National Electrical Code Top Ten Tips:
Article 502, Class II Locations
- Article 500 provides the basis for interpreting and correctly
applying Articles 501 - 516. For one thing, you will find the
definitions for those Articles in Article 500. So, do not work with
Article 501 until you have read and understood Article 500.
- Class II locations are those in which combustible dust is
(or may be) present in sufficient quantities to produce a hazard of
explosion or ignition 500.5(C)].
- Class locations are further broken down into Division 1 (normal
operations) and Division 2 (abnormal operations). That is, point #2
above applies in normal or abnormal conditions.
- You must use Division 1 wiring methods when combustibles are
present under normal operations [502.10(A)].
- You must use Division 2 wiring methods when combustibles are
present under abnormal operations [502.10(B)].
- Seal requirements for Class II locations [502.15] are very
simple, compared to the highly detailed and far more extensive
seal requirements of Class I locations [501.15]. Do not confuse the
two.
- Any electrical parts that operate at more than 30V can't be
exposed, but this drops to 15V under wet conditions. Further, you
must apply the appropriate protection technique from 500.7(E), (F),
or (G) to these parts [501.25.
- The grounding and bonding requirements for Class II locations are
in 502.30. If you ground where you should, instead, bond, you will
create a difference of potential that violates 502.30 and will pose
a threat to people and property. To avoid catastrophic consequences,
read the definitions of grounding and bonding in Article 100, and
take some time to study Article 250, Part V.
- You cannot use multiwire branch circuits in a Class II, Division
1 location unless the disconnect for the circuit opens all
ungrounded conductors simultaneously [502.40].
- Any luminaire used in a Class II must be identified for use in
Class II locations [502.130(A)(1)] and [502.130(B)(1)].
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