Additional Consumer Unit

[b0b]

Afternoon fellaz,

Your thoughts please, I'm in the process of converting my garage into 50:50 workspace/office. I plan to install:

A Consumer Unit with 6A mcd for 2 sets of 4 spotlight on a radial circuit (1.5mm2 cable 10m run).
A 20A mcd for 5 2g sockets wired in a ring main circuit (2.5mm2 cable 15m run).
A 64A 30mA rcd.

The additional CU will be connected to the Main CU (32A mcd) in the house by a 4mm2 core cable running in trunking under paving flags for 10 meters. I plan to run 2 computers in the office and power tools in the workshop, are there any problems with this?

 

[plugwash]

normal cable in conduit underground is not a brilliant idea.
better to use SWA (steel wire armoured) which is designed for the job

remember to use glands for the SWA

while you can use 2 core swa and use the armour as earth most sparks consider it better paractice to use 3 core with a core as earth THE ARMOUR MUST STILL BE EARTHED THROUGH THE GLANDS AND THE TAGS THEY COME WITH THOUGH

also it needs to be burried about half a meter (i think officially its 450mm but im not sure)

im goning to take 20m as an estimate for the total length of the run to cover lengths in the house etc

my personal preference is to wire it as follows
40A mcb in non rcd side of CU
twin and earth cable
rcd in metal 2 module box (this also allows you to compeltely isolate the outdoor wiring in the event of damage)
SWA cable
metalclad non rcd CU
32A ring and 6A lighting cuircuits

with this design 6mm is a suitable sise for the cable from the main CU to the RCD and the cable from the rcd to the metalclad non rcd CU

it may even be worth going one size larger and useing 10mm cable in case you want to add any large loads in the garage in future (digging cable trenches is hard work burying small cables is a false economy)

 

[b0b]

Thank you for the advice.

 

[supersparks]

normal cable in conduit underground is not a brilliant idea.
better to use SWA (steel wire armoured) which is designed for the job

remember to use glands for the SWA

while you can use 2 core swa and use the armour as earth most sparks consider it better paractice to use 3 core with a core as earth THE ARMOUR MUST STILL BE EARTHED THROUGH THE GLANDS AND THE TAGS THEY COME WITH THOUGH

also it needs to be burried about half a meter (i think officially its 450mm but im not sure)

im goning to take 20m as an estimate for the total length of the run to cover lengths in the house etc

my personal preference is to wire it as follows
40A mcb in non rcd side of CU
twin and earth cable
rcd in metal 2 module box (this also allows you to compeltely isolate the outdoor wiring in the event of damage)
SWA cable
metalclad non rcd CU
32A ring and 6A lighting cuircuits

with this design 6mm is a suitable sise for the cable from the main CU to the RCD and the cable from the rcd to the metalclad non rcd CU

it may even be worth going one size larger and useing 10mm cable in case you want to add any large loads in the garage in future (digging cable trenches is hard work burying small cables is a false economy)

there is no minimum depth for this
- its advised only-
if you were going to run under a flower bed it would be stupid to run it 4 inch under the ground.
40A mcb on 30 amp 4mm cable.........erm....yes

this maybe a personal questiopn but;

rcd in metal 2 module box (this also allows you to compeltely isolate the outdoor wiring in the event of damage)

do you have a fetish for small consumer units and rcds in 2 module metal enclosures???

 

[plugwash]

it seems the best way to me as it provides

seperation of rcd from the house rcd
rcd at source of cable
a suitable box to terminate armoured cable to

 

[plugwash]

btw i went through the design i suggest and at the end i told him over his distance he should use 6mm to wire it