How much space do I need for CU units and isolators in an external box?

[Jess Shannon]

We're planning a big renovation and the electric board have agreed to install the meter in an external pillar box. This one I'm looking at has a separate compartment for our side (datasheet here).

We want to have a couple of panel mount outdoor sockets (IEC309) that we can use now, before the house is ready, for a caravan and power tools. We're also getting a sewage treatment plant that has a pump and fan (should draw about 0.6kw peak).

Then when the house is built we want to run the power from the box into another CU in the house, about 7 metres away. Then eventually another CU in an outbuilding for a studio/workshop space, a similar distance.

 

We'd need a switch inside the locking cabinet to turn off the outdoor sockets.

Do we need to have two separate fused isolators for those two tails going to the house and studio? Or could they share one?

If we wanted to add a car charger, would that need a dedicated CU to fit into this box, or could we branch off the tails to a CU in the outbuilding or house for the charger?

If we have solar on the roof and want to sell back to the grid does that change this setup?

Is there anything we need to plan for when trenching and laying the ducting? Should I plan for 25mm SWA to go in for the tails?

We'll be getting a qualified electrician to do this of course. I just want to understand all the implications so we don't make a problem for ourselves down the line.

This is actually in Ireland, I know some of the rules may differ, but any advice would be helpful.

Thank you!

[Kelvin]

I installed a 3 phase cabinet (we have a single phase supply) as I thought that would big enough to future proof us. However this was a year before we started building the house so was a bit of guesswork. Our meter is in the cabinet and the house 25m away so needs a big cable and an isolator. I hadn’t considered how big the isolator is. Fast forward 3 years and we installed the EV charger which needs its own small CU. It was installed at the meter end and there wasn’t room in the cabinet for it so I had to install a second smaller cabinet just for the EV CU. Bit annoying. It’s a different colour too so shall have to paint it at some point or possibly build a wooden cabinet around them both as I have plenty of wood left. 
 

We also have a workshop and sewage plant but I ducted them into the house on the main CU rather than into the electricity kiosk. My cabinet has three ducts. One in for the mains supply, one for the house supply, and a spare just in case.