UNDERSTANDING CIRCUIT BREAKER Icu Ics

There is much written on the front label or face of a circuit breaker. It is very important to understand what these symbols or values mean.
If you understand these then you are able to correctly determine if the breaker is correctly applied.

[@erman5176]

That is su useful, Kevin Thanks

[@luketanner6963]

How does one determine suitable Icu, Ics and Icw rating values on a circuit breaker for say a system with a full load current of 1200A and a Symmetrical fault current of 26kA?

[@kevinflack502]

Hi Luke, given your system has indicated 26kA as the required safe level of circuit breaker requirement a circuit breaker is required to be selected with the Icu/Ics of at least this value eg 26kA and of course the current rating would require the breaker to be 12000A as well. At 12000A the kA would indeed be higher than the 26kA in any event. remember you can use a higher kA but never lower. The Icw relates more to the isolator and is a bit more of a challenge as the the system/panel withstand levels require to be known. however if the isolator is chosen from the same model match up as the breaker this would be in line with the breaker. Kevin

[@luketanner6963]

@@kevinflack502 Thank you for your response. I appreciate your reply and content

[@Sky-lm1gu]

Not good