Garden Electrics - To add a consumer unit or not?

[ov_sjo]

When my house was built I got the builder/sparky to add a 6mm2 feed to the rear of the house for future expansion. Now i've landscaped the garden, I want to get the power hooked up.

I've done a basic sketch below. My original plan was to add a CU where the "?" is on the top-left corner (this is the rear wall of the garden). Not found anything the right size/water resistance rating yet. Could do a box-within-a-box but then it gets bulky.

I don't have any RCBO's in the primary CU, yet. Just wondering on thoughts/opinions on how to achieve the use cases on the diagram. There is nothing other than the cables laid at present.

 

[Uhtred]

I can't add anything regarding the CU but I wanted to ask, presumably that external socket is rated for 32amps?

 

[SimonR]

Why did you only run 4mm SWAC when you had a 6mm feed ? Surely it would have been better to run a 6mm SWAC to the greenhouse, then it would have been under cover and you could have put an external CU in there and fed everything from a 40A rather than 32A supply. That said I did something similar but ran a 6mm SWAC from the top of the garden straight into the CU and downrated the cable to a 32A with a 32A RCBO (I wanted the potential for a 40A supply in case SWMBO ever decided to go TOWIE' and install a hot tub). Currently it only feeds 3 outdoor sockets and 2 sets of lights (controlled with a Shelly 2). I didnt bother with a CU. The 6mm cable feeds into an IP rated JB. That then splits to a 4mm SWAC radial for the plugs and a 2.5mm feed into a switched fused spur for the lights. That feeds into double IP rated switch and Shelly for the lighting. I looked at a CU for the garden but decided that it was overkill. My sparky (who I have worked with before) came and tested and Part P certified all of my work. He also did my final termination into the CU.

 

[K.C. Leblanc]

I think if you're having to ask you really need to think about weather you have the electrical knowledge to carry out this work.

From a legal point of view if you are adding new circuits to the system then this needs either to be inspected by building control or carried out by electrician who can notify their own work.

Depending on how much stuff you need to power you could probably get away with having a fused spur at your ? point as long as the circuit is RCD protected in the main board.

 

[ov_sjo]

I can't add anything regarding the CU but I wanted to ask, presumably that external socket is rated for 32amps?

It's a good and valid question. I suspect not, and the external socket was really there just to act as a junction box and get the house built/signed off. It's cheeky.

Why did you only run 4mm SWAC when you had a 6mm feed ?

IIRC it was because the paving happened all of a sudden and the local electrical wholesaler only had 4mm in stock. It's definitely a compromise, although i'm fairly confident 32A will suffice all the garden needs.

I think if you're having to ask you really need to think about weather you have the electrical knowledge to carry out this work.

From a legal point of view if you are adding new circuits to the system then this needs either to be inspected by building control or carried out by electrician who can notify their own work.

I have reasonable electrical knowledge, my question was about products on the market, not electrical theory. Thanks, though.

 

[ov_sjo]

So after some thoughts and discussions, I will probably replace "?" with a simple junction box/outdoor sockets and use a 20A RCBO in the primary CU for now. If and when have additional circuit needs, I will reassess.

What's actually more pertinent is how the grounding will work. I've confirmed this is a PME configuration, but I may run my own earth spike in the groundhouse and isolate from the rear of the house.

And yes, it'll be certified by a sparky.