C1,Div2,Group B,C,D T3 with Ex-d

[cdcabrera]

I have a customer mixing and matching NEC and IEC and the sales guy agreed to the technical clarifications that support this conflict. Everything I have read in the code book, checked with vendors, and such indicates I am about to open a can of worms and want to be prepared as possible.

C1, D2, Gr B, T3 is the area classification that I was given for the project. Customer has opted for IS wiring, my responsibility is to get signals to the edge of the my package in a JB, so they are handling all the hard work.

JB just has TBs in it, so simple devices.

The local control panel will have PL, PB, HOA, HMI, ethernet switch, and power supplies will be purged, so I don't believe additional the a

I got my Panel Layout drawings back with the comment
"Ensure JB is complying with Nema 4x and C1,Div2,Group B,C,D T3 with Ex-d"

Based on 504.10(C) the JB does not need additional safety ratings since there are simple devices. 500.7(D) solves the problem for the LCP.

Is there something I am missing in my considerations? If i am going to to NEC and explosion proof then I get to step up to NEMA 7 enclosure which I am trying to do.

 

[rbalex]

Folks that "opt" for IS or NI generally have no idea what they are doing. The first thing to ask is, "Where is the 'control drawing'?" This is a requirement for either wiring method. See Sections 504.10(A) and 501.10(B)(3).

"Mixing and matching" NEC Divisions and NEC Zones equipment is possible under limited conditions [See Sections 501.5 and 505.9(C)(1)] but "mixing and matching" NEC and IEC equipment is a no-no. No US domestic jurisdiction (especially FedOSHA) recognizes IEC equipment legally. A few may accept it from ignorance. Also, see NEC Zone labeling requirements in See Section 505.9(C) and 505.9(C)(2), especially 505.9(C)(2)(3).

Mixing and matching NEC Divisions and NEC Zones electrical area classifications is also extremely limited. See Section 505.7. Read the whole thing carefully several times.

The panel comment is essentially a nonsequitur, i.e., you can't get there from the requirements.

The real question that should be asked is, "What are the components inside the JB suited for?" - then select an appropriate enclosure.

 

[petersonra]

I got my Panel Layout drawings back with the comment
"Ensure JB is complying with Nema 4x and C1,Div2,Group B,C,D T3 with Ex-d"

I think EX-d is IEC flame proof, something more or less akin to explosion proof in the US, but I don't know how that relates to it being intrinsically safe or neema 4X.

 

[tortuga]

rbalex: not to nit pick as I 99.99999% agree
except with:

No US domestic jurisdiction (especially FedOSHA) recognizes IEC equipment legally.

But I am open to examples.
I find in specialized manufacturing processes that tend to be international the current has shifted to favor international standards.

 

[rbalex]

I think EX-d is IEC flame proof, something more or less akin to explosion proof in the US, but I don't know how that relates to it being intrinsically safe or neema 4X.

Yeah - that’s why it’s a nonsequitur.

 

[rbalex]

…
But I am open to examples …

BTW - I don’t consider this ‘nitpicking’ as it could be a case for Section 500.8(A)(3). The problem is AHJs have very little (usually no) design responsibility but nevertheless they are extremely cautious when approaching a design they aren’t familiar with. I have laid my professional reputation on the line several times in my career to secure the best outcome for a client. But the proposed OP design as I understand it? - I wouldn’t. As I said, tell me what you’re putting in the enclosure and I will tell you what enclosure to use.

 

[cdcabrera]

The real question that should be asked is, "What are the components inside the JB suited for?" - then select an appropriate enclosure.

JB
- BN proximity transmitters, labeled and rated for Class 1, Division 2
- TBs for skid mounted instrumentation

UCP - getting a Z-Purge derating the inside of the enclosure to non-hazardous
- power supplies, breakers, ethernet switch
- AB HMI, PB, PL, and HOAs on the door all rated for Class 1, Division 2

I think EX-d is IEC flame proof, something more or less akin to explosion proof in the US, but I don't know how that relates to it being intrinsically safe or neema 4X.

And that is the rub. This is for a hydrogen gas compression system, so I think they are applying the IS to minimize the energy potential on the skid as a way to increase safety. The 4X is sealed from dust, water, etc with a material selected to be corrosive resistant which is fairly standard for what we do. If they want to push the Ex-d rating, that changes everything making it in essence a Class 1, Division 1 installation if i understand things correctly.

 

[rbalex]

… If they want to push the Ex-d rating, that changes everything making it in essence a Class 1, Division 1 installation if i understand things correctly.

Not quite; see Section 500.8(B)(2). With a few (often no) minor “adjustments”, Division 1 equipment is perfectly acceptable in Division 2. Of course, no matter how modified, a Type 4X enclosure would neither be explosionproof nor “AEx d”.

I would still want to see a control drawing AND press the fact that the desired design has gone way beyond “belt and suspenders” and is rapidly approaching baling wire as well.

I would note “Ex d” equipment does not meet the marking requirements of Section 505.9(C)(2)(3).

Of course, your client can have whatever he pays for as long as it is safe and otherwise meats statutory requirements.

 

[cdcabrera]

Did some more studying today and think that 504.10(C) is the key and now makes clear on why Bob keeps pushing the control drawing. If the control drawing lists the JB contents as simple (Based on surface temp in Table 504.10(D), then the discussion is essentially over on the addition requirements. Addition 501.10(B)(4) also helps with the explosion proof rating.

I will have to do some more digging on the difference between NI and IS but I have more confidence in pushing back that the requirements are not needed.