/images/PowerCableUpdate.jpg/images/southwire_100x70.jpgMC Cables Cut Hazardous Locations Wiring CostsMCCablesCutHazLocationsWiringCosts.htmFor years, conductors in conduit have been the standard wiring method in hazardous locations. Conduit gives good protection but it’s expensive and time-consuming to install. Now, more and more cable specifiers are turning to a lower-cost alternative.
ENU
Register Now Forgot Password?

MC Cables Cut Hazardous Locations Wiring Costs

Alternatives to conduit can reduce costs and compress installation schedules.

For years, conductors in conduit have been the standard wiring method in hazardous locations. Conduit gives good protection but it’s expensive and time-consuming to install. Now, more and more cable specifiers are turning to a lower-cost alternative: Type MC cable with either flexible armor or seamless welded armor.

“Pipe-and-wire systems are labor-intensive and require careful installation.” says Doug Ramsey, Southwire director of industrial products. “You can install type MC cable in less time than it takes to hang empty conduit, and with far less risk of cable damage. Southwire offers the broadest line of MC cable products in the industry.”

Seamless armor takes MC into high-hazard environments

Article 500 in the National Electrical Code (NEC) defines environments where hazardous liquids or vapors are present during normal operations as Class I, Division 1 locations. (See Table 1.) In these settings, you can save money over conduit by using a properly listed seamless armored type MC cable such as Southwire’s ARMOR-X.

HL-listed ARMOR-X products meet the tough impact- and crush-resistance requirements of UL standard 2225. ARMOR-X is available in 600V and MV-90 constructions, with conductors up to 500kcmil.

Jacketed, interlocked-armor MC works in less demanding locations

In many hazardous locations, the hazard is only present in abnormal conditions. These are Division II locations. There, non-welded interlocked-armor cable such as Southwire’s Aluminum MC can cut costs even further over conduit.

“One way to view the distinction between Division I and Division II requirements is to look at where the gas/vapor barrier function takes place,” says Ramsey. In Division 1, the metallic sheath is expected to provide the barrier. In Division 2, the armor doesn’t have to be a vapor barrier. It’s sufficient to have a polymeric outer sheath as the vapor barrier.

Here’s help with Classes, Divisions and zones

The NEC defines hazardous locations by classes and divisions. In Article 500, hazard classes describe the type of hazard: Class I is flammable gases and liquids, Class II is combustible dust, and Class III is ignitable fibers. Hazard divisions refer to the presence or absence of the hazard. (See Table 1.) Articles 501 - 503 list allowable wiring methods for each of these environments.

The European zone system (Zones 0, 1 and 2) overlaps with the North American Division definitions. NEC Articles 505 and 506 repeat the hazardous location wiring methods in terms of the zone system.

Because the NEC sections are organized by Class and Division, it can be tricky—or at least tedious—to track down all the areas where a specific wiring method is—or is not—allowed. To simplify the task, Table 2 will help you trace the usability of a specific wiring method through the NEC hazard classes. The table is based on IEEE Standard 141-1993, with an update for type MC cable. Be sure to check the details of your specific installation with the appropriate NEC sections.

Ramsey adds, “Whichever construction you use, be sure your terminations and fittings are listed for the application. Just as with conduit, it’s important to keep hazardous vapors and liquids from migrating through the cable system. If there’s any question, check with the hardware manufacturer.”

Table 1: Divisions? Zones? Which is Which?

These Division and Zone definitions apply to NEC hazard Classes I, II and III.

When The Hazard Is Likely To Be Present:

 
In Normal Operation   
In Abnormal Conditions   

 

Intermittently

Continuously

 
Europe

Zone 0

Zone 1

Zone 2

US/Canada

Division 1

Division 2

 

Table 2: Wiring Methods for Hazardous Locations in Industrial Applications

 

Class I, division

Class II, division

Class III, division

Wiring Method

1

2

1

2

1 or 2

Threaded rigid metal conduit

x

x

x

x

x

Threaded steel intermediate metal conduit

x

x

x

x

x

Rigid metal conduit

 

 

 

x

x

Intermediate metal conduit

 

 

 

x

x

Electrical metallic tubing

 

 

 

x

x

Rigid nonmetallic conduit

 

 

 

 

x

Type MI mineral insulated cable

x

x

x

x

x

Type MC metal-clad cable

x

x

x

x

x

Type SNM shielded non-metallic cable

 

x

 

x

x

Type MV medium-voltage cable

 

x

 

 

 

Type TC power and control tray cable

 

x

 

 

 

Type PLTC power-limited tray cable

 

x

 

 

 

Enclosed gasketed busways or wireways

 

x

 

 

 

Dust-tight wireways

 

 

 

x

x

Sources: IEEE Standard 141-1993, 2005 NEC