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Thread: Seal off's in class 1 div2

  1. #1
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    Jan 2012
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    San Diego,CA, USA
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    Seal off's in class 1 div2

    We are currenty doing a remodel of an existing spray room that is classified as a class 1 division 2 hazardous location. The original build was done in the 70's. I had some questions regarding the current locations of the conduit seal off's. For the lighting there are seal off's on each side of a junction box that splits off to feed the (3) seperate switch locations. Being that the switches are less then three feet from the j box there is only the one seal off in each run. Leaving each switch there is a seal off on each conduit that goes up to it's respective row of class 1 div 2 lights in the spray room. There is not a seal off on the conduit as it enters the explosion proof light, nor are there any on the conduits between the next 6 lights in each. At these lights the conduit enters a box that is part of the fixture that has the 3/4" hubs along with another threaded access hole on the side that appears that it is there for makeup purposes. Are seal off's not required at boxes used for makeup? In some of these runs between lights that don't have seal off's there are unions. Does this change whether or not a seal off is required between makeup boxes?

    We will also be adding some new fire alarm devices in this room. Currently there is a heat detector in the room that doesn't have a seal off at the device, but has one in the run after it exists the classified location. Is this a proper install? Does fire alarm need seal offs between devices inside a hazardous location?

    Lastly, there are a couple added "hazmat" rooms (sounds like it may be for paint storage) that are all sharing common walls. Are seal offs required when going from one classified location into another, or are they only required when exiting/entering a hazardous location?

  2. #2
    Join Date
    Jan 2008
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    The interior of a spray room, the exhaust plenum, and the exhaust stack are all Class I, Division 1 areas (for liquid paint, Class II for powder). Suggest you review Article 516, especially 516.3(C)(4) for classifications.

  3. #3
    Join Date
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    I concur with sgunsel with regard to checking the correct classification(s). Assuming the locations are classified correctly:

    Quote Originally Posted by Andy Nagel View Post
    We are currenty doing a remodel of an existing spray room that is classified as a class 1 division 2 hazardous location. The original build was done in the 70's. I had some questions regarding the current locations of the conduit seal off's. For the lighting there are seal off's on each side of a junction box [OK] that splits off to feed the (3) seperate switch locations. Being that the switches are less then three feet from the j box there is only the one seal off in each run. [OK if each seal is within 18” of both J-box and switch] Leaving each switch there is a seal off on each conduit [OK] that goes up to it's respective row of class 1 div 2 lights in the spray room. There is not a seal off on the conduit as it enters the explosion proof light [OK], nor are there any on the conduits between the next 6 lights in each [OK]. At these lights the conduit enters a box that is part of the fixture that has the 3/4" hubs along with another threaded access hole on the side that appears that it is there for makeup purposes. Are seal off's not required at boxes used for makeup? [Not in Division 2] In some of these runs between lights that don't have seal off's there are unions. [Still OK] Does this change whether or not a seal off is required between makeup boxes? [NO]

    We will also be adding some new fire alarm devices in this room. Currently there is a heat detector in the room that doesn't have a seal off at the device, but has one in the run after it exists the classified location. Is this a proper install? [Possibly, would need to know the enclosure ratings of the detector] Does fire alarm need seal offs between devices inside a hazardous location? [Possibly, would need to know the enclosure ratings and internals of the devices]

    Lastly, there are a couple added "hazmat" rooms (sounds like it may be for paint storage) that are all sharing common walls. Are seal offs required when going from one classified location into another, [I prefer it when the locations are not classified by the exact same source(s); however, it is technically not an NEC requirement as long as the locations are the exact same Class, Division, Group and “T”-rating] or are they only required when exiting/entering a hazardous location?
    "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)

  4. #4
    Join Date
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    Rblax,
    You responded "not in Div 2" to my question about seal off's for j-boxes that are just for makeup. If this is in fact a div. 1 location would the seal off's be required at that point? In section 501.5 (A)(1)(1) it doesn't mention taps or splices in a division 1 location either. Am I reading this correctly?

    Thanks for the earlier prompt response.

  5. #5
    Join Date
    Apr 2004
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    See 501.15(A)(1)(2)
    "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)

  6. #6
    Join Date
    Jan 2012
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    San Diego,CA, USA
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    thank you


    I previously mentioned some "hazmat" rooms ( I believe they are for storage of paints, etc.) above. One of the doors opens into a classroom. Is there a perimeter outside this door that is still considered a classified area? Per NEC 511.3(B)(4) it appears that as long as it is ventilated properly or the authority declares it not hazardous that the area is not classified. Does this mean the devices that are recessed on the common wall just outside the door with the classified area, but are aiming the opposite way, can be installed per non-classified requirements?

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