Garage circuits

[SparkJ]

Hi all

I have been asked to install three sockets and two lights in a detached garage. The garage is 30m from the house. Total expected load in the garage is 3KW.

The house has a TT earthing system with an old style consumer unit with wired fuses. There is a 100ma RCD in place. I did an EFLI test from a socket in the kitchen and got a reading of 70 ohms.

There is already in existence a 2.5mm2 3 core armoured cable running from a spare way in the consumer unit in the house to a two way consumer unit in the garage which has breakers fitted to it. There is no RCD in this consumer unit.

My questions are:-

1 Should I trash the mini consumer unit in the garage and fit a replacement 2 way unit with 30ma RCD or is there a cheaper solution that will comply with the regs?

2 Do I need an earth spike attached to the mini consumer unit earth in the garage or will the earthing provided by the SWA cable suffice? There are no extraneous conductive pipes etc in the garage

3 Do I need a double pole isolating switch at the house end of the circuit or can I just use the fact that it is a previously installed circuit?

 

[Apache]

SparkJ - all I can say is it's a good job Steptoe is still table dancing at Stringfellows!



If it's a TT system then AFAIK there's less of an issue exporting the earth, but banging a rod in at the garage may be a good plan?

Proper isolation for the SWA may not be a bad plan - in the house - but existing circuit and you'll be keaving it safer than it was before........

A little garage CU with two MCB's and an RCD is only ~

 

[M107]

1 Should I trash the mini consumer unit in the garage and fit a replacement 2 way unit with 30ma RCD or is there a cheaper solution that will comply with the regs?

Is the 100mA rcd a time delay?

You could run the 2.5swa through a 30mA rcd at the house end & make sure the 100mA is TD type rcd & leave the cu in garage as is.

2 Do I need an earth spike attached to the mini consumer unit earth in the garage or will the earthing provided by the SWA cable suffice? There are no extraneous conductive pipes etc in the garage

Can't see a problem using the house rod/earth, but personally I always tend to keep both separate.

3 Do I need a double pole isolating switch at the house end of the circuit or can I just use the fact that it is a previously installed circuit?

If you run it through a 30mA rcd at the house end it will have dp isolation.

 

[SLIPSHOD & SLAPDASH]

Living in the big city i rarely work on TT systems. However it is clear in the regulations that 1 Rcd is not acceptable and since you are carrying out work on a circuit this should be addressed.