Class 1 div 1, Class 1 div 2

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1 division :)


(Thats to properly welcome you to the Forum )

It would propably be best if you read 505.5, I don't think there is a one word simple answer, however, you might realte it to the probability of a hazardous substace being present.
 
The difference is $$$. There are major installation differences between Division 1 and Division 2 with Division 1 costing a lot more money. If possible you try to keep electrical equipment out of Division 1 areas. You need to spend some time with Article 501.
 
basically (in my own words) the explosive atmosphere is assumed to be present all the time in div I whereas it is assumed to only be present occasionally or when something is malfunctioning in div II, but as others said, you need to read all the documentation and rules for each division
 
In a nutshell ...
Div 1 is an area in which an explosive atmosphere is prevalent under normal operating conditions. Example: a natural gas system vent.

Div 2 is an area where all explosive components are contained and (under normal operating conditions) are not released to the adjacent atmosphere unless a fault condition occurs such as a seal rupture or component failure.

If you need more info, respond with specifics.
 
Thanks everyone for the input, I recently had that question on a masters test and although it seemed like a simple question the more I thought about it it wasn't such a simple answer. Thanks again!
 
The answers given are correct as I understand the NEC, but what I have never understood is why the equipment in the C1Div2 is okay when the conditions change to a C1Div1 under the conditions stated. Seems that the
hazard would then be greater.
 
Coyote said:
The answers given are correct as I understand the NEC, but what I have never understood is why the equipment in the C1Div2 is okay when the conditions change to a C1Div1 under the conditions stated. Seems that the hazard would then be greater.
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What may not be obvious is the conditions don't change - even if an ignitable mixture may be present in Division 2. The "conditions" are whether the mixture is present under normal or abnormal system operation.

Division 1 deals with the idea that an ingnitable mixture may be present at any time the system is operating "normally" therefore "abnormal" ignition sources, such as a short-circuit, must also be considered. However, Division 2 primarily deals with "normal" igtnition sources operating as they should, without an ingnitable mixture present. If a condition arises that an "abnormal" ignition source would cause or be caused by an event that would simultaneously release an ignitable mixture - the location is then Division 1. See Section 500.5(B)(1)(3).
 
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