Rcd or isolator.

[davy d]

Hi Guys.

I have a new build house waiting for the meter to be fitted by the NIE. What are the requirements for isolation in the outside metering cubicle on a tt system. Would a 100a isolator be ok or do I need an RCD here as well as the 2 x 30mA ones in the con unit.
Con Unit is back to back with the meter cubicle, tails through wall in conduit and everything is plastic.

Whats the correct method please,

Davy

 

[malcolmsanford]

Well there is no need for any outside isolation to be fitted at all that is totally your call, unless the DNO have asked you to to this.

Because it is a TT system your correct that there is every chance you will need to provide RCD protection for additional protection for ADS, as well as all the other reasons outlines in the regulations.

As your tails are coming through the wall and not buried, then into an insulated enclosure there is no need to have that isolator to be an RCD

There is of course an argument for a better design to fit regardless of need perhaps a 100mA time delayed or S typoe RCD upfront. This will definitely give you added protection on the 30mA RCDs, as well as flexibility in the installation for say an outside supply in future.

Of course the extra 100mA RCD, especially a time delayed one is going to add cost