New extension - 2nd fuse box connection

[Rodrayner]

Hi,
We are building a new extension which is the opposite side of the property to where the current mains in and fuse box is located ( which are on the opposite side of an external wall ).

The extension will be a new kitchen with an electric oven and hob, utility room with washing machine / tumble dryer a garage and upstairs a new bedroom and en-suite. So i guess what i'm saying is there is quite a bit of electrics going in and some of it such as the oven & hob will have a decent load.

Between the existing fuse box and new extension are several solid concrete floors with the new extension also being a solid concrete floor.

To get round all this and make life easier i was thinking of having a trench dug outside from the existing fuse box down to the extension and then run new cable into the garage and put in a second fuse box. The total distance being 35 mtrs. At around 15 mtrs along the trench from the fuse box i need a trench anyway for drainage services so the plan is to lay the electrics into that trench if i'm allowed to, it will include soil pipe and blue MDPE water pipe.

Can anyone give me an idea of what size armored cable i will need, i have read suuggestions that it needs to be around 16mm but want to ask the experts.

Thanks in advance.

 

[Cid]

Yeah 16mm is more than adequate for an extension.

 

[Deleted member 105166]

want to ask the experts.

Your local electrician will discuss loads with you, he/she will then do all the calculations, taking into account rating factors, to specify the cable he/she will then supply.
If you offer to dig and back fill any trench required, you will save yourself money.
The 35m distance seems excessive, but maybe I'm not visualising it correctly. You're not proposing running a submain from the house to a detached garage and then running final circuits from that back into the house, are you? Or is the garage attached to the house?

 

[telectrix]

16mm should be adequate. your trenching method looks OK from here, but please get advice from a competent electrician on site.

 

[shaun1]

As others have said, get an electrician on board now as they may be reluctant to connect a cable that just appears out of the slab if they cant see the whole route. Also, you will want to split the meter tails and feed it from a switch fuse or similar, rather than a breaker in the existing CU. If your meter is in an outside meter cabinet, you might need to aim for there (but may have issues with where you can locate the switch fuse). You will probably need 3 core SWA to take care of any bonding requirements. Best to get someone out to have a look.