Are Molded Case Switches 100% rated? And other general information about Molded Case Switches.
Molded Case Switches
Application of UL489 listed molded case switches
Application and labeling not clear.
Yes. Molded Case Switches are ampere rated and can be used up to 100% of their ampere rating. Please note that molded case switches need to be protected by a fuse or a breaker of equal ampere rating.
The protective breaker may be either an 80% or 100% rated breaker. Therefore the molded case switch takes on the rating of the fuse or breaker protecting it, and can be 100% rated.
Per the NEC paragraph 210.20(A) and 215.3, the line side overcurrent device is what determines the loading of the switch.
If the line side overcurrent device is 80% rated then the switch is rated 80% and the same is true if the line side overcurrent device is 100% rated.
General Information about Molded Case Switches:
Automatic molded case switches open instantaneously at a factory preset magnetic trip point, calibrated to protect only
the molded case switch itself, when it is subjected to high fault currents. The trip point is nonadjustable and provides no
overload or low level fault protection.
Molded case switches open when the handle is switched to the OFF position or in response to an auxiliary tripping
device such as a shunt trip.
All molded case switches will accept the same lugs and accessories as equivalent thermal-magnetic circuit breakers,
with the exception of Q-frame switches which do not have electrical accessories available.
Automatic molded case switches are UL Listed per UL 489 and are CSA Certified.