National Electrical Code Top Ten Tips: Article 620, Elevators, Dumbwaiters, Escalators, Moving Walks, Platform Lifts, and Stairway Chair Lifts
- Article 620 is on the short list of NEC articles with the longest titles.
It's really a catch-all for any kind of lifting device not covered by other
Articles. It includes lifting devices for humans and lifting devices not for
humans. Moving walks are tossed in there, too.
- Half of the dozen definitions in Article 620 pertain to elevators and
dumbwaiters only. The other six definitions apply to all types of equipment
covered by Article 620.
- Article 620 limits supply voltage to 300V between conductors [620.3],
possibly under the theory that this voltage level is safe while 480V is not. We
can't explain why this limit exists. But there are some exceptions permitted:
lighting circuits, HVAC circuits, and certain kinds of power circuits.
- All live parts must be enclosed to protect against accidental contact
[620.4]. This is already an Article 110 requirement, and the informational note
for this section refers to 110.27.
- Working space must be provided [620.5]. This is already an Article 110 requirement, and 620.5 says the clearance cannot be less than that specified in 110.26. This suggests that 620.5 is emphasizing the idea that the work space be adequate, not that it meet some minimum in a chart and yet not be adequate for the worker to perform maintenance.
- All conductors to the hoistway door interlocks must have flame-retardant insulation, unless they are physically protected to acheive the same thing [620.11(A)]. There are additional requirements for traveling cables and for
hoistway door interlock wiring.
- When calculating ampacity, use Figure 620.13 to determine the applicable
other Articles and which specific sections of Article 620 apply to that part of the system for
which you are performing conductor ampacity calculations.
- Not all Chapter 3 wiring methods are allowed for this kind of equipment. In
fact, there's a fairly short list of allowable raceway types
To size the overload protection for the motors in this equipment, follow Article
430 requirements, and rate the duty based on the application identified in 620.61(B)(1) through (4)..
- Part IX used to be titled "Grounding", though the language of the requirements says
"bonding." Read the Article 100 definitions of grounding and bonding. It's very
clear that you must bond. Grounding instead of bonding will result in an unsafe
installation. With the 2020 NEC, this title has been changed to "Gounding and Bonding." Other than the fact you are required to bond to the equipment grounding conductor (which is, electrically, a bonding conductor not a grounding conductor), there are no grouding requirements here. Perhaps with the 2023 revision they will finally get this right.