Old MICC cable underground to garage, extraneous conductive parts

[catdog1121]

Ok so the scenario is there is an old MICC or pyro 1.5mm 2 core cable supplying the garage run underground on a 16A circuit breaker that is RCD protected.

In the garage there is a water pipe fed from the house, at the house it is bonded using 10mm, at the garage bonded with 6mm. I think the water pipe from the house bonding to the garage has continuity but need to double check this.

In an ideal world I would replace the MICC with 10mm 3 core SWA and then up the bonding to 10mm in the garage just to be safe and put the RCD on the garage side only. However the consumer unit is in the middle of the house and the home owner really does not want to run a new supply.

I dont really want to remove the RCD protection from the MICC cable as its not clear where it is buried and at what depth etc.


My thinking was if I remove the 6mm bonding at the garage and check continuity from the 10mm bond in the house to the water pipe in the garage, if I get a low reading then its effectively bonded with 10mm anyway so not an issue...

If it is not then as it has been in place for a while with no sign of damage it could stay with 6mm or potentially I could keep the micc on rcd protection, then change the earthing arrangement to TT system in the garage and put 30ma RCD in the garage..

What are your guys thoughts?

 

[freddo]

There's loads of micc chucked in the ground feeding outside lights in local pubs, all working fine. A lot is bare imperial so must have been installed a while ago.