Garden Lighting help

[Roberts7286]

Just after some general advice.

Been asked to look at a job where a builder/landscaper has already laid cable for some garden lighting.1.5mm 3 core SWA ran in 4 seperate radial circuits from a CU at the shed, each about 20M in length, looped in/out at each point. Customer wants spike lights in the trees (which isn't an issue) and walk-over spotlights around the pathway (this is where my issue is). Having posted on a different forum I have been advised to avoid 230v lights and use ELV. I haven't ever had to do buried lights before.

My idea is to use a swa branch resin joint to terminate the swa and cable out to each light. Then connect either straight to a 230v light or to a IP68 driver.

My main concern is water ingress so my questions are:
1) I think I will need to use a driver at each light due to voltdrop. What is the best way to bury/hide them? Which ones are best for this?
2) Why is 230v such a bad idea? Surely if a good waterproof buried connection is made it shouldn't be an issue.
3) If there wasn't already the cable there how would you usually do an install of this type? (i.e over this sort of distance etc)

Regards

Tom

 

[mattg4321]

1.5 mm2 swa. Already in situ when I arrived

 

[Roberts7286]

Oh that's interesting to know. How was the swa terminated at each point?

 

[HappyHippyDad]

Oh that's interesting to know. How was the swa terminated at each point?

I have never fitted the lights you mention, but I have come across non working garden lights many times. It has mostly been to underground joints full of muck, water and ants. I have usually managed to persuade the customer to have a neatly placed post next to the light to house a weatherproof junction box. Of course, this is no help to you unfortunately!

When I was considering underground junction box for SWA the pratley box was mentioned on this site.
Here is a link Pratley 3 Way IP68 SWA Underground Armoured Cable Junction Box Size 0 - https://qvsdirect.com/products/pratley-3-way-swa-tee-box-under-ground-ip68-c-w-glands-shrouds-box-size-0

However well you do it, you may well find that in a few years you are called back because they are either not working, or tripping the RCD. It would be a good idea to make the customer aware that problems may arise down the line. I think I would also take some pictures of exactly where I had buried the boxes and save for future use as you may be digging them up again in the future.

 

[mattg4321]

No chance of RCD tripping with ELV, one big reason why I use them.

I usually use gel filled wiska boxes or wiska shark or similar. Resin is fine, until you need to re enter.

 

[Dranok]

What ever you do none of them will be working in a couple of years.

Ooh you synic! (Regrettably I agree, the only exception in my experience has been some stupidly expensive "designer" lights in a mansion I did, costing £238 per spike...)

@Roberts7286 , the prime reason for using extra-low voltage (ELV) outside is the inherent hazard of potential cable damage and the absolute requirement for RCD protection: anything electrical in the presence of water (damp/humid atmosphere, equipment like kettles and washing machines, outdoors, etc) will slowly experience it insulation breaking down and will produce nuisance tripping as over time an increasing amount of current starts to leak the wrong direction, capacitance increases, and other issues appear. Nearly always that part of the installation remains perfectly safe, but the rare occasion of actual fault in those environments involves elevated risk of shock or of causing undesirable influences on the rest of the installation and gives us the necessity to use RCDs. You can't avoid them, and they will produce nuisance tripping over time.

Also, because of the significant elevated risk of shock if you damage a cable in a wet enviroment, it must be installed with appropriate mechanical protection 100% of the way, requiring you to feed it through conduit and into junction boxes with IP-rated connections. Even SWA may be considered inadequate to directly bury at shallow depths, because a fork stabbed straight down over the centre of the cable will simply push the wire armour out of the way on its way down, like a bodkin arrowhead passing through chainmail into your loyal squire. If you damage ELV, on the other hand, it only causes your lights to inconveniently stop working. But as you will already be aware, the volts drop associated with ELV means installing thicker cabling than you first expect. Certainly at 20m length and multiple fittings I'd want to install at least 2.5mm or even 4mm (if a single fitting is at the end of 20m, your 1.5mm is probably adequate for 12V and certainly 50V). The only way to avoid that is more expensive Constant Current drivers and some proper maths to ensure it doesn't accidentally push more volts than is deemed safe.

Edit: my browser just refeshed and reveals a whole pile more messages in this thread! I only saw 3 to begin with. So this may be a repeat of other comments. I'll go do some reading now