Help With My Electricians Course

[Andy_C]

I'm stuck on a question, I've looked through the text book and cant find the answer anywhere. 

The question reads -

The correct size of main bonding conductor for a TN-S system having 25mm² phase and neutral conductors is -

A) 6mm²

B) 10mm²

C) 16mm²

D) 25mm²

Can someone tell me what the answer would be but also explain it to me and show me how I can work it out for myself. 

 

[Andy™]

have a read of 544.1

 

[Murdoch]

have a read of 544.1

Which means buying the latest copy of BS 7671 ( the yellow one)

 

[Andy_C]

I've had a look at 544.1 so from what I understand the answer is 10mm, but I've read on other forums the answer would be 25mm.

I don't really understand what I'm reading as I've only been studying for my qualification for 2months, this is my 2 assignment.

Thanks for your help.

Which means buying the latest copy of BS 7671 ( the yellow one)

I'm supposed to get the new regulations from Trades Gateway. But haven't received it yet because it was being updated.

 

[Andy™]

I've had a look at 544.1 so from what I understand the answer is 10mm,

correct, assuming 16mm earthing conductor with the 25mm tails

 

[Rob_the_rich]

It is possible for 6mm to be the correct answer, depending on whether you use the adiabatic equation to calculate the size of the earthing  conductor. If it comes out to 10mm or under, then 544.1 allows 6mm main bonding conductors. I would still use 10mm though, don't have 6mm in the van

 

[Murdoch]

I've had a look at 544.1 so from what I understand the answer is 10mm, but I've read on other forums the answer would be 25mm.

I don't really understand what I'm reading as I've only been studying for my qualification for 2months, this is my 2 assignment.

Thanks for your help.

I'm supposed to get the new regulations from Trades Gateway. But haven't received it yet because it was being updated.

Hum the latest copy of BS 7671 has been available since about the beginning of this year