Garden wiring - how should it be done?

I'm having a patio built, which includes a water feature and some lights. Both the water feature pump and the lights are 240V. The builder has wired these using black 3-core flex, run to the house in plastic ducting. This ducting runs under a flowerbed, then about 10cm below ground level immediately next to a wall, then under a bit of patio just beneath the flags and the sand they sit on. The cable emerges from the duct by the wall of the house, and I believe it is the builder's intention to run it up the wall outside the house, then drill through the wall and connect it to the back of a plug socket inside. I don't know whether he intends to use an FCU or not.

Is this all generally OK? From reading on here I was half expecting to need an armoured cable, buried x deep, with warning tape above etc. etc., but maybe that is just for supplies to garages/sheds?

In ducting as long as there is some tape or tiles above it to show there is an electric cable it is unlikely to cause a big problem. However as to connecting you really need some protection, and you don't want to lose all sorts in the house specially the freezer because water has got into the garden lights, so 10 mA RCD plugged into the house general 30 mA RCD or direct back to consumer unit and a RCBO. Behind the socket you could draw 32 amp before the overload trips, so does need to be a FCU or a RCD FCU or even a simple plug going into the socket.

Technically if a fuse is used then it is a new circuit, I would not be too worried about the completion or compliance certificate unless you live in Wales, which you don't it seems, but would want either an installation certificate or minor works certificate, not so much because them must issue them, but by issuing them they are saying in writing that they have followed the regulations.

There is no indication in the garden that the cable duct is there. Clearly I know it is there so it isn't ever going to be a hazard to me - but it could be to a future owner.

I think it will inevitably be spurred off the existing ring main. Which is the kitchen ring main and does have the freezer plugged in to it. The consumer unit currently has a 100mA RCD. The socket it will spur off is redundant i.e. doesn't ever get used, so it could be replaced by an FCU RCD - they only seem to come in 30mA rather than 10mA, and would there then be a possible discrimination issue between the RCDs?

When you say "black three core flex" is it just flex or high tough whiich offers a small amount of mechanical preotection? Think it would be better deeper either way and as Eric suggests some electrical warning tape at the very least. Ideal scenario is this supplied in SWA and since this doesn't sound like a long length odd to not do it in the most suitable cable.

chivers67 said:

Ideal scenario is this supplied in SWA and since this doesn't sound like a long length odd to not do it in the most suitable cable.

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It's been done by a builder, remember...