tt best method cheapest method?

[thekingiam]

i was just wondering where do people buy there s type td rcd's from? there seems alot of different prices on line from 30 pounds to 80 pounds.
i have split load cu with two 63 amp 30ma rcd's on a tt installation, original rcd is 80amp 30ma so trips out when a fault.
could i use 80 amp stype 100ma or 100amp s type 100ma? would a 63 amp also work?
do i need an upfront rcd at all as discrimination is already in cu via split load rcd?
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[Octopus]

OK,
This has got to go!,

you have 4 choices here

1) You could replace the tails from the meter to go directly to the CU, but this would mean cutting the seals on the meter, not recommended.

2) just fit a 100A DP Isolator and enclosure, in place of it

3) fit a 100A (maybe 80A if you know what the DNO's fuse is) 100mA T/D RCD and enclosure

4) Henly block it to join the tails

The way to go, IMHO, is rip out the existing 30ma "upfront" RCD and replace it with a 100 DP isolation switch. There is no need for an up front RCD in this case as you have used an plastic CU.

PS. don't forget all the obligatory labels too, plus the laminated schedule of tests results and nice biscuits!

 

[spark 68]

The way to go, IMHO, is rip out the existing 30ma "upfront" RCD and replace it with a 100 DP isolation switch. There is no need for an up front RCD in this case as you have used an plastic CU.

PS. don't forget all the obligatory labels too, plus the laminated schedule of tests results and nice biscuits!

Yes Murdoch, this would have been my choice here too, in this situation.

Just for the sake of completeness, I would have included an up front 100mA T/D RCD if for example I was using a hi-integrity threeway board, with one of the non RCD'd ways providing a sub main or dist. cable to a shed or outbuilding or the like.

Or using a metal CU.

 

[Knobhead]

At the end of the day Spark, we could carry on with “what if” forever.
It all comes down to getting the right solution for each situation.