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Thread: Intrinsically safe wiring requirements for Class 1 Div2.

  1. #11
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    Quote Originally Posted by petersonra View Post

    It is also possible that the IS barrier is in a separate box located outside the main cabinet. I have seen this done where someone wants to provide a UL508a listing for the control panel. UL does not allow IS devices inside of a UL508a control panel.
    I was not aware of this - is this for barriers? for I.S. wiring and devices?

    Would that mean it is not possible to put a AB Flex-Ex IO module or system into a UL508A panel?

  2. #12
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    Quote Originally Posted by nhee2 View Post
    I was not aware of this - is this for barriers? for I.S. wiring and devices?

    Would that mean it is not possible to put a AB Flex-Ex IO module or system into a UL508A panel?

    SA1.2 Where a Listed device is provided in an industrial control panel and specific component
    requirements are not described in this standard, any Listed component is able to be used.
    Exception No. 1: Equipment intended to be connected to a source of supply greater than 600 volts shall
    not be used.
    Exception No. 2: The following hazardous locations equipment and associated apparatus shall not be
    used as part of an ordinary locations industrial control panel:

    a) An explosion-proof enclosure marked for Class I hazardous locations (or Type 7).
    b) A dust-ignition-proof enclosure marked for Class II hazardous locations (or Type 9),
    c) A barrier that provides intrinsically safe input/output connections for use in Class I, II, and III
    hazardous locations.
    Pretty clear.
    Bob

  3. #13
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    Intrinsic Safety is a protection method for Class I Div 1 locations. It works for Class I Div 2 locations as well, but so does being nonincendive to begin with. There are some hoops to jump before you can decide a component non-incendive, but it is certainly better than having to go the whole 9 yards to make it IS with control drawings, etc. Voltage does not have anything to do with it. You could have a standard 480Y/277Vac 3 phase motor in a Class I Div 2 location, and that would be ok, but if you tried to put a 24VAC safety switch in the same space that would be forbidden without using some kind of protection method.

    I've seen a lot of time people use the English definition of "Intrinsically Safe", and not meaning the NFPA 70 definition of "Intrinsically Safe". That should definitely be avoided, but something to look out for when discussing this type of stuff with people.
    Time is of the essence, and I am low on essence. ~ Graham Hill

  4. #14
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    Quote Originally Posted by fifty60 View Post
    Intrinsic Safety is a protection method for Class I Div 1 locations. It works for Class I Div 2 locations as well, but so does being nonincendive to begin with. There are some hoops to jump before you can decide a component non-incendive, but it is certainly better than having to go the whole 9 yards to make it IS with control drawings, etc. Voltage does not have anything to do with it. You could have a standard 480Y/277Vac 3 phase motor in a Class I Div 2 location, and that would be ok, but if you tried to put a 24VAC safety switch in the same space that would be forbidden without using some kind of protection method.

    I've seen a lot of time people use the English definition of "Intrinsically Safe", and not meaning the NFPA 70 definition of "Intrinsically Safe". That should definitely be avoided, but something to look out for when discussing this type of stuff with people.
    You are aware that nonincendive wiring also requires a control drawing, right? [Section 501.10(B)(3)] Ever since our colleagues at ISA became the US's representative to the IEC HAZLOC Committees, they have attempted to mangle hazardous locations a fair amount. Effectively, with the various NEC Informational Note (IN) references to ANSI/ISA-12.12.01-xxxx, Nonincendive Electrical Equipment for Use in Class I and II, Division 2, and Class III, Divisions I and 2 Hazardous (Classified) Locations, nonincendive isn't much more forgiving than IS.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  5. #15
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    My mistake in calling in confusing nonincendive with sections in 501 that allow for certain "Instruments" to use general purpose enclosures. I did not actually mean to refer to the protection method of nonincendive circuits, but I meant the allowance to use general purpose enclosures.

    For example, in a Class I Div 2 location, if I have an air solenoid valve bank that is driven via ethernet, I believe that section 501.105 of the 2017 NFPA 70 is saying that I can am permitted to use this instrument in its normal general purpose enclosure, as long as I follow the wiring methods for Class I Div 2.

    Is this correct? I am looking for the correct rationale to use standard general purpose equipment that that is not arcing or in any other way an ignition source for the Class I Div 2 location.
    Time is of the essence, and I am low on essence. ~ Graham Hill

  6. #16
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    Quote Originally Posted by fifty60 View Post
    My mistake in calling in confusing nonincendive with sections in 501 that allow for certain "Instruments" to use general purpose enclosures. I did not actually mean to refer to the protection method of nonincendive circuits, but I meant the allowance to use general purpose enclosures.

    For example, in a Class I Div 2 location, if I have an air solenoid valve bank that is driven via ethernet, I believe that section 501.105 of the 2017 NFPA 70 is saying that I can am permitted to use this instrument in its normal general purpose enclosure, as long as I follow the wiring methods for Class I Div 2.

    Is this correct? I am looking for the correct rationale to use standard general purpose equipment that that is not arcing or in any other way an ignition source for the Class I Div 2 location.
    That's correct; just don't confuse non - arcing, non-sparking, nor non-high temperature with nonincendive which is very narrowly defined. You should also review Section 500.8, especially Subsections 500.8(B), (C) and (D) thoroughly; but give the whole Section a good going over.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  7. #17
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    Thanks for the clarification. To use the ethernet driven solenoid valve bank example again, it does not have any arcing/sparking or other ignition sources. However, if it has a small fuse inside of it to protect the electronics, would this then make it unusable in a Class 1 Div 2 location? Most electronics are protected by internal/integral standard general purpose fuses, right? So that would make most electronic devices not usable in a Class I Div 2 location?
    Time is of the essence, and I am low on essence. ~ Graham Hill

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