Cabling of LED luminaires in different control systems
LED luminaire cabling is one of the most important aspects of a lighting system. Correctly selected and installed cables ensure that the lights operate smoothly, the controls work as they should and the lighting remains safe.
We'll look at the types of cabling needed for LED lighting in different systems - DALI, Zigbee, TRIAC and other control modes - and how luminaire characteristics and transformer types affect wiring. At the end, you'll also get practical tips for safe and efficient installation.
Home automation and control systems
DALI (Digital Addressable Lighting Interface) is a professional, two-way lighting control system. It uses its own control bus, which can be carried on the same cable as the supply voltage - as long as the cabling is done according to the DALI standard.
Typically, DALI control uses 5x1.5 mm² cable or equivalent.
The length of the control line can be up to 300 m, as long as the total resistance is kept below 2 ohms.
A DALI line can connect several luminaires and controllers on the same bus.
A centralised DALI group transformer facilitates installations in large sites. Remember that one DALI master can typically handle 64 devices. Save addresses by using group transformers.
Zigbee and other wireless systems
Zigbee, WiFi and Bluetooth Mesh allow wireless control, but cabling is still required for power supply. Control signals go wirelessly, but the LED lights still need a DC cable from the transformer. So you don't need cables for the switches!
Avoid long (+15m) cable runs to keep voltage drop from the transformer low
Use shielded cable if the cables run alongside other electrical wiring.
We recommend group transformers (usually 24V), for ease of control.
TRIAC dimmer(230V)
Triac dimming is a traditional and simple way to control LED luminaires directly from the 230V mains. The wiring is usually similar to that of conventional halogen lamps.
Typically 3-conductor cable (L, N, Earth) is used, although almost all good quality transformers are Class 2 (double insulated) and do not need earth.
A dimmable LED requires a Triac-compatible transformer.
Typically a MMJ wire is used, e.g. 3x1.5 mm².
Triac dimming cabling - 2-wire connection for dimmable LED.
Luminaire characteristics and number of cables
The technical characteristics of the luminaire determine the number of wires required in the cable. This is particularly important when luminaires are controlled by different shades or colours.
So now we are talking about the cable between the transformer and the luminaire(s).
Single-colour LED (on/off or dimming)
Single-colour LED lamps use a 2-wire cable: positive (+) and negative (-). So install as shown in the TRIAC picture above
Connection: + red (usually), - black (usually)
Use 2x0.5 mm² cable for short (max 15m) runs, for longer runs use 2x0.75 mm² or thicker.
CCT luminaires (adjustable colour temperature)
CCT (Correlated Color Temperature) luminaires have warm and cold white LED elements that are controlled separately. This requires a 2-3 conductor cable.
2 Conduction CCT works by the positive and negative changing polarisation at 1000krt per second, so it is not visible to the eye. This is how we change the temperature and brightness.
Switching: - CW (cold white), + WW (warm white).
Use 2x0,5 mm² cable for short (max 15m) runs, for longer runs 2x0,75 mm² or thicker.
HERE IMAGE: caption "2-conductor CCT cabling"
3 Conduction (most common) CCT luminaire works with the positive (+) being split, but the voltage between the cold and hot conductor is varied so that the total voltage remains the same. Halfway through, therefore, the voltage must not double (full power to cold and hot simultaneously), which would break the luminaire.
Switching: + (common), CW (cold white), WW (warm white).
Use 3x0.5 mm² cable for short (max 15m) runs, 3x0.75 mm² for longer runs.
HERE IMAGE: caption "3-conductor CCT cabling - colour temperature control warm-cold."
RGB and RGBW luminaires
In RGB luminaires, each colour (red, green, blue) needs its own conductor and a common positive. RGBW adds a fourth channel for the white LED.
Connection: + (common), RGB = 4 wires, (R, G, B, +)
Connection: + (common) RGBW = 5 wires (R, G, B, W, +)
Use 4/5x0,0,32 mm² cable for short (max 10m) runs, 4/5x0,5 mm² for longer runs.
HERE IMAGE: caption "5-conductor RGBW cabling."
RGB+CCT systems
RGB+CCT combines colour and adjustable white in the same luminaire. This means 6-conductor cabling.
Connection RGB, warm and cold = 6 wires (R, G, B, warm, cold, +)
Always use high quality, soft-shell, double insulated LED cable.
Check that the driver and the luminaire support the same wiring map.
HERE IMAGE: caption "6-conductor RGB+CCT cabling."
Cabling with dedicated transformers vs. group transformers
Luminaires with dedicated transformers
Some luminaires have a dedicated transformer for each individual. This is a quick and easy solution, for example in renovation projects where centralised controls are not desired or where a service hatch is not wanted/not possible.
Each luminaire comes with its own 230V supply.
The transformer can be hidden in the ceiling structures or behind the luminaire from the same opening
Less design, but more connections.
Triac - colour selection from the transformer
DALI / Zigbee each luminaire has its own address (tedious!)
Group transformers and centralised solutions
A system with a group transformer means that one efficient transformer feeds several luminaires. This reduces heat sources and makes maintenance easier, as well as ensuring that all luminaires operate as a group.
in 24V systems, cable thickness plays a major role: too thin a cable will cause voltage drops. e.g. 0.5 mm² max, 10/15 m
Keep the total cable length from the transformer to the luminaires below 15 m or increase the cross-section.
Install the transformer in an easily accessible place, e.g. service hatch, on top of cabinets, in an electrical cabinet.
Learn more about LED transformers
Practical tips and installation recommendations
Choose the right cross-section: less than 10m: 0.5mm² / 5-15 m: 0.75-1.5 mm² / over 15 m: 2.5 mm²+
Note the voltage: in 12V systems the voltage drop is higher than 24V!
Place controllers and transformers sensibly: easy to service, but hidden.
Use high quality connectors and tapes: resistant to time and heat.
Document the installation: mark transformers, cable runs and controllers for maintenance.
Make sure the cables are installed, check for signs and labels, and make sure the cables are secured for maintenance
Luminaire typeNumber of cablesTypical voltageControl modeOne colour212/24VOn/Off or dimmingCCT2/312/24VColour temperature controlRGB412/24VColour controlRGBW512/24VColour control + whiteRGB+CCT612/24VFull colour and temperature controlTotal number of wires for different LED luminaires according to characteristics
Summary
Proper LED lighting wiring ensures that your lighting works exactly as designed - dims smoothly, changes colors accurately, and lasts for years without problems. A well thought-out (lighting and electrical design) avoids problems during the installation phase.