A short circuit on a motor feeder is cleared in a few milliseconds. The breaker did its job, nobody was hurt, the plant is ready to restart. Then someone opens the compartment and finds the contactor tips welded shut and the overload relay out of calibration.

Nothing failed. The starter was coordinated to Type 1.

The two types describe acceptable damage

IEC 60947-4-1 classifies the short-circuit coordination of a starter into two types. Both require the fault to be cleared without danger to people and without damage outside the enclosure. The difference is the condition the starter is left in afterwards.

Type 1 permits the contactor and overload relay to be damaged. They may need replacement. The only requirement is that the damage stays inside the enclosure.

Type 2 permits no damage except light welding of the contactor tips, and those must be separable with a screwdriver without significant deformation. After the fault, the starter has to be fit for continued service.

It is a tested combination, not a calculation

Type 2 cannot be derived from device ratings. It is established by testing one specific combination: this breaker or fuse, with this contactor, with this overload relay, at a stated prospective fault current.

Change any one of the three and the classification no longer applies. Swapping in an equivalent contactor from another maker because of a stock shortage quietly voids it.

Every major manufacturer publishes coordination tables for their own combinations. Those tables are the evidence. A rule of thumb is not.

What to ask for

  • Which type is required, and at what prospective fault current
  • The manufacturer coordination table reference for each starter combination, not just a device list
  • Confirmation that the devices actually supplied are the ones named in that table

Type 1 is cheaper to buy and more expensive the first time a fault happens. On a process line where one stopped motor stops everything, the arithmetic usually favours Type 2 across the whole motor control centre.

Frequently asked questions

What is the difference between Type 1 and Type 2 coordination?

Both clear a short circuit without danger to people and without damage outside the enclosure. Type 1 allows the contactor and overload relay to be damaged, so they may need replacing. Type 2 allows no damage except light welding of the contactor tips, which must be separable with a screwdriver, so the starter is fit for service after the fault. IEC 60947-4-1 defines both.

Can Type 2 be worked out from the device ratings?

No. It is established by testing one specific combination of short circuit protective device, contactor and overload relay at a stated prospective fault current. The manufacturer coordination table for that combination is the evidence, not a rule of thumb.

Can I substitute a contactor from another maker if mine is out of stock?

Not without losing the classification. Change any one of the three devices and the tested combination no longer applies, so the starter is no longer Type 2 even if the replacement has the same ratings.

What should I ask my panel builder for?

Which type is required and at what prospective fault current, the coordination table reference for each starter combination rather than just a device list, and confirmation that the devices actually supplied are the ones named in that table.

Is Type 2 worth the extra cost?

Type 1 is cheaper to buy and more expensive the first time a fault happens. On a process line where one stopped motor stops everything, the arithmetic usually favours Type 2 across the whole motor control centre. Where a stopped starter costs little to replace, Type 1 can still make sense.