Black Box Explains: The ANSI/ISA Standard for Hazardous Locations

Fires and explosions are a major safety concern in industrial plants. Electrical equipment that must be installed in these locations should be specifically designed and tested to operate under extreme conditions. The hazardous location classification system was designed to promote the safe use of electrical equipment in those areas “where fire or explosion hazards may exist due to flammable gases or vapors, flammable liquids, combustible dust, or ignitable fibers of flyings.”

The NEC and CSA define hazardous locations by three classes:

Class 1: Gas or vapor hazards
Class 2: Dust hazards
Class 3: Fibers and flyings

And two divisions:
Division 1: An environment where ignitable gases, liquids, vapors or dusts can exist
Division 2: Locations where ignitables are not likely to exist

Hazardous classes are further defined by groups A, B, C, D, E, F, and G:

A. Acetylene
B. Hydrogen
C. Ethlene, carbon monoxide
D. Hydrocarbons, fuels, solvents
E. Metals
F. Carbonaceous dusts including coal, carbon black, coke
G. Flour, starch, grain, combustible plastic or chemical dust

The difference between CAT6 and CAT6A cable diameters

Although shielded cable has the reputation of being bigger, bulkier, and more difficult to handle and install than unshielded cable, this is not the case with CAT6A F/UTP cable. It is actually easier to handle than CAT6A UTP; requires less space to maintain proper bend radius; and uses smaller conduits, cable trays, and pathways.

CAT6A UTP is significantly larger than CAT6 and CAT6A F/UTP cable because it is designed with more interior space between the pairs to minimize ANEXT. The outside diameter of CAT6A F/UTP can be as large as 0.354” compared to 0.265” – 0.30” for CAT6A F/UTP, and 0.21” – 9.24” for CAT6.

CAT6A UTP cable design differs among manufacturers. It may have double interior pair separators and/or a rigid jacket with a gear-shaped interior wall to create interior air space and decrease crosstalk.

CAT6A UTP is constructed with larger conductors, usually 23 AWG, and tighter twists than are used in CAT6 and CAT5e cable. The heavier conductors and heavier, larger, rigid jacket combine to make CAT6A UTP more difficult to install. It also requires bend radius of 4x O.D., which is significantly larger than CAT6 and CAT6A F/UTP.

The CAT6A UTP outside diameter creates a difference in the fill rate of cabling pathways.

TIA-569 recommends a maximum conduit fill ratio of 40% to accommodate bend radius requirements and to allow for future expansion. An increase in the outside diameter (O.D.) of 0.1”, from 0.25” to 0.35”, represents a 21% increase in fill volume.

In general, CAT6A F/UTP cable provides a minimum of 35% more fill capacity than CAT6A UTP cable. For example, at a 40% fill ratio, you can run three CAT6A UTP cables in a ¾” conduit verses five CAT6 cables, and three CAT6A F/UTP cables.

In addition, innovations in connector technology have made terminating CAT6A F/UTP cable actually easier than terminating bulkier CAT6A UTP cable.