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Thread: Class II Div 2 group G enclosure

  1. #1
    Join Date
    Oct 2005
    Location
    Interior Alaska
    Posts
    18

    Class II Div 2 group G enclosure

    Specing out install of 100 HP Motor on Agricultural Feed Pellet Mill. 502.115(B) specifies enclosures for Class II Div 2 to be dust tight.It appears to me that NEMA Type 12 enclosures meet this specification. Wholesale House priced a Class I Div 1 disconnect enclosure which does carry rating for compliances for Class II Div 1 and 2 Groups E,F, and G. Price is also 5 times price of Type 12 disconnect. Also what are the seal requirements if any for Class II Div 2 locations. 502.15 appears to me to say seals are not necessary.

  2. #2
    Join Date
    Apr 2004
    Location
    Mission Viejo, CA
    Posts
    4,012
    In Class II locations, proper electrical area classification is largely a matter of housekeeping. I usually encourage clients to (honestly) review their housekeeping practices closely.

    Assuming the location is correctly classified Class II, Division 2, equipment selection is usually straightforward.

    You will find it difficult to find a NEMA 12 motor. NEMA MG-1 just doesn’t classify motor enclosures that way. Newer motors are more likely to be identified with a “degrees of protection” (IP) mark. You will probably want IP6x, although particle size may permit IP5x. Even more likely the enclosure will simply be described as “Totally Enclosed” such as TEFC or TENV, or possibly dust-ignitionproof. With exceptional housekeeping some open-type motors are acceptable. I usually don’t recommend open-type though and generally prefer TEFC. I highly recommend IEEE 841 motors.

    NEMA 12 would be acceptable for switches; however, other environmental conditions beyond dust should also be considered and NEMA 12 alone may not be sufficient. Dust-ignitionproof is not required.

    You don’t need explosionproof seals; but, depending on the raceway orientation, you still may need some form of dust ingress prevention. Reread 502.15 and review your raceway installation. If you still need to seal the FPN notes electrical sealing putty is acceptable.
    "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)

  3. #3
    Join Date
    Oct 2005
    Location
    Interior Alaska
    Posts
    18

    Class II Div 2 enclossure

    Rablex:

    I concur fully with your answers. The motor was purchased prior to my involment. It is an IP55 motor. I have Data sheets if you need more info. What other info do we need to determine if Type 12 enclosures are satisfactory for the motor disconnect near the Motor. One point to be kept in mind is we are in sub-arctic climate and building for Mill is unheated. I have addressed motor winding heater for condensation. Might this also be of concern for switch enclosures? Motor controls will be in unclassified area.

  4. #4
    Join Date
    Apr 2004
    Location
    Mission Viejo, CA
    Posts
    4,012
    The design ambient for most enclosed switches is -30C to 40C. Outside that range contact a manufacturer.

    It is important to note the switch will also need to be horsepower rated. [430.108 and 430.109(A)(1)]
    "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)

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