Can you wire two lights from one switch?

Wiring two lights to one switch is entirely possible with some basic electrical knowledge. The key considerations when wiring multiple lights to a single switch are ensuring the lights are on the same circuit, calculating proper load, and wiring the lights in parallel. With careful planning and adherence to electrical codes, lighting multiple fixtures from one switch can be safe, effective, and convenient.

Quick Answer

Yes, you can wire two lights from one switch. This is done by wiring the lights in parallel on the same circuit so that supplying power to the switch completes the circuit and turns on both lights. Proper load calculations must be made to ensure the circuit can handle the amperage draw of both fixtures.

Overview

Wiring two or more lights to one switch, also known as switch legs, involves running power from the switch to each light fixture. This allows you to control multiple lights from one location. For example, you may want both the front and back porch lights to turn on from a switch by the front door. Or a stairwell may have overhead lighting on both the top and bottom landings that should be controlled by the same switch.

Some key considerations when wiring multiple lights to one switch include:

• The lights must be on the same circuit – Lighting fixtures powered from different circuit breakers cannot be wired to a single switch.
• Proper load calculations – Add up the wattage of all fixtures on the circuit to ensure it is not overloaded.
• Cable size – Increased load may require larger gauge cable than lighting circuits typically use.
• Wiring in parallel – The lights must be wired in parallel, not in series, for the switch to control both.
• Following electrical codes – NEC and local regulations must be followed, including proper junction boxes.

With good planning and attention to safety, it is perfectly acceptable and commonplace to control multiple light fixtures from a single switch. Continued below are more details about how to wire lights in this configuration.

Lighting Circuit Basics

To understand how to wire two lights from one switch, it helps to review some fundamentals about lighting circuits in residential electrical systems:

• Lighting circuits are usually wired with 14/2 or 12/2 NM cable from the circuit breaker panel to light switch boxes and fixtures.
• A typical lighting circuit breaker is either 15 or 20 amps.
• Lighting circuits are usually wired using the switch loop method, with a hot line to the switch and a switched hot from the switch to the light(s).
• Multiple lights can be connected in parallel as part of the same lighting circuit.
• Residential lighting circuits are generally 120 volt.
• Good wiring practice dictates each fixture have its own neutral return to avoid overloading shared neutrals.

Understanding these basics about lighting circuits will help you plan the wiring, sizes, and layout when wiring multiple lights to one switch. Keep these principles in mind as you design the circuit and select components.

Calculating the Load

When wiring two or more lights to a single switch, it is important to calculate the total load in watts to ensure it does not exceed the circuit capacity. Add up the wattage of all lights that will be on the circuit to make sure that it is less than 80% of the circuit breaker rating. This allows headroom for safety and future additions.

For example, say you want to wire two 60W porch lights to a single 15A lighting circuit. The total load would be:

• Light 1: 60W
• Light 2: 60W
• Total load: 120W

120W would be 80% of a 15A circuit capacity, so this would be an acceptable and safe load for that circuit. If the total load exceeds 80% of the circuit rating, you may need to split the lights onto separate circuits or upgrade to a 20A circuit breaker.

Wiring Diagram

Here is a wiring diagram showing the basic setup for wiring two lights from one switch:

As shown in this diagram:

• An incoming hot line is connected to the switch.
• The switch has one hot line in, and one switched hot line out.
• The switched hot connects to both lights, providing the hot connection when the switch is on.
• The neutral from each light fixture is tied together in the switch box and connected to the panel neutral bus.
• Ground wires are all joined together and tied to ground at the panel.

This configuration creates a parallel circuit where power flows through the switch and is distributed to each light when turned on. The neutrals are shared but the hot wires remain separate for each fixture.

Cable Size

Typically 14 gauge or 12 gauge NM (nonmetallic) cable is used for lighting circuits. With increased load from multiple fixtures on the circuit, you may need to go up to a thicker 12 gauge wire if voltage drop over long cable runs becomes an issue. The longer the wiring distance between the panel, switch, and light fixtures, the greater opportunity for voltage drop.

To determine if you should use 12 gauge instead of 14 gauge cable, you can use a voltage drop calculator based on the total wattage load and length of the circuit. Generally speaking, thicker 12 gauge wire may be a good idea if you have more than 200W on the circuit or the wires exceed 75 feet in length.

Installing the Wiring

Here are some step-by-step installation tips when wiring two lights to one switch:

1. Turn off the circuit breaker for the lighting circuit you will be working on.
2. Run NM cable from the switch box to each light fixture location.
3. Make wire connections by stripping sheath and connecting hot, neutral, and ground wires with wire nuts.
4. Connect the incoming hot wire to the common terminal on the light switch.
5. Connect the switched hot to the hot terminals on each light.
6. Connect all neutral wires together in the switch box.
7. Connect all ground wires together in the switch box.
8. Install switch and light fixtures, ensuring proper wire connections to device terminals.
9. Turn circuit breaker back on and test operation of lights from the switch.

Be sure to make tight wire connections and follow codes for junction boxes, cable clamping, and securing wires with staples as needed. Use cable clamps on all wire entries to prevent abrasion.

Multiple Lights in Parallel

For the switch to control two or more lights correctly, the lights must be wired in parallel, not in series. Parallel wiring allows voltage to reach each fixture separately by branching from the switch output. Series wiring connects fixtures along a single path and does not work well for lighting control.

Parallel connections involve running a hot wire from the switch output to the hot terminal on each light fixture. The neutral wires are connected together to create a return path. This allows the switch to interrupt the hot path and turn all the lights off while maintaining a neutral return at all times.

Parallel wiring allows consistent voltage to reach each light. Voltage drop is minimized because the fixtures share a common return path through the neutral wires back to the panel. The total wattage of all fixtures must be considered for proper circuit load calculations.

Same Circuit Requirement

An important requirement when wiring two lights to one switch is that the lights must be on the same branch lighting circuit controlled by the same circuit breaker. You cannot put lights on different circuits together onto one switch.

The switch controls a single hot path from the breaker panel out to the multiple lights. All the lights downstream from the switch must connect back to that same circuit at the panel. Lights wired to separate breakers have fully isolated hot and neutral paths and cannot be mixed together.

You can confirm the lights are on the same circuit by checking continuity between light fixture hot terminals. No continuity indicates they are isolated circuits. Good continuity means they are wired to the same circuit hot wire and can be controlled together by one switch.

Junction Boxes

Electrical codes require junction boxes anytime you have wire splices, connections, or taps. When wiring two lights to one switch, junction boxes are often needed in the following locations:

• Switch box – For joining the incoming and outgoing hot wires
• Light fixtures – For connecting the switch loop wires to the light wires
• Intermediate access points – If fixtures are far apart, an accessible junction box placed between them may be required

Properly sized junction boxes with cable clamps provide containment for splices and help protect wires from damage. Using code-compliant junction boxes is an essential part of safe switch and light installation.

Cable Stapling

When running NM cables between fixtures, switches, and the main panel, it is important to properly strap and staple the cables every 4-1/2 feet and within 12 inches of junction boxes. Cable staples securely fasten the cables in place and prevent damage from pulling or abrasion.

Be sure to avoid over-tightening cable staples which can pinch or pierce the cable jacket. Use insulated staples when fastening cables to joists and masonry walls to prevent ground faults. Proper cable securing keeps wiring neat, safe, and code-compliant.

Grounding

Properly grounding all components is crucial for safety when wiring lights and switches. Make sure ground wires are securely connected using approved methods like wire nuts or terminal blocks. Ground all fixtures, the switch, and junction boxes back to the panel ground bar.

Ground provides a safe path for fault currents to prevent shock hazards. Always use code-compliant grounding when working with electrical wiring of any kind. Properly installed grounds also help minimize electrical noise that can cause flickering in lights.

Electrical Codes

All electrical work must comply with NEC (National Electrical Code) standards as well as any applicable local building codes. These codes provide minimum requirements to ensure safe electrical installations. Codes relevant to wiring lights include:

• Use of approved junction boxes for splices and taps – NEC 314
• Amperage capacity of wires must match circuit breaker – NEC 240.4
• Cables secured within 12 inches of boxes and every 4-1/2 feet – NEC 334.30
• Minimum bending radius for cables to avoid damage – NEC 300.34
• Proper use of cable clamps and connectors in boxes – NEC 314

Always check the latest edition of the NEC code book or lookup relevant codes online when planning any electrical project. Permitted wiring methods can vary by location, so also check local codes before performing electrical work.

Conclusion

Wiring two lights from a single switch is a common and safe practice when done correctly. The lights must be in parallel on the same circuit with adequate load capacity. Following basic code guidelines for junction boxes, cable sizing, stapling, and grounding will ensure a safe installation.

With good circuit planning and safe wiring practices, multiple lights can easily be switched from one location. Just be sure to shut off power, make solid connections, and test operation before completing the project. The ability to control multiple lights from one switch location provides added convenience and functionality.