Type 2 Coordination for Motor Starters

Type 2 coordination is a protection philosophy defined in IEC 60947-4-1 for motor starters. After a short-circuit fault, the starter components must remain suitable for further service, with only minor contact welding allowed if it can be cleared easily without damaging the apparatus. In practice, this means the MCCB, contactor, and overload relay are selected and tested as a coordinated combination, not as separate devices. For panel builders, Type 2 coordination is preferred where continuity of service matters, because the starter can often be returned to operation after fault clearing without replacing the contactor or overload relay. The coordination level depends on the tested pairings published by the manufacturer, fault current, fuse or MCCB characteristics, and the motor’s utilization category, typically AC-3.

Start with the motor full-load current, voltage, starting duty, and expected prospective short-circuit current at the point of installation. Then select an MCCB with sufficient breaking capacity and instantaneous trip performance, followed by a contactor and overload relay that are specifically listed by the manufacturer as Type 2 coordinated under IEC 60947-4-1. Schneider Electric TeSys combinations, ABB AF contactors with matching overloads, and Siemens Sirius starters are common examples where published coordination tables simplify selection. The MCCB must protect the branch circuit and limit let-through energy enough for the starter pair to survive the fault. Always verify the tested coordination at the exact supply voltage and fault level, because Type 2 ratings are not generic across all frame sizes. The overload setting must match the motor nameplate current and service factor.

Type 1 coordination allows damage to the contactor or overload relay after a short-circuit, but no hazard to personnel or adjacent equipment. The starter may need replacement before restarting the motor. Type 2 coordination, by contrast, requires the starter to remain fit for further use after fault clearing, with only limited contact welding permitted if the contacts can be separated by a simple manual operation. Both are recognized in IEC 60947-4-1, but Type 2 is the higher performance level and is usually specified for critical processes, pumping stations, HVAC plants, and conveyor systems where downtime is costly. The key practical difference is maintenance impact: Type 1 may protect safely but consume hardware, while Type 2 is designed to preserve the starter assembly after the fault.

Both MCCBs and fuses can be used, but the coordination tables must explicitly support the chosen protective device. Historically, fuse-based coordination has been common because current-limiting fuses can reduce thermal and electrodynamic stress on the contactor and overload relay. However, many modern panel designs use MCCBs for easier resetting, isolation, and integration with feeder protection. If you use an MCCB, its instantaneous magnetic trip and let-through energy must align with the manufacturer’s Type 2 test results. IEC 60947-4-1 does not say every MCCB will automatically deliver Type 2 coordination; the specific breaker, contactor, and overload relay combination must be validated. In short, fuses are often easier to coordinate, but a properly tested MCCB-based starter is fully acceptable and widely used in industrial panels.

The overload relay is part of the starter’s coordinated thermal path and must survive the fault without losing calibration, insulation integrity, or terminal connections. Even though the MCCB clears the short-circuit, the overload relay may still experience fault energy and mechanical shock through the contactor and wiring. IEC 60947-4-1 coordination testing evaluates the complete combination, not just the breaker. That is why manufacturers publish exact starter combinations, such as a specific MCCB with a matched contactor and thermal or electronic overload relay. In many modern designs, electronic overload relays from product families like Schneider TeSys LRD/LR9, ABB TA-series, or Siemens overload units are used because they provide more stable trip characteristics and better diagnostic functions. The relay must also be set correctly to the motor rated current to maintain both protection and coordination.

Yes, that is the main purpose of Type 2 coordination, but reuse is only permitted if the devices pass post-fault inspection and the manufacturer’s instructions are followed. Under IEC 60947-4-1, limited contact welding may be acceptable if the contacts can be separated without tools beyond normal operational means, and the contactor remains electrically and mechanically functional. After any short-circuit event, panel builders should inspect the MCCB, contactor, overload relay, terminals, insulation, and conductors for heat discoloration, deformation, or arc damage. Even when the coordination is rated Type 2, replacement may still be required if the fault current approached the tested limit or if the manufacturer specifies mandatory renewal after a severe fault. In safety-critical applications, many engineers treat the first fault as a maintenance event and document the inspection before re-energizing.

You need a published coordination table or test certificate showing the exact MCCB, contactor, overload relay, and sometimes the line side protection device, tested at the applicable voltage and fault level. The documentation should reference IEC 60947-4-1 and identify the utilization category, typically AC-3 for squirrel-cage motor starting. It should also state the prospective short-circuit current, the protective device ratings, and whether the combination is Type 1 or Type 2. For compliance files, keep the manufacturer’s catalog page, technical guide, and any declaration of conformity tied to the specific product family. Examples include coordination data from Schneider Electric, Siemens, ABB, Eaton, and Lovato Electric. Without this published evidence, you cannot assume Type 2 coordination simply because the breaker and contactor are both suitably rated. The exact pairing is what matters.

The most common mistake is mixing products that are individually rated correctly but not tested together as a coordinated set. Another frequent error is ignoring the actual prospective short-circuit current at the installation point and assuming the MCCB’s breaking capacity alone guarantees Type 2 performance. Engineers also misapply the overload relay setting, leaving it above the motor nameplate current and weakening protection. In addition, Type 2 coordination is often confused with mechanical endurance or normal service ratings; they are not the same thing. Using long cable runs, undersized conductors, or a different coil voltage than the tested combination can also invalidate the coordination claim. To avoid these issues, rely on the manufacturer’s IEC 60947-4-1 coordination tables, match the exact catalog numbers, and verify the starter under the real site fault level and supply voltage before panel release.