Outdoor Wiring Project

[EdtheDuck]

Hi all,

Thanks in advance for any help/tips

About to start an outdoor wiring project in a couple of weeks and just wanted to clarify what I am planning to do is ok.

I've drawn a basic diagram to make things a little clearer, please dont laugh

As you may or may not be able to see I am planning on installing a 6A RCBO in the non-RCD protected side of the CCU (Splitload) then running 1.5mm2 T+E to an adaptable box on the outside wall via two FCU's and Two Single Pole switches. From here I will run 1.5mm 4-core SWA (2 independandtly switched phases) to 3 or 4 adaptable boxes throughout the garden to supply 4/5 spotlights and one small feature fountain pump.

Hopefully this sounds ok so far? If so a few questions:

1. Do i need to run a separate 6mm earth from the CCU to the point where the SWA terminates on the house wall?

2. Do the adaptable boxes in the flower beds need to be physically attached to a support or can they freestand on the bed? (I am planning on filling these with some of that clever gel - like resin but doesnt set)

Any other pointers would be much appriciated and thanks again for any help

 

[Taylortwocities]

1. Cable sheath must be earthed and earthing carried right through to the end section.

2. The boxes will need to be IPx8 to allow them to be buried/submerged. If your resin achieves this, then fine. Dont forget that the cable glands will also need to achieve this.

extra:

How will the SWA be laid? are you digging a trench as we speak?
Who is going to do the work and test and notify?
If you then you need to inform the local authority before you start.

 

[ColJack]

outside electrics come under part P of the building regulations and need to be either done by an electrician registered with a competent persons scheme, or notified to the council by you and a fee paid before you start work.

 

[Lectrician]

You CANNOT have two fuses and share the neutral.

Use one fuse.

 

[Steve]

My setup involves one 5 amp fuse. And its the same as yours except all wiring is flex as its attached to the house. Two lights and a pump (and a UV filter)

 

[ColJack]

You CANNOT have two fuses and share the neutral.

Use one fuse.

and what do you think happens in your fuse board? all the neutrals are wired together and then you have 8-12 fused lives..

 

[flameport]

The FCUs are redundant. The cables are already protected by the 6A RCBO - an extra 5A or 3A fuse will do nothing.

Untitled

• flameport
• 24 Jun 2009
• 1

 

[Lectrician]

You CANNOT have two fuses and share the neutral.

Use one fuse.

and what do you think happens in your fuse board? all the neutrals are wired together and then you have 8-12 fused lives..

When I first glanced at the pic, I thought it was just two fuses in the CU, not seperate from it.

I still don't like it though.

The pic in the post above is how it should be done. You should not use the fused spurs.

 

[EdtheDuck]

Many thanks for all your comments, much appriciated.

Just the clarify then...

I wont bother with any FCU's, just the 6A RCBO. I presume as no one has commented, that 1.5mm T+E/SWA will be sufficient? I believe this is rated at 16A anyway correct?

Finally, what about earthing? Ive read comments that an additional earth should be run alongside the T+E to where the SWA initially terminates due to the fact that the earth i the SWA will be via the armour and one of the four cores... I cant see why myself as surely the earthing in the T+E will be sufficiently rated for a 16A supply if the cable itself is...

Thanks again.

 

[Taylortwocities]

The more you talk, the more worried i am about your competence to do this.....

But in the spirit of this being a DIY forum...

First of all, what is a fuse for? It is there to protect the cable.
You have a 6amp RCBO, the cable is rated more than 6amps. If the manufacturer of the load (the lamps) does not ask for a fuse to protect the lamps then thats it. end of.

The T&E needs an earth in its cpc (that's the conductor in the middle of the cable). You should not need a supplementary earth conductor unless your EFLI is too high. But you'll be checking that with your calibrated test equipment, won't you?

 

[Lectrician]

You should not need a supplementary earth conductor unless your EFLI is too high. But you'll be checking that with your calibrated test equipment, won't you?

Actually, I would hope they would verify it with their test kit, and initially ensure it wont be too high by correctly calculating the cable size

 

[Taylortwocities]

He's already decided its 1.5mm from start to finish.

I don't remember being told how long the run is from the consumer unit or what the supply characteristics are.

So lets just use 1.5mm and throw it behind the bushes and through the flower beds - that's going to be alright then.

 

[EdtheDuck]

The T+E length will be approx 14 meters (approx 1.61V drop) and the SWA approx 20M (Approx 1.41V drop) - recommended cable size = 1.5mm, correct me if im wrong?

The SWA will be run from an adaptable on the outside wall and buried >400mm under concrete slabbing into the flower bed where it will either be distributed above ground clearly marked or buried >750mm deep, probably the first option as the lawn was laid on builders rubble