NEMA vs IEC Starters
- Thread starter spsnyder
- Start date
- Status
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
Re: NEMA vs IEC Starters
IEC starters are much less costly, take up less panel space, and are more flexible than NEMA starters so you often see them in custom designed panels, especially when cost is a major issue (and thats a lot of the time).
Combination starters are generally NEMA design (I'm not even sure if there is a combination IEC starter).
NEMA starters are heftier and hold up better against rough service (like plugging).
But for most applications, IEC starters hold up very well and are a good, cost efficient choice.
One very nice feature of IEC starters is the variety of gizmos you can tack on to them. All kinds of nifty stuff.
The NEC does not care. As long as they are used and installed properly, either is acceptable.
IEC starters are much less costly, take up less panel space, and are more flexible than NEMA starters so you often see them in custom designed panels, especially when cost is a major issue (and thats a lot of the time).
Combination starters are generally NEMA design (I'm not even sure if there is a combination IEC starter).
NEMA starters are heftier and hold up better against rough service (like plugging).
But for most applications, IEC starters hold up very well and are a good, cost efficient choice.
One very nice feature of IEC starters is the variety of gizmos you can tack on to them. All kinds of nifty stuff.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: NEMA vs IEC Starters
NEMA starters are more rugged, reliable and repairable. IEC are delicate, dainty and destructible. I have had a lot of problems with IEC starters overheating, you need to oversize them. IEC starters are designed with about 300,000 operations and NEMA with millions
The biggest issue with IEC starters is they have to be protected with current limiting fuses otherwise they will be destroyed on a short circuit, you just can't always replace a NEMA with IEC.
Having said that, I do prefer the IEC overloads, they are more sensitive on phase loss, and are class 10 ambinent compensated, and heaters are part of the overload. I use NEMA starters with IEC overloads.
NEMA starters are more rugged, reliable and repairable. IEC are delicate, dainty and destructible. I have had a lot of problems with IEC starters overheating, you need to oversize them. IEC starters are designed with about 300,000 operations and NEMA with millions
The biggest issue with IEC starters is they have to be protected with current limiting fuses otherwise they will be destroyed on a short circuit, you just can't always replace a NEMA with IEC.
Having said that, I do prefer the IEC overloads, they are more sensitive on phase loss, and are class 10 ambinent compensated, and heaters are part of the overload. I use NEMA starters with IEC overloads.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re: NEMA vs IEC Starters
NEMA and IEC starters are both rated for 1 million electical operations. The UL testing is identical. NEMA startes can have the contacts replaced so they are rated for 10 million mechanical operations, while IEC devices are usually throw away.
The problem with IEC starters is that people tend to chose them based only on their horsepower rating and do not take into account actual current ratings. For example, a non-plugging/jogging NEMA Size 1 starter, 10HP @ 480V, has a continuous rating of 27 amps (even though the NEC FLA is 14A) while an equivalent IEC is rated for only 18A.
I have been using IEC devices for over 15 years and have not experienced any more failures than with NEMA devices. I leave 30% extra capacity when sizing my IEC starters. For a 10HP 480V motor I would "upsize" to a 25A device which is comparable to the Size 1 rating. But, for a 2HP 480V motor I would stay with the suggested 9A IEC starter, which is identical to the NEMA Size 00 rating.
NEMA and IEC starters are both rated for 1 million electical operations. The UL testing is identical. NEMA startes can have the contacts replaced so they are rated for 10 million mechanical operations, while IEC devices are usually throw away.
The problem with IEC starters is that people tend to chose them based only on their horsepower rating and do not take into account actual current ratings. For example, a non-plugging/jogging NEMA Size 1 starter, 10HP @ 480V, has a continuous rating of 27 amps (even though the NEC FLA is 14A) while an equivalent IEC is rated for only 18A.
I have been using IEC devices for over 15 years and have not experienced any more failures than with NEMA devices. I leave 30% extra capacity when sizing my IEC starters. For a 10HP 480V motor I would "upsize" to a 25A device which is comparable to the Size 1 rating. But, for a 2HP 480V motor I would stay with the suggested 9A IEC starter, which is identical to the NEMA Size 00 rating.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: NEMA vs IEC Starters
Jim "I leave 30% extra capacity when sizing my IEC starters"
Thats the key to successfull use of IEC equipment.
My numbers on life came from Allen Bradley, in their Practical Guide to Motor Control which is a interactive CD rom
Jim "I leave 30% extra capacity when sizing my IEC starters"
Thats the key to successfull use of IEC equipment.
My numbers on life came from Allen Bradley, in their Practical Guide to Motor Control which is a interactive CD rom
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re: NEMA vs IEC Starters
NEMA sizes were purposely chosen so no "thought" would be needed regardless of motor or starter manufacturer. Sometimes we forget to "engineer" a project and just do it the way we always have. I feel that correctly using IEC starters is no more difficult than correctly applying derating factors to 90C wire instead of simplying sizing everything from the 60C column. The quick lookup method is safe, but it is not always the best design.
P.S. My IEC contactor life data came from the publish life curves in Square D publication 8502CT9901R9/02.
NEMA sizes were purposely chosen so no "thought" would be needed regardless of motor or starter manufacturer. Sometimes we forget to "engineer" a project and just do it the way we always have. I feel that correctly using IEC starters is no more difficult than correctly applying derating factors to 90C wire instead of simplying sizing everything from the 60C column. The quick lookup method is safe, but it is not always the best design.
P.S. My IEC contactor life data came from the publish life curves in Square D publication 8502CT9901R9/02.
- Status