Ethernet cabling in Class I Division 2 locations.

[CFrick]

OK, I'm up n the Bakken again and my client is trying to run Ethernet IP from a GP Electrical Module via cable tray to various Class I Division 2 modules. Their prefered wiring method has been MC-HL cables for power and control. Labor rates are high in the Bakken and schedule time is a premium, so RMC is not their preference. Sealing is handled with TMCX fittings where required. Even the 480 volt cables in the same tray as the lower voltage control and signal cables w/o dividers should be fine since Everything is in armored cables hense effectively their own conduits.


OK so far so good. Now we come to Ethernet I/P communications for the control system:

Per NEC 501.10 (B), I can use RMC, MC/MC-HL, ITC/ITC-HL, PLTC/PLTC-ER and TC/TC-ER as wiring methods. Seems easy right? Lots of choices besides RMC. Div 2 does not need continuous armor so just pick an interlocked armored "MC Ethernet cable" right? Yeah, By NEC 330.1 definition, MC cable must be 18 AWG or larger. Hmm well that's why i can't find a 22 or 24 AWG "MC Ethernet cable". hunh.... Well there are some MC looking cables the Belden 121700R seems nice, but since it is a communication cable it is labeled as type CM and is not suitable for Class I Division 2 unless i put it in RMC per 501.10 (B). At least in the US. (It actually looks as if it might be approved for the application if I was an hour North in Canada because it has a CEC: CMG, HL rating. This is assuming that in Canadian the HL still means Hazardous Location and not "Harsh Location". Does anyone know that by the way. I am curious.) Belden does have an unarmored, unshielded Ethernet cable that is labeled PLTC that I could use but I wuld still have to run it in conduit to get from the Roxtec wall penetration to the control cabinet for support and physical protection.

Any way it looks like my only approved method here is to lay CM or PLTC in the tray and install conduit in the hazardous location buildings (This would be all new and a retrofit of well over a hundred existing ones). Unless one of my colleges here has another recomendation.

Thank you for your consideration of my post.

 

[rbalex]

Ever since the ISA/control systems/telecom crew started convincing the CMPs that the ultimate purpose of various "low power" Articles was to protect their signals rather than to reduce fire/shock hazards, this has become a difficult issue to deal with.

Article 727 (ITC) was added in 1999 to get on the "other side" of Article 725. Unfortunately, its Scope was handed to CMP16, which also controlled 725. The infighting got so bad that the "old" CMP16 was dissolved between the 2002 and 2005 and its various scopes were handed off to other CMPs. Articles 725 and 727 went to CMP3. There was great rejoicing among those of us that understood a 2" separation was about all that was needed to actually to protect most signals - even unshielded/untwisted. (That is still essentially recognized in the main text of Section 725.136(I).)

NOTE: it wasn't until 2002 where "compatible barriers" were required in cable trays. The Proposal gave no technical basis for it - it just sounded like a good idea to CMP16. The fact is a "compatible barrier" would make no difference unless it completely enclosed either the power or the signal circuits.​

Unfortunately, the damage was done and CMP3 rejected all Proposals to remove the requirement for cable trays - for lack of technical substantiation for something that had no technical substantiation for being required in the first place.

You have now had your history lesson. That said, you have already basically outlined your options although you may want to consider an ITC-ER if it's available and an Article 727 installation. Some PLTC-ERs are dual rated. Note: neither Section 500.15(B)(1)(4) nor its reference to Section 727.4 requires raceway installation.

Side thought: You probably don't need the bulkhead barrier (Roxtec) unless it's necessary for maintaining a fire rating, but it does make a neat installation.