LED Strip Lights and LED Drivers: An Electrician's Installation Guide

Why LED Strip Lights Need an Electrician's Approach

LED strip lights have moved firmly into commercial and domestic specification projects — under-cabinet kitchen lighting, cove and cornice details, staircase accent lighting, retail display lighting, and bathroom mirror surrounds. But the apparent simplicity of a 12V or 24V low-voltage system masks a series of design decisions that, if wrong, produce flickering, premature failure, uneven brightness, or — in the worst case — a fire risk from overloaded wiring or an undersized driver.

This guide covers the full system: strip selection, driver sizing, wiring, IP rating for wet locations, and the BS 7671 requirements that apply to low-voltage lighting circuits.

LED Strip Light Types

By LED chip type

• SMD 2835: Slim, efficient. Used in high-density (120 LEDs/m) strips for general illumination. Good lumen output per watt. Standard choice for under-cabinet and cove lighting.
• SMD 5050: Larger chip, historically used for RGB colour-changing strips. Still common in RGB and RGBW colour-change applications. Slightly less efficient than 2835 for white light.
• SMD 3528: Older, lower-power chip. Still available but largely superseded by 2835 for new installs.
• COB (Chip on Board): Multiple LED chips mounted directly on a circuit board strip, no visible individual dots. Produces a continuous linear light source — no hotspots. Ideal for high-end architectural details, mirror surrounds, and anywhere a seamless line of light is needed.

By colour

• Single colour (white): Available in warm white (2700–3000K), natural white (4000K), cool white (5000–6500K), and daylight (6500K+). For domestic and hospitality use, 2700–3000K; for retail, offices, and kitchens, 4000K.
• Colour temperature tuneable (CCT): Two-channel strips with warm and cool white LEDs. A CCT driver or smart controller adjusts the mix to achieve any colour temperature in range. Used where mood lighting control is required.
• RGB: Red, Green, Blue channels. An RGB controller mixes colours. Output looks saturated; white produced by RGB mixing is not true white (lacks green/yellow wavelengths for accurate colour rendering). CRI ~65–70 in RGB white mode.
• RGBW / RGBWW: Adds a dedicated white (or warm white) LED chip alongside the RGB. Overcomes the poor white quality of RGB-only strips. Better colour rendering for mixed colour/white applications.

Key specification parameters

LED Drivers: Constant Voltage vs. Constant Current

The driver is the most important — and most frequently underspecified — component in an LED strip system.

Constant voltage (CV) drivers

Output a fixed voltage: 12V DC or 24V DC. The most common type for strip light applications. The LED strip itself has current-limiting resistors built in — the strip draws whatever current it needs at the set voltage. Simple to use: connect the driver output to the strip, respect the polarity, done.

When to use: Standard monochrome and RGB LED strips that specify a constant voltage input.

Constant current (CC) drivers

Output a fixed current (e.g., 350mA, 700mA, 1050mA) at a variable voltage. Used with LED modules and downlights that require precise current control for consistent brightness and long life. Not typically used with standard LED strips (which have their own resistors) but used with some high-power COB strip systems and LED modules.

Dimmable drivers

Enable dimming of the LED strip output. Three main dimming methods:

• Trailing edge / TRIAC: Compatible with standard trailing-edge wall dimmers. The driver accepts mains-level dim signal. This is what most residential LED dimming uses.
• 0–10V: Low-voltage analogue signal from a compatible controller. Common in commercial and hospitality fit-outs for smooth, precise dimming.
• DALI (Digital Addressable Lighting Interface): Digital bus protocol. Each driver or driver channel has a unique address and can be controlled individually. Used in commercial and office installs for scene setting and building management system integration.
• PWM (Pulse Width Modulation): The driver receives a PWM signal (e.g., from a smart controller or DMX system) and varies brightness by rapidly switching the LED output on and off. Compatible with most RGB/RGBW controllers.

Driver Sizing

Critical rule: never load a driver to 100% of its rated wattage. Load to a maximum of 80% to prevent overheating, tripping, and premature failure.

Sizing calculation

1. Determine strip wattage per metre (W/m) from the datasheet.
2. Multiply by total strip length in metres → Total load in watts.
3. Divide by 0.8 → Minimum driver wattage required.

Example: 5 m of 14.4 W/m strip = 72W load. ÷ 0.8 = 90W minimum driver. Select a 100W driver.

Multiple runs from one driver

One driver can feed multiple strip runs provided the total load doesn't exceed 80% of driver rating. Star topology (one driver, multiple parallel strip runs from the output) is preferred over daisy-chaining end-to-end (which compounds voltage drop). Use a driver with screw-terminal output block rated for the total current.

Voltage Drop: The Critical 24V vs 12V Choice

LED strips are resistive loads distributed along their length. As current flows along the strip, voltage drops from the feed end to the far end. The result: LEDs at the far end are dimmer than those at the feed end — visible as a brightness gradient, most obvious with higher W/m strips and longer runs.

Maximum run lengths before visible voltage drop

Solutions for longer runs:

• Feed from both ends (halves the effective run length)
• Use 24V strip instead of 12V (for the same W/m, 24V draws half the current → quarter of the voltage drop)
• Use larger cross-section DC feed cable between driver and strip (at 24V, 1.5mm² covers most runs; at 12V, consider 2.5mm² for runs over 3m)
• Insert a mid-run injection point (additional feed from the driver partway along the strip)

IP Ratings for Wet Locations

LED strip lights in bathrooms, shower rooms, and external locations must carry an appropriate IP rating. Refer to our IP ratings guide for the full zone map.

Important: In Zone 0, only SELV (Separated Extra Low Voltage) is permitted. 12V DC from an isolating transformer qualifies. 24V DC also qualifies under BS 7671 SELV provisions (≤30V DC). The driver must be located outside the zone and meet double-insulation requirements.

BS 7671 Requirements

LED strip installations form part of a fixed electrical installation and must comply with BS 7671:2018 (Amendment 2, 2022):

• Driver location: Drivers must be located outside zones 0, 1, and 2 of bathrooms. A driver in an airing cupboard or above the bathroom ceiling void is acceptable if the enclosure is appropriate for the environment.
• Circuit protection: The mains supply to the driver must be protected by a suitable MCB (typically 6A or 10A B-curve) and RCD protection (RCD or RCBO at the consumer unit). The 18th Edition (and Amendment 2) requires RCD protection on all circuits in domestic premises.
• Isolating transformer vs. switched mode power supply (SMPS): Most LED drivers are SMPS — they provide separated ELV output. Verify the driver is rated as a SAFETY ISOLATING TRANSFORMER equivalent (PELV or SELV output), particularly for Zone 0/1 applications. Cheap unbranded drivers may not provide true isolation.
• Cable sizing: Mains-side cable to the driver: follow normal cable sizing rules (CIBSE/IET) for the circuit length and load. DC output side: size for the DC current at the operating voltage. At 12V and 100W load, current is 8.3A — requires 1.5mm² minimum, 2.5mm² for longer DC runs.
• Earthing of driver enclosure: Metal driver enclosures must be earthed. Most plastic-cased domestic LED drivers don't require earthing of the enclosure but should be double-insulated (Class II).
• Part P notification: Installing a new circuit (e.g., a dedicated lighting circuit for an LED strip installation) in a domestic dwelling requires notification to Building Control (Part P) unless the installer is a registered competent person (NAPIT, NICEIC, etc.).

Smart LED Control Systems

Smart LED strip systems (Philips Hue Gradient, LIFX Lightstrip, Casambi, DALI) are increasingly specified in new build and refurbishment projects. Key integration points for electricians:

• Smart-ready drivers still require a dedicated mains circuit and correct protection — the intelligence is in the controller, not the supply wiring.
• Wireless systems (Zigbee, Z-Wave, Wi-Fi) need adequate wireless coverage. In concrete or steel-framed structures, confirm signal strength before specifying wireless control.
• For commercial fit-outs, DALI-2 certified drivers and controllers provide the most reliable scene control and emergency lighting integration.
• DALI emergency circuits require a separate emergency DALI bus — do not mix emergency and standard DALI addressing without careful design.

Installation Checklist

1. Calculate total strip load (W) and select a driver at ≥125% of that load (i.e., load no more than 80% of driver rating)
2. Choose 24V strip for any single run over 3m; 12V acceptable for shorter decorative runs
3. Confirm IP rating matches the installation zone
4. Position driver outside any wet zone; ensure adequate ventilation around the driver (don't enclose in a sealed box)
5. Size DC output cable for the current at operating voltage
6. Use proper screw-terminal or soldered connections — never rely on strip push-pin connectors for permanent installations (use soldered joints or quality screw-terminal strip connectors)
7. Secure strip with adhesive backing + mechanical clips at ≤300mm intervals; adhesive alone fails over time with heat cycling
8. Fit aluminium channel/extrusion for runs on plasterboard or timber (dissipates heat; protects strip; improves appearance)
9. Test under load before closing in walls or ceilings
10. For Part P notifiable work, notify Building Control or use a registered competent person scheme

Aluminium LED Profiles and Channels

Surface-mount and recessed aluminium extrusions serve two purposes: heat sinking (extending strip life) and aesthetics (diffuser cover produces a continuous line of light without visible LED dots). Standard profiles:

• Surface mount (U-profile): Mounts on any flat surface. Available in white, silver, and black anodised finish.
• Recessed (plaster-in): Sits flush in a routed channel cut into plasterboard or timber. Gives an architectural, flush-finished look.
• Corner (45°): For cove lighting in ceiling-wall junctions or staircase string details.
• Stair-nose: Built into the leading edge of a stair tread. Requires IP44 or higher strip.

Diffuser covers come in clear (maximum light output, visible strip underneath), frosted (even diffusion, hides LED dots), and opal (maximum diffusion). For tight spaces or mirror lighting, clear profiles with 120/m+ density strips work well; for cove and architectural lighting, frosted diffusers are standard.

Common Faults

LED Strip Lights and Drivers at APM

All products below are available for same-day collection from our West London trade counter or for UK delivery.

Integral LED IP33 5M Strip 4000K 24V 11.28W Cool White

24V constant-voltage strip, 4000K natural white, IP33, 960lm/m — ideal for under-cabinet and cove lighting.

Integral LED Strip Light 24V 12W/M 5M RGBW IP33

5m RGBW strip with dedicated white LED channel for accurate colour rendering alongside full RGB colour mixing.

Integral LED 2M Recessed Aluminium Strip Profile Frosted

Plaster-in recessed aluminium extrusion with frosted diffuser — flush finish for ceilings and joinery.

Integral LED Constant Voltage Driver 12V 30W Slim

Slim-profile 12V constant-voltage LED driver, 30W — sized for up to 2.5m of 9.6 W/m strip at 80% load.

40W Constant Voltage LED Driver 12V DC

Non-dimmable 40W CV driver at 12V DC — suitable for up to 3.3m of 9.6 W/m strip within the 80% load rule.

For trade advice and orders, contact APM Electricals at 1 Hartington Road, Southall, UB2 5AL or call 020 8574 3233.