Oh No Another Shed Electrics Question

[DHSIRT]

With apologies if this is a rerun of several old threads but I can't seem to see one that answers my question. I hope somebody can help.

I have an outbuilding that has its own consumer unit which is fed from the main consumer unit in the house. The consumer unit supplies three double sockets in the outbuilding on 2.5mm T&E run as a radial circuit protected with a 16a MCB and a lighting circuit for a couple of strip lights inside and a couple of motion lights fixed to the outside protected with 6a. Running a battery charger/ drill charger/ radio if that off the sockets. All good.

Next to this building (literally 2 meters away) is another outbuilding that I am keen to have a couple of internal sockets/ socket on the outside and a couple of internal strip lights/ outside light etc. Nothing too heavy going on.

My question is what is the best way to get power into this other outbuilding? I don't really want to run a separate supply from the mains unit as that is quite the arse. Can I run another consumer unit off the existing consumer unit that is located in the 'powered shed'?, or perhaps carry on the radial circuit using all the necessary SWA and weatherproof junction boxes and a 13 amp rcd as the supply comes into this other outbuilding and then use a FCU for the lights?

You get the idea...

Thanks in advance.

I will definitely read Part P tonight

 

[ProDave]

Does the CU in the first outbuilding have spare space to add 2 new circuits?

If so radial socket circuit and lights for outbuilding no 2?

How do you propose to get the cables between the two? above ground?, buried?

Does the existing CU in the outbuilding have an rcd or is it fed from an rcd in the house?

How is it fed from the house? what size cable and what size mcb?

 

[DHSIRT]

HI ProDave

Thanks for the response.

No space in the CU in the outbuilding. Happy for cable to go above ground or buried, though buried would be preference. Its a very short run from the inside of one building to the inside of the other. Maybe 2 meters.

The existing CU in the outbuilding has an RCD 40a

Not sure what gauge cable is supplying the CU. Its an SWA and was put in by a qualified electrician so I assume it is suitable for the light use. How could I easily find out the cable size?

Looks like the mcb in the main is mtn 125 b25?

Hope this helps!

 

[Murdoch]

Why don't you get the electrician back to do the work?

 

[DHSIRT]

Unfortunately he has passed away.

 

[ProDave]

This isn't so straightforward.

If I were doing it I might consider extending from the feed into the first outbuilding into the second and another mini cu there, but I would want to be doing some measurements first to determine if the cable can support that. And if as I suspect it's only a small cable you might be very limited on what loads you can have in both outbuildings.

I really think you need an electrician for this one, there's too many unknowns to be advising a DIY job I'm afraid,

 

[DHSIRT]

Thanks ProDave. I guess if I could turn the unknowns into knowns then I am back in the game. Apart from the cable size (which I will find out) what are the other unknowns (run from main box?/ area of outbuilding one/ outbuilding two? etc)

I guess I'm keen to learn a little from those on the forum who are far more experienced than me! Rest assured that I would get anything I have done checked out and signed off by people who are qualified to do so. I'm just trying to scratch that itch that comes with being human, the desire to learn (without hopefully electrocuting yourself in the process!)

 

[Blue Duck]

If am admin is nice they can upgrade you account to allow you to post images. Take pictures of the main cu and any other supply equipment and earthing and take a picture of the mini cu and we may be able to help a bit more but as PD says it may not be straight forward.

 

[ProDave]

Unfortunately I doubt you have the equipment to measure what we need.

I would be looking at measuring Zdb at the first outbuilding, and looking at the cable size.  From that we can work out the maximum load the cable can supply.  That will give the size of mcb in the house (which may or may not be correct as it is)

Then add in the extra cable, which will increase Zdb at the second outbuilding which may well reduce the size of the house mcb further and see what load capacity you are left with.  It could end up being very low.

 

[Southcoast2015]

What are you wanting to run in the 2nd shed?

 

[septiclecky]

What are you wanting to run in the 2nd shed?

Cannabis farm

 

[Southcoast2015]

Cannabis farm

in that case it's just a bit of T&E jammed in with meter tails isn't it?