Motor Circuit Breaker

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templdl

Senior Member
Location
Wisconsin
If a combination motor starter has been UL listed as an assembly with an MCP, OLR and contactor then to substitute a TM breaker, even of the same frame size, may vary well be in violation of the UL508 listing unless the TM breaker has been included in that UL listing.
Yes, a mag only breaker can not be used by itself because it can not protect itself from an overload. That rating, such as 10a that often is found on an MCP is never to be assumed that it has thermal protection. It must rely on the OLR for that or it can get fried.
Unlike a TM breaker you will also not that the mag only breaker does not have an interrupting rating on it either. The interrupting rating is placed on the enclosure of the combination starter as it is tested as an assembly.

If I'm not mistaken the interrupting rating of a pieced together combination starter that is not UL listed can only have an interrupting rating of no more than the interrupting rating that is the lowest of the components or 5kaic maximum.
 

Jraef

Moderator, OTD
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San Francisco Bay Area, CA, USA
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Electrical Engineer
templdl said:
... If I'm not mistaken the interrupting rating of a pieced together combination starter that is not UL listed can only have an interrupting rating of no more than the interrupting rating that is the lowest of the components or 5kaic maximum.

Correct, unless of course the combination has been tested by the manufacturer with the TM breaker as well, which as I mentioned is now the norm rather than the exception.
 
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