Former electrician Chris Hudson, now owner of Hudson Lighting, shares his top tips for ensuring longevity in garden lighting installations.
If you can, use extra low voltage (ELV) over low voltage (LV) every time. Very few reading this will have worked with anything higher voltage and, for most, that’s probably the first time you’ve realised the definition of low voltage was being used incorrectly. However, many manufacturers are still labelling their products with the wrong information, so looking at the voltage used is the best way to determine this.
ELV (<50V AC or <120V DC) installations are far safer, simpler and can be less troublesome – providing you use quality components. You can use flexible cables, HI-Tuffs of similar length for their installation rather than armoured, and you don’t need to bury the cables approximately 600mm, as you do with LV (50V to 1000V AC, 120V to 1500V DC) installations. You can chop through the cable with a shovel without incident; the worst thing that can happen is the lights may stop working and you may need to replace a transformer or driver. Believe me: a shovel can go through armoured too, just to be clear for anyone thinking it offers enough protection.
Armoured is used in LV installs to ensure the fault current goes down the Earth to disconnect the circuit quickly – although, in most armoured installs I’ve seen, the armour is not connected properly so this is now pointless. ELV installations also mean reliability will be better as the lighting can tolerate water in light fittings without causing the safety device to trip.
Whereas, with LV installations, the amount of water in any part of the installation can cause tripping issues – and we all know that few have the luxury of having a dedicated circuit for outdoor lighting. Instead, 90% of the time, we have the lighting installation feed from some part of the kitchen.
Your customer will be really upset if they don’t have a working kitchen because of your outdoor lighting installation causing tripping issues. The best method is to place all of your LED drivers or transformers in an accessible location, ideally inside the property or on the outside wall. Then, run all of the cables needed for the outdoor lighting from this point.
I would personally add more cables, or cables with spare cores, so that if extra lights are needed they can be added, since transformers and LED drivers have limits to the number of lights they can power.
Ducting, ducting and more ducting
Running cables around an outdoor space has its challenges. Normally, the installation is carried out in a newly-installed garden. If a cable becomes damaged three years later when the garden has matured, replacing that cable is going to be a challenge without ducting. Anyone who has installed lighting outdoors for a few years will have no doubt come across a fox, squirrel or rat having a good chew on some of the cables – ducting can be a real lifesaver and preventer too.
If you can install a larger 50-63mm duct between joint boxes, it will make pulling cables through easier. Ground-type permitting, burying the duct 600mm will save it from being damaged later on. For those pesky foxes, use a 10 or 20mm flexible conduit for the small, pre-installed flexes on the lights, e.g. spike lights – these always seem to be a fox favourite for some reason.
Cable entry on boxes – strain relief
Cables half pulling out of joint boxes can be a problem. From an electrical standpoint, if the installation is LV and there are exposed single insulated cores outside of the box, then we have a potentially dangerous installation. It also means water can get in and corrode the connections or cause tripping. Generally, this is only really an issue for lights than can be moved, e.g. spike lights.
It’s inevitable either the client will one day reposition a fitting or someone doing maintenance will move it out of their way. Stuffing glands and strain relief clamps provide the best means to ensure the cable doesn’t pull out easily. Checking they are fully tight is important though, too often are these glands installed but left loose.
If you are using Wiska boxes with the soft membrane, then a cable tie on the inside of the box around each cable can be enough to stop it from being pulled out.
Connection boxes and their mounting
Often, being able to access and maintain a connection box is vital in an outdoor installation. Burial of connection boxes should be avoided where possible.
It can be a nightmare to fault find, so consider that the person coming back to carry out repairs may be several years in the future, and buried boxes can be impossible to find in a mature garden.
The best practice is to mount all boxes to a fixed position, be that to a wall, fence or appropriate stake/post.
The electrical supply
In 90% of cases, the outdoor lighting is a complete afterthought to the building. Therefore, it’s often taken from an existing circuit, commonly via the kitchen sockets through a fused spur.
Ideally, the supply to the garden lighting installation should be an independent circuit with an independent RCD/RCBO so that, if tripping issues do occur, they don’t affect the rest of the installation.
Selection of lighting fittings
LV light fittings work well for surface or inset wall lights, where the water can drain away fairly easily. In the case of ground or spike lights, it’s my opinion that only ELV should be used.
Inevitably, most light fittings will have some water ingress at some point. With LV, this will not only cause the light fitting to fail, but also the circuit to trip. If ELV fittings are used then this issue will be mitigated as the supply is separated by a transformer/driver.
Something commonly missed is the fact that electrical work within a garden (low voltage) is notifiable under Part P to building control for additions, alterations and new installations. The work will also require an electrical installation certificate, if a new circuit has been run, or a minor electrical installation certificate, if it’s an alteration to an existing circuit.
If the installation is completely extra low voltage, then this may not be required.
For more information on Hudson Lighting, visit: www.hudsonlighting.co.uk.