garage unit wiring again!!!!

[Nose]

Been asked to look at a job at my mothers house and want to ensure i comply with bs 7671 and good practice before i start.

I currently have 6mm cable running from the consumer unit to where i will be running 6mm swa cable under the garden. Overall total distance of about 15 meters

I will ensure it is min 450mm deep. There is no massive drains to be placed on the cable onlt a 16a redial for the sockets and a 6 a breaker for the lights, both protected by a RCD

Questions. What size breaker should be in the main consumer unit? and what is the best way of joining the 6mm twin flat and the swa cable out to the garage?

Is all that i have mentioned above o.k?

 

[Taylortwocities]

Depends on the installation method for the 6mm cable, but (except for a short on the cable) your load is never going to exceed 16A+6A from the garage so I suggest a 32A cb in the consumer unit.

What is the supply characteristic, TT, TN-S, something else?

Are the MEBs up to scratch?

How will you comply with this? //www.diynot.com/wiki/electrics:part_p:diy_electrical_work_and_the_law

 

[sparkyspike]

If the SWA is running into the ground outside the house, then use a waterproof adaptable box on the outside wall. The t&e can enter from the back, then use an external gland and banjo to connect the SWA to one side of the box.

Or if you are going straight into the ground from inside the house, join conduit from the CU to an adaptable box with bush adaptors, then use an internal gland and banjo to connect the SWA. Don't forget to earth the banjo to the CPC.

As TTC hinted, you need to consider how you are going to acheive equipotential bonding in the garage, if at all.

 

[ericmark]

Taking power to a garage has been covered in Wiring Matters from IET. See Electrical installations outdoors: a supply to a detached outbuilding (243 k) this was published in 2005 under old regulations but not too much has changed.

There has been much debate on how they should be earthed and it really needs distance between house and garage and the existence or not of earthed extraneous-conductive-parts to be taken into consideration.

With a single 16A radial and 6A lighting a 20A supply MCB is ample although nothing to stop you going bigger you could go up to 40A with that size cable so long as the earth fault loop impedance and volt drop etc. and within limits.

As to how to terminate the SWA much depends on local conditions. I have used a metal clad FCU box and a blanking plate and took SWA into house. But using a box outside is also an option. You could fill the box with resin or other compound if likely to get wet. I have used re-enterable compound in past which you can dig out again with screw driver. Also used an outside socket although 6mm is little on big side for that.

Problem today is Part P as for it to be signed off either LABC or Electrician has to view cable in trench etc. And so arranging for viewing can be a pain especially if the trench causes danger and requires back filling ASP.

Remember if the earthing arrangement is not the same as house the RCD in house may not cover the garage and you may need a second in garage.