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Thread: Article 100: Intrinsically Safe wiring vs Nonincendive wiring

  1. #1
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    Article 100: Intrinsically Safe wiring vs Nonincendive wiring

    Are these essentially the same thing? Is one superior to the other in terms of arc/spark capability? I'm in a Class I, Division 2, Gp's C&D environment.
    Thanks in advance.

  2. #2
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    Quote Originally Posted by Dale001289 View Post
    Are these essentially the same thing? Is one superior to the other in terms of arc/spark capability? I'm in a Class I, Division 2, Gp's C&D environment.
    Thanks in advance.
    If you are asking about the wiring methods generally they are similar. IS requires some labeling and if you want to run multiple circuits in a single cable has some additional requirements.

    IS reduces the risk of an arc by limiting the energy available in the circuit to the point where no arc is possible. It can be used in both D1 and D2 areas.

    NI wiring is only available for D2 areas and reduces the risk of an arc by design choices but does not reduce the level of available energy to a limit where no arc is possible.

    I don't think either one is "superior" to the other. They are design choices.
    Bob

  3. #3
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    As petersonra said, for a Div 2 location, both can be used. So both can be treated the same in this situation.

    They are not quite identical. For example, "non-incendive" allows currents up to the ignition limit of the atmosphere; "intrinsically safe" only allows current up to 2/3 of the ignition limit.

    The reason is that non-incendive is only OK for Div 2 locations, where gas is not routinely present, and so lower risk. Intrinsically safe is allowed in Div 1 areas where gas is continually present, which is a much higher degree of risk. Hence, a safety factor is applied in Div 1 situations.

    They both do limit the available energy to prevent ignition, which is why the wiring methods are similar.

  4. #4
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    I think non-incendive circuits are some of the most misunderstood in Hazardous Area Design. To this day, I have never seen the protection technique used.
    Time is of the essence, and I am low on essence. ~ Graham Hill

  5. #5
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    Quote Originally Posted by fifty60 View Post
    I think non-incendive circuits are some of the most misunderstood in Hazardous Area Design. To this day, I have never seen the protection technique used.
    I have seen mostly portable electrical equipment where the UL file labels it as non-incendive.

  6. #6
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    Quote Originally Posted by fifty60 View Post
    I think non-incendive circuits are some of the most misunderstood in Hazardous Area Design. To this day, I have never seen the protection technique used.
    I don't think there is a 'technique" as such.

    It is a design choice where the equipment is designed under UL guidelines so the risk of creating a spark or high temperature that could ignite flammable gases is low enough that it is considered an acceptable risk. That's why standard relay contacts cannot be used. They might create a spark. Solid state outputs have no such issue.
    Bob

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