Evaluating a C1D2 installation

Status
Not open for further replies.
B

bwrams

Member
Location
South Carolina
Occupation
Engineer
First, sorry for the long post!

I am a novice to hazardous area installations but have been tasked with assisting a team that is evaluating a contractor's design for a C1D2 installation. I've read NEC500, 501, & 504 and ANSI/ISA 12.12.01 but am having difficulty addressing some outstanding questions I have. Before I engage with this contractor and team, I would like to minimize my knowledge deficiencies in this area. The summary of the installation and my outstanding questions are below. If anyone can help answer these or even better, point me toward documentation / standards that would address these topics, I would be grateful.

Control Panel will be installed in a non-hazardous area. Basic panel design is Allen Bradley CompactLogix IO with all 24VDC powered IO (analog and discrete). There are no IS barriers in this panel design. The Power supply and CompactLogix IO are listed as suitable for installation in C1D2 area (but again panel is in the non-hazardous area). The panel design is not distinguishable from any general purpose PLC panel.

The field hardware is a mix of pressure/temperature transmitters, actuated valves, flowmeters, and level switches.
The transmitters are rated C1D1 explosion proof, as well as have IS and nonincendive ratings.
The flowmeters are rated C1D1 explosion proof.
The valves (solenoids and position switches) are rated as C1D2 (not certain if they are listed as nonincendive).
The level switches are rated as C1D2.

The contractor has specified PLTC for most of the connections between the field hardware and the control panel. And they have noted that seals are required.

I have been able to locate control drawings for some of the field hardware and for some, I have only been able to locate manufacture's installation instructions.

My difficulty is determining whether the contractor has provided a design that meets all NEC installation requirements and incorporates the necessary panel design requirements for the associated field hardware (and their corresponding C1D1 or C1D2 ratings). I think it can be further stated that my misunderstandings are rooted in my lack of knowledge with the protection methods (Explosion Proof, IS, nonincendive, etc.) and when they can and cannot be applied.

My questions are as follows (and they are overlapping and probably somewhat redundant/repetitive)
1) If the Field Hardware is rated for C1D2 or C1D1 and installed in a C1D2 area, AND the conduit/cabling meets the requirements of 501.10(A) or 501.10(B)(1)&(2), does the design of the control panel in the non-hazardous area even matter? In other words, the field hardware meets the area rating, the wire/conduit is correctly installed, therefore the control panel is irrelevant?!?
2) Are the Control Drawings to be adhered to for the field hardware even if the conduit/cabling meets 501.10(A) or 501.10(B)(1)&(2)? For example, the pressure transmitter control drawing states for C1D1 installation and connection to a non-hazardous location, an associated equipment (IS barrier?) must be installed between the transmitter and the control equipment and must have certain parameters for Uo, Io, and Po. The control drawing further states the associated equipment (IS barrier) can be eliminated for C1D2 installation but a different set of parameters for Uo, Io, and Po are provided for the Control Equipment the transmitter will be connected to. In other words, even with properly rated field hardware and correct wire/conduit installation, the control panel hardware selection matters?!
3) Since the control panel design uses C1D2 rated IO hardware and 24VDC power supply, is this potentially resulting in a design that adheres to the Control Drawings for the field instruments? I say potentially, because I assume I would need to get control drawings for all field hardware and compare the Uo, Io, and Po ratings to the PLC hardware ratings to confirm?
4) Since the control panel design uses C1D2 rated IO hardware and 24VDC power supply AND the field hardware is rated C1D1 or C1D2, are the Control Drawings irrelevant? Install the wire/conduit to 501.10(A) or 501.10(B)(1)&(2) and call it a day??

TLDR:
Can someone tell me where to find a document / standard / text book that explains control panel and installation design for a non-hazardous area located control panel connected to C1D2 area located instrumentation?
 
1) In and of itself, the control panel and it’s devices are not required to be Class I, Division 2 rated.
2) Technically, control drawings are not required except for intrinsically safe or nonincentive systems; however, depending on the systems involved, a control drawing might affect the devices in the control panel. That is, if you are using and intrinsically safe or non-incentive system you may need components inside the control panel that are consistent with the control drawing.
3) Not necessarily. Only if the systems are specifically intrinsically safe or nonincendive.
4) Maybe. Are the systems intended to be intrinsically safe or nonincentive?

UL 508A is the commonly accepted product standard; the NEC is the installation standard.
 
rbalex - Thank you so much for your reply. It is helpful.

After creating the post above, I continued scouring NEC and searching the internet for examples of this situation. I have drawn some conclusions that I am trying to trust but verify, and your answers seem to be confirming some of my conclusions. But what I'm still failing to understand is what the C1D2 rating for field hardware/instruments actually means for the install and panel design. So, I'll quickly try to explain the conclusions I have drawn and pose my question about C1D2 ratings.

Basically, NEC appears to be telling me there are three choices for designing and installing instruments in a C1D2 area and connecting to a control panel in a non-hazardous area:
1) Use Explosion Proof rated Instruments and install per 501.10(A). In this scenario there would be no special design requirements for the control panel. The panel could be designed and built to UL508A.
2) Use Intrinsically Safe rated Instruments and install per 501.10(A). In this scenario, the panel design would need to incorporate the entity parameter requirements of the Instrument Control Drawing.
3) Use Nonincendive rated instruments and install per 501.10(B)(3) (Nonincendive FIeld Wiring). In this scenario, the panel design would need to incorporate the entity parameter requirements of the Instrument Control Drawing.

So, assuming the three conclusions above are correct, I am unclear as to what a C1D2 rating actually means for an instrument and for the subsequent install and panel design. Does C1D2 rating for an instrument mean the device is nonincendive and bullet (3) above needs to be applied to the panel design and install? Or Does C1D2 rating for an instrument mean the device can be installed in a C1D2 area using the NEC techniques of 501.10(A) or 501.10(B)(1)&(2) and the panel design needs to adhere to UL508A? Or Does C1D2 rating for an instrument mean something else entirely? Is there another design and install method (other than the 3 I listed above) for using C1D2 rated field hardware connected to a nonhazardous control panel?

I wish there was a guideline/standard that specifically addressed C1D2 hardware connected to nonhazardous general purpose control panel. It seems all other possibilities are covered. UL698A takes care of C1D1 hardware connected to nonhazardous area control panel and UL1203 takes care of panels installed in C1D1 or C1D2 areas, but it seems my scenario is just not specifically addressed. Or I'm not interpreting these documents (NEC, UL508A, UL698A) correctly?

I am very familiar with UL508A and it's only reference to hazardous areas is directing the user to review UL698A and UL1203. For the system I've described (C1D2 connected to nonhazardous panel), it doesn't seem either of these two UL documents would apply (unless I wanted to dictate one of these standards to the contractor, but that would be overkill, right?). So, the three UL documents referenced are not helping clear things up in my little brain....
 
In the broadest sense, Class I, Division 2 equipment are those that meet the “(B) Subsection” requirements of Article 501, Part III Equipment (beginning in Section 501.100) there are many types of equipment that are described as suitable [500.8(A)] for Class I, Division 2. Also note they may not necessarily be required to be listed for Class I, Division 2. [See 500.8(C)(6)]

As discussed earlier, unless intrinsically safe or nonincentive systems are under consideration, field wiring may have no effect on the control panel. Further note that, while some of the components in the panel may be suitable for Class I, Division 2, it may not be required.
 
Mr. Bob, Thank you!

Reading Article 501, Part III with your comments in mind gave me the insight to understand this section much better than when I had previously read it.

Now having a better grasp of Explosion Proof, Intrinsically Safe Systems, and Nonincendive systems, plus a clearer picture of how to interpret 501, Part III, I feel much more prepared to engage with this contractor and ask questions about their field hardware selection and design methodology.

Thank you again for spending your time sharing a little knowledge with a novice! I do appreciate it!
 
Your contractor may not be used to that level of oversight. Some are good at working with the end customer and some are not.
 
Yes, definitely have to treat some of these guys with kid gloves sometimes. Part of the reason I wanted to improve my knowledge base before we have any review meetings. Seems to take the edge off of reviews sometimes if you're not going in completely ignorant of the subject matter.
 
Status
Not open for further replies.
Top