Division vs Zone

[jhammer619]

Hello everyone,

The NEC says that the Zone system is "an alternative" to the Division system. Does this mean an American electrical designer truly has the choice of which system he uses to classify a hazardous location on a drawing? Or is it implied (preferred?) that he will be using the Division system since he is designing an American facility. If so, why is the zone system included in the NEC? For reference?

Can an electrical designer use both? (Similar to using both Feet and Meters, for crude comparison.)

Sorry if I missed a previous thread discussing the same topic. Please refer me if I did.

Thanks in advance,
-J

 

[rbalex]

Either system as specifically applied in the NEC is acceptable; neither is ?preferred.? However, NEC Zones are not the same as IEC Zones. Article 505 is a ?force-fit? of Zones into a Division philosophy.

There are some economic benefits using NEC Zone rated equipment in Division 2 installations but, for the most part, that could have simply been covered by Section 501.5. Where an NEC "Zone 1" classification is properly applied there are significant economic benefits. Finding where it is "properly applied" though is another matter.

 

[RICK NAPIER]

You cannot use both systems. There is no mixing of the two designs your either divisions or zones.

 

[rbalex]

You cannot use both systems. There is no mixing of the two designs your either divisions or zones.

This is not entirely true. While a single point in a facility cannot be classified by both systems, the facility may use either or both systems in different locations. [See Section 505.7, especially 505.7(B)]. In addition, there are specific permissions to use equipment identified for one system to be used in the other.

 

[G._S._Ohm]

From
http://www.google.com/search?client=safari&rls=en&q=NEC+zone+division+hazard&ie=UTF-8&oe=UTF-8

"Zones and Divisions and safety categories: a measure of the likelihood of the hazard being present. This defines the method of protection which may be used."

seems to say that you first figure out your hazard likelihood.

The other cites expand on this. The Wiki link looks like a good overview.

Resolving conflicting conclusions and overlaps between these is a whole 'nother problem involving definitions, interpretations and logic.

 

[jumpingspidermedia]

There are two significant changes that electrical inspectors must be cognizant of with the new zone classification system. First, all zone-rated equipment can be used in Division 2, which is 90 percent of classified areas. Second, zone-rated products will have different markings and labels.

 

[jhammer619]

Thank you for all of your commentary! This has clarified much for me.