TT Distribution Best Practice

owenskinner · Feb 24, 2012

NMc said:
You are doing a barn conversion 45m from an existing supply and taking 80A off that supply. Are you sure that the existing will take the additional load?

It is a new supply for the Barn Conversion so has no other load. I did recommend to the client to have the new supply put in straight to the Barn but he didn't want his driveway (mud and a few cobble stones) dug up! I have done the cable calcs and it came up with 35mm so I am putting in 2 Core 35mm SWA buried 600mm down.

JD6400 · Feb 24, 2012

Re: TY Distribution Best Practice

spinlondon said:
No it doesn't require RCD protection, if the Ra of the earth electrode is sufficiently low enough to allow the OCPD to operate.
However, as that is probably not going to be the case, then an RCD is the only option to achieve the required disconnection times (1s for TT distribution circuits).

Thanks spin , I was starting to think i was losing the plot and had been doing it wrong all this time !