RCD problem...nuisance tripping

[Spark123]

I mean if he is to attempt to change the 30mA device himself he may end up getting a shock.
Still think getting a sparky in will be better.

 

[Spark123]

ok thanks, clears that up.

as the other circuits are non domestic out buildings supplied in SWA from the main fuse box, will they comply with the 100ma RCD?

Very possible, can't say for 100% sure as I don't know what is connected.

 

[ColJack]

I mean if he is to attempt to change the 30mA device himself he may end up getting a shock.
Still think getting a sparky in will be better.

ah I get you now.. yes he's obviously best getting a pro in, but surely there will be a fuse in the cutout and as it's TT then likely a neutral link that can be pulled also?
never done any TT so I don't know for sure..

 

[xr4x4]

fuse in live cutout yes, but no way of isolating neutral link that i can see..

ill have to look into the other circuits and see whats what.

 

[mfarrow]

I'd replace the 30mA RCD incomer with a 100mA S-curve RCD as already identified, then for each outgoing circuit of that MG board:

Where:

• No socket outlets are provided on the outgoing circuit of the sub-distribution board and
  No cables are concealed less than 50mm into a partition unless protected by conduit/SWA/flexishield and
  No circuits on the sub-distribution board feed a 'special location' requiring RCD protection (e.g. a shower)

then I would leave that circuit MCB alone.

Where the supply cable to the sub-distribution board is not shielded and is buried, or more than one circuit of the sub-distribution board meets the following criteria:

• Socket outlets are provided on the outgoing circuit of the sub-distribution board
  Cables are concealed less than 50mm into a partition and not protected by conduit/SWA/flexishield
  A circuit on the sub-distribution board feeds a 'special location' requiring RCD protection (e.g. a shower)

then I would install an RCBO in your MG board.

Where the sub-distribution board feed cable is earth shielded or not buried, and only one circuit of the sub-distribution board meets the above criteria, then I would investigate installing an RCBO on that circuit requiring RCD protection, subject to the sub-distribution board being of a suitable age/type to accept an RCBO. This would limit the loss of supplies in the outbuilding in the event of a fault, and should leave you with lights on etc. The cost is still the same as had you replaced the MCB in the MG board, but the final solution is more robust.

You should also consider measuring the Ze value of the installation to ensure you can fit a 100mA RCD without increasing touch potentials to comply with Table 41.5.

 

[xr4x4]

ok thanks, i think i understand most of that.

looks like ive got some more investigation to do..!!