Molded Case Switch 100% rated?

[sparkyguy545]

In general terms, are molded case switches (no thermal or magnetic trip mechanism) subject to the UL 80% ampacity limitations? Since no overcurrent mechanism is involved, I would expect they could be loaded to 100% of rating but cannot verify. I need a NEMA 7 local disco on a 300 HP (361 FLA @ 460V) motor (Classified location). As far as I know, noboty makes a NEMA 7 switch that big. Therefore, I was looking into using a NEMA 7 circuit breaker enclosure with a molded case switch. Then the question comes up whether a 400 A unit is suitable or if I need to go to a 600 A unit since 361A x 1.25 = 451.25 A.

 

[charlie]

Since a molded case switch has not got thermal trip unit installed to produce heat, I would expect it would carry 100% but that is a guess. Also, even though you have an instantaneous trip set at several times the size of the switch (it does have a magnetic trip mechanism), you will still need to have an overcurrent device in front of the switch. I would size the switch to match the overcurrent device that is upstream of it.