carter circut
- Thread starter powerguy
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al hildenbrand
Senior Member
- Location
- Minnesota
- Occupation
- Electrical Contractor, Electrical Consultant, Electrical Engineer
Re: carter circut
Unfortunately the definition of "Carter circuit" is confused. You stand a chance of getting a couple answers, depending upon who you reference.
Here's my take.
The Carter circuit was a way to wire threeways that saved on wire and installation time by hooking up the switches in one of two different ways than are commonly done today.
The first method is non-code today as the polarity in the controlled lampholder is switch position dependant. Half the time, the lampholder screw shell will be hot. A common hookup of this type was the light in the main stairwell of a two story dwelling. Each threeway would have the two "traveller terminals" connected to a branch circuit hot and neutral. Each "common terminal" is run to the light. As long as the two hot branch circuit conductors are from the same circuit (or at least, the same side of the service bus), the threeway hookup works.
I have, over the years, serviced a couple dwellings with the main stair light actually wired between two different circuits.
The other variation of a threeway that some might label a Carter circuit is what I've come to know as the Travelling Bus Threeway. This diagram is done by our own Ronald Coleman.
The travelling bus threeway is not likely to cause any wiring difficulty, so as to cause a wireman to label the panel with "Carter circuit". In my opinion, I'd keep the original circuits supplying, and supplied by, that old panel you found on the same side of the service bus as you have found them connected on first inspection. That is, unless you can map the system and know what is hooked up to what.
Unfortunately the definition of "Carter circuit" is confused. You stand a chance of getting a couple answers, depending upon who you reference.
Here's my take.
The Carter circuit was a way to wire threeways that saved on wire and installation time by hooking up the switches in one of two different ways than are commonly done today.
The first method is non-code today as the polarity in the controlled lampholder is switch position dependant. Half the time, the lampholder screw shell will be hot. A common hookup of this type was the light in the main stairwell of a two story dwelling. Each threeway would have the two "traveller terminals" connected to a branch circuit hot and neutral. Each "common terminal" is run to the light. As long as the two hot branch circuit conductors are from the same circuit (or at least, the same side of the service bus), the threeway hookup works.
I have, over the years, serviced a couple dwellings with the main stair light actually wired between two different circuits.
The other variation of a threeway that some might label a Carter circuit is what I've come to know as the Travelling Bus Threeway. This diagram is done by our own Ronald Coleman.
The travelling bus threeway is not likely to cause any wiring difficulty, so as to cause a wireman to label the panel with "Carter circuit". In my opinion, I'd keep the original circuits supplying, and supplied by, that old panel you found on the same side of the service bus as you have found them connected on first inspection. That is, unless you can map the system and know what is hooked up to what.
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