Switching and Protection Products Selection Guide
Switching and protection devices do different jobs in a panel and are not interchangeable; overload, leakage current, overvoltage and arc faults are covered separately.
This guide covers the points to look at when choosing products in the Switching and Protection Products category.
Which device does which job in a panel
The product groups in this category are designed for different jobs; none of them can replace another:
- Overload and short-circuit protection: miniature circuit breakers, molded case and open-type circuit breakers, blade-type and cartridge fuses with a fusible element.
- Residual current protection: residual current relays and miniature circuit breakers with residual current protection. A miniature circuit breaker does not detect current leaking to earth; a residual current relay on its own does not detect overload or a phase-neutral short circuit.
- Surge-type overvoltages: surge arresters.
- Arc faults: arc fault detection devices (AFDD).
- Load switching: contactors and motor starters. A contactor is not designed to interrupt short-circuit current.
- Manual switching and isolation: cam switches and load break switches.
- Monitoring: phase, voltage and current protection relays; they mostly send the trip command to a contactor or to the shunt trip coil of a breaker.
A motor feeder therefore combines three functions: short-circuit protection, switching and overload protection.
Subcategories
- Switches: molded case, open-type and motor protection circuit breakers, cam switches, transfer switches and load break switches.
- Fuses: miniature circuit breakers, miniature circuit breakers with residual current protection, blade-type (NH) and cylindrical cartridge fuses.
- Contactors: power contactors, auxiliary contactors and lighting contactors.
- Relays: residual current relays and thermal overload relays.
- Protection Relays: current, voltage, phase and motor protection relays.
- Motor Starters: enclosed direct-on-line starters and soft starters. Motor management modules are listed separately under Motor Control Equipment.
- Low Voltage Surge Arresters: T1, T2 and T3 type surge arresters and replacement cartridges.
- Arc Fault Detection Devices: AFDD models combined with a miniature circuit breaker.
- Switch Accessories: connection terminals, handles, coils and socket kits. Contactor accessories, auxiliary contacts and shunt trip coils are listed in their own categories.
Electric meters, voltage and current protection devices, and insulation monitoring devices are also under this category.
How to read the values on the label
Rated current (In) is the highest current the device is designed to carry continuously. If only the power of the load is known, the line current can be found with the Current and Fuse Calculation from Active Power tool.
Breaking capacity is given in kA; it appears in product names as 36 kA, 70 kA and so on. The short-circuit current expected at the point where the device is connected must not exceed this value; if it does, interruption of the current is not guaranteed. The value is taken from the short-circuit calculation in the project.
Tripping curve (B, C, D) shows the instantaneous tripping threshold of a miniature circuit breaker; for loads with high inrush current, a curve with a higher threshold is selected.
Number of poles indicates the conductors that are protected and disconnected: 1P, 1P+N or 2P on a single-phase line; 3P, 3P+N or 4P on a three-phase line.
For contactors, coil voltage and the utilization category given according to the load type (such as AC-1, AC-3) are added to these.
Coordination and selectivity
Protective devices connected in series are selected in relation to each other. Selectivity means that, in a fault, only the device closest to the fault trips; which device pairs operate selectively is verified from the manufacturer's tables. For motor feeders, IEC 60947-4-1 defines two coordination types. In Type 1, after a short circuit the starter may not be fit for further use without repair or parts replacement. In Type 2, the starter must remain usable; only the risk of contact welding is accepted. In both types, no danger to persons or the installation may arise. Which fuse or breaker achieves which type with which contactor and thermal overload relay is stated in the manufacturer's coordination table.
Brands in this category
- Schneider Electric: NSX and EasyPact CVS molded case circuit breakers, MTZ open-type circuit breakers, Acti9 and Easy9 miniature circuit breakers, TeSys contactors, thermal overload relays and motor protection circuit breakers.
- ABB: miniature circuit breakers, molded case and open-type circuit breakers, transfer switches, load break switches, AF contactors, F200 residual current devices and OVR surge arresters.
- Siemens: 3VA, 3VJ and 3VM molded case power circuit breakers, 3WA open-type power circuit breakers, 5SL miniature circuit breakers, 3RT contactors, 3RU2 thermal overload relays and accessories for these series.
- Metop: on-off, changeover and multi-step cam switches. Opaş is also listed with the same product group.
Chint is listed with contactors, molded case circuit breakers and miniature circuit breakers; Tense with contactors and protection relays; Entes with protection relays.
Ordering notes
All products are sold by the piece. Some of the products are listed as lead-time items; for these, the delivery time is confirmed before ordering. You can reach a product directly by typing the manufacturer order code (for example LV833170SP or 3VJ9417-0AD21) into the site search.
Switching and Protection Product Groups Comparison Table
| Switchgear Group | Rated Current and Breaking Capacity | Primary Protection / Switching Function | Typical Application | Category Link |
|---|---|---|---|---|
| Miniature Circuit Breakers (MCB) & NH Fuses | 2 A – 125 A (MCB) · 6 kA / 10 kA · B, C, D curves | Overload and short-circuit protection on branch circuits | Residential, commercial building and industrial sub-distribution boards | Miniature Circuit Breakers |
| Residual Current Devices (RCCB / RCBO) | 25 A – 125 A · 30 mA (personnel) / 300 mA (fire) | Earth leakage protection against electric shock and fire | Wet rooms, socket circuits, main incoming feeders and EV chargers | Residual Current Circuit Breakers |
| Molded Case (MCCB) & Air Circuit Breakers (ACB) | 16 A – 1600 A (MCCB) · 800 A – 6300 A (ACB) · 18–100 kA | Main feeder protection and selective fault coordination | Transformer incomers, factory main switchboards and generator panels | Switches and Breakers |
| Contactors, Motor Breakers & Protection Relays | 9 A – 800 A (AC-3) · 0.16–100 A (MPCB) | Remote load/motor switching and phase/thermal protection | Motor starter panels, power factor correction and automation systems | Contactors |
Frequently asked questions
What is the difference between B, C and D curve miniature circuit breakers?
The letter shows the instantaneous (magnetic) tripping threshold of the breaker. The B curve trips without delay at 3-5 times the rated current, the C curve at 5-10 times and the D curve at 10-20 times; the difference lies in the tolerance for brief current surges. B or C is used on lighting and socket circuits, and D on loads with high inrush current such as transformers and motors. As the curve number goes up, it must be verified in the project that the tripping condition is met for a short circuit at the end of the line.
How is the breaking capacity (kA) selected?
It is selected according to the expected short-circuit current at the point where the device will be connected; this current must not exceed the breaking capacity of the device, otherwise interruption of the fault current is not guaranteed. The short-circuit current depends on the impedance of the supply side, that is, on the transformer power and the cross-section and length of the cable; for this reason it is high at the main panel and lower at remote sub-panels. The value is taken from the short-circuit calculation in the project and compared with the kA value in the product name or in the technical table.
Which switching products are used together on a motor feeder?
Three functions are needed: short-circuit protection, switching and overload protection. In the classic arrangement these are provided by a fuse, a contactor and a thermal overload relay. In the second arrangement, a thermal-magnetic motor protection circuit breaker handles short-circuit and overload protection in a single housing, and the contactor only does the switching. In enclosed starters, the contactor and the overload relay come ready assembled together. The compatibility of the devices with each other is verified from the manufacturer's coordination table.
Is a miniature circuit breaker still needed in a panel with a residual current relay?
Yes. A residual current relay only monitors the difference between the outgoing and returning currents; it does not detect current above the rated value flowing through the line, nor a short circuit between phase and neutral. The cable is protected against overload and short circuit by a miniature circuit breaker or switch. For those who want both functions in a single housing, miniature circuit breakers with residual current protection are listed in a separate subgroup in the Fuses category.
Can a switch accessory be fitted to another brand or series?
Mostly no. Parts such as auxiliary contacts, shunt trip coils, undervoltage coils, rotary handles and terminals are designed for a specific series and frame size of a manufacturer; they may not even be interchangeable between different frame sizes of the same brand. For coils, the control voltage and whether it is AC or DC must also match. The compatibility value in the product information needs to be compared with the type code on the label of the main device.