Page 1 of 2 12 LastLast
Results 1 to 10 of 18

Thread: Class I Div 2 Grp. B

  1. #1
    Join Date
    Apr 2013
    Location
    Kennedy Space Center, Florida
    Posts
    32

    Class I Div 2 Grp. B

    Good Afternoon

    I have an area that has been classified Class I Div 2 group B

    Does a panel installed in this area need to be explosion-proof ?

    I am using the 2014 NEC and and looking at 501.115 (B)(1) and
    I do not meet any of the 1-4 exceptions.

    Thank you for your help. Scott

  2. #2
    Join Date
    Apr 2004
    Location
    Mission Viejo, CA
    Posts
    4,684
    Of course it depends on what's in the panel but, since you are referring to Section 501.115(B) with none of the "exceptions" applying, I'm assuming there is a switching or current interrupting device of some kind. If that be the case, then an enclosure identified for Class I, Division 1 must be used.

    NOTE: Explosionproof is not the only protection technique identified for Class I, Division 1 [See Section 500.7] but it is the most common and, in my opinion, the most reliable. Further note, if you do use an explosionproof enclosure, it must also be specifically suitable for Group B. [500.8(B)]
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  3. #3
    Join Date
    Apr 2006
    Location
    Upstate S.C.
    Posts
    799
    A panelboard in a classified area is EXPEN$IVE AND DIFFICULT TO WORK ON.

    I have worked in various industrial plants and it at all possible, put the panelboard OUTside the classified area.

    If it HAS to go in the classified area, there are some newer style panelboards for classified areas that have the breaker in a factory sealed area with the wiring in a separate compartment. That's the way to go.


    RC
    It's my name going on that drawing, not yours. If what you want ain't right, it ain't going on the drawings!

  4. #4
    Join Date
    Apr 2013
    Location
    Kennedy Space Center, Florida
    Posts
    32
    Thank you for the help.
    The panels were already in place when the area
    changed classification .

    The panels are 4X gasketed and well maintained
    i put seal offs on the conduits leaving and
    entering the panels . We are considering purge
    and pressuratizion.
    Any thoughts.

  5. #5
    Join Date
    Aug 2004
    Location
    Northern illinois
    Posts
    14,523
    Quote Originally Posted by scott minter View Post
    Thank you for the help.
    The panels were already in place when the area
    changed classification .

    The panels are 4X gasketed and well maintained
    i put seal offs on the conduits leaving and
    entering the panels . We are considering purge
    and pressuratizion.
    Any thoughts.
    That would seem to be one option. Keep in mind it will suck up a lot of air and compressed air is not cheap.

    Another option would be to install the whole thing inside of an XP enclosure.

    Really the best answer is to see if you can move it. It might also be possible to have a knowledgeable person look very closely at how the area came to be classified this way and see if maybe there is justification to unclassify where the panel is located.
    Bob

  6. #6
    Join Date
    Apr 2004
    Location
    Mission Viejo, CA
    Posts
    4,684
    Quote Originally Posted by petersonra View Post
    That would seem to be one option. Keep in mind it will suck up a lot of air and compressed air is not cheap.

    Another option would be to install the whole thing inside of an XP enclosure.

    Really the best answer is to see if you can move it. It might also be possible to have a knowledgeable person look very closely at how the area came to be classified this way and see if maybe there is justification to unclassify where the panel is located.
    Pressurizing is probably your best overall option, keeping petersonra's comments in mind.

    I would also note that simply sealing without pressurizing a non-explosionproof enclosure is useless; it only guarantees that you will blow the doors off and ignite the surrounding location if an internal explosion occurs.

    I very much concur with reviewing how the location was reclassified in the first place. Over-classifying is a very common problem when it is done "just to be safe".

    Relocating and/or reviewing the classification can cause additional problems with boundary seals.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  7. #7
    Join Date
    Apr 2013
    Location
    Kennedy Space Center, Florida
    Posts
    32
    Thank you for all the help.

    https://www.youtube.com/watch?v=J1wvdA56bks

    These are umbilicales we test.

    The classification was made early on and now has shifted, the determination is made with the AHJ.

    Now electrical equipment I had outside classified areas have fallen inside due to new piping, flowing LH2.

    We have plenty of GN2.

    The the system we are going to install : Pepperl+Fuchs 1000 series type Z purge system.

    I think this would "fix" the panel issues ?

    I also have a well maintained, gasketed SS splice/pull box. Also now in class I div 2 grp. b area.

    Am I correct that I do not have to do anything with this box if no conduits leaving the box leave the area?

    Thank you again. Scott

  8. #8
    Join Date
    Apr 2004
    Location
    Mission Viejo, CA
    Posts
    4,684
    Cool animation.

    Well, let's see. Unless the electrical area classification was determined directly from Article 511 to 515, in my nearly 50 years experience, I've never seen a Building Official AHJ classify in any manner other than, "just to be safe." I've seen one or two Fire Marshalls do a credible job. I suspect this location has been overclassified; but I can't tell without knowing the full mechanical set up of the piping. I have done a few launch pads at Vandenberg, but never involving an umbilical assembly.

    Nevertheless, a Type "Z" pressurization system sounds fine.

    As long as there are only terminals inside the junction box, it may be any "ordinary location" enclosure type that is otherwise appropriate for the location. It doesn't need to be pressurized nor does it require seals. Your raceways will require seals at the boundaries; however, they are not required to be explosion proof.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  9. #9
    Join Date
    Apr 2013
    Location
    Kennedy Space Center, Florida
    Posts
    32
    Thank you for you help.

    This is a clip of the real thing to compare against the animation .

    https://www.youtube.com/watch?v=Nw1Kr3YvgBM.

    As I continue checking the the new boundaries I might need some more advice.

    Thanks, Scott

  10. #10
    Join Date
    Jul 2005
    Location
    Tennessee
    Posts
    15,085
    WOW! Videos are humbling. Reminds me how small my little inspection world is
    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.

Posting Permissions

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