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Thread: RTDs in Class I, Div 2 location

  1. #1
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    RTDs in Class I, Div 2 location

    Hi All,
    First post, but longtime lurker and want to say that I have learned a great deal from browsing this forum a few times a week. Finally registered because I need some help.

    I have a Class I, Div 2 location that I need to install some RTDs in. These would be just PT100 RTDs, sensing element only, no transmitter. According to 501.105(B)(2) exception, I believe that I can use an RTD and junction box that isn't marked for Class I, Div 2. Is my assumption correct?

    Additionally, they are going to be connected to an Allen Bradley Point IO RTD input card in a cabinet in the unclassified space. The input card is p/n 1734-IR2 which is listed for Class I, Div 2 installations, and the data sheet has a drawing showing the connection for RTDs. Does this allow me to use a general purpose RTD and junction box?

    Appreciate the help,
    -Chris

  2. #2
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    Quote Originally Posted by cpickett View Post
    Hi All,
    First post, but longtime lurker and want to say that I have learned a great deal from browsing this forum a few times a week. Finally registered because I need some help.

    I have a Class I, Div 2 location that I need to install some RTDs in. These would be just PT100 RTDs, sensing element only, no transmitter. According to 501.105(B)(2) exception, I believe that I can use an RTD and junction box that isn't marked for Class I, Div 2. Is my assumption correct?

    Additionally, they are going to be connected to an Allen Bradley Point IO RTD input card in a cabinet in the unclassified space. The input card is p/n 1734-IR2 which is listed for Class I, Div 2 installations, and the data sheet has a drawing showing the connection for RTDs. Does this allow me to use a general purpose RTD and junction box?

    Appreciate the help,
    -Chris
    I don't think the AB I/O rating matters any since it is not in the classified area. But it does give you some ammunition if someone questions it.

    I have not seen an enclosure marked for class I division 2. In CID2 areas, junction boxes are allowed to be general purpose. Note: just because you can use GP boxes as junction boxes does not mean you can put just anything in that box. For instance, a selector switch that did not employ a recognized protection technique would not be allowed.
    Bob

  3. #3
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    Quote Originally Posted by petersonra View Post
    I don't think the AB I/O rating matters any since it is not in the classified area. But it does give you some ammunition if someone questions it.

    I have not seen an enclosure marked for class I division 2. In CID2 areas, junction boxes are allowed to be general purpose. Note: just because you can use GP boxes as junction boxes does not mean you can put just anything in that box. For instance, a selector switch that did not employ a recognized protection technique would not be allowed.

    Thanks for the reply, and the reassurance about the j-box. That is a misconception I have been up against here a few times, there seems to be the insistence that everything has to be marked Class I Div 2.

    So that leaves the RTD. Since it is a just a resistor (without make-or break contacts, or sliding contacts) would that not have to be marked Class I Div 2? Although I see 501.105(B)(4) which says the assembly would have to be marked with the maximum obtainable temperature or with a temp class. That may prove to be a challenge.

  4. #4
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    You also need to become familiar with Section 500.8 (all of it) especially Subsection 500.8(C)(6)(a),
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  5. #5
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    Quote Originally Posted by rbalex View Post
    You also need to become familiar with Section 500.8 (all of it) especially Subsection 500.8(C)(6)(a),
    you are going to give him a headache.

    It is like when I read article 725. I can get physically ill just thinking about it.
    Bob

  6. #6
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    Quote Originally Posted by petersonra View Post
    you are going to give him a headache.

    It is like when I read article 725. I can get physically ill just thinking about it.
    I think the Subsection will actually relieve his headache about specific markings for GP in Division 2.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  7. #7
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    Quote Originally Posted by rbalex View Post
    I think the Subsection will actually relieve his headache about specific markings for GP in Division 2.
    good point about those few sentences.
    Bob

  8. #8
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    Thank you for the input! Simple Apparatus is what I was looking for.

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