Help with circuit breaker hook ups

Thread Starter


Joined Jun 22, 2007
I have just started a millwright job. I need to know which terminals are the control circuit for the common breakers. It seems the manufacturer's web sites assume you already know, and I've had very little luck finding what the little resets and terminals are.
The plant is running a lot of 480 volt motors, and I understand much of the power side. I have books on control circuit schematics and ladder diagrams. The connection is lost in going to practical picture identification of the actual various breaker features.
Thanks for your help in getting up to speed on some of my weak points.


Joined Nov 1, 2006
Some of the larger 3-phase breakers [100A & above] have shunt trip solenoids in them which trip them when 120V or other control signal is applied, typically from an emergency stop button or the like. Other than that I've never seen any control circuits for breakers; most are opened, closed, & reset manually via the operating levers. If you have a print for the machine you're working on, check out the E-stop/master stop circuit. Also, if the control wires to the solenoid are numbered see if these wire numbers are on the print. The breaker could also be bad. Other than that I doubt that any of us can be of much help without more info about the breaker & the controls for it.