My First TT

[Sherbertlion]

Went to a job today to install an extra socket. System is TT and I've not worked on these before so just wanted to check my assumptions.

A quick Zs at an existing socket before starting work gave me 284 ohms, carrying on testing (using method 2 for earth electrode testing) it seems as if the rod isn't doing anything and the 284 ohms was through the gas and water bonding.

No RCD up front although I think there used to be one as and old Seeboard notice to that effect was still near the head. New split load Wylex installed 3 years ago with some circuits covered by 30ma RCD but cooker and other kitchen circuits left on and old 3036 board.

Continuity of main earthing conductor from board to electrode was jumping all over the place around the 2 ohm region but connections tight unless there is a joint somewhere.

Advised that electrode and main earthing conductor need further testing/renewing and that either a 100ma S type RCD up front or new dual 30ma RCD board installed to incorporate all circuits.

Have i got it right?!


Sorry for long post..........

 

[plugwash]

Putting a type S up front will only make the system 16th edition compliant not 17th edition complaint (unless it's under the supervision of a skilled or instructed person or the cooker and shower circuits don't have concealed cables less than 50mm deep without mechanical protection or an earthed metal layer)

If you use RCBOs on a TT you should make sure they are the type that also isolate the neutral (generally recognisable from the fact they are two modules wide)

 

[sparkybird]

I didn't know you could get double pole isolataing rcbos! Are they only used on TT? Which manufacturer makes them?

sorry for the list of Q's but I'm eager to learn!

SB

 

[RF Lighting]

Hager do them, as do MK and Merlin.

I expect other manufacturers will do too.

They are sometimes specified on some commercial jobs, but generally SP will suffice for that.