Zs confusion. What am I missing here?

[Chri5]

Hi all.

Can anybody explain this to me please.

The maximum Zs values for types A to C circuit breakers in table 41.3 on page 49 in the regs book, are different to those in table 2D, page 103 of the on site guide.

for example a 6A type B breaker show's 7.67 in the regs and 6.18 in the guide.? :|

Can anybody tell me why please.

Cheers

Chris

 

[Andy™]

OSG are 80% values. use them (its also B to D)

 

[Chri5]

Your right it is B to D. Better than 1 to 3 which what I wrote to start with. :Blushing

Can you quickly me why we need to use the 80%. I know I should know this but I just won't come back to me.

Cheers

 

[Andy™]

those in 7671 dont take into account heating of the cable during a fault etc

 

[m4tty]

For temperature correction mAte

 

[Chri5]

Of course it.

I knew it was something obvious.

Thanks for the quick replies guys.

 

[Megaohm7]

It's the corrected values in the OSG. Use these to compare your readings on your meter. 80% rule of thumb!!