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#11108 07/02/02 12:19 AM
Joined: Oct 2001
Posts: 30
T
Member
A IEC contactor has a better overload trip mechanism. It it more sesnsative to single phasing than a NEMA starter.

The IEC contactor is amperage rated, not hP rated like a NEMA. Good practice is to use the next larger size IEC. An IEC starter is not a robust as a NEMA, and I have found them to be more suspectable to overheating. But they are easier to install, smaller, are touch safe (as all IEC products are).

One big disadvantage of the IEC is they are more suspectable to damage. They need to be protected against fault currents by the proper fusing (Bussman has good info on this)

I like IEC starters as they do offer superior overload protections and have more options than NEMA, and you can even get them that will run on Device Net. And you don't have to buy new heaters when the motor is swapped out.

And you can have the best of both worlds, you can use a NEMA contactor with IEC overloads.

Don't foget to use the next larger size IEC contactor.

#11109 07/03/02 12:53 PM
Joined: Oct 2000
Posts: 3,682
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Posted for CTolbert:

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I had a customer who installed this starter following art 430-53c. (group motor rating) The issue is, when you do not fuse the branch circuits, the IEC starters reclass to type 1 coordination. You have to understand the differences with the starter types. A NEMA starter can be re-used if the withstand rating is not exceeded during a short-circuit condition based on group motor rating, an IEC starter will destroy itself when the conditions are correct and branch fusing (type 2 coordination) is not used based on the IEC specification. Just a caveat.

Carl

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