How to fit an outdoor PIR security light

Helpful video reference. We use this tutorial by DNA Power Solutions, qualified electricians based in Corby, Northamptonshire. Their video "How To setup a PIR outside light (Security Light/PIR Sensor)" covers the practical wiring and then, usefully, goes through the PIR adjustment dials — lux level (dusk sensor), range, and duration. Getting those settings right after the fitting is half the job, and their walkthrough is the clearest explanation I have found for how each dial actually works in practice.

1. Plan the position and check the supply

If you are replacing an existing outside light, the supply cable is already run. If you want a security light somewhere new — above a garage door or at the end of a garden wall — a new cable run from the house is involved, and that is Part P notifiable work in most cases. See the "When to call us" section at the bottom.

Check the IP rating on the new light before you buy. Most wall-mounted security lights are at least IP44. If the fitting is under a canopy, IP44 is fine. On a very exposed wall facing the prevailing weather, IP65 is worth the small extra cost.

2. Isolate the circuit

Identify the outdoor lighting circuit on your consumer unit and switch the MCB off. If the board is an older rewireable type, pull the fuse and keep it. Go back to the light location and confirm dead with a voltage tester — touch each conductor and the metalwork of the backplate. Dead everywhere? Good. If you cannot identify which MCB feeds the outdoor light, switch off each one in turn and check with the voltage tester.

3. Remove the old fitting

Unscrew the light from the wall. Most are fixed with two screws through a plastic or metal backplate. Ease the fitting away carefully — the cable may have very little slack. Take a clear photo of the existing wiring before you disconnect anything. Note which colour goes to which terminal.

If the existing light is mounted on a junction box in the wall rather than directly on the surface, leave the junction box in place and reconnect the new light's fly leads to the same junctions. Do not disturb the joint inside the wall unless you need to.

4. Understand the new light's terminals

Most PIR security lights connect via a short length of heat-resistant flex coming out of the body of the light. Inside the body or in a separate terminal housing, you will find three terminals: L (or Line/Live), N (Neutral), and E (Earth). A small number of lights also have a separate terminal for a permanent live — check the wiring diagram in the box. The dusk-to-dawn sensor inside the PIR head needs a continuous supply to detect ambient light levels, separate from the switched supply that runs the lamp.

5. Make the connections

Using exterior-rated lever connectors or a weatherproof junction box if the connection is made outside the fitting body, connect:

• Brown conductor from the supply to L on the light
• Blue conductor to N
• Green-and-yellow conductor to E

If the existing cable is old two-core-and-earth with red and black insulation: red goes to L, black to N, bare copper to E with a length of green-and-yellow sleeving fitted over it. Tighten each connection and give each conductor a gentle pull to confirm it will not come loose.

6. Weatherproof the installation

Feed the cable carefully through the backplate entry gland. On most lights, there is a rubber grommet — make sure it compresses against the cable jacket rather than being pushed to one side. Seal any gap between the backplate and the masonry with a thin bead of exterior silicone if there is one. Mount the light securely, using appropriate fixings for the wall type (masonry plugs for brick or render, timber fixings for soffit boards).

7. Set the PIR and test

Switch the circuit back on. Most PIR lights have three adjustable dials:

• Lux (dusk sensor): controls how dark it needs to be before the PIR will respond. Turn clockwise for more darkness required, anti-clockwise for earlier triggering.
• Range (sensitivity): sets the PIR detection distance. Start at mid-range and test by walking across the detection zone.
• Time (duration): how long the light stays on after being triggered. Typically 10 seconds to 7 minutes.

To test the PIR in daylight, cover the lens with a piece of black tape — this fools the dusk sensor into thinking it is dark. Walk across the zone. Once you are happy with the sensitivity and duration, remove the tape and set the lux dial to your preferred level.

When to call us

Swapping one outside light for another on an existing circuit is a task most careful homeowners can handle safely. Anything that involves running new cable — from house to garage, along the outside of the building, or up into the roof to a soffit light — is a different job. Those cable runs need to be correctly rated, protected from mechanical damage, and routed so they will still be safe in 20 years. Richard covers outdoor lighting installations across Sandwich, Deal, Dover and the surrounding area.