Advice please

[Danny Hartup]

Afternoon all.
Just looking for abit of advice really as don't really deal with domestic installations. A friend of mine has asked for abit of information on a supply to an outbuilding that will have a few sockets in, lights, electric cooker and electric shower, and also space for a hot tub supply for future install.
A new CU is planned for inside the house so I was thinking of coming out the new CU with a 40a 30ma double poll rcd to feed new CU in the outbuilding, looked at cable size and was thinking 3c 10mm SWA would suffice. there will be gas installed in the outbuilding so that will need to be bonded, is there any special requirements for that.

House is on TNS and has 100amp fuse.
Outbuilding is 20m from house

many thanks

Dan

 

[Leesparkykent]

Afternoon all.
Just looking for abit of advice really as don't really deal with domestic installations. A friend of mine has asked for abit of information on a supply to an outbuilding that will have a few sockets in, lights, electric cooker and electric shower, and also space for a hot tub supply for future install.
A new CU is planned for inside the house so I was thinking of coming out the new CU with a 40a 30ma double poll rcd to feed new CU in the outbuilding, looked at cable size and was thinking 3c 10mm SWA would suffice. there will be gas installed in the outbuilding so that will need to be bonded, is there any special requirements for that.

House is on TNS and has 100amp fuse.
Outbuilding is 20m from house

many thanks

Dan

The RCD wont provide overcurrent protection.

 

[Taylortwocities]

With respect, there so many bits in your post that you don't have the competence to do this.

Firstly: this work is notifiable. Are you a member of a CPS scheme? ie NICEIC, NAPIT? you'll need to be

other bits I've spotted
Lights, cooker, electric shower, hot tub - you havent mentioned heating....what is your demand calculations. Its more like an all electric small house. 60amp maybe.
You'll need a lot more than 10mm over 20metres. You need to do cable size calculations, but I'll bet your volt drop would be waaaaay off for 10mm.
Next up

40a 30ma double poll rcd to feed new CU in the outbuilding,

what is that supposed to be for??? 40amp, the shower might pull nearly that. In any case the 40 amps is the rating of the RCD contacts. an RCD does not limit the current in any way.
I would have a switch/fuse at the house supply end. RCD in the outbuilding otherwise the shed resident will have to tramp up to the house should the RCD trip.

Sorry to be hard, but you aint got a clue. You wont do your friend any favours by taking this on.
He needs a proper registered competent electrician. If you want to help out, you could dig the trench for the cable.

 

[Danny Hartup]

Basically to cut a long story short, I won't be doing the work but will be getting the cable for the supply to the outbuilding from work as a favour to keep the cost down for my friend. So thoughts on that would be appreciated.

 

[Octopus]

Why would you just get the supply cable.... That doesn't make sense

 

[Danny Hartup]

Well if I can help out with keeping money in my friends pocket every little helps. And want to get the supply installed before other building work takes place so will be easier to do now so it's ready to be completed at a later date. He will be having a lot of work done so fully aware building control will be involved and all certifications will be required.

 

[HandySparks]

You can't do cable sizing by guesswork. What's your assessment of maximum load?

 

[westward10]

If he can't afford it don't do it, live with what you have. Pilfering cable from work to keep a few quid in your friends pocket so he can afford to waste it on a future hot tub is likely to put you in hot water.

 

[Anthony S]

Put a cable duct in position prior to any building works and when the electrician does the work he pull one in. Quite simple really, saves you trying to work out something you don't fully understand and picking the brains for free of qualified people who have spent time and money becoming electricians.