6/2/2010
Page 4 of 25
Electrobar 8-Bar Instruction Manual
005-1044-R8
Chapter 2.0: Disconnecting Means/Overcurrent Protection
Note: Magnetek recommends using the following Disconnecting Means and Overcurrent Protection
Guidelines as published in the 2005 National Electrical Code, copyright 2004.
2.1: Disconnecting Means
2.1.(a):
610.31 Runway Conductor Disconnecting Means:
A disconnecting means,
having a continuous ampere rating not less than that computed in Sections 610.41(e) and
(f), shall be provided between the runway contact conductors and the power supply. Such
disconnecting means shall consist of a motor circuit switch, circuit breaker, or molded case
switch.
This disconnecting means shall:
2.1.(a).(i):
Be readily accessible and operate from the ground or floor level.
2.1.(a.(ii):
Be arranged to be locked in the open position.
2.1.(a.(iii):
Open all ungrounded conductors simultaneously.
2.1.(a).(iv):
Be placed within view of the crane or hoist, and the runway contact conductors.
2.2:
610.32 Disconnecting Means for Crane and Monorail Hoists:
A motor circuit switch or
circuit breaker, arranged to be locked in the open position, shall be provided in the leads from the
runway contact conductors or other power supply on all cranes and monorail hoists. Where
disconnecting means is not readily accessible from the crane or monorail hoist operating station,
means shall be provided at the operating station to open the power circuit to all motors of the
crane or monorail hoists.
2.3:
610.33 Rating of Disconnecting Means:
The continuous ampere rating of the switch or circuit
breaker, required by Section 610.32, shall not be less than 50 percent of the combined short-time
ampere rating of the motors, or less than 75 percent of the sum of the short-time ampere rating of
the motors required for any single motion.
2.4: Overcurrent
Protection
The use of Overcurrent Protection shall be provided in accordance with NEC Standard 610.41
through 610.43. Excerpts from 2005 National Electrical Code, copyright 2004.
2.5:
610-41. Feeders, Runway Conductors:
2.5.(a).(i):
Single Feeder.
The runway supply conductors and main contact conductors of a
crane or monorail shall be protected by an overcurrent device(s) that shall not be greater than the
largest rating or setting of any branch circuit protective device, plus the sum of the nameplate
ratings of all the other loads with application of the demand factors from Table 610-14(e).
2.5.(a).(ii):
More Than One Feeder Circuit.
Where more than one feeder circuit is installed to
supply runway conductors, each feeder circuit shall be sized and protected in compliance with
610.41(A).
2.6:
610-42. Branch-Circuit, Short Circuit Ground Fault Protection
. Branch circuits shall be
protected in accordance with 610.42(A). Branch-circuit taps, where made, shall comply with 610-
42(B).
2.6.(a).(i):
Fuse or Circuit Breaker Rating
. Crane, hoist, and monorail hoist motor branch
circuits shall be protected by fuses or inverse-time circuit breakers having a rating in accordance
