Adding a garage consumer unit

[Paddington]

hi, am newly qualified and need to do two circuits for registration process, so want to get this right. Main CU in garage is under sized for mcb's (only holds 6). So going to install additional garage consumer unit populated with 1 x 20a rcbo for 2.5mm radial circuit and 1x 6a rcbo for garage and external led lighting. Supply will be from a 32a mcb (this is rcd protected) which will be a sole supply as I will remove a soon to be redundant electric shower supply. I will be using 6mm t&e supply for the garage, all and any advice regarding testing for the additional CU (not the circuits). I am going to test it as though it were a new radial circuit, then obviously do a full test on the 20a and 6a circuits when I've completed those. Any helpful advice welcome.

 

[westward10]

So you are going to install a separate CU to off load some of the circuits from the main CU?? Would sound more sensible to up grade the main CU.

 

[Midwest]

Why not.......duuuuur, what he said ^^^^^^^^

 

[Paddington]

So you are going to install a separate CU to off load some of the circuits from the main CU?? Would sound more sensible to up grade the main CU.

Simplest way of getting 2 new circuits for inspection, relieve space on mainCU, segregate supply for working in garage / workshop from house. Get registration then upgrade CU to new 17th edition 10'way rcbo board. Garage electrics need sorting anyway so this kills many birds with one stone.

 

[Midwest]

Why bother doing it twice?

 

[Paddington]

Why bother doing it twice?

Oh and practice / confidence building, but good quality inspection circuits mainly.

 

[Midwest]

If you've the confidence to install two new circuits, you should have the confidence to replace the original CU. The tests are the same

 

[westward10]

The best way to show a job you have done is to test the place, replace the main CU and resolve any issues. Adding on a two way board will look ad hoc and you may well get asked about discrimination between protective devices which you will want to avoid.

 

[Midwest]

It would look ****.

 

[telectrix]

why fit a RCBO for garage sockets when there is already RCD protection in the main CU? If the CU is hi-integrity and the T/E cable to the sub is surface, then feed sub from a non-RCD way. better way is as said before. upgrade the main CU.

 

[Paddington]

The best way to show a job you have done is to test the place, replace the main CU and resolve any issues. Adding on a two way board will look ad hoc and you may well get asked about discrimination between protective devices which you will want to avoid.

Eventually want totally separate spark to outside / workshop garage, so when I do new main CU will split tails with henleys then have power in the event of main CU problem. Discrimination a good point though, hoping testing will show rcbo is faster than rcd, if not then all resolved with upgraded main CU as you said but this route the positives out way the negatives.

 

[Midwest]

If you installed a high integrity CU, you could achieve independent supply to the garage.

Why would an RCBO be faster than an RCD?

 

[westward10]

Why would an RCBO be faster than an RCD?[/QUOTE]
Doesn't weigh as much?

 

[westward10]

Eventually want totally separate spark to outside / workshop garage, so when I do new main CU will split tails with henleys then have power in the event of main CU problem. Discrimination a good point though, hoping testing will show rcbo is faster than rcd, if not then all resolved with upgraded main CU as you said but this route the positives out way the negatives.

Don't know what to say to that really.

 

[Midwest]

Haven't put someone else off have we. OP you seem suitably qualified, come back and discuss, there's a lot to learn from members here. Perhaps start at the beginning?