A - B - C Circuit Breakers

[haveaniceday]

I don't find much information on line. When to use each breaker is my question?

My distribution boxes main 63A switches are 'C' types, which I believe are good for motors as they delay popping when a motor has its initial 1 second draw down.

All the other breakers are 'B' types.

Also, I see references on here to A types for Air cons, what are these?

Look Fwd to tips.

[Crossy]

I'm not aware of any company making Type A breakers (or even if they still exist), you see B, C and (occasionally) D curves in the shops.

Basically an MCB has two tripping mechanisms, Thermal and Magnetic.

The thermal trip is the same in a type B, C or D of the same rating and deals with relatively small but sustained overloads.

The magnetic trip is designed to take out short circuits and it either trips or it doesn't. If the magnetic trip point is hit the breaker will trip extremely quickly (0.1 sec is the standard but some manufacturers claim even faster). The type of the breaker determines how many times the rated current is needed to take out the magnetic trip, type B is 3-5 times C is 5-10 times and D is 10-20 times.

[electau]

"C" frame MCBs are the standard for most lighting and power applications D frame are used for equipment with high inrush currents.

All must trip on a equivilent zero ohms earth fault in less than 0.4secs and must trip on a load of 1.45 x rated current the actual time depending on temperature of the protective device.

Residential installations use C frame. Standard curve.

Edited February 22, 2012 by electau

[haveaniceday]

Is this isn Thailand as well, when you look at asembled distrbution boxes here, the main breaker is a C63 (or about 50) and the rest are B10, B16, B20 etc

IS this the same as wiring colours are back wards int he boxes here as well, namely SAFETY-CUT and CKY