MCB's 230V/110V Zs Earth fault loop impedance values

[sparkymalarky]

I give these out to some of our younger electricians in the aim to get them familiar with such values. Probably old news to most of you fellas but sure it won't do any harm. Calculations from BS7671 anyway, just handy to have a hard copy other than BGB.

Cheers

John

 

[telectrix]

useful tables to have in the van. ta.

 

[markythesparky]

I dont get it im afraid chaps. probably missing something!

Max values for MCB's and other overcurrent devices are in BS7671. And they are listed by available MCB/ fuse sizes.

Why have you listed as multiples when you cant buy a 35A MCB for example. Also when would you need these on 110V and what voltage are you trying to keep below?

I never stop learning on this forum you know!!

 

[sparkymalarky]

Not all of them are listed in BS7671 actually! And I don't think I included a 35A MCB in the tables, but as I said in the OP, this is mainly for younger guys to carry with them to double check values as they go, as some times #1 they cannot correctly calculate the values and #2 Do not know what value they are looking for. I'm not telling grannies how to suck eggs!

P.S you'll find that if, like me, your testing all of the time, chances are you'll find most of your max Zs's outside of BS7671 like GV2ME06's, 60947-2 thermal magnetic trips etc.