National Electrical Code Top Ten Tips: Article 610, Cranes and Hoists
- In Chapter 6, Article 610 is the first that really gets into a meaty topic,
and it's one many industrial electricians must understand. The other three
Articles preceding it are 600 (Electric Signs and Outline Lighting), Article 604
(Manufactured Wiring Systems), and Article 605 (Office Furnishings). While 600
seems like a lot of detail for electric signs, the other two Articles are quite
- Article 600 contains only one definition, and unfortunately it does not
define crane or hoist. Most of us know what these are, but if you don't then
here's a working definition applicable to Article 610. A crane or hoist is a
motor-driven mechanical device used to lift an object deemed too heavy or
awkward for humans to lift. Within that definition, there are many possible
variations. You don't need to know the difference between a crane or a hoist to
know that it's time to apply Article 610 (but if you're interested, then by all
means do some research).
- Since cranes and hoists are motor-driven devices, Article 610 is really
about a particular motor application. Article 430 provides the requirements for
motors. Table 430.5 lists “Other Articles,” based on equipment/occupancy.
Article 610 is one of those other Articles, and it provides the requirements for
cranes and hoists. Article 610 is an “amend and append” of Chapters 1 -4, as
they pertain to cranes and hoists.
- Don't use solid conductors for flexible
connections. Use flexible stranded conductors [610.11(C)].
- Conductors leaving raceways or cables must be
properly protected from abrasion via a separately bushed hole or a bushing in
lieu of a box [610.12].
- You can use only the conductors specified in
Table 610.14(A), and there aren't very many. Which conductor you use, and which
part of the table you can apply for ampacity, depends on several factors. These
factors are identified in the table notes, in 610.13, and in 610.14.
- While it may not be advisable from an
engineering standpoint (though it might), you can use a common return conductor
in cases where two or more motors operate a crane or hoist [610.15]. Just make sure it is of the proper ampacity.
- Contact conductors are tricky, because they must move. The requirements are
in Part III. The main consideration is the protection of these conductors from
mechanical damage while they are moving. Proper support, for example, is
critical. That's why 610.21 has requirements for the supports along runways, for
those on bridges, and for rigid conductors.
- You need a disconnecting means for the runway contact conductors, and you
need a disconnecting means for cranes and monorail hoists [610.32].
- The overcurrent protection calculations are the same as for other motors,
except you must use the demand factors of Table 610.14(E) and comply with a few
other Article 610 amendments.