akreel
Member
For my third and final question of the day, I want to reach out to the motor gurus. I’ve asked these questions of several sources and they all gave hesitant answers. Again, thanks for the help, Tom. This topic could become very political for me, so please let me know if I can contact you on your feedback.
1) When wiring an overload & contactor combination it is customary to connect the overload on the load side of the contactor. Every motor SCHEMATIC I’ve ever seen has this arrangement. I stressed schematic because although my shop draws the circuit this way, the shop wires them with the overload FEEDING the contactor. Even if you neglect the fact that the schematics become confusing, this still doesn’t feel right to me. Is this arrangement completely Kosher, or does it violate some regulation somewhere? The NEC doesn’t seem to specify the preferred sequence.
2) When using two contactors to create a reversing start circuit, is a hard-wired connection between the two required by code? Currently, only the PLC prevents the two from pulling in at the same time. The only hardwired protection in the circuit is an E-STOP, which disables a master control relay and cuts all control power to motor contactors and control circuits.
3) When multiple motors (of HP ratings typically 5 thru 15) are sharing a connection to a secondary fuse (assuming this also meets code), can that fusing be replaced by a circuit breaker? I have read a few pamphlets on supplimental breaker protection and asked a few “experts.” As far as I can tell, it is OK to use a breaker for group motor protection as long as the panel has a primary fuse. The NEC does specifically mention branch circuits with motors under 1HP, but is less forthcoming on the arrangement I’m speaking of. So, at this point I do know that my hairdryer, sump-pump, and power drill can share a breaker but I’m not so sure I can group three pumps on the same circuit. All motors also have individual overload protection, if this makes a difference.
1) When wiring an overload & contactor combination it is customary to connect the overload on the load side of the contactor. Every motor SCHEMATIC I’ve ever seen has this arrangement. I stressed schematic because although my shop draws the circuit this way, the shop wires them with the overload FEEDING the contactor. Even if you neglect the fact that the schematics become confusing, this still doesn’t feel right to me. Is this arrangement completely Kosher, or does it violate some regulation somewhere? The NEC doesn’t seem to specify the preferred sequence.
2) When using two contactors to create a reversing start circuit, is a hard-wired connection between the two required by code? Currently, only the PLC prevents the two from pulling in at the same time. The only hardwired protection in the circuit is an E-STOP, which disables a master control relay and cuts all control power to motor contactors and control circuits.
3) When multiple motors (of HP ratings typically 5 thru 15) are sharing a connection to a secondary fuse (assuming this also meets code), can that fusing be replaced by a circuit breaker? I have read a few pamphlets on supplimental breaker protection and asked a few “experts.” As far as I can tell, it is OK to use a breaker for group motor protection as long as the panel has a primary fuse. The NEC does specifically mention branch circuits with motors under 1HP, but is less forthcoming on the arrangement I’m speaking of. So, at this point I do know that my hairdryer, sump-pump, and power drill can share a breaker but I’m not so sure I can group three pumps on the same circuit. All motors also have individual overload protection, if this makes a difference.