Available Short Circuit Current?

[Ronaldrc]

Available Short Circuit Current?

How does the Canadian code deal with the available short circuit current available from the utility transformer feeding say a residence or dwelling?

We in the US have to have a Main overcurrent device that can shut the systems power off before the max. can build up to a dangerous level.


Ronald

Just curious how canada deals with this problem?

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[electric-ed]

Ronald,
There are no specific rules regarding available fault currents in dwellings. There is only a general rule stating "equipment required to interrupt fault currents shall have ratings sufficient for the fault current available at the terminals".
I guess they are assuming the transformers used to supply a typical single family residential service would not produce fault currents exceeding the 5000 A interrupting rating of a standard circuit breaker.

Ed

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[Ronaldrc]

Hello Ed:

Sorry took so long answering your reply.
About ten years ago we had one electrical inspector that was a fanatic on Ic rating of Main Breakers.

But now the newer breakers usually have an Ic rating to do the job without having to speacial order them.

Just curious about some of the differences between the Canadian and US codes.

Thanks very much for the reply.

Ronald

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