undersized SWA to garage code?

[TheDaddy]

Thanks for this TD , very useful.
Problems:
You say that:
<Resistance> Will be lower when calculated with armour.
But according to this manufacturers tables the resistance of the armour (8.8 ohms/km) is a higher than the 2.5 copper(7.41ohms/km). how does this affect your calcs?

Exported earth TN-S:
The armour is too small to for the earthing requirements at the garage end?

Any thoughts
many thanks for this.
Regads
Steve


best regards
Steve


Appendix 4 - Cable Data-Resistance, Impedance and []R1 + R2? Values - Guide to the Wiring Regulations - Locke - Wiley Online Library

Hi Steve

The actual CSA of the steel for 2.5mm SWA is 17mm, minimum CSA required as per table 54.7 is 5.7mm.

It's more for disconnection times really! The max zs at 80% for a bs3036 is 1.944ohms. Your actual is more on the lines of 1.603 (best to test Zdb at the garage).

Cheers


Cheers

 

[Stevesplatto]

Many thanks TD. I didnt realise that it doesnt matter if its steel or copper. I thought the CSA was a representation of the resistance/km.. If it is then obviously the material is relevant.
I'm installing a new CU. I'm thinking of putting the garage on a timed RCD in the house to a garage box with a std RCD a 6a and 16a MCB.
Thanks again.
S

 

[Octopus]

Many thanks TD. I didnt realise that it doesnt matter if its steel or copper. I thought the CSA was a representation of the resistance/km.. If it is then obviously the material is relevant.
I'm installing a new CU. I'm thinking of putting the garage on a timed RCD in the house to a garage box with a std RCD a 6a and 16a MCB.
Thanks again.
S

a what?

 

[Dave OCD]

Obviously he means a time delay RCD.

 

[davesparks]

Many thanks TD. I didnt realise that it doesnt matter if its steel or copper. I thought the CSA was a representation of the resistance/km.. If it is then obviously the material is relevant.
I'm installing a new CU. I'm thinking of putting the garage on a timed RCD in the house to a garage box with a std RCD a 6a and 16a MCB.
Thanks again.
S

It does matter what material it is made of, and you use the relevant K factors to calculate for different materials.

Why does it need a time delayed RCD?

 

[Stevesplatto]

Thank you Dave.
S

 

[Stevesplatto]

You are right Davesparks. Better do the math I suppose!

 

[TheDaddy]

You are right Davesparks. Better do the math I suppose!

Or you could just measure it, why are making life difficult for yourself?. Seems like you don't want this cable to be adequate. [emoji57]