Tt Submain

[Oakley]

I'm after abit of advice

I've run a 25mm 3 core swa 60 metres underground to an outbuilding from a house, the outbuilding is being converted into accommodation. Do I need to put a separate rod in for the consumer unit in the outbuilding or should I use the existing earth in the house? I was thinking a separate rod and just leave the 3rd core unterminated at the meter end. The swa will be protected by a 100ma rcd with 50amp mcb.

 

[Marvo]

You're gong to have to give lots more details. What supply are you running, is it single phase or 2 phases and neutral or 3-phase without neutral? What is the existing supply and earth setup at the main house?

 

[Oakley]

The house is a tt system working off 230v single phase with an earth rod as earth electrode. I will be splitting the tails with a 100amp db pole connection block.

 

[batty]

You could do it either way although for that distance I think I would have used 2 core and rodded it submain end. I think there will be different opinions on this though. Welcome to the forum though Phil.

 

[SLIPSHOD & SLAPDASH]

Daddy....... :slap

 

[kme]

I`d be tempted to connect BOTH ends, AND put a rod at the outbuilding end.

Whichever way you do it, the outbuilding is TT

But by connecting the earths, you`re essentially dividing the rod resistance, giving a lower Ra.

 

[steptoe]

+1 KME

I'd put a rod in at both ends of the SWA

a man can never drive too many rods in,

That's a long run to be just using the incoming rod,

 

[OnOff]

Just thinking out loud here...............and maybe I shouldn't, but.............the exiting supply at the house is TT so we're advocating connecting all the earths. With a bit of forethought on a job like this and COST aside would it be beneficial to LINK the rods along the base of the trench with uninsulated earth tape..............or would that just lower the Ra below already acceptable levels?

 

[ProDave]

Just thinking out loud here...............and maybe I shouldn't, but.............the exiting supply at the house is TT so we're advocating connecting all the earths. With a bit of forethought on a job like this and COST aside would it be beneficial to LINK the rods along the base of the trench with uninsulated earth tape..............or would that just lower the Ra below already acceptable levels?

That's what I have seen the DNO do when laying the supply to a new build fed from it's own transformer.

An HV earth ran one way in the trench (away from the house) and the run from the transformer to the house had a bare copper wire burried, which was strapped to the neutral of the transformer, then they stuck a PME sticker on the cut out.