Nonincendive Transmitter Outputs in a Class 1 Div. 2

[jstpie5]

I was hoping to find some clarity on the proper installation for a particular transmitter in a Class 1 Division 2 location.

The transmitter in question is a MicroMotion 2700R12DBAEZZZ. This transmitter requires a power source (which will be 24vdc) and intrinsically safe outputs. It is not connected to a process source (therefore no process seals required).

After looking at the datasheet (page 13 link) it appears that the device "provides nonincendive sensor outputs for use in Class I, Div. 2, Groups A, B, C, and D..." or intrinsically safe outputs for Class 1 Div 1 locations.

After reading NEC 501 until I have a headache, I am still a little unclear on how this device needs to be installed.

Field Wiring:
My thinking is that this device would be best categorized as a nonincendive device as defined by 500.2. As such it should be wired per 501.13 (B)(3) - Nonincendive field wiring. According to this article, I can use any of the wiring methods permitted for unclassified areas as long as it is consistent with the control drawing.

Are control drawings always this difficult to find? I have called the manufacturer and they said "All you should need to do for a class 1 div 2 is install a conduit seal and you are nonincendive." You are joking right?

Frustrated with this response and thinking that I was missing some key piece of understanding I accepted this explanation (temporarily). Because this didn't sit straight with me, I did another google search and found an installation manual that shows hazardous area mA output wiring (page 90 link).

Does this mean that I still need an ISB for the mA output even if I use nonincendive field wiring?

What about the power supply to the transmitter?
I couldn't find anything remotely close to a control drawing for that.

Lastly, once I get all that sorted out, do I need a conduit seal at the transmitter? My interpretation of 501.15(B) is that no conduit seal is required at the transmitter; only need one when leaving the Class1 Div.2 location.

Thanks for all the help.

 

[rbalex]

It has gotten to where the first question I ask when someone starts talking intrinsically safe or nonincendive is, "Do you have a control drawing?" You did very well in asking the question yourself. FWIW, in my opinion, Emerson owes you a control drawing. Technically, without a control drawing, you don't have nonincendive field wiring. [I think you meant to reference Section 501.10(B)(3)]

Sealing could be a problem depending on the actual wiring method. I'm personally inclined to endorse your "final" interpretation; i.e., no seal at the transmitter, but one at the boundary. However, since it appears you are using a cable in conduit wiring method, consider Section 501.15(E) with regard to cable seals; especially cables in conduits as referenced in Section 501.15(E)(1) because it then references back to Section 501.15(D) as if the wiring originated in a Division 1 location.

 

[jstpie5]

Bob,

You are correct - I meant to reference article 501.10.

Thanks for the response. At least I'm not (totally) crazy.

That last sentence of Article 501.15(E)(1) "Multiconductor or optical multifiber cables installed in conduit shall be sealed as described in 501.15(D)" is sneaky.

Definitely didn't catch that the first time.

As I expected, it still seems like a fair amount depends on this control drawing.

Thanks again for the assistance.

 

[jstpie5]

Found the control drawing online, I think.

Just to close this post for anyone else that might have this issue in the future (or me if I forget):

The control drawing attached ( View attachment 2700R Control Drawing.pdf ) shows that when installed in a Class 1 Div 2 location, this device is a non-incendive component (I am accepting this even though the NEC only defines nonincendive, but I'm sure that's hair splitting).

There is also a warning that a listed XP cable seal or conduit seals must be installed within 2 inches of the wiring compartment enclosure.

As a result, I will be using a 4 pair 18 AWG twisted shielded ITC cable with conduit seals at the boundaries and an XP cable seal at the instrument.

Feel free to point out any error or incorrect assumptions.

 

[rbalex]

Looks ok to me; however, somewhere in ANSI/ISA-12.12.01 I believe the document should actually say it is a control drawing. I’m retired now and no longer have access to the ISA Standards, but they are actually “auxiliary” to the NEC and should be referenced for intrinsically safe and nonincendive applications.

You should also reread Sections 501.15 (D) and (E) carefully to be comfortable that you don’t need to separate the shielded conductors in the enclosure seal and you won’t need to “open” the jacket at the boundary. (Personally, I don’t believe you need the enclosure seal for this particular installation in Class I, Division 2, in the first place - but that’s just me.)

Note Section 501.15(B)(2) won’t require the boundary seal to be explosionproof.