Switches Selection Guide
Switches come in molded case, open type power, motor protection, cam, load break and transfer types; select by rated current and application.
This guide explains what to look at when choosing products in the Switches category.
Switch types and what they are used for
- Molded Case Circuit Breakers: circuit breakers with a molded insulating housing. They provide overload and short-circuit protection at the incomers and outgoers of distribution panels; models with thermal-magnetic or electronic trip units are listed in rated currents such as 63 A, 250 A and 630 A.
- Air Circuit Breakers: high-current breakers fitted at transformer and generator incomers in main distribution panels. They are available in rated currents such as 800 A, 1600 A and 4000 A, in fixed or drawout versions.
- Motor Protection Circuit Breakers: breakers dedicated to motor feeders, with the thermal setting made according to the motor current.
- Cam Switches: cam switches whose position is selected by turning the handle; made with on-off, step, changeover and star-delta schemes.
- Load Break Switches: switches that open and close the circuit under load and provide isolation in the open position. Fused load break switches and DC isolators for photovoltaic systems are also in this group.
- Transfer Switches: transfer the load between two sources such as mains and generator; manually operated, motorized and automatic types are available.
- Medium Voltage Circuit Breakers: vacuum breakers in rated voltages such as 12 kV, 24 kV and 36 kV.
- Modular Switches: modular group and changeover switches with a 25 A rated current.
Which switch protects and which only switches
Circuit breakers (molded case, open type and motor protection circuit breakers) sense and interrupt overcurrent with their own trip unit. Cam switches and load break switches do not sense overcurrent; for this reason, the data of a load break switch gives the utilization category (AC-21, AC-22, AC-23) and the conditional short-circuit current it can withstand together with the fuse or breaker upstream, instead of a short-circuit breaking capacity. If both protection and isolation are wanted on one feeder, the two functions are provided with separate devices or with a breaker declared suitable for isolation.
The standard line on the product card also shows this distinction: IEC 60947-2 covers circuit breakers, IEC 60947-3 covers switches, disconnectors, load break switches and fuse-combination units, and IEC 60947-6-1 covers transfer switching equipment. For motor protection circuit breakers, IEC 60947-4-1, the contactor and motor starter standard, is also declared in addition to IEC 60947-2. For the medium voltage vacuum breakers in this category, the manufacturer's declaration is IEC 62271-100.
Values to check when choosing a circuit breaker
- Rated current and setting range. The deciding factor is the load current of the line. On adjustable models the overload threshold is selected within a range: the notation "100 A 40 ... 100 A" in a product name denotes a breaker with a rated current of 100 A that is adjustable between 40 and 100 A.
- Short-circuit breaking capacity (Icu). It must not be lower than the prospective short-circuit current at the point where the breaker will be installed. The same frame is made with different breaking capacities such as 25 kA, 36 kA, 50 kA and 70 kA, and the value changes with voltage; on the product card, read the value next to your own mains voltage.
- Number of poles. In three-phase circuits, 3-pole or 4-pole models are used; whether the neutral will be switched is decided according to the mains type and the project.
- Trip unit. Thermal-magnetic units (TMF, TMD, TMA or TM in product names) are fixed or have limited adjustment. In electronic units (ABB Ekip, Schneider Electric Micrologic), the letters L, S and I in the product name indicate overload, short-time delay short-circuit and instantaneous protection; because a delay can be given to the S protection, it becomes easier to establish selectivity between breakers connected in series.
- Mounting and operation. For open type breakers, the fixed or drawout frame and the manual or motorized charging are stated in the product name. Parts such as the shunt trip coil, auxiliary contact and rotary handle are in the Switch Accessories category and are selected according to the breaker's series and frame size.
Brands in this category
- Schneider Electric: NSX, NS and GoPact molded case circuit breakers, MTZ series open type circuit breakers, TeSys GV motor protection circuit breakers and TeSys VARIO load break switches.
- ABB: XT and T series molded case circuit breakers, open type breakers in E1.2, E2.2, E4.2 and E6.2 frames, VD4 medium voltage breakers, OT and OX transfer switches.
- Siemens: 3VA, 3VJ and 3VM molded case power circuit breakers, 3WA and 3WJ open type power circuit breakers, 3RV and 3MV motor protection circuit breakers.
- Metop and Opaş: on-off, step, pole-changing and star-delta cam switches.
Order notes
Products in this category are sold by the piece. Some of them are listed with a lead time; for these products, the delivery time is confirmed before ordering. You can reach a product directly by typing a manufacturer code such as G40N3A400 or 3VA2110-5HL32-0AA0 into the site search. If you are buying a coil, contact or motor mechanism together with the breaker, verify on the product card that the accessory is made for the same series and frame size.
Switch and breaker comparison table
| Switch / Breaker Type | Standard | Typical Current Range | Primary Function | Product Group |
|---|---|---|---|---|
| Molded case circuit breaker (MCCB) | IEC 60947-2 | 16 A – 1600 A | Main and sub-distribution overload and short-circuit protection | Molded Case Circuit Breakers |
| Air circuit breaker (ACB) | IEC 60947-2 | 630 A – 6300 A | Main switchboard incoming/bus-coupler protection and selectivity | Air Circuit Breakers |
| Motor protection circuit breaker (MPCB) | IEC 60947-2 / 60947-4-1 | 0.16 A – 100 A | Thermal overload and magnetic short-circuit protection for motors | Motor Protection Switches |
| Rotary cam switch | IEC 60947-3 | 10 A – 200 A | On-off switching, changeover (reversing), and multi-step control | Cam Switches |
| Transfer and load break switch | IEC 60947-3 / 60947-6-1 | 16 A – 3200 A | Safe isolation under load and mains-generator source transfer | Transfer Switches |
Frequently asked questions
What is the difference between a molded case circuit breaker and an open type circuit breaker?
The mechanism of a molded case circuit breaker is inside a molded insulating housing; it is used at the incomers and outgoers of distribution panels. An open type breaker is fitted at the transformer or generator incomer in the main panel; the drawout type can be removed from its cradle for maintenance. The product card also gives the short-time withstand current (Icw): because the breaker can carry the short-circuit current for the set delay, tripping priority can be left to the downstream breaker. In the category, molded case models are listed in rated currents such as 250 A and 630 A, and open type models in rated currents such as 1600 A and 4000 A.
What do Icu and Ics mean in breaker data?
Icu is the ultimate short-circuit breaking capacity: the highest short-circuit current the breaker can interrupt at the stated voltage. Ics is the service short-circuit breaking capacity; it is verified with a longer open-close test sequence and can also be given as a percentage of Icu. When selecting, Icu is compared with the prospective short-circuit current at the installation point. Both values are written in kA and separately for each voltage.
How do you choose between a thermal-magnetic and an electronic trip unit?
A thermal-magnetic unit works with a bimetal and a coil, has limited adjustability and is used on standard distribution feeders. An electronic unit measures the current and trips; because its trip thresholds and delays can be adjusted over a wide range, it is preferred on main and intermediate levels where selectivity is wanted, and where metering or communication is needed. Which settings are available varies with the unit model; check the product card.
What is the difference between a load break switch and a molded case circuit breaker?
A load break switch opens and closes the circuit by hand and provides isolation in the open position; it has no trip unit that senses overcurrent, so a fuse or breaker is placed upstream of it. A molded case circuit breaker is a circuit breaker that trips by itself on overload and short circuit. A fused load break switch combines the two functions in one housing together with blade fuses; after a fault the fuse link is replaced, while the breaker is simply reset.
Which switch is used between the mains and the generator in an installation with a generator?
A transfer switch, which transfers the load between two sources, is used. IEC 60947-6-1 covers three kinds: manually operated, remotely operated, and automatic transfer switching equipment with a control unit. In selection, the rated current, the number of poles, the control voltage and whether the changeover is made manually or automatically are decisive. The changeover arrangement and interlocking conditions are designed according to the distribution company's requirements and the project.