10mm² SWA to outhouse Advise needed Pls

[Adam_123]

Hello Experts

Need some advise please, due to getting conflicting information from electricians.

Background info:
4 years ago done the whole house with an extention, new wiring and plumbing. The original builder left the job after 2 leaking roofs and a failed building inspection. Since then spent more money rectifying his faults.
At the time we wanted power to our out building for a later date as we couldn't afford to have the works done then. We told the electrician (builders electrician) that we want a small kitchen, storage and gym space. The total space of the outbuilding is 7.7m X 3.6m (the gym, storage space and kitchen are all within that space) The electrician said a 10mm2 swa will be adequate for our needs.

Forward to present times, I'm trying to get a electrician in to quote for the work but it's been a real struggle. The information I've been given is conflicting which has left me bemused. I've tried to do as much research as possible but I will not do any works myself as I know how dangerous gas and electrics can be. I was hoping if the information I can get from here will match what the electrician says then I'll give the job to that sparky.
I've had one say the swa is wrong size and would need to run a new swa. Not possible as all 5meters of open plane with underfloor heating and gardens all slabbed.
Another said I would need a sub main with a link box, and the 3rd said I need 50amp mcb in the house CU and connect the swa in the CU.

Here is what I have in place and what I will be having in the outbuilding.

3 core 10mm² swa cable fully buried underground. Only exposure is 1.5m at CU & 2m in the outbuilding. Total length is 18 meters.

I have a metal Hager CU with rcbos, 100A main fuse. Tails coming of from there going into the electric meter then 2 tails from there into isolation switch then from from the iso into the CU.

I have made an attempt at working out the appliance usage with data badges and with my limited knowledge.

Hob 1amp (3amp fuse)
Extractor cooker hood 1amp ( 3amp fuse)
Boiler 0.48A (3amp fuse)
Tv 1.2 amp
Soundbar 0.09amp
2x 15w led batten light 0.13amp
1x 30w led batten light 0.13amp
WiFi extender & Alexa echo dot.
Would like to have an undercoated freezer but not needed if the load would be too much.

In outbuilding 2 way CU
50amp mcb
Kitchen, storage and gym all on 32amp rcbo 2.5mm² ring
Lighting 1.5mm² 6amp rcbo

Sorry for the long post but I've tried to give as much details as I can, (I know some with the wrong terminology)
Really hope someone can guild me in the right direction as I've been stung before relying on tradesman without doing any research.
I just want the information I receive from here to match what the electrician would say.

Thank you.
Regards Adam

 

[Rockingit]

At face value I'd say that a 10mm cable would be more than sufficient for those types of loads at that distance. You'd need to terminate it into a small 4ish way consumer unit, RCD protected, and inside the house it would need to be made off into the consumer unit and a 32a MCB would happily suffice.

 

[Adam_123]

At face value I'd say that a 10mm cable would be more than sufficient for those types of loads at that distance. You'd need to terminate it into a small 4ish way consumer unit, RCD protected, and inside the house it would need to be made off into the consumer unit and a 32a MCB would happily suffice.

Thanks for your input.

I hope you don't mind, but can I ask why a 4 way CU?
I was thinking a 2 way as its only a 32a & 6a rcbo. I was recommended this one

Hager Consumer Unit RCD 2 Way 40A VML402AH

WE WONT BE BEATEN ON PRICEWe regularly check our prices against our competitors, to ensure we can offer you the best deal possible.

www.electricpoint.com

Regarding the connection in the house, the swa would go directly into the CU and connect to a 32amp MCB.
I do recall one electrician saying he would do it like this. I only concern was when another said I would need a separate box near the house cu

 

[Rockingit]

Size of consumer unit is entirely up to you - a two module will suffice but for the couple of quid more then personally I'd go a size up so that you've some future proofing if ever needed.

As for the making off of the SWA - your electrician will have to decide if it's feasible to make off the armoured gland straight into the house CU or not (sometimes it is, sometimes it isn't) - if it isn't then you'll end up with an inexpensive small (4"x4" kind of size) metal box adjacent. The reason is purely mechanical - an SWA cable doesn't bend easily and the strands of the steel armouring need to be sound in the gland, preferably attached to metal rather than plastic.