Double-Pole Switch Diagram: Switching Both Live and Neutral
This is a free printable double pole switch diagram: download the diagram as SVG or open it and print to paper or PDF.
A double-pole switch disconnects both the line (live) and neutral conductors simultaneously, providing true isolation. This guide explains why, when, and how to wire a double-pole switch safely and to code.
A double-pole switch is mechanically identical to a single-pole switch in operation — you flip it and something turns on or off — but electrically it is fundamentally different. Where a single-pole switch interrupts only the line (live) conductor, a double-pole switch breaks both the line and the neutral conductor in a single action. This distinction is not academic: it is the basis for true electrical isolation.
In a standard single-pole switched circuit, when the switch is open the load is de-energised in the sense that no current flows through it. However, the neutral terminal of the load remains connected to the supply neutral, and in a correctly wired installation the load's line terminal sits at line potential with only an open switch contact between it and the supply. The load chassis, terminal block, or heating element may still be at a hazardous potential if the supply neutral is lifted or if the polarity of the supply is inadvertently reversed at some point upstream.
A double-pole switch eliminates this uncertainty. When it opens, both conductors are interrupted and the load is fully isolated from supply — regardless of polarity or neutral integrity upstream. This is why double-pole switching is required by most wiring codes for fixed appliances, HVAC equipment, cookers, water heaters, and industrial machinery that must be safely isolated for maintenance. Codes including IEC 60364, BS 7671, AS/NZS 3000, and NEC/NFPA 70 each specify circumstances where double-pole (or all-pole) isolation is mandatory.
The wiring is straightforward: the line conductor from supply enters pole 1 input, leaves pole 1 output to the load's line terminal. The neutral conductor enters pole 2 input, leaves pole 2 output to the load's neutral terminal. The earth (ground) conductor is never switched — it connects continuously from supply earth terminal to load earth terminal regardless of switch position. Interrupting the protective earth is prohibited by all wiring codes.
In three-phase applications, a three-pole or four-pole switch achieves the same total isolation across all supply conductors. The double-pole principle scales directly.
A common point of confusion is the difference between a double-pole switch and a two-way switch. A two-way switch has one common and two switching contacts on a single pole — it is used in staircase lighting circuits. A double-pole switch has two independent poles that switch simultaneously. They are not interchangeable.
How to wire double pole switch diagram
- Isolate the circuit and verify it is dead Switch off the relevant circuit breaker and lock it out or apply a warning notice. Use a calibrated non-contact voltage tester or a multimeter set to AC voltage to verify all conductors at the switch location are at zero volts before touching any terminal. Verify the tester on a known live source before and after testing to confirm it is functioning.
- Identify conductors at the switch location In a typical single-phase installation you will have three conductors: line (live — brown in IEC colour convention, red in older UK or Australian installations), neutral (blue in IEC, black in older conventions), and earth/ground (green-yellow). Some older installations may have non-standard colouring — use a multimeter to confirm conductor identity, never rely on colour alone in older premises.
- Prepare conductor terminations Strip insulation to the length specified by the switch manufacturer (typically 6–10mm). Do not nick the conductor. For solid conductors, a clean straight cut is sufficient. For stranded conductors, twist the strands together and verify no individual strands will escape the terminal and contact adjacent terminals. If ferrules (wire end sleeves) are specified by the terminal type, crimp them onto stranded conductors.
- Connect line conductor to pole 1 Insert the line (live) supply conductor into pole 1's supply-side (input) terminal and tighten to the specified torque. Run the line conductor from pole 1's load-side (output) terminal to the load's line (live) input terminal. In a loop-in wiring arrangement, verify no line conductor is inadvertently landed on a neutral terminal.
- Connect neutral conductor to pole 2 Insert the supply neutral into pole 2's supply-side terminal and tighten to specified torque. Run the neutral conductor from pole 2's load-side terminal to the load's neutral terminal. The earth conductor is connected directly from the supply earth to the load earth terminal via the earth bar — it does not pass through the switch.
- Connect the earth conductor continuously Run the earth (ground) conductor from the supply earth terminal directly to the load's earth terminal without interruption. If the switch has an earth terminal on its body (some metal-bodied switches do), connect the earth there as well as continuing to the load. The earth conductor is never routed through the switching contacts.
- Test before energising With the switch in the OFF position and circuit still isolated, use a multimeter to confirm continuity between the load's line and neutral terminals is open (infinite resistance for a resistive load like a heater, or through the load resistance for a heating element). Switch to ON and confirm continuity from supply terminals through the switch to load terminals. Re-energise only after all covers and enclosures are reinstated.
Specifications
| Switch type | Double-pole (DP) — two independent simultaneous break contacts |
|---|---|
| Typical AC voltage rating | 250V AC or 415V AC (per product — verify for application) |
| Typical current rating | 16A, 20A, 32A, or 45A — select at or above circuit demand |
| Conductors switched | Line (L) and Neutral (N) — earth (PE) is never switched |
| Terminal torque (typical screw terminal) | 0.8 N·m to 1.2 N·m — refer to switch manufacturer's datasheet |
| IP rating (indoors, dry) | IP20 minimum; IP44 or IP55 for damp or outdoor enclosures |
| Applicable standards | IEC 60669-1, BS EN 60669-1 (general purpose switches) |
Safety warnings
- All fixed wiring work on mains voltage circuits must be carried out by a licensed or registered electrician in accordance with applicable wiring codes (NEC/NFPA 70, BS 7671, AS/NZS 3000, IEC 60364, or the applicable local standard). This guide is for illustrative and reference purposes only.
- Always isolate the circuit at the distribution board, lock out or label the breaker, and verify the circuit is dead using a calibrated voltage tester before touching any conductor or terminal. Verify the tester on a known live source before and after the dead test.
- Never switch or interrupt the protective earth (ground) conductor. The earth must remain continuously connected at all times, including when the double-pole switch is in the off position.
- Verify the switch's rated voltage and current meet or exceed the circuit requirements before installation. An undersized switch will arc, overheat, and fail — potentially causing fire.
- Do not assume conductor colour coding is correct in older or modified installations. Always confirm conductor identity with a multimeter before connection.
Tools needed
- Calibrated non-contact voltage tester or multimeter (CAT III or CAT IV rated for mains work)
- Flat-blade and Phillips screwdrivers (insulated handles)
- Wire stripper (calibrated to conductor gauge)
- Crimp tool and insulated ferrules (for stranded conductors)
- Torque screwdriver (for correct terminal tightening)
- Lockout/tagout device for circuit breaker
- Personal protective equipment: safety glasses, insulated gloves rated for the working voltage
Common mistakes
- Wiring the switch on the neutral conductor only and leaving the line unswitched: this is single-pole switching on the wrong conductor and leaves the load live when the switch is open — a dangerous error.
- Connecting the earth conductor through the switch: the earth must never be switched. Running earth through a switch contact means the load loses its earth protection whenever the switch is opened.
- Using a single-pole switch where double-pole isolation is required by code: appliances such as cookers, water heaters, and air conditioning units typically require double-pole isolation per most wiring regulations.
- Confusing a double-pole switch with a two-way switch: a two-way switch has one common and two alternate contacts on a single pole — it is structurally and functionally different from a double-pole switch and cannot substitute for it.
- Over-tightening terminal screws: excessive torque can crack terminal bodies or sever stranded conductors internally, leading to a high-resistance joint that overheats under load.
Troubleshooting
- Load remains energised (live) when switch is in off position
- Cause: Switch is wired on neutral only (single-pole on neutral), or one pole is internally welded (contact sticking closed) Fix: Isolate the circuit. Verify with a multimeter that both poles are interrupting their respective conductors in the OFF position. If one pole shows continuity in the OFF position, the switch has a welded contact and must be replaced. If only neutral is switched, rewire to include the line conductor through the second pole.
- Switch overheats during normal operation
- Cause: Switch current rating is insufficient for the load, or a loose terminal connection is creating a high-resistance joint Fix: Isolate the circuit. Verify the load current does not exceed the switch rating (use a clamp meter if possible). Check all terminals for correct tightness to the manufacturer's torque specification. Replace the switch if it is undersized or if the contacts show signs of arcing or burning.
- Earth fault protection trips when load is operated
- Cause: Earth conductor has been inadvertently routed through the switch, causing the earth to be open when the switch is in one position Fix: Isolate the circuit. Trace the earth conductor from the supply earth bar to the load earth terminal and verify it is continuous regardless of switch position. Re-route the earth conductor to bypass the switch entirely.
Frequently asked questions
Why would I use a double-pole switch instead of a single-pole switch?
A double-pole switch provides true isolation by disconnecting both the line and neutral conductors simultaneously. This is required by wiring codes for fixed appliances like cookers, water heaters, and HVAC units, where maintenance personnel must be confident the load is fully de-energised and not merely de-current'd. A single-pole switch leaves the neutral connected, which is not considered safe isolation.
Is the earth (ground) wire switched with a double-pole switch?
No. The protective earth conductor must never be switched. It remains continuously connected from the supply earth to the load's earth terminal regardless of switch position. Interrupting the earth conductor through a switch is prohibited under all major wiring standards including IEC 60364, BS 7671, NEC, and AS/NZS 3000.
Can a double-pole switch be used for a single-phase 230V circuit?
Yes. In single-phase 230V circuits, one pole switches the line (live) conductor and the second pole switches the neutral conductor. This is the standard application for a double-pole switch on fixed appliances. Ensure the switch's voltage and current ratings meet or exceed the circuit requirements.
What is the difference between a double-pole switch and a double-pole circuit breaker?
Both switch two conductors simultaneously. A circuit breaker adds overcurrent protection — it trips automatically on overload or short circuit. A double-pole switch has no automatic trip mechanism; it is a manual isolation device only. Many installations use both: a circuit breaker for overcurrent protection and a double-pole isolating switch adjacent to the appliance for local isolation.
How do I tell which terminal is line-in and which is line-out on a double-pole switch?
On most double-pole switches, the input terminals are on one side (often labelled 1 and 3, or marked with an arrow pointing in) and the outputs on the other (labelled 2 and 4, or marked with an arrow pointing out). Always consult the switch's terminal diagram printed on the body or in the datasheet. Wiring input to output terminal is critical — reversed wiring can cause the switch to arc at the wrong contact.
Related diagrams
- double pole double throw switch diagram
- double pole single throw switch diagram
- 2 pole changeover switch wiring diagram
- 3 pole switch wiring
- 3 way switch single pole wiring diagram
- 4 pole ignition switch wiring diagram