New Outdoor Wiring/Consumer Unit

[bjblackmore]

Hi,

We moved into our house about a year ago, and we've spent the past several months putting right a whole bunch of half arsed DIY that the previous owners had done (including lighting in the extension wired into the same circuit as downstairs sockets, and exposed wiring hidden behind a cooker spalsh back). Anyway I'm now starting in the garden, and want to install some decking, with LED deck lighting, possibly a water feature with pump, and improve/fix the shed electrics.

The current setup is that the shed electrics has a long (15m) extension cable which is plugged into the conservatory 13A socket, with the cable poked through the wall, and running along the side of the house along the fense, and into the shed. This then has a 4-way entension block, with a lamp plugged in for lighting.

Knowing that this setup is pretty unsafe, I'd like to remove the extension cable not spur it off the internal socket, and instead change it for an external IP65 rated consumer unit, which itself will be connected to the internal CU (in the understairs cupboard) on its own circuit. Then in the external CU, have 1 MCB/Curcuit for the shed, one for the deck lighting, and 1 for the water feature. Also to replace the 4-way extension block in the shed with metalclad RCD sockets.

The below pics show how things are currently, with the shed spurred off the 13A socket in the conservatory. And with the new CU, running back along the side of the house (Study/Utility) using Armoured Cable, into the garage, through the garage using twin & earth, and in to the existing CU. I can't run the cable through the kitchen/consevatory, as I can't see any voids in the conservatory for the cable.

View media item 75009
A few things I'd like to know; What size cable is best to use, between the 2 consumer units, 1.5mm or 2.5mm? The total length between the 2 CUs is 15m. The load will potentially be: 15(ish) LED deck lights; 1 pond pump; and the shed electrics - which will be 1 fluorescent tube light, and a mitre saw/drill/jigsaw power tools (not all in use at the same time). The CU I was thinking of using is the IP65 rated MK Sentry http://www.tlc-direct.co.uk/Products/MK5702.html. Is there anything I need to be aware of doing this? Any pitfalls, tips, suggestions?

Thanks

Ben

 

[Aragorn84]

I'd put the CU in the shed. Then run the LED lights and pond supply from there. It might be IP65, but theres no reason to expose it to more bad weather than is neccesary.

How big a cable depends how much power you need. Personally i'd be running a 6mm out to the workshop, to give you the capacity to stick a heater or whatever out there that you might want in future. Obviously depends on your requirements ofcourse 2.5mm might be fine.

I would also run the SWA off a switchfuse, rather than off the house CU.

 

[winston1]

You don't really need a second consumer unit. Run it off a 20 MCB in the house CU and run the lights, pump etc off fused connection units in the shed.

 

[PrenticeBoyofDerry]

The work you are proposing to do, will require notification to building controls and a compliance to both BS761 and Part P of the building regulations.
The best possible advice that can be offered is contact a registered electrician as the will be able design, install, inspect, test, certificate and notify the work for you.

I am not saying this is not a task that a very electrically competent DIYer cannot perform but by the time you have messed about calculating loads, factoring and de-rating factors due to installation methods and voltage drop, then dug a trench, installed in compliance, inspected, tested (using the specialised calibrated equipment required to do this, which will also include and understanding of what the results relate to and if they satisfactory), documented your findings within an electrical installation certificate and prior to starting work applied to building controls for approval of the work and paid the rather hefty fee associated with the notification procedure.
But it could be possible that employing someone that can competently perform this task for you, would be a logical step.

 

[Norcon]

"Any pitfalls, tips, suggestions?"

Yeah. Don't ask on here.

Do all my own wiring and never had to ask armchair numnuts ready for the zimmerframes how to do it.

 

[PrenticeBoyofDerry]

Do all my own wiring and never had to ask armchair numnuts ready for the zimmerframes how to do it.

Could you show the schedules of inspection and testing of this work that proves what you have done is compliant and safe?
The only " numnuts" is the one that does not appreciate the aspects of design, installation and the very important need to prove what has been done is safe!
There is also the legal requirements that concerns part p to consider, and suggesting that anyone did work outside the law is something I would not recommend and install anything unsafely, that would be truly something a incompetent numnuts would suggest!
Now is that a category that you fall into?

 

[Norcon]

Do all my own wiring and never had to ask armchair numnuts ready for the zimmerframes how to do it.

Could you show the schedules of inspection and testing of this work that proves what you have done is compliant and safe?
The only " numnuts" is the one that does not appreciate the aspects of design, installation and the very important need to prove what has been done is safe!
There is also the legal requirements that concerns part p to consider, and suggesting that anyone did work outside the law is something I would not recommend and install anything unsafely, that would be truly something a incompetent numnuts would suggest!
Now is that a category that you fall into?

Schedules of inspection doesn't prove its safe. All its proves is that some numpty ticked a few boxes and was well paid for it.

 

[PrenticeBoyofDerry]

They will prove it is unsafe and non-compliant and if done correctly cannot be done from ones armchair and would be difficult while using a zimmer!!

 

[PrenticeBoyofDerry]

[remove].

I think your calculations on design and testing require some modification.
Even if the technique described above was a suitable test to prove the cable size was inadequate, just going the next size up does not mean the job is done, maybe the next size up would also fail your testing procedures, so do we keep repeating this until the steam has ceased or alternatively someone has deceased! And how would we document this test and it's finding within the BS7671 schedules of tests results?

 

[bernardgreen]

If any steam rises its undersized.
Then fit the next size cable up. Job done.

Or install a sprinkler system to keep the cable cool when running maximum (over) load current.

 

[ekmdgrf]

If any steam rises its undersized.
Then fit the next size cable up. Job done.

Or install a sprinkler system to keep the cable cool when running maximum (over) load current.

That'll be one of those Superconductors?

 

[PrenticeBoyofDerry]

If any steam rises its undersized.
Then fit the next size cable up. Job done.

Or install a sprinkler system to keep the cable cool when running maximum (over) load current.

I think that OP would consider that suitable, must be as numnuts as Norcon, as they seem to think his post was a useful contribution !

 

[EFLImpudence]

Norcon will only be useful if the OP wants it demolished.

 

[bjblackmore]

If any steam rises its undersized.
Then fit the next size cable up. Job done.

Or install a sprinkler system to keep the cable cool when running maximum (over) load current.

I think that OP would consider that suitable, must be as numnuts as Norcon, as they seem to think his post was a useful contribution !

Hmm, actually I just thought his post was funny. I didn't reply earlier cause I was at work, and also didn't want to inturrupt the little tête-à-tête that was going on.

Coincidentally our site electrician was in our office today, and I did ask him & showed him this thread. He went through everything needed, correct ampage of MCBs, size of cable 6mm, as Aragorn84 said, and agreed the shed would be a better place for the CU, again as Aragorn84 said, and explained the regs. I can also buy the SWA, external glads, CU, etc though the company account, which will save me about 20%. He also said it only needs to be tested, and a certificate issued if installed by an actual electrician, if a resident does it to their own property, it doesn't have to be. Whether I perform the install, and then get someone qualified in to check it over for safety after is always an option.

I guess at the end of the day, if this is our forever home, as long as it's safe I'm fine with it. If we were doing the house up to sell on, or to rent, I'd be more worried about the certificates & paperwork.

 

[EFLImpudence]

He also said it only needs to be tested, and a certificate issued if installed by an actual electrician,

All work has to be tested so the results may as well be recorded.

if a resident does it to their own property, it doesn't have to be.

You don't know how to do it.
How would you know if it was safe?
If you don't want a certificate, that's up to you.

Whether I perform the install, and then get someone qualified in to check it over for safety after is always an option.

They could supervise throughout then issue the certificates.

I guess at the end of the day, if this is our forever home, as long as it's safe I'm fine with it.

But you won't know.

If we were doing the house up to sell on, or to rent, I'd be more
worried about the certificates & paperwork.

That's good to here.