Double-Pole Breaker Symbol
Definition: The Double-Pole Breaker symbol represents a two-pole circuit breaker in residential and light commercial wiring diagrams that simultaneously interrupts both ungrounded (hot) conductors of a 240 V single-phase circuit—depicted as two mechanically linked single-pole breaker symbols with terminals L1 and L2 on the supply side and Load1 and Load2 on the load side—referenced in IEC 60947-2 and UL 489 / ANSI C37.29, and used for 240 V branch circuits and feeder protection.
Also known as: 2-pole breaker, two-pole breaker, double pole MCB, 240V breaker, tandem double-pole breaker, DP breaker.
What the Double-Pole Breaker symbol means
The Double-Pole Breaker symbol denotes a circuit breaker that occupies two adjacent slots in a residential load centre or distribution panel, connecting to both the L1 and L2 buses simultaneously to obtain 240 V across the two hot conductors. The symbol indicates that both hot legs of a 240 V circuit will be simultaneously de-energised when the breaker trips or is manually switched off, satisfying NEC requirements for simultaneous pole opening on multi-wire circuits.
In residential wiring diagrams the Double-Pole Breaker is used for high-power 240 V appliances—electric ranges, clothes dryers, water heaters, air conditioners, and sub-panels. The L1 and L2 terminals connect to the two phase buses in the load centre, and Load1 and Load2 connect to the two hot conductors of the branch circuit cable.
How to identify the Double-Pole Breaker symbol
The Double-Pole Breaker glyph is drawn as two vertically aligned or side-by-side single-pole breaker symbols (each with the characteristic trip lever and thermal-magnetic trip element) mechanically coupled by a dashed or solid bar indicating ganged operation—both trip simultaneously and both must be manually reset together. The symbol has four terminals: L1 and L2 at the top (connected to the panel buses) and Load1 and Load2 at the bottom (connected to the branch circuit conductors). The mechanical coupling bar distinguishes the double-pole breaker from two independent single-pole breakers.
Function in a circuit
A double-pole circuit breaker provides overcurrent protection and a manual switching means for both hot conductors of a 240 V single-phase circuit simultaneously. The thermal-magnetic trip mechanism monitors current through both poles; if either pole exceeds the rated current for a sustained period (thermal trip for overloads) or instantaneously (magnetic trip for short-circuit faults), both poles open together via the mechanical gang. This simultaneous opening ensures that neither hot conductor remains energised after a fault—a critical safety requirement for 240 V appliances.
Standards: IEC vs ANSI
| IEC 60617 | IEC 60947-2 governs miniature circuit breakers (MCBs) and moulded-case circuit breakers (MCCBs) including multi-pole types. IEC 60898-1 covers household and similar MCBs. In IEC practice, a two-pole breaker is designated by '2P' and the poles are labelled L1 and L2 (or L and N for 1P+N types). The IEC symbol shows two linked switch symbols. |
|---|---|
| ANSI/IEEE 315 | UL 489 is the North American standard for molded case circuit breakers; ANSI C37.29 covers low-voltage AC circuit breakers. NEC (NFPA 70) Article 240 requires that multi-wire branch circuits have a means to simultaneously disconnect all ungrounded conductors—a double-pole breaker satisfies this requirement. NEC Article 210.4(B) specifically mandates simultaneous tripping for multi-wire branch circuits. |
| Key difference | IEC 60947-2 / IEC 60898-1 specify tripping characteristics (Type B, C, D) based on current multiples. UL 489 uses trip curves rated by the handle ampere rating. The physical symbol is identical—two linked single-pole breaker symbols. European IEC practice distinguishes 2P (both poles are protected) from 1P+N (only one pole is protected, neutral is switched but unprotected); NEC mandates full two-pole protection. |
Terminals / pins
| Pin | Name |
|---|---|
| l1 | L1 |
| l2 | L2 |
| load1 | Load1 |
| load2 | Load2 |
Typical values
Common residential ratings: 15 A, 20 A, 30 A, 40 A, 50 A, 60 A at 240 V single-phase (North America) or 230/400 V two-pole (IEC). Standard frame sizes: 1-inch per pole (North America). Interrupt rating: 10 kAIC standard (residential); 22 kAIC or 42 kAIC for higher-rated panels. IEC tripping characteristics: Type B (3–5× In), Type C (5–10× In), Type D (10–20× In).
Where the Double-Pole Breaker symbol is used
- Electric clothes dryer branch circuits: 30 A, 240 V (NEMA 14-30 outlet), L1 and L2 providing 240 V across both hot conductors
- Electric range and cooktop circuits: 40 A or 50 A, 240 V (NEMA 14-50 outlet)
- Central air conditioning condenser unit circuits: 20 A to 60 A, 240 V, two-pole protection
- Electric water heater branch circuits: 30 A, 240 V, dedicated circuit per NEC Article 422
- Sub-panel feeder protection in garages, outbuildings, or additional distribution points
- EV charger (Level 2) circuits: 30 A to 50 A, 240 V, per NEC Article 625
- Pool pump and spa heater circuits: 20 A to 40 A, 240 V, per NEC Article 680
Example
In a residential load centre layout, a Double-Pole Breaker symbol (30 A) is drawn occupying slots 4 and 6 of the panel; L1 connects to the left-side bus bar and L2 connects to the right-side bus bar, providing 240 V between the two poles. Load1 and Load2 connect via 10 AWG conductors (plus 10 AWG ground) in a 10/3 NM-B cable to a NEMA 14-30 dryer outlet in the laundry room.
Key facts
- The Double-Pole Breaker symbol has four terminals: L1 and L2 (supply-side, connected to both phase buses in the panel) and Load1 and Load2 (load-side, connected to the two hot conductors of the 240 V branch circuit).
- A double-pole breaker occupies two adjacent slots in a residential load centre, connecting to both the L1 and L2 phase buses to provide 240 V between the two poles; each pole carries 120 V to neutral.
- NEC Article 210.4(B) requires that multi-wire branch circuits have a means to simultaneously disconnect all ungrounded conductors; a double-pole breaker satisfies this by ganging both poles so they trip and switch together.
- The mechanical gang (coupling bar) between the two poles ensures that both hot conductors are simultaneously interrupted on overcurrent, overload, or manual trip—neither pole can remain energised while the other is open.
- Common residential double-pole breaker amperage ratings: 30 A (dryer), 40 A (range), 50 A (range/EV charger), 20 A (A/C unit), 30 A (water heater). Wire sizing per NEC Table 310.15 must match the breaker rating.
- IEC 60947-2 and IEC 60898-1 govern double-pole MCBs internationally; they specify tripping characteristics (Type B, C, D) and rated interrupting capacity (Icn). North American equivalents are tested to UL 489.
- A double-pole breaker is NOT the same as two single-pole breakers installed side by side; the double-pole unit has a mechanical interlock ensuring simultaneous tripping of both poles, which individual breakers cannot guarantee.
Frequently asked questions
What does the double-pole breaker symbol mean in a wiring diagram?
The Double-Pole Breaker symbol represents a two-pole circuit breaker that simultaneously protects and switches both hot conductors of a 240 V single-phase circuit. It indicates that both L1 and L2 (the two phase buses in the panel) are connected through this breaker, which will trip both poles simultaneously on overcurrent or short circuit.
What does the double-pole breaker symbol look like?
The Double-Pole Breaker symbol is drawn as two single-pole breaker symbols placed side by side or stacked vertically, connected by a dashed or solid mechanical coupling bar indicating they operate as a ganged pair. Four terminals are shown: L1 and L2 at the supply side and Load1 and Load2 at the load side.
What is the voltage of a double-pole breaker?
A double-pole breaker provides 240 V AC (North America) or 230/240 V AC (IEC regions) across its two load terminals because it connects to both phase buses in the panel, which are 180° out of phase in a single-split-phase system. Each pole individually provides 120 V (North America) or 115–120 V to neutral.
What is the difference between a double-pole breaker and two single-pole breakers?
A double-pole breaker has a mechanical interlock (gang) that forces both poles to trip simultaneously when either pole detects an overcurrent. Two independent single-pole breakers have no interlock and can trip individually, leaving one hot conductor energised—a safety hazard on 240 V circuits. NEC Article 210.4(B) requires simultaneous disconnection, which only a double-pole breaker (or a factory handle-tied pair) satisfies.
What appliances require a double-pole breaker?
240 V single-phase appliances require a double-pole breaker: electric clothes dryers (30 A), electric ranges and cooktops (40–50 A), electric water heaters (30 A), central air conditioners (20–60 A), Level 2 EV chargers (30–50 A), pool pumps (20–40 A), and sub-panel feeders. Any appliance requiring 240 V or a multi-wire branch circuit with two hot conductors needs a double-pole breaker.
What standard governs double-pole breakers?
North American double-pole breakers are tested to UL 489 (Molded-Case Circuit Breakers) and must comply with NEC Article 240 for overcurrent protection requirements. Internationally, IEC 60947-2 governs moulded-case circuit breakers and IEC 60898-1 governs household MCBs; both cover multi-pole (2P, 3P, 4P) versions.
What wire size is required for a 30 A double-pole breaker?
A 30 A double-pole breaker requires 10 AWG copper conductors per NEC Table 310.15(B)(16) for a 240 V branch circuit. The cable is typically 10/3 NM-B (10 AWG, 3 conductors + ground) for a 240/120 V circuit, or 10/2 NM-B for a straight 240 V circuit without a neutral. All conductors (L1, L2, and equipment ground) must be properly sized and terminated.
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