Garage

[JKMRK1]

I have a 40amp typeB MCB (RCD protected) supply to an IP66 junction box in my garden which the runs in 4mm swa cable under my garden to the garage into a 13amp socket.

I want to fit a new consumer unit I'm my garage to run a lighting / ring main socket circuit. Question is can I just use the 32amp/6mp MCB supplied for this and do away with the 40amp 30mA RCD as it's RCD protected from the supply consumer unit in the house?

 

[radiohead]

When you say selectivity between devices can you explain more please?

Yes of course.

Best design practice is for only the device immediately upstream of a fault to trip, in the case of MCB's it's likely that a fault of negligible impedance at the load end will take out all upstream MCB's. Better practice is to have fuses at the supply end and MCB's at the load end