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Could someone shed some light on the following please?

411.3.2.1 implies that the 5s / 0.4s disconnection times only apply to earth faults. I've not found anything else in the regs that suggests they apply to short circuits.

435.5.2 says faults should be disconnected before the fault current causes the conductor limiting temperature to be exceeded. It goes on to give an equation to calculate the approx time that a conductor would reach its temperature limit.

Can I use this equation to find a maximum short circuit current for a circuit protected by, say, a BS 60898 MCB?
 
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Ian1981

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