Providing Overload Protection for Cables

[Ravenclau]

Hello everyone,,
In a scenario where the breaker rating is lower than cable ampacity that the breaker is protecting, isn't the overload protection automatically applied by the virtue of the CB rating being lower than the cable ampacity? For example, 100A mains protecting 1/0 service conductors. If the breaker is equipped with thermal magnetic overload or long time delay function, it will eventually trip before the allowed amperage of the 1/0 cable is exceeded.

Am I right on this? I could see a scenario where a 30 Amp breaker is protecting a #10 conductor, you'd not want to use MCP, you'd need a long time delay element on the breaker.

Thank you for your feedback.
God Bless.

 

[waross]

Cable overload protection under the codes that I use must not exceed the cable ampacity.
The cable ampacity may and in the case of long runs where voltage drop is a concern, exceed the overload settings.
Overcurrent (short circuit protection) must be at the supply end of the cable.
Overload protection may be at either end of the cable.
Motor feeder protection is an example of overload protection at the load end of the feeder.
example:
A motor rated FLA is 100 Amps.
The overload trips are set at a maximum of 125% of the motor FLA Amps or 125 Amps.
The feeder is sized for 125% of the motor FLA.

The feeder breaker may be 250% of the motor FLA. This provides short circuit protection but not overload protection.
The overload trips in the motor starter set at 125% of the motor FLA provide overload protection.

Bill
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"Why not the best?"
Jimmy Carter

 

[waross]

https://100001.onl/[/URL]

https://1921681254.mx/

]10.0.0.0.1 – 10.0.0.1 is the default IP address to login admin panel of a router. It is often mistyped as 10.0.0.0.1 which will return an invalid webpage.

Bill
--------------------
"Why not the best?"
Jimmy Carter