wires no?

Yes there’s a neutral in there too.

 

[Buxfan]

It is not advisable to use a ground wire as a hot wire. The ground wire is used for safety and to direct any stray electrical current to the ground, so it is important to keep it separate from the hot wire.
It sounds like the wiring in your commercial building is not set up correctly. They can ensure that the wiring is up to code and that the circuit is properly grounded for safety.
One option for your switch box is to install a "3-way switch" which are specially designed for situations where you have two switches controlling one light. Another option is to install a "switch loop" which involves running a separate conductor between the two switches to control the light. This will require rewiring and should be done by a professional.

 

[Wrench97]

Yes there’s a neutral in there too.

Why can't you use the red as the traveler?
Or if the circuit ends at the second switch use the white as the switched wire.

 

[EasyE]

Why can't you use the red as the traveler?
Or if the circuit ends at the second switch use the white as the switched wire.

Guess I am not explaining this well. From what I understand a three way switch cannot have the feed line in and the line out to the light in the same box. There is only one black screw on the switch. The traveler legs pulled between the two switches were pull in 12/3 + ground. What I am proposing is to use the green wire to move the feed in to the other switch.

This would still be grounded from other switches in that box and also the MC jacket grounding back to the panel.

 

[Shiftless]

Same box no go? Why not?

edit: I am still trying to think of a way to accomplish that. Maybe power has to go from switch box to switch box to light. Or power to light first and then to switches.

Sparky 1971 (below) says it better. He’s the electrician… I am not.

 

[sparky 1971]

I have a commercial building wired with MC. One switch box has the line in and the line out to the light. Is there a way to make this work? In the past the black is line in on one switch and the black on the other switch goes to the light.

Can I steal a ground wire to turn into a hot and run back to the other switch to make it work? There are other grounds in the box and the box is metal if that matters? Or is there an easier way?

You can make a set of three way switches work with both the power and switch leg at the same box, but they won't both be hooked to the same swithch

The traveler leg is 12/3 with ground so I have an insulated green wire that’s really not doing anything.

If you have a set of travelers, what is the problem? Are there currently two switches or one for the light(s)?

 

[EasyE]

You can make a set of three way switches work with both the power and switch leg at the same box, but they won't both be hooked to the same swithch

If you have a set of travelers, what is the problem? Are there currently two switches or one for the light(s)?

Ok explain how in your first comment.

There are two switches on different sides of the room. One switch has the line in and line to the light. The other just the travelers, neutral and ground pulled over in the 12/3.

 

[PCustoms]

Ok explain how in your first comment.

There are two switches on different sides of the room. One switch has the line in and line to the light. The other just the travelers, neutral and ground pulled over in the 12/3.

That's the old way of doing it.

 

[wyliesdiesels]

If you have 12/3 (2 hots, neutral, EGC/grnd) between the switches it is doable

Blk and red would be travellers, white would get taped black, connect to black screw on remote switch and connect to black cnd going to light in first switch box

BTW NEVER use an EGC for something other than a ground wire

 

[Jim greengo]

You can not use a ground wire bare or green for anything but for grounding.

Why not pull more wires when you have mc or are they full?

We used to call that a California 3w back when I started in the trades.

 

[sparky 1971]

Ok explain how in your first comment.

There are two switches on different sides of the room. One switch has the line in and line to the light. The other just the travelers, neutral and ground pulled over in the 12/3.

At the box with the hot and switch leg, put the hot wire on the black screw of the switch. Now, mark the white wire from the 12/3 and mark it black with tape and put it on one of the brass colored screws. Put the black wire from the 12/3 on the other brass colored screw. Take the red from the 12/3 and wire nut it to the switch leg. Now go to the other switch and put the red wire on the black screw. Mark the white wire with black tape and put it on a brass screw, the black on the other. Use the green for ground at both ends. Done.

 

[wyliesdiesels]

You can not use a ground wire bare or green for anything but for grounding.

Why not pull more wires when you have mc or are they full?

How do you pull additional wires through MC? Have you ever tried to do that? Are you thinking of FMC/greenfield?

 

[wyliesdiesels]

We used to call that a California 3w back when I started in the trades.

Yup and Ive seen them here in cali lol!

 

[sparky 1971]

We used to call that a California 3w back when I started in the trades.

What I've seen called a California three way is the damndest thing I've ever seen, where either the hot or neutral are switched depending on the position of the switches. I'd swear it wouldn't work if someone told me about it, but then when it's drawn out on a diagram it sure as the world will. I've never wired one, but did get in on a repair where Harry Homeowner watched a Youtube video and tried to change his own switches from brown to white, didn't pay attention to what he was doing and had it all messed up. It took me a long time to figure it out.

The one described in this thread I've always called a backfed three way, others have called it a dead end three way.

 

[acer66]

How do you pull additional wires through MC? Have you ever tried to do that? Are you thinking of FMC/greenfield?

Yes my bad.

 

[EasyE]

What I've seen called a California three way is the damndest thing I've ever seen, where either the hot or neutral are switched depending on the position of the switches. I'd swear it wouldn't work if someone told me about it, but then when it's drawn out on a diagram it sure as the world will. I've never wired one, but did get in on a repair where Harry Homeowner watched a Youtube video and tried to change his own switches from brown to white, didn't pay attention to what he was doing and had it all messed up. It took me a long time to figure it out.

The one described in this thread I've always called a backfed three way, others have called it a dead end three way.

Cool that looks like it will work. I will check later this week and let you know!

 

[sparky 1971]

Cool that looks like it will work. I will check later this week and let you know!

I know it will work. Just make sure the right wires wind up on the black screws.

 

[EasyE]

Update - Ok I had 3 separate circuits like this two already had fixtures and bulbs so I just wired up switches like discussed above and they functioned as they should.

The third circuit I wired the same as the other two and I just had the three wires at the fixture wire nutted off. I figured I would use my meter and check for power on the hot leg to make sure everything was functioning. When the fixture leg was hot (in the light on position) I was reading 122V to both neutral and ground (from black). When one switch was off I was getting 38v on the black fixture leg. When I turned the other switch to off I was getting 76v to the black fixture leg. How is this possible? The only other items on this circuit are 4 receptacles with nothing plugged in.

I wonder if my other two circuits are doing the same thing. I didn’t test them since they had bulbs already and seemed to function normally. Any thoughts?

 

[kaffine]

Update - Ok I had 3 separate circuits like this two already had fixtures and bulbs so I just wired up switches like discussed above and they functioned as they should.

The third circuit I wired the same as the other two and I just had the three wires at the fixture wire nutted off. I figured I would use my meter and check for power on the hot leg to make sure everything was functioning. When the fixture leg was hot (in the light on position) I was reading 122V to both neutral and ground (from black). When one switch was off I was getting 38v on the black fixture leg. When I turned the other switch to off I was getting 76v to the black fixture leg. How is this possible? The only other items on this circuit are 4 receptacles with nothing plugged in.

I wonder if my other two circuits are doing the same thing. I didn’t test them since they had bulbs already and seemed to function normally. Any thoughts?

Are either of the switches lighted or smart switches?

 

[kaffine]

That's the old way of doing it.

Shouldn't the relabled white wire be connected to the incoming power? Or is that only on normal switch loops that is required?

 

[EasyE]

Are either of the switches lighted or smart switches?

No just a normal switch.

 

[dave*99]

Update - Ok I had 3 separate circuits like this two already had fixtures and bulbs so I just wired up switches like discussed above and they functioned as they should.

The third circuit I wired the same as the other two and I just had the three wires at the fixture wire nutted off. I figured I would use my meter and check for power on the hot leg to make sure everything was functioning. When the fixture leg was hot (in the light on position) I was reading 122V to both neutral and ground (from black). When one switch was off I was getting 38v on the black fixture leg. When I turned the other switch to off I was getting 76v to the black fixture leg. How is this possible? The only other items on this circuit are 4 receptacles with nothing plugged in.

I wonder if my other two circuits are doing the same thing. I didn’t test them since they had bulbs already and seemed to function normally. Any thoughts?

Nutted off---meaning there was no load where the light bulb would normally be attached? If this is true, you could be seeing a capacitively coupled voltage on those wires. Sometimes this is called a ghost or phantom voltage.

Are you using a digital meter? These have a high input impedance and can respond in this fashion.

Old fashioned Wiggins solenoid testers and analog meters have a lower impedance and do not respond this way.
Some modern digital meters have a 3000 ohm input impedance that can be switched in to eliminate this measurement artifact.

Have you tried connecting a light bulb? Does it work?

 

[EasyE]

Nutted off---meaning there was no load where the light bulb would normally be attached? If this is true, you could be seeing a capacitively coupled voltage on those wires. Sometimes this is called a ghost or phantom voltage.

Are you using a digital meter? These have a high input impedance and can respond in this fashion.

Old fashioned Wiggins solenoid testers and analog meters have a lower impedance and do not respond this way.
Some modern digital meters have a 3000 ohm input impedance that can be switched in to eliminate this measurement artifact.

Have you tried connecting a light bulb? Does it work?

Yes
Yes
I will connect one tonight. I am suspecting the same thing now after doing some googling on it. Will report back.

 

[dave*99]

Bingo