100ma rcd onn tt system

[unclebubble]

Could anyone tell me what the 17th edition says about a tt system.
The house in question is in T&E and just buried in the walls.It has an old rewirable board.What is the lay out now will it still have to have a 100ma rcd then individual rcbo's protecting each socket,or just a main switch then rcbo's protecting each socket?Hopefully someone's come against this!Cheers for any help

 

[ricicle]

All buried (unprotected) cables must now be 30 mA RCD protected (unless deeper than 50mm from both sides). A main switch with all RCBOs is the ideal solution but can prove costly.
This new regulation on the most common of installs virtually wipes out the need for the 100 mA RCD. The old way was the 100 mA RCD main switch (time delayed to provide discrimination) and then 30mA on the necessary circuits.
It is not correct though now to have one 30 mA for the whole installation as regulations say that not all circuits must be affected (words to that effect)
The most economical way is to have one main switch and split board with 2 30 mA RCDs.
In all cases on a TT (except under certain circumstances) the CU must be of an insulated constuction.

 

[Spark123]

The concealed cables in the wall will need to be protected with a 30mA device
You could use a 100mA (T) device to feed RCBOs, this will be costly!
The OSG shows a main switch and RCBOs is acceptabe for a TT system on page 25 - providing the CU enclosure is insulating or the meter tails have additional mech protection.