LED strip: getting indirect lighting right

Choosing the right strip

An LED strip is chosen according to four criteria: the type of LED, the voltage, the power and the protection rating.

• 12 V or 24 V: the most common indoors, used with a driver. 24 V allows longer runs before the light fades at the end of the strip.
• Power: about 4–8 W per metre for ambient light, 10–14 W per metre for a cove or worktop lighting.
• Protection: IP20 in a dry room, IP44 to IP65 in a bathroom, an exposed kitchen area or outdoors under cover.
• Colour: 2700–3000 K for ambience, 3000–4000 K for the kitchen or a dressing room, and a CRI of 90 if possible.

Sizing the driver

A 12 V or 24 V strip connects to a power supply (driver) whose wattage is calculated as follows: strip wattage per metre × length × 1.2 (a 20% margin).

Example: 8 m of strip at 12 W/m = 96 W, or about 115 W with the margin: choose a driver of 120 W or more.

Over long runs, the voltage drops along the strip and the far end becomes dimmer or more yellow. Feed the strip from both ends, or roughly every 5 m at 12 V and roughly every 10 m at 24 V.

The aluminium profile: finish, diffusion, lifespan

An aluminium profile with an opal diffuser makes all the difference: it hides the LED dots, protects the strip from dust and draws away heat, which extends its lifespan. Profiles come in stick-on, plaster-recessed and corner versions.

With a COB strip, the line is already continuous: the profile is still useful for the finish and for heat, but a thinner diffuser is enough.

Installations that work

• Cove (light trough): the strip is hidden in a cove and lights the ceiling. Leave at least ten centimetres or so between the strip and the ceiling for a soft gradient, with no bright line.
• Under kitchen wall cabinets: towards the front of the cabinet, to light the whole worktop without glare.
• Shelves and niches: under each shelf, in an aluminium profile, with warm light.
• Headboard and TV unit: behind them, for a halo on the wall.
• Steps and skirting: under the stair nosing or at the bottom of the wall, as night-time guide lighting.

Installation, step by step

1. Switch off the power at the consumer unit before any work; connecting the driver to the 220 V mains is a job for an electrician.
2. Cut the strip only at the marks shown on it (small scissors or lines).
3. Join sections with connectors suited to the width and type of strip, or by soldering.
4. Clean and degrease the surface before sticking the strip down, preferably inside the aluminium profile.
5. Respect the polarity (+ and −) and test before closing up.
6. Avoid tight bends: use a corner connector rather than folding the strip.

A 220 V strip is connected directly to the mains: every badly insulated cut or connection is dangerous. Never cut or handle it while it is plugged in; have it installed by an electrician, on a circuit protected by a 30 mA RCD, with the manufacturer’s end caps and power cords.

• The right type: COB if the strip may be seen.
• A driver sized with a 20% margin.
• An aluminium profile and a diffuser.
• An accessible, ventilated driver.
• A suitable IP rating in damp rooms and outdoors.