Lighting Circuit Wiring Diagram: Multiple Lights Using the Loop-In Method

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A lighting circuit wiring diagram for multiple lights shows how the loop-in (loop-at-the-switch or loop-at-the-ceiling) method connects several luminaires to a single circuit, with the supply looped through each ceiling rose and switched live returning to each fitting.

The loop-in wiring method is the standard approach for wiring multiple luminaires on a single lighting circuit in the UK and many other countries that follow the IEC wiring tradition. Rather than running all conductors back to a central junction box, the supply cable loops from one ceiling rose directly to the next, with only a switch cable dropping to each wall switch.

In the loop-in method, each ceiling rose has three sets of terminals: 1. Loop-in terminals (sometimes called supply terminals): incoming line, outgoing line (looped to next rose), incoming neutral, and outgoing neutral (looped to next rose). Permanent live and neutral pass through every rose in the circuit. 2. Switch terminals: switched live goes down to the wall switch and returns to this pair. Some ceiling roses label these as 'switch' or 'L out / L in'. 3. Pendant (load) terminals: the switched live and neutral connect here, providing the supply to the lamp via the pendant flex.

The result at each ceiling rose: permanent neutral from the loop connects directly to the pendant (lamp). Permanent live passes through but does not connect to the pendant. The switched live returns from the switch, connects to the switch terminal, and then bridges to the pendant live. When the switch closes, the pendant receives switched live on one side and permanent neutral on the other, illuminating the lamp.

Switch cables: in traditional UK wiring (pre-2006 colours), a 2-core + earth cable runs between the ceiling rose and the switch. Both conductors (red and black, or the older red/black) are used as live conductors in the switch cable — one carries permanent live down to the switch, one carries switched live back. The black conductor in a switch cable must be sleeved or taped brown/red at terminations to indicate it is not a neutral.

In junction box method (less common today in new work): a central junction box receives the supply, and four-terminal junction boxes connect the supply to each switch and each lamp independently. This uses more junction boxes but less cable where lights are widely spaced.

Ring circuit or radial circuit: lighting circuits in the UK are nearly always radial — the cable originates at the distribution board, loops through each fitting, and terminates. Unlike ring final circuits used for socket outlets, UK lighting circuits do not form a ring.

For North American (NEC) wiring: the equivalent multi-light circuit uses a different approach — supply enters at the first switch box or at a junction box, and cable runs from box to fitting to fitting. Each fitting receives its switched hot conductor from the switch circuit. The cable routing and box fill calculations follow NEC Articles 300 and 314.

Maximum number of luminaires: not determined by a fixed rule but by the total connected load (wattage) relative to the circuit's current rating. A typical 6 A (UK) or 15 A (North American) lighting circuit can supply many LED luminaires since modern LEDs are 5–20 W each. Total design load should not exceed 80% of the circuit's maximum current rating.

How to wire lighting circuit wiring diagram multiple lights

Plan the circuit layout and calculate total load List all planned luminaires and their wattages. Sum the total connected load. Confirm it does not exceed 80% of the circuit's rated current (e.g., 80% × 6 A × 230 V = 1,104 W for a standard UK 6 A lighting circuit). Plan the cable route from the distribution board through each ceiling rose location and down to each switch position.
Isolate the circuit at the distribution board Switch off and lock out the MCB for the lighting circuit. Apply lockout/tagout. Verify dead with a non-contact voltage tester at the distribution board and at every ceiling rose location before working.
Install first ceiling rose and connect supply cable At the first ceiling rose (closest to the distribution board), connect the supply cable: permanent live to the loop-in terminal, neutral to the neutral block (looped), and earth to the earth terminal. This rose receives the incoming supply from the MCB.
Loop supply cable to subsequent ceiling roses Run a 2-core + earth cable from the first ceiling rose loop-in terminals to the second, and from the second to the third, and so on. At each rose, connect incoming and outgoing live conductors together at the loop-in terminals, and incoming/outgoing neutrals together at the neutral block. Earth connects to the earth terminal at each rose.
Run switch cables from each ceiling rose to the corresponding wall switch At each ceiling rose, run a 2-core + earth cable to the switch position below. Both current-carrying conductors in this cable will carry live — one takes permanent live to the switch, the other returns switched live. At the rose, connect permanent live to the switch terminal (line out) and the return switched live conductor to the load side. Sleeve or tape all black conductors brown at both ends.
Wire each wall switch At each switch, connect the permanent live (arriving from the rose) to one terminal and the switch return (switched live going back up to the rose) to the other terminal. Earth connects to the switch terminal or back-box earth screw. A single-pole switch simply interrupts and connects this single live conductor.
Connect pendant flex to each ceiling rose and restore supply Connect the pendant flex to the load terminals at each ceiling rose: switched live and neutral to the lamp. Confirm the cord grip is engaged on the flex sheath. Reinstall all ceiling rose covers and switch faceplates. Remove lockout/tagout, restore the MCB, and test each switch and luminaire individually.

Specifications

Standard UK domestic lighting circuit rating	6 A MCB (Type B or C); maximum design load approximately 80% of rated current
Standard cable size — UK domestic lighting	1.5 mm² two-core + earth flat twin, PVC insulated, 300/500 V rated
Wiring method — UK domestic multiple lights	Loop-in at ceiling rose (loop-in method) — BS 7671 compliant; junction box method used where loop-in is not practicable
Switch cable conductor re-identification requirement (UK)	Black (or grey) conductors used as switched live must be sleeved brown at all terminations — BS 7671 Regulation 514.3
Applicable UK standard	BS 7671 (IET Wiring Regulations, current edition); IET On-Site Guide Chapter 6 for domestic installation guidance
USA equivalent multi-light circuit standard	NEC/NFPA 70 Article 410 (Luminaires) and Article 314 (Outlet Boxes and Junction Boxes)
Maximum safe design load as percentage of circuit rating	80% of rated current (i.e., 4.8 A for a 6 A circuit) — consistent with general design practice

Safety warnings

Lighting circuit wiring is fixed electrical installation work and must be designed and installed by a licensed electrician in compliance with the applicable standard: NEC/NFPA 70 (USA), BS 7671 (UK), AS/NZS 3000 (Australia/NZ), or IEC 60364 (international). Always determine which standard applies in your jurisdiction before commencing work.
Always isolate the circuit breaker at the distribution board and verify the circuit is dead at every ceiling rose and switch position with a calibrated voltage tester before touching any wiring. A switch in the off position does not make the permanent live conductor in the ceiling rose safe.
In a loop-in switch cable, the black (or grey) conductor that returns the switched live is NOT a neutral — it is a live conductor and must be sleeved or taped brown or red at every termination per BS 7671 (and equivalent standards). Failure to re-identify these conductors creates a life-threatening misidentification risk for future maintenance personnel.
Ensure the total connected wattage of all luminaires on the circuit does not exceed approximately 80% of the circuit's rated current capacity. Overloading a lighting circuit causes persistent MCB tripping and, in extreme cases, conductor overheating.
All connections must be made inside the ceiling rose, switch back-box, or a suitable accessory box. No exposed conductors, bare wire joints, or unsupported connections are permitted outside of these enclosures.

Tools needed

Non-contact voltage tester
Multimeter (AC voltage, continuity)
Insulated screwdrivers (flat and Phillips)
Wire strippers
Electrician's pliers
Conductor identification sleeves (brown) and sleeving pliers
Lockout/tagout device
Fish tape or cable puller (for concealed cable runs)
Stable access equipment (ladder or platform)

Common mistakes

Connecting the switch to interrupt the neutral conductor instead of the live conductor — the luminaire remains energised at both contacts even when the switch is off, creating a shock hazard during lamp changing.
Failing to sleeve or tape black switch-cable conductors as brown — future electricians or homeowners assume a black conductor is neutral and may touch it while the circuit is live.
Overloading the circuit by adding too many luminaires without recalculating the total connected load — this causes the MCB to trip or, if the MCB is incorrectly rated, causes conductor overheating.
Making conductor joints outside of ceiling roses, switch boxes, or listed junction boxes — unsupported joints can arc or disconnect and are not accessible for future maintenance.
Connecting the neutral of one ceiling rose's pendant to the switched live terminal instead of the neutral terminal — the lamp operates but one side of the neutral system is broken, causing voltage to appear on the neutral conductor downstream.
Running multiple circuits on the same switch cable route without identifying conductors clearly — this creates serious confusion during fault-finding and increases the risk of cross-connection errors.

Troubleshooting

All lights on the circuit fail at once: Cause: MCB has tripped (overload or fault), the supply cable has an open circuit at the first ceiling rose, or a neutral conductor is disconnected at the distribution board or first rose Fix: Check and reset the MCB — if it trips immediately or repeatedly, do not continue resetting; diagnose the fault. With circuit isolated, check supply voltage at the first ceiling rose. Use a multimeter to verify continuity of both supply conductors from the distribution board to the first rose.
One light does not work; all others on the circuit operate: Cause: Fault is localised to that luminaire's switched live, neutral pendant connection, or lamp holder; or the switch for that light is faulty Fix: Isolate and verify dead. Check the lamp first. Then check that the pendant flex connections at the ceiling rose are secure. Check switch operation with a multimeter — should show continuity when pressed. If the switch tests good, trace the switch cable for open-circuit conductors.
MCB trips when a specific switch is operated: Cause: Short circuit in the switch cable or at the switch — possibly a stray conductor strand bridging between live conductors, or insulation damage on the switch cable Fix: Isolate the circuit. Disconnect the switch cable from both ends (ceiling rose and switch). Use a multimeter to test insulation resistance between the two conductors and between each conductor and earth. If resistance is low (below 1 MΩ for a simple check, or test per BS 7671 requirements), the cable has insulation damage and must be replaced.
Lights flicker on multiple fittings simultaneously: Cause: Loose connection at the supply terminals in one of the ceiling roses in the loop — all downstream roses are affected by an intermittent supply at that point Fix: Isolate and verify dead. Systematically check all ceiling rose loop-in terminal connections for tightness. The rose closest to the distribution board is the most likely cause if all roses flicker together. Re-terminate any loose conductors and tighten all terminal screws to the recommended torque.
Switch works but lamp stays permanently on: Cause: The switch is wired in the neutral conductor instead of the live conductor — opening the switch disconnects the neutral but the lamp's centre contact remains live and the shell remains connected via the circuit Fix: Isolate and verify dead. At the ceiling rose, identify and confirm which switch cable conductor connects to the switch. Verify that the switched live (returning from the switch) connects to the pendant live terminal, not that the neutral is interrupted. Rewire so the switch interrupts only the live conductor.

Frequently asked questions

What is the loop-in method of wiring multiple lights?

The loop-in method passes the supply (live and neutral) cable from the distribution board through each ceiling rose in sequence, then on to the next, forming a daisy-chain. Each rose taps off the permanent live and neutral. A switch cable drops from each rose to the wall switch and returns the switched live. No separate central junction boxes are required at each fitting position.

How many lights can I put on one lighting circuit?

There is no fixed maximum count — the limit is the total connected wattage relative to the circuit's current rating. A 6 A lighting circuit (UK) can safely carry up to 1,380 W (6 A × 230 V), though design practice limits loading to approximately 80% (1,104 W). Modern LED luminaires at 8–15 W each allow many tens of fittings on one circuit, far more than with incandescent lamps.

Why must the switch cable's black conductor be sleeved brown in UK wiring?

In the loop-in method, the switch cable carries both the permanent live (going down to the switch) and the switched live (returning from the switch). In older twin + earth cable (red/black), the black conductor is used as a second live conductor — not as a neutral. BS 7671 requires it to be sleeved or taped brown or red at both ends to warn future electricians that this conductor is not neutral.

What is the difference between the loop-in method and the junction box method for multiple lights?

In the loop-in method, the supply loops through the ceiling rose of each fitting — no separate junction boxes are needed for the supply distribution. In the junction box method, a four-terminal junction box serves each fitting, with separate cables to the switch and fitting. Loop-in is now standard for new UK domestic installation; junction box method is used where ceiling rose access is awkward or non-standard fittings are used.

Can I add another light to an existing loop-in circuit?

Yes, provided the total circuit load remains within the design limit. The new fitting is connected by looping from the last existing ceiling rose to the new one, or by adding a spur from any accessible ceiling rose's loop terminals, and running a switch cable to the new switch. Always verify the circuit's current rating and total connected load before adding luminaires.