consumer unit for TT system

[staffok]

Hi all, can anyone tell me the definitive requirements for a comsumer unit with a tt system.
Will a split load cu with a double pole 100ma timedelayed rcd used as the incomer suffice, and a standard rcd for the other side. Can i then split the circuits between the two to ensure lights etc are not all off at once if a fault occurs.

Seen so many different solutions i am confused. Any help appreciated.

 

[Spudnik]

Insulated 30mA dual RCD CU is fine with 100A main switch.

 

[calv68]

hi mate use a std 17th edition board with a 100ma time delayed rcd in a seperate enclosure between the meter and new db

 

[Spudnik]

hi mate use a std 17th edition board with a 100ma time delayed rcd in a seperate enclosure between the meter and new db

No need for the 100mA

 

[calv68]

page 23 & 24 on site guide

 

[MCB]

Hello M8
Your right about what it says but its only a guide Might be worth checking the regs got the same prob NAPPIT say its ok for my assement on dual rcd 30ma

 

[calv68]

thats the way i did it for my nic inspection and was told that was the correct way. ive done loads m8 most housing assosiations insist on it being like this .but who are we to say.

 

[baldsparkies]

No need for the 100mA

Jason is right. Whilst the minimum value for an RCD on a TT system use to be 100ma at the mains position (16th Edition) This is no longer the case on the 17th. Instead Table 41.5 of regulation 411.5.3 should be used. Provided the listed values can be met a 30ma dual RCD board is fine.

 

[staffok]

Thanks for the replies people. Still a little confused.
Can the configeration i quoted be used. Time delayed rcd as incomer, standard rcd on split, if not anyone wanna buy a time delayed RCD.

 

[ajelec10]

Even the lighting circuits will need 30mA protection so the short answer is no, we sue a straight board with a 100A main switch an RCBOs on each circiut which is the most expensive way but the best and complys with a TT
regards
AJ

 

[staffok]

thanks to all. no longer confused. getting 16th and 17th mixed.