UK Outdoor Consumer Unit

[Youcandoit]

Hi all, I'm looking for advice on fitting an outdoor consumer unit, which will be run from the consumer unit in my house.(1)(2)

I am then installing an outdoor socket (2) from the outdoor CU and also running cable to my shed (1)(2), where I will be fitting another CU - to run a light and double sockets for my tumble dryer and chest freezer (2).

(1) what size cable is suffice for this?
(2) what size mcb is suffice?

I am very competent in doing all this work myself however I just want to know the above items for safety reasons. Any help would be greatly appreciated. Thanks in advance.

 

[westward10]

What I would do it connect the external socket from an existing circuit. Then install a new supply to the shed. If you are very competent with these works you should be able to calculate the cable size and circuit protection.

 

[Youcandoit]

Hi, there is already an external socket there which is fitted using 2.5mm t&e from house CU. I want an outdoor CU in its place to save work on wiring (if this wiring is suffice that is), from there I can supply hut and old outdoor socket (moved along wall from where it used to be).
I just need to know for safety reasons as posted originally.
I'm competent in doing the work however I'm no spark and lack knowledge of cable sizing needed and mcbs, etc.

 

[ferg]

I'm not sure anyone here will give you the information you are looking for.

From a safety perspective what you have planned is not really a DIY job and there is a lot more to it than just the size of the cable.

 

[Deleted account]

Sorry youcandoit “ lack knowledge” means non competency in my book.

The job is a bit more than aDIY project as Ferg says.

 

[Youcandoit]

I get that nobody would want to give advice blindly, however there's surely not that much to consider (I don't mean to offend). All I'm asking is to be pointed in right direction.
4mm swa cable or is that only needed if outdoors and exposed or buried. I was going to put all my cabling in conduit.
16a mcb inside shed feeding sockets or is a bigger/smaller one needed/suffice.
32a mcb at outdoor CU feeding shed CU or different size needed.
16a mcb supplying outdoor socket from outdoor CU.

I get sparks prefer us diyers get someone in I do, but looking to save money and do it myself if I can get the guidance needed.

 

[Andy78]

I get that nobody would want to give advice blindly, however there's surely not that much to consider (I don't mean to offend). All I'm asking is to be pointed in right direction.
4mm swa cable or is that only needed if outdoors and exposed or buried. I was going to put all my cabling in conduit.
16a mcb inside shed feeding sockets or is a bigger/smaller one needed/suffice.
32a mcb at outdoor CU feeding shed CU or different size needed.
16a mcb supplying outdoor socket from outdoor CU.

I get sparks prefer us diyers get someone in I do, but looking to save money and do it myself if I can get the guidance needed.

Your best bet is to contact a local electrician and ask for their help with design, verification, and testing, saying you want to do the majority of manual work yourself. You may be able to reach a compromise of levels of involvement.

Even if you do manage to pick enough brains on the internet to figure out what size cables to use, you still won't possess the equipment or knowledge to be able to test your work for safety requirements, arguably the most important part.

 

[Deleted account]

I get that nobody would want to give advice blindly, however there's surely not that much to consider (I don't mean to offend). All I'm asking is to be pointed in right direction.
4mm swa cable or is that only needed if outdoors and exposed or buried. I was going to put all my cabling in conduit.
16a mcb inside shed feeding sockets or is a bigger/smaller one needed/suffice.
32a mcb at outdoor CU feeding shed CU or different size needed.
16a mcb supplying outdoor socket from outdoor CU.

I get sparks prefer us diyers get someone in I do, but looking to save money and do it myself if I can get the guidance needed.

I actually don’t know the answer to your questions because there is a lot “to consider”.
It would take considerable time to calculate the appropriate size cables dependant on distance load and numerous correction factors etc..

We have a British standards regs book that states all the different correction factors and maximum disconnection times and maximum allowed impedance.
There are many facts and figures that are impossible to memorise. Not one spark anywhere could possibly know without consulting the book.
I would have to consult that book in order to know what size cable and what correction factors are applied.

We are genuinely not being awkward, there is really a lot more to choosing a cable size than just listing what is going to be the load.

I could guess the cable size you need and possibly be correct but I wouldn’t state it without the actual calculations to back it up.
It may be I undersize it, not a good thing for obvious reasons or over size it making you pay more than you should.

 

[Youcandoit]

I actually don’t know the answer to your questions because there is a lot “to consider”.
It would take considerable time to calculate the appropriate size cables dependant on distance load and numerous correction factors etc..

We have a British standards regs book that states all the different correction factors and maximum disconnection times and maximum allowed impedance.
There are many facts and figures that are impossible to memorise. Not one spark anywhere could possibly know without consulting the book.
I would have to consult that book in order to know what size cable and what correction factors are applied.

We are genuinely not being awkward, there is really a lot more to choosing a cable size than just listing what is going to be the load.

I could guess the cable size you need and possibly be correct but I wouldn’t state it without the actual calculations to back it up.
It may be I undersize it, not a good thing for obvious reasons or over size it making you pay more than you should.

Ok then, thanks anyway

 

[telectrix]

i would run supply to shed CU, then feed the outside socket from there, saving the need for an outside IP rated CU. however, cable sizing anf loads need to be considered. also testing of the installation is required, along with a certificate and notification to LABC> this means getting a qualified sparks in.

 

[Youcandoit]

i would run supply to shed CU, then feed the outside socket from there, saving the need for an outside IP rated CU. however, cable sizing anf loads need to be considered. also testing of the installation is required, along with a certificate and notification to LABC> this means getting a qualified sparks in.

Thanks for replying, does this apply in Scotland though?

 

[telectrix]

the labc bit is different in scotland. need a scottish member to clarify.

 

[Youcandoit]

the labc bit is different in scotland. need a scottish member to clarify.

Does this even apply to homeowners, as doing work to my own property? Hardly going to report myself lol?
Sorry but just wanna be sure of everything, you've been the most helpful so far on here so thanks.

 

[DPG]

Out of interest, what RCD protection do you have, what type of earthing system, and are there any extraneous conductive parts in the outbuildings?

 

[Youcandoit]

Out of interest, what RCD protection do you have, what type of earthing system, and are there any extraneous conductive parts in the outbuildings?

It's a pme system with CU in property, having 100a rcd with mcbs. No extraneous conductive parts in shed.

 

[DPG]

It's a pme system with CU in property, having 100a rcd with mcbs. No extraneous conductive parts in shed.

Good answer, ta.

 

[Youcandoit]

Good answer, ta.

Well it's a 100a main switch with 2 rcds and mcbs lol.

 

[richy3333]

You'll need to establish whether you need a building warrant or not for this work. The work needs signing off with an EIC as if you sell the property the lawyers will be hot on asking for proof it is safe etc.

Dont know what you mean by an outdoor CU but if you mean IP rated to replace the socket outlet then you are not permitted too use plastic CU's in domestic circumstances.

I really dont understand why you expect people here to tell you what to do. Many of us have spent years learning our trade. If for example you are a lawyer would you sell my house free of charge? In any event it is against forum rules to give DIYers this type of guidance - even if you had supplied all the information required.

 

[Youcandoit]

Wind your neck in,
why are there forums then giving advice, if it wasn't there I wouldn't have asked and as for your lawyer comment, I'm not asking you to do the work only advice so if I were a lawyer and member of a forum giving advice then Yes, I would give advice on how to sell your house - do you want to sell your house?

 

[telectrix]

post #10 gave you all the advice you need. regarding testing, have you got a spare £600+ to buy the required test equipment, and the knowledge to use it? if not, then you cannot do the work to comply with regulations, so there's no point in further free advice