Results 1 to 8 of 8

Thread: Class 1 div 1, Class 1 div 2

  1. #1
    Join Date
    May 2009
    Posts
    2

    Class 1 div 1, Class 1 div 2

    What is the difference between class 1 div 1 and class 1 div 2?

  2. #2
    Join Date
    Jul 2005
    Location
    Tennessee
    Posts
    11,845
    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.
    At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.

  3. #3
    Join Date
    Feb 2003
    Location
    Illinois
    Posts
    18,574
    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.
    Don, Illinois
    "It is the first responsibility of every citizen to question authority." B Franklin

  4. #4
    Join Date
    Aug 2007
    Posts
    2,754
    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

  5. #5
    Join Date
    May 2008
    Posts
    5
    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.

  6. #6
    Join Date
    May 2009
    Posts
    2
    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!

  7. #7
    Join Date
    Aug 2006
    Posts
    23
    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.

  8. #8
    Join Date
    Apr 2004
    Location
    Mission Viejo, CA
    Posts
    3,864
    Quote Originally Posted by Coyote View Post
    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.
    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).
    Last edited by rbalex; 05-08-09 at 07:45 PM.
    "Bob"
    Robert B. Alexander, P.E.
    "I know that you believe you understand what you think the NEC says, but I am not sure you realize that what you read is not what it means." (Corollary to Charlie's Rule)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •