Electrics I know the answer to but just can't recall

[alexandersmith1986]

I am a newly qualified electrician still a bit new to the game.
How do you determine what type of rcd you need from a consumer unit to a separate unit over 30 meters away.
I know its all about the amperage and the voltage drop just can't find it in the regs.

 

[ricicle]

I wouldn't be fitting an RCD at source for an external sub-main unless the system earthing was TT.
A buried SWA cable does not require RCD protection (unless the above applies). Far better to fit the RCD protection (if required) at the load end.
Load amperage and VD have nothing to do with RCD trip rating, unless you are determining what load the RCD is rated for.

 

[PrenticeBoyofDerry]

Are you talking about two RCDs proctecting the same circuit, so offerring discrimination?
If so it's a class S, not sure where Voltage Drop comes into it?

 

[1john]

If you are newly qualified then why haven't you supplied all the relevant details which would enable us to help you. What on earth has voltage drop got to do with the rating of an RCD?