Honeywell ST 3000 manual 93

Appendix B —Hazardous Locations Reference

Reference	Information is provided to clarify the Hazardous Location installation
Information	requirements in North America and internationally. An explanaition of
	the applicalbel enclosure classification systems is also provided.

B.1 North American Classification of Hazardous Locations

Electrical Codes	Installation of electrical apparatus within hazardous (classified)
	locations of the United States is conducted under the provisions of the
	National Electrical Code (NEC), ANSI/NFPA 70, Article 500; and
	within Canada, under the provisions of the Canadian Electrical Code
	(CEC) C22.1, Part 1, Section 18.
Classifications
	In both the United States and Canada, hazardous locations are classified
	into one of these three classes.
	Class	Description of Hazardous Location
	I	Presence of flammable gases or vapors may be present in
		quantities sufficient to produce explosive or ignitable mixtures.
	II	Presence of combustible dusts, powders or grains.
	III	Presence of easily ignitable fibers or flyings.
Divisions
	The classes listed above are further classified into one of the following
	divisions based upon the level of risk present.
	Division	Description of Risk
	1	Locations in which hazardous concentrations of flammable gases
		or vapors, or combustible dust in suspension are continuously,
		intermittently or periodically present under normal operating
		conditions.
	2	Locations in which flammable gases or vapors are present, but
		normally confined within closed containers or systems from which
		they can escape only under abnormal or fault conditions.
		Combustible dusts are not normally in suspension nor likely to be
		thrown into suspension.
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2/05 ST 3000 Release 300 Installation Guide 83