First and foremost we strongly recommend all new external electrical works be installed by a qualified electrician and they must comply with the current IET Wiring Regulations BS 7671 & UK Building Regulations incorporating  PART P which applies to electrical installations located on land around dwellings such as garden lighting.  The contractor must supply you with full certification once the work is completed. 


Steel Wire Armoured (SWA)

For a mains 220v  - 240v supply you should use high quality Steel Wire Armoured (SWA) cable. WA ( steel wired armour)  cable. FIG 1 below shows.

1.5mm² copper conductor size, Nominal Overall Diameter 11.54mm 3 Core Cable with Brown, Black & Grey coloured cores as indicators High quality Class 2 plain annealed stranded copper cores to BSEN 60228:2005 (Previously BS6360) Insulated with XLPE (Cross linked polyethylene), Bedded with PVC (Polyvinyl Chloride), Armoured with SWA (Steel Wire Armoured) and Sheathed with Black PVC (Polyvinyl Chloride) Suitable for voltages up to a maximum voltage of 600/1000V Maximum current of 23A Suitable for Temperatures between -15°C and 90°C Conforms to BS5467, IEC 60502, BSEN (IEC) 60332-1-2 and BSEN 60332 Steel Wire Armoured Cable, commonly known as SWA Cable, is a hard wearing power cable which is designed for the supply of mains electricity. Suitable for use in power networks, underground, internal, external applications and for use in cable ducting. It can also be connected to an earth via a Cable Gland which will give the cable further protection. The steel wire armour sits below the cable sheath to provide protection to the conductor and insulating layers which means the cable can withstand high stress and be buried directly underground. Cable supplied as 50 meter Reels.

FIG 1  SWA Cable

Mains 220 - 240v Rubber butyl cabling

Many mains 220 -240v fittings will come supplied with a length of 3 core cable to enable your electrician to connect the cable to the SWA cable supplying your mains electricity to your light fittings.  However, not all fittings will come supplied with mains cabling and therefore we recommend you use HO7RN-F 3-core rubber cable (rubber butyl). This is the best type of mains cabling you can use when installing your mains light fittings to your mains SWA electricity supply. It will tolerate high and low temperatures and is extremely hard Waring.  DO NOT USE PVC cable to connect to your SWA supply as PVC breaks down over time especially with exposure to UV ray and is responsible for the many poor installations we hear about due to capillary action where moisture gets into the connections and leads to the fittings breaking down and short circuits blowing the LED chips and often tripping the RCD unit. Mains cabling is more temperamental than 12v due to 220v - 240v going directly to your fittings, therefore is less tolerant of any water ingress issues.  So for peace of mind stick with rubber not PVC and ensure all connections are totally watertight.  The cable should be buried to a safe depth to avoid any unnecessary risk due to garden forks or spades. The thickness of the cable helps with the voltage distribution over distances.  FIG 2 below shows an example of 3 core HO7RN-F rubber cable.

FIG 2 Rubber butyl 3 core cable - HO7RN-F cable        

 12v rubber double insulated cable                                                               

If a 12v low voltage system is being installed then flexible rubber round double insulated cable should be used. DO NOT USE PVC cable Again using HO7RN-F but as 2-core rubber cable would be the best low voltage cable we would recommend for your 12v installation.  The thickness of the cable helps with the voltage distribution over distances and unlike 220v - 240v the low voltage 12v cabling is better using thickness of 1.75mm² or more for long runs over 15 metres.  We can supply 12v cabling too. FIG 3 below shows an example of 2 core HO7RN-F rubber cable.

FIG 3 Rubber double insulated 2 core cable - HO7RN-F 2 cable    

 Cable Ducting Electric (PE) pipe

We get asked a lot about how to protect 12v 2 core cable in the ground. Unlike SWA cable 12v 2 core cable is not steel wire armoured and therefore rodents can chew into 2 core cable in the ground.  An easy solution would be to protect the 2 core cabling inside Electrical cable ducting conduit tubing. This is a cheap and simple way to protect the cabling and against being accidentally cut with garden equipment or garden forks. FIG 5 below shows an example of conduit pipe and FIG 4 of Electrical cable ducting pipe you can obtain online for many building and hardware suppliers.  Electrical Cable Ducting is available in 32mm bore, 38mm bore and 48mm bore, in both 50m and 100m coils.  PLEASE MAKE SURE YOU MARK THE CABLING SO EVERYONE KNOWS YOU HAVE ELECTRICAL CABLE INSIDE.  Do not use water pipe as it could be assumed that water or gas pipes are inside and could then cause electric shocks if cut through. 


 FIG 4 Electrical cable ducting pipe                                                                                                                                                                                                                             

FiG 5 Conduit Pipe


RCD Consumer unit

Always put your outdoor lighting on it's own consumer unit RCD.  Basically ring fence it from your home lighting. That way should anything outdoors trip your outdoor lighting circuit it should not affect the power in your home. The example below is a 30Ma 2 pole which will provide protection against earth fault currents in residential and light commercial applications. FIG 5 below shows an example of an RCD. 

FIG 5 RCD Consumer unit        

RCBO Consumer unit 

Where alarms and CCTV installations are concerned it is more efficient to have a dedicated RCBO protecting each individual circuit, especially where mains voltage exterior lighting is concerned.  The example below is a 32 amp 30mA RCBO Single module 30mA sensitivity combined MCB/RCD. New compact size RCBO allowing for maximum usage of cable space within the Consumer Unit and easy installation. FIG 6 below shows an example of an RCBO.

FIG 6 RCBO Consumer unit        

Cable Joints

Equally as important and probably the weakest link in any exterior cable run is the joining of cables. Each joint will need to be 100% water tight and this can be achieved by the use of Magic Gel poured into exterior weather-tight junction boxes once the termination is complete or you could use heat shrink kits. See FIG 7 and FIG 8 below. Burial resin mixes are also available to use in weatherproof junction boxes and this product sets to a very hard resin and not ideal if you need to get to a joint later on, but ideal as a permanent water tight fix.Where possible try and keep all low voltage transformers and joint boxes above ground, this will reduce the risk of water ingress. 


FIG 7  Magic Gel  

FIG 8 Heat shrink

Mains 220- 240v or Low Voltage 12v installations

Another thing in determining the type of light fitting you can use is the type of installation you are going to have in the garden i.e mains 240v or 12v. There are pro's and cons to both system which we will explain below.

Mains Voltage

Mains voltage systems are in some ways easy to use as most electricians are already familiar with using 220v - 240v and probably less so with a 12v lighting system. The obvious advantage to a mains supply is there is no need for a transformer to step the load from 220v - 240v down to 12v. There is also next to no restriction on the lamp wattage that you can use in a mains 220v- 240v supply.  You also have a much wider choice of lamp source including metal halide lamps.

    However one of the main disadvantages is that nearly all the 220 - 240v volt cables in the garden must be SWA ( steel wired armoured ) or have some other suitable protection against accidental damage like buried conduit. Only the last 2 metres to the light can be a rubber flexible cable. This generally means that more junction boxes are required.

    Another big disadvantage is that 220- 240 volt lamps blowing will often trip out a circuit breaker, whereas this rarely happens with 12 volt lamps as the current surge is absorbed by the transformer.

    Installing mains 240v light fittings

    We recommend no more than twelve mains 220 - 240v lights are put on any one circuit to reduce the risk of overloading and tripping the mains supply.  As with all external lighting installations it is important that all cable joints are made 100% watertight inside a jointing box. This can be further improved on by using a heat shrink cable joint kit and also a resin mix poured into the box which then sets hard and stops the penetration of water. Many of the newer mains 220- 240v ground buried lights now only come with one cable entry gland and this is to reduce the risk of water ingress into the light fitting.  This also means that a recessed IP rated junction box will be required to make the terminations when linking luminaries together. When using a mains 220- 240v light fitting it is essential that the cable is kept well away from areas that may have the potential of being damaged by gardening work etc. Each burial should be on a sand bed and marked with tape where possible. Every mains buried light fitting should have adequate drainage especially in clay based soil , otherwise the fitting will constantly be sitting in water and will eventually lead to potential failure.

    Installing 12v low voltage fittings

    The low voltage system is much safer to use in a garden environment and has a more flexible cable system. Should you accidental hit a 12v cable with a spade or fork the worst that will happen is the lighting system will trip out. A little bit of dampness might not affect a 12 volt circuit but it could render a 220- 240v circuit unusable. Although the low voltage MR16 lamps tend to be less brighter than an equivalent mains GU10 lamp there are a few more selections with beam angles. The other type of LED system is the dedicated LED light fittings which has to run off a transformer and be wired in a very specific manner such as in series.

    One disadvantage is that you have to decide on what total wattage lamps you need before choosing the correct transformer as you shouldn't under load or over load a transformer as this will stop it operating at it's maximum potential. Voltage drop is less of an issue with LED lighting and on a 12v system a transformer can be placed up to 30 metres away from the light fittings which gives the installer greater flexibility. See FIG 9 below on how to load a 12v transformer.

    24v installations

    Low voltage installations can include the use of 24v LED strip which run off of 24v DC LED drivers (transformers). LED strip is a very popular form of illumination for outdoor use and ideal for creating a wall wash of light on garden walls and decking areas.  It is super slim and gives an amazing linear (continuous) light. Most of the LED strip we supply runs off of 24v drivers and these are better for long runs of 10m and reduces the voltage drop.

    Plug and Play systems

    Many low voltage fittings now come with Plug and Play cabling, 3 way/5 way connector/splitters, extension cables and transformers.  What this means is they have a 2 pin male connection to connect to a female 3 way or 5 way connector/splitter or transformer which will come with a mains 240v plug. The 240v AC mains input then converts to 12v AC output via the transformer.   Many customers like this type of low voltage system as it cuts down on electricians costs and waterproof junction boxes and waterproof connections.  The plug and play systems are all compatible with each other with a very high IP rating.

    Series or Parallel Wiring

    There are two ways that lighting in installed, in series which is daisy chaining the fittings from one to the next and so on or in Parallel where you loop in and back from each fitting.  It is important to understand that wiring the wrong way round could blow all of the lights with 12v systems, so care must be taken and all instructions should be followed to the letter.

    1. In series

    This must be done when using 12v constant current transformers and example being 350mA, 500mA and 700mA.  The higher the number the brighter the light output and more wattage is used from the LED chip.  These are used with sealed unit LED fittings You cannot wire these in parallel. if you do you can blow up the transformer. 

    2. In parallel

    12v Constant Voltage fittings will need to be wired in parallel and use DC current LED drivers.  Likewise 12v toroidal transformers which use an ac current. Another thing to understand is that if you did daisy chain Constant Voltage DC fittings and toroidal 12v ac fittings and one of the fittings in the chain fails then the whole lot will go out and it is a process of identifying which one in group has failed.  Much like Christmas tree lights. Also with series wiring the more lamps you add to the circuit the less current will flow. Whereas in Parallel the more lamps you add the more power will flow. 

    Types of transformers and loadings

    There are currently 4 types of transformers used for outdoor lighting. In all cases you should use IP rated transformers for outdoor use, if not then they must be put into a waterproof enclosure. 

    1. Toroidal - Magnetic wire wound transformer. 
    2. DC Constant Voltage LED transformer.
    3. DC Constant Current LED transformers
    4. Electronic Transformers

    Toroidal Transformer

    They use Alternating Current (AC), have cooler operating temperatures and low magnetising current. They are very efficient, lower operating temperature and lower noise. Historically they have been used to power Halogen low voltage fittings but they will work ok with certain LED bulbs providing you load the transformer to approximately 80% capacity. Always check the type of voltage the fitting uses and the lamps recommended before you choose a transformer. 

    DC Constant Voltage LED transformers.
    These transformers use single direct current (DC) and can be supplied as 12v  or 24v and used primarily for LED strip and fittings with built in LED chips. A constant voltage power supply receives standard line voltage (120-277VAC). This is the type of power that is typically output from your wall outlets around the home. Constant Voltage Drivers switch this alternating current voltage (VAC) to a low direct current voltage (VDC). The driver will always maintain a constant voltage no matter what kind of current load is put on it. DC transformers are more tolerant with lighter loading but again we recommend should be loaded to around 80% to 85% loading. Again always check the voltage of the fitting and lamps recommended before you choose a transformer.

    DC Constant Voltage LED transformers.
    These transformers are designed for designated range of output voltages and a fixed output current (mA). LED's that are rated to operate on a constant current driver require a designated supply of current usually specified in Milliamps (mA) or amps (A). These drivers vary the voltage along an electronic circuit which allows current to remain constant throughout the LED system. They will run at low wattage levels but ideally suited to running up to 80% of their capacity.   Higher current ratings do make the LED brighter, but if not regulated, the LED will draw more current than it is rated for. All fittings using Constant current LED drivers will stipulate their wattage capacity, i.e. 350mA, 500mA or 700mA.  Always check the voltage of the fitting and wattage for the LED chip before choosing a transformer. 

    Electronic Transformers
    These transformers are ok for indoor lighting, but we strongly recommend you do not use electronic transformers for LED Lighting outdoors.  They do not react well outdoors with the change in temperatures and damp conditions and will lead to premature lamp failure.



       Transformer loading

      A transformer will be required when installing low voltage light fittings. To work out the size of the transformer required to run the light fittings you take the lamp wattage and times it by the amount being used. For example you have 4 x 5w  LED ground spikes and 5 x 3.5w LED buried lights,  4 x 5 = 20  and 5 x 35 = 17.5  now add the 17.5 to the 20 and you have a total of 37.5 watts  so the transformer required would be a 40va. You should always allow about 10% extra on the transformer for start up current.  Using low voltage cable is both cheaper and much safer in the garden than a mains 220- 240v supply. Try not to put any more than 10 lights on any one run of cable to avoid voltage drop and possible loading issues. Every cable joint should be made 100% watertight by using a heat shrink kit, IP rated junction boxes and also a resin sealing compound. Please also ensure that all ground mounted light fittings have adequate drainage channels beneath them especially in clay based soil beds.  

      LED lighting

      Incandescent, Compact Fluorescent and Halogen light sources are gradually being superseded for an LED equivalent. LED technology has moved on over the last 5 years and the quality and light colour index of them are improving tremendously.  

      LED's (Light Emitting Diodes) are cool to touch and use only a fraction of the wattage therefore making them more economical and friendlier to the planet.  They give out good lumen output and the colour temperatures range from 2700k (kelvin) which is a very warm white to 6500k which is a very cool blue white colour temperature.  Most homes are between 2700k to 3000k which is soft and cosy.  This is also ideal for border and pathway lighting. The cooler spectrum is usually only required for security lighting and where a crisper whiter light is preferred. Also you can have colour either singularly with shades such as red, blue and green or you can buy RGB LED which are used for LED strip and create a change colour effect.

      LED's are semiconductors. As electrons pass through this type of semiconductor, it turns into light. Compared to incandescent and compact fluorescent lamps, LED lamps are more efficient at turning energy into light, therefore less of the energy radiates from the lamp as heat.  In fact they run very cool to touch. The average life cycle of an LED lamp is between 20,000 to 30,000 dependent upon the quality of the lamp and the components that make up the LED. 

      More an more applications are turning to LED technology.  They can be dimmed and they can be put onto lighting control systems. 

      They work well for LED strip lighting systems and can be managed by controllers, and can range from RGB, RGBW or CCT.  RGB give you the colour spectrum from red to green to blue.  Add W and you get Red, to green to blue and then white.  CCT is correlated colour temperature in LED terms and defines the colour appearance of a white LED where warm light at 2700k moves to a neutral white at around 4000k to cool white 5000k or more. 

      Using Metal Halide

      Metal Halide fittings were the fitting of choice for retail outlets on track lighting systems, up lighting facades and tall buildings as well as tall trees. The lamps were either a warm white, cool white or you could have coloured Metal Halide lamps in red, blue, yellow and green.  The wattage's ranged from 35w, 70w, 150w, 250w, 400w to 1000w.  Naturally the higher the wattage the more powerful levels of illumination you could have.  The downside is they got very very hot to touch and they used igniters and control gear to operate them which meant if you switched the lamp off you really needed to give it a minute to light up again if you switched it off and then back on quickly. Lamps typically lasted 6000 hours. The colour index of them were very high and they always gave a pure colour with no lamp colour or power degradation until the lamp failed.  They cannot work on a PIR but they can be linked to an external Photocell (dusk to dawn sensor).

      They are still used for very tall lit applications over 15 metres and LED technology is getting better but to provide the same high levels of lumen putput of say 150w metal halide lamp you would be paying a lot more for the lumen output.  But as LED's are moving quickly with better technology so will the efficiency of their lumen output.


      Dimmable LED bulbs are available and likewise a number of constant current type fittings using milliamp (mA) drivers and also LED strip can be dimmable too.  In all cases you must consult with us to establish which fittings will provide you with this capability and you will have to have a trailing edge dimming system in your home to currently operate them.  LED strip however can come supplied with dimmable controllers.

      In most applications we do not feel it necessary to dim exterior lighting. In doors is different due to different light sources the light is competing with for example recessed down lights, lounge table lamps or kitchen LED strip lights. In these cases it is understandable to want to dim lights especially for the bedroom and lounge.  But outdoors can be done more subtle using lower wattage and lower lumen output lamps.  Having the lamps placed where they will give the most benefit, for example pathways, floor beds, trees and wall lighting.  Your eye will automatically adjust to darkness and where there is light it will automatically focus on the area of light and space around it until the light disappears.  There is nothing worse than a flood light put on the back of a house just throwing light everywhere and causing glare at the same time.  Often illuminating objects you'd probably rather not look at, like the garden shed.  We give ideas in the Garden Ideas section to assist with the type of lighting and effects it will give. 

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