4-20ma conduit Requirements in CL1 DIV1 Area

[cizzle21p]

We are installing 4-20ma Current gage for a motor that is in a CL1 DIV1 area due to high grain dust and explosion concerns. There are no conduits that go directly from the motor leads to the operator control station for the motor where we will be installing the gage. Can we use EMT to run the 18/3 signal wire from the motor to the local operator station? Or do we have to use rigid conduit?

Any help, guidance or reference material from the NEC would be greatly appreciated! thanks

 

[renosteinke]

I believe you'll be fine with EMT.

Hazardous location equipment is tested under circumstances that do their best to create ignition. In the case of dust-ignition, the primary factor is whether anything gets hot enough to ignite the dust. They literally bury the stuff in the appropriate dust, then try to get it to light.

Or, more often, bury stuff under their 'test' dust and monitor temperatures. If nothing gets hot enough, you're good to go.

I have trouble imagining any circumstance where any part of your circuit can get hot enough to be a worry.

 

[rbalex]

First, I would check the Class. If grain is the volatile material in question, then I doubt it will be Class I (Gases/Vapors). It is more likely to be Class II (Dusts), Group G.

Second, EMT is not a recognized wiring method in either Class I or II unless it is part of an intrinsically safe or nonincendive system. See Section 501.10 and 502.10 (Read ALL of it)

NOTE: Sealing requirements for enclosures in either Class are not altered by the wiring methods, but the wiring method may alter the type of seal necessary.

 

[Smart $]

We are installing 4-20ma Current gage for a motor that is in a CL1 DIV1 area due to high grain dust and explosion concerns. There are no conduits that go directly from the motor leads to the operator control station for the motor where we will be installing the gage. Can we use EMT to run the 18/3 signal wire from the motor to the local operator station? Or do we have to use rigid conduit?

Any help, guidance or reference material from the NEC would be greatly appreciated! thanks

Is it just combustible [grain] dust, or are there also "ignitible concentrations of flammable gases, flammable liquid–produced vapors, or combustible liquid–produced vapors". If just the former, it would be a Class II location.

In Class I and II, Division 1, and Class I Division 2, EMT is not a permitted wiring method... unless it is a non-incendive or intrinsically safe circuit.

EMT is a permitted wiring method in Class II Division 2 locations.

(I see 'Bob" beat me to it... but he missed what I wrote in my last sentence [prior to this one])

 

[renosteinke]

I agree, Smart $. I had passed over the "Class 1" part, and latched onto the "dust" part of the description.

As posted, I can't answer the question.

 

[cizzle21p]

CLASS II DIV I

CLASS II DIV I

After further research I found the area to actually be a CLASS II DIV I location. So I either run rigid or use MI or MC-HL cable. Thanks for the NEC reference, I will be sure to tab this section in my copy of the NEC.

 

[Smart $]

After further research I found the area to actually be a CLASS II DIV I location. So I either run rigid or use MI or MC-HL cable. Thanks for the NEC reference, I will be sure to tab this section in my copy of the NEC.

If any part of this gage is supported by the motor itself, don't forget that flexible connections are also permitted. See 502.10(A)(2).