Help please

[Jones1981]

Hi,
New to the forum. I’ve recently qualified and past part P. Doing my first assessment and want everything to go right lol. Any issues please point out and correct while making fun of them.

Friend wants sockets and lights outside in his garden. (lights 2gang switch one for flood light and one for decking lights) and 3 sockets (socket run of approx. 30m one is at far end of garden).

CU (TN-C-S) in house and I’m going to use the only spare 32mcb (Non RCD) with 6mm T&E and run to a ‘garage CU’ (in house about 5m away, inside house, from old CU). Will be 40A 30mA RCD 2way with 20A MCB (radial for sockets) and 6A (lighting). He travels frequently and wants to be able to switch them off when he goes away to avoid them been abused).

6A with 1mm T&E for run of approx. 25m including all runs and switch drop
20A with 2.5 radial in conduit (in with 1.0 cable for first 10m in conduit) then approx. additional 15m in conduit for final 2 sockets (large distance between them).

Lengths will be ran in conduit along the house for lighting and first socket and by the side of fence along a wooden batten for the final 2 sockets (friend won’t pay for trench to be dug). There will be several bends throughout to get to the initial ‘starting place’.

4mm T&E makes the job double the price and would be cheaper to go to 32A ring rather than 4mm radial. Opinions on that??

Depending on Zs would consider 6mm earth to earthing block however due to short distance of the 6mm T&E linking CU’s I’m guessing it will be ok (or should it be done regardless).
Any advice or ‘look out for’s I’m happy to hear.
Thanks in advance. )

 

[Jones1981]

Sorry forgot to say obviously all switches, lights and sockets are IP66.

 

[securespark]

If you have a 32A ring final, what issue may you have with compliance?

How is the conduit going to traverse the space between the garage and the first external point?

As the wiring run for the sockets is a long one have you made sure the cable CSA does not need increasing to keep voltage drop and EFLI within the bounds of the CPD?

What conduit are you considering using?

Does the user really want to go outside every time to switch the lights on?

 

[stillp]

and by the side of fence along a wooden batten for the final 2 sockets

Rough. How is this going to be protected against damage? What if the fence is blown down?

 

[Jones1981]

Right sorry this is long . . .
From the start (CU original) is in utility room the new CU is across the
room about 2m away. The 6mm from 32Amcb will travel up in conduit, along
ceiling and back down into new CU 40A 30mA RCD protected. (nothing eternal)

From the new RCD protected CU the 1.0 and the 2.5 will run through the wall
(in conduit and down to a lower point) the along the side wall of the house
(4.5m) round the corner to the back of the house (another 3.5m approx)where
the sockets and 2gang switch are. One switch is wired and goes to spot
light. That's the install ended.

He has text saying as well as extending the lighting to the decking lights
in summer he also wants 2 additional sockets placed. One is a short run of
approx 5m and would be in conduit fixed to wall the furthest is the problem
one which is a long run. The long run is the issue with it being along the
fence and long. The conduit would be ran along a batten connected to a
flowerbed and the fence posts (very little chance of it all coming down).
Won't be extended until summer so will have time to look extensively into
all paths and situations for that one. But obviously have to plan ahead to
use 2.5mm for the run or 4mm for the run as I can't just switch half way
round. Going to measure the exact run length when I'm there and see.

I was originally working on A3 radial which would deffo be ok with the first
two sockets as its well within the CSA including voltage drop for length and
the CPC would be fine required EFLI. Testing would obviously confirm that. I
am tempted to go to 32A and 4mm for the A2 radial and play it safe. Still
doesn't get out of the head ache of getting wire to the furthest point but
at this point more interested in getting right CSA in knowing that I'll
pass.

Using 20mm round ridged conduit (tower)
He wasn't switch outside as sits out and lights on when it gets dark as he's
already out there.

Hope that answers everything...

 

[securespark]

Conduit OK on house.

Where cable goes through wall, I'd put conduit through as well.

I'd use SWA elsewhere.

If you have 2 32A MCB's, you have no discrimination between them.

 

[Jones1981]

Yeah installation been watched is all on house and did say conduit is going through wall.
I have 20A for 2.5mm A3 rad and 6A for 1mm lighting run. Those are both in the new RCD protected CU. Zs should be less than 0.35 and run is only half of the 31m allowed. So testing should all be ok unless I mess up.
Will use SWA for any additional runs but that wi be in summer (hopefully not as wet behind the ears then).
Can you see anything I'll be pulled for?

 

[Jones1981]

Shouldn't need additional earth to earthing block (TN-C-S) due to 6mm from 32mbc in CU to new CU due to short run should I?
I need some sleep!

Just seen external light and has no place for conduit to terminate. Is it worth changing to black rubber flex to get best IP (IP54 I think). Flex run would be about 5m from switch and would still be in conduit until the light maybe 10cm including a drip loop. Thoughts please? Oh and could I get away with 0.75 or should I stick with 1 same as T&E.
Thanks

 

[ban-all-sheds]

I’ve recently qualified and past part P.

Any other qualifications?

2382? 2396? 2365?


Do you genuinely think you should be offering your services to the public yet?

 

[Jones1981]

Looking to work with sparky for a year or so but smaller jobs I'll be more than fine with. I just want everything right for this install. What's your thoughts on the rubber flex as that's what's suggested and would be best for seal into light. 0.75mm would be ok or would you go safe and go 1mm?

 

[bernardgreen]

Looking to work with sparky for a year or so but smaller jobs I'll be more than fine with.

A mistake on a small job can be as fatal for the client as a mistake on a big job can be. The fine for negligence can be large. Work with an experience spark to get the experience you need to work safely on your own on both large and small jobs.

 

[Jones1981]

With the greatest of respects I know my ability and what I can do safely and what are my weaknesses.
What I asked are opinions on the install specified above. That is what the topic was about. Thanks for all those posting helpful questions/ suggestions.

 

[ban-all-sheds]

friend won’t pay for trench to be dug

That's perfectly fine - no reason why he can't dig it himself. Somebody has to.

4mm T&E makes the job double the price and would be cheaper to go to 32A ring rather than 4mm radial. Opinions on that??

4mm² is not 2x the price of 2.5mm², and you'd need less, so how does the job double in price?

And in any event, the difference must be trivial, so you design what's most appropriate, not compromise the design for the sake of a few quid.

 

[ban-all-sheds]

The 6mm from 32Amcb will travel up in conduit, along
ceiling and back down into new CU

Good luck pulling 6mm² T/E through all that conduit and bends. Have you a good reason for not wanting to use singles? And why are you using conduit in the first place?

Using 20mm round ridged conduit (tower)

Everywhere?

Not only will it look sh*te, it won't be a suitable alternative to SWA or steel conduit where those are required.

 

[ban-all-sheds]

Looking to work with sparky for a year or so but smaller jobs I'll be more than fine with.

Not enough.

The Domestic Installer VRQ does NOT make you an electrician, no matter what the prostitutes at NICEIC etc would have you believe.

What's your thoughts on the rubber flex as that's what's suggested and would be best for seal into light.

Why do you still want to run it in conduit?

0.75mm would be ok or would you go safe and go 1mm?

You're the qualified electrician - you tell us what's dangerous about 0.75mm².