Outdoor Electrics

[andy]

depending on how tough the plastic CU is and what size SWA is used, you can often terminated 6mm or less onto the plastic CU rather than a metal box. and the plastic CU has a thinner plastic then you may struggle and possbile crack the case

 

[Andy Fenn]

Thanks.
The SWA will be 4mm so would I still use a banjo or the CU MET to terminate

 

[ban-all-sheds]

However, unlike your diagram, my house CU is on one side of a wall

They usually are...

and on the other side I would like to try to fix your metal box, prepare the SWA then pass it through the normal size garage wall into the house CU, thus having no junction boxes and making the connection directly within the house CU.

You could do that - is the other side in the garage, or outside? If outside, you'll need to use a weatherproof box and a CW gland for the SWA.

Can't really put the metal box next to or near the house CU as it is in a utility room and not sure this would look tidy.

Would these look that bad in a utility room

Alternatively, use a plastic box inside:

you'll need to take more care to avoid straining it, and you may have to cut your own holes, but the same would apply if you needed such a box outside.

 

[Andy Fenn]

Many thanks, if I did use a plastic box or took my chances and went directly for the house CU, is it ok to earth using the MET?

Yes, the outside of the wall is the inside of a garage,if that makes sense.

 

[ban-all-sheds]

Many thanks, if I did use a plastic box or took my chances and went directly for the house CU, is it ok to earth using the MET?

You don't do that - the cpc of the SWA and the flylead from the banjo go to the earth bar in the CU.

That's assuming, of course, that you should be exporting your earth to the summerhouse...

 

[Andy Fenn]

Thanks again ban.

Do you spend all your time helping out others?

I find it frustrating that you can ask a question, no matter who you speak to and most people come up with different answers or solutions. It seems these regs are so open to interpetation.

On that note, wot is the norm and why?

Connect SWA on house RCD side, new outbuilding(shed) RCD CU or both.

On a personal note, would you install an earth spike for this job?

Thanks in advance.

 

[Adam_151]

Do you spend all your time helping out others?

Yeah, there are a few of here that have made electrics a bit of a hobby for ourselves and generally spend far too much time here for our own good

I find it frustrating that you can ask a question, no matter who you speak to and most people come up with different answers or solutions. It seems these regs are so open to interpetation.

That is indeed the case, the regs don't have the answers of how things are to be done, they just set out things which need to be done to keep the installation safe, best practice, and preference of the person doing the job has a big impact on how the job is done, its like driving, the highway code doesn't tell me how to drive to the otherside of town, but it does tell me I can't drive the wrong way down a one way street for example.

On that note, wot is the norm and why?

Connect SWA on house RCD side, new outbuilding(shed) RCD CU or both.

No need for two rcds unless the one further upstream is higher trip current and time delayed, I'd personally put it on the non rcd side, and use a board with an rcd main switch the other end.

On a personal note, would you install an earth spike for this job?

Is it PME/TNC-S (sorry if its further up the threa, probably missed it)

if so, i'd make a judgement based on whether the outbuilding has extranous conductive parts, how far away its from the main board, etc.

In this house, the external garage is nearer to the the main baord than some parts of the house, so using a socket in the garage with exported TNC-S earth is no worse than using an extension lead in the garden outside the back bedroom