Class I, Division II Field Wiring

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scottmarston

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Meridian, ID
I’m trying to familiarize myself with the installation of Instruments and the field wiring rules required from my enclosure to the instruments in a Class I, Division II application. I will be running wires from a non-classified area to a Class I, Division II area. My I/O cards are 24VDC, Allen Bradley and are rated to be installed into a Class I, Division II environment. I have analog inputs, analog outputs, 24VDC inputs, 24VDC outputs and RTDs. Here’s my question:

If my instruments are rated for Class I, Division II and my I/O cards are rated for Class I, Division II, is the wiring between them considered Class I, Division II by proxy, if sized correctly (the plant requires a minimum of 16AWG)? If they are both rated for Class I, Division II, wouldn’t that make them a non-incendiary device for that area and by proxy, the field wiring between them would be non-incendive? I would just have to have a seal in the conduit leaving the control panel in the non-classified area out into the classified area and the rest is golden, right?
 
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rbalex

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Location
Mission Viejo, CA
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Professional Electrical Engineer
...
If my instruments are rated for Class I, Division II and my I/O cards are rated for Class I, Division II, is the wiring between them considered Class I, Division II by proxy, if sized correctly (the plant requires a minimum of 16AWG)?
They are most likely acceptable, but not necessarily. They must still use wiring methods listed in Section 501.10(B).

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If they are both rated for Class I, Division II, wouldn?t that make them a non-incendiary device for that area and by proxy, the field wiring between them would be non-incendive? I would just have to have a seal in the conduit leaving the control panel in the non-classified area out into the classified area and the rest is golden, right?
They are not nonincendive by default. They may be but there are MANY rules for nonincendive systems. Most important: the power supplies must be specifically identified as nonincendive and the circuits must be installed per a control drawing supplied by the manufacturer [See 501.10(B)(3)] A boundary seal will be necessary, an enclosure seal will depend on the interior of the enclosure.
 

rbalex

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Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
Thanks for the help. To clarify, the instrument I was looking at was Class I, Division II, Non-Incindive. Do I need to use intrinsically safe barriers?
You will need to install it per the control drawing which will indicate if barriers are necessary.

You must have a control drawing to install per 501.10(B)(3). See the definition of in Section 500.2. You cannot install nonincendive or intrinsically safe systems without a control drawing provided by the manufacturer. You may, in fact, need several manufacturer's control drawings depending on the complexity of the system.
 

scottmarston

Member
Location
Meridian, ID
You will need to install it per the control drawing which will indicate if barriers are necessary.

You must have a control drawing to install per 501.10(B)(3). See the definition of in Section 500.2. You cannot install nonincendive or intrinsically safe systems without a control drawing provided by the manufacturer. You may, in fact, need several manufacturer's control drawings depending on the complexity of the system.

Got it. Thanks.
 
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