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Overload device negate requirement for In<Iz?

E95

Hi all,

For context this is a TP, N & E socket circuit supplying a machine. The machine supplier has recommended that the circuit be supplied from a 125A MCB, however the machining cabling is not supplied from a cable rated to 125A.

I'm being told that a cable size doesn't need to be sufficiently sized for the upstream breaker, when there is an overload unit downstream and that the cabling would withstand a short circuit disconnecting quickly

Is this true? I can't find anything explicit in the regs confirming either way, aside from Ib<In<Iz

  • 0

    Please note amendment 4 will see regulation 433.3 updated - it appears you won't be able to omit overload protection as easily. 

    Although what's in the DPC isn't necessarily what'll end up in the final version ... there might be some debate about this one - outlawing unfused spurs from ring finals and having to cable industrial motor circuits for the full starting current, might ruffle a few feathers....

       - Andy.

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