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NOTE: This is an unformatted excerpt from our online fire protection training library.

Zone Classification

Zone Wiring Methods

Zone 1

As noted previously, the wiring methods that may be used in Class I, Zone 1 areas are the same as those permitted in Class I, Division 1 areas. These methods include threaded RMC or IMC threaded RMC or IMC:
Section 505.9(E) requires the use of standard NPT threads, made up wrenchtight to avoid any arcing or sparking at the connections. At least five threads must be fully engaged for entries into flameproof equipment. Adapters must be used where enclosures have metric threads., MI cable MI cable:
Termination fittings must be listed for either Class I, Zone 1 or Class I, Division 1 applications., and restricted uses of Type MC-HL and ITC-HL Type MC-HL and ITC-HL:
These cables are restricted to industrial installations. Listed cable fittings may have standard NPT threads for connections to enclosures and fittings, or they may be equipped with metric threads. cables and RNC RNC:
Rigid nonmetallic conduit is limited to underground installations where the conduit is encased in 2 inches of concrete and buried at least 24 inches deep from final grade to the top of the conduit. Threaded RMC or IMC must be used for at least the last 24 inches where transitions are made to above-ground conduits. .

Flexible connections must be made with fittings listed for Class I, Zone 1 or Division 1 except that some uses of flexible cord are allowed according to 505.17.


Type MI cable and fitting listed for use in hazardous locations. The screw-on pot contains field-installed sealing compound to seal the end of the cable. (Courtesy of Pyrotenax Cables, Ltd.)
NOTE: This is an unformatted excerpt from our online fire protection training library.

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