Please Clarify the concept of Amp Frame and Amp Trip.
Please Clarify the concept of Amp Frame and Amp Trip.
(OP)
Hello;
I am an electrical engineer with an MEP consulting firm. I have done tonnes of single line diagrams however, I am unclear as to what the AF and AT really are.
From what I understand, say I have a 100Amp frame, the size of the circuit breaker that can be used has to be less or equal to 100 Amps. So what I get from that is that the AF is just an enclosure for the actuall circuit breaker.
I would appreciate if you guys could shed some more light on this.
Thanks
I am an electrical engineer with an MEP consulting firm. I have done tonnes of single line diagrams however, I am unclear as to what the AF and AT really are.
From what I understand, say I have a 100Amp frame, the size of the circuit breaker that can be used has to be less or equal to 100 Amps. So what I get from that is that the AF is just an enclosure for the actuall circuit breaker.
I would appreciate if you guys could shed some more light on this.
Thanks






RE: Please Clarify the concept of Amp Frame and Amp Trip.
Manufacturers don't make a seperate case or frame for every ampere rating.
Frame size gives the physical dimensions of the breaker case.
Trips are the actual amps rating of the breaker.
yours
RE: Please Clarify the concept of Amp Frame and Amp Trip.
Trip unit could be fix or interchangeable. Molded case circuit breakers (MCCB) with the same frame size often are available in wide range of trip amp rating.
RE: Please Clarify the concept of Amp Frame and Amp Trip.
You can have a 1600 amp frame breaker with different amp trip settings up to 1600.
The amp trip will not go over the amp frame rating. The amp trip is what you use to size the trip rating of the breaker to protect down stream devices and cables.
JTK
RE: Please Clarify the concept of Amp Frame and Amp Trip.
But many manufacturers may offer a 1600AF/1600AT, and a 2000AF/1600AT, so in that case it becomes important for the design engineer to consider his future requirements. You would do so if you were sizing the cables for a planned future service upgrade. By specifying the larger frame, you make it simple for someone to increase the service later by just changing the trip plug on the breaker. So the practice of listing both the frame and trip settings is just a convention used to maintain consistency.
Eng-Tips: Help for your job, not for your homework Read FAQ731-376
RE: Please Clarify the concept of Amp Frame and Amp Trip.
SquareD does offer a 225 amp 240 volt circuit breaker frame with a 100 amp fixed trip which is rather handy for a 100 amp feeder with a 180 amp or 200 amp neutral.