Equipmet Requirement

[Electriman]

Dear Friends,

I have a question that is bothering me for a long time and I tried to find the answer to this for a long time with no success, please help me with that.

Some of the electrical equipment we can use in any area Hazard or non hazard. For example a TEFC motor that is meant to be used in non classified area can also be used in C1D2. The motor has to changed to EX if we will be using it in in C1D1.

I was wondering what are the rules for other electrical equipment. Especially the following

1- Transformers
2- Wiring and conduits
3-Junction boxes

Is there any rule of thumb that we can use to avoid confusion?

Thanks,

 

[rbalex]

There are some specific rules:

1. For transformers; Section 501.100
2. For wiring methods (wiring and conduits) and enclosures (junction boxes): Section 501.10

As for "rules of thumb" in Class I, the simplest concept is Division 1 attempts to control sources of ignition for both common and uncommon (but not necessarily catastrophic) conditions. Division 2 only attempts to control common sources of ignition; i.e., things that arc, spark or create high temperatures (ASH) while operating under regular design conditions.

In a sense, this is the inverse of classification: Division 1 can produce ignitable materials under common conditions. Division 2 will produce ignitable materials only under unusual (but not necessarily catastrophic) conditions.

The NEC does not define normal with respect to classified locations (or anywhere else for that matter). Catastrophic isn't defined either it is usually considered events that require emergency response.

 

[rbalex]

BTW, some motors, especially single-phase that use some form of internal switch to start them, are required to be explosionproof even in Division 2. See Section 501.125(B).

 

[Electriman]

Thanks

 

[just the cowboy]

What I was taught

What I was taught

A class 1 div 1 equipment will contain the explosion if gases get into an enclosure.
A class 1 div 2 equipment will try to keep out them gases from an enclosure (purged panel )

 

[rbalex]

A class 1 div 1 equipment will contain the explosion if gases get into an enclosure.
A class 1 div 2 equipment will try to keep out them gases from an enclosure (purged panel )

Actually, gases will get into all explosionproof enclosures (there's no "if" about it) and many Division 2 enclosures don't necessarily prevent it. Purged/pressurized is applicable in both Divisions.

There are many more applicable protection techniques for both Divisions [Section 500.8]

 

[rbalex]

Correction to above post. Various protection techniques are defined in Section 500.2. Their applications and limits are described in Section 500.7 rather than 500.?8.