C1D2 for R&D LPG Engine Testing

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dont_blow_up

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mechanical engineer
Hello all. I really love this forum and have anonymously used it for years, but this is my first post. Go easy on me since I'm just a mechanical engineer who happens to also do electrical stuff sometimes.

Scenario 1 (fixed equipment):

I have a C1D2 classified area, which is an entire room in the building. In the C1D2 area, there is various process control equipment (sensors, solenoids, etc.) that all gets controlled with a PLC. The room is basically a weird LPG engine test chamber. I'd like to get confirmation of my understanding of the NEC as it relates to the low voltage control field wiring.

Options for field wiring:
  • Use ex proof process control equipment -> conduit run out to the non-classified area with conduit seals -> wire into the PLC enclosure in the non-hazardous area (I believe this meets NEC requirements)
  • Use ex proof process control equipment -> conduit run to an ex proof junction box inside the classified area -> listed connectors in the classified area -> PLTC-ER cable route from the connector in the hazardous area to the non-hazardous area -> wire into the PLC enclosure in the non-hazardous area (I believe this meets NEC requirements)
    • Option 1 for passing through the wall between the C1D2 and non-haz locations: route the PLTC-ER in conduit with a seal through the wall (I believe this meets NEC requirements)
    • Option 2 for passing through the wall between the C1D2 and non-haz locations: route the PLTC-ER through a fire rated passthrough through the wall
      • The gas cannot be transmitted through the cable and into the PLC enclosure because of the listed connectors, so I believe this meets NEC requirements; however, it also means that there is a way for gas to leave the room, in general. I believe this would (or could) result in a small classified area outside of the room per NFPA 497. The AHJ signed off on this, FWIW, and I would like to get some feedback here.
  • Use nonincendive process control equipment in the classified area -> any wiring method to PLC -> wire into the PLC enclosure (I believe this meets NEC requirements)
    • This assumes the wiring is done per the control drawings of the PLC hardware and the nonincendive field device, of course
    • Similar options for the passthrough in the wall as stated above
  • Intrinsically safe stuff (not used, but I understand that this is also an option along with purged enclosures and ex proof boxes)
I'm just looking for confirmation of my understanding here. Also I'd be curious if anyone has other ideas on how to do the wiring. Since the test setup changes almost weekly, re-running conduit all the time isn't really an option here, which is why I opted for the listed connectors so that I can swap the control system around as needed.

Scenario 2 (temporary equipment, LPG engine):
The other scenario is the LPG engine that is being tested in the room. It is not rated nor listed in any way, and it never will be since it's all R&D. I need to get something like 100A at 24VDC to this engine to crank it over, and I'm not sure how to do it. So far, I have the DC power supplies located outside of the C1D2 area, and I have massive 24V cables and many smaller data cables running through that fire proof passthrough to the equipment. I would like to have something more permanent, but I don't know how to achieve this since the test equipment is not rated for the area. Any ideas?
 
There are a few misconceptions, so I’m going to deal with Scenario 2 first: See Section 590.2(A). “Temporary” means very little in Classified locations. Be sure to review Section 501.140 carefully.
 
My first question would be, “How was the room determined to be Class I, Division 2 in the first place?” There are several things that need to be addressed for enclosed spaces.
 
  • Use ex proof process control equipment -> conduit run out to the non-classified area with conduit seals -> wire into the PLC enclosure in the non-hazardous area (I believe this meets NEC requirements)
Yes, this is probably OK. Make sure you review Section 501.17 for process control equipment seals. Also review Sections 501.100 to 501.120 for some specifics on equipment.
 
  • Intrinsically safe stuff (not used, but I understand that this is also an option along with purged enclosures and ex proof boxes)
Sure, OK - it’s just not as easy as you may think.

EDIT ADD: General Comment: IS is far more complicated than just installing per a control drawing. That’s why it has its own Article (504).
Purged/pressure even has its own Standard (NFPA 496)
 
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  • Use ex proof process control equipment -> conduit run to an ex proof junction box inside the classified area -> listed connectors in the classified area -> PLTC-ER cable route from the connector in the hazardous area to the non-hazardous area -> wire into the PLC enclosure in the non-hazardous area (I believe this meets NEC requirements)
    • Option 1 for passing through the wall between the C1D2 and non-haz locations: route the PLTC-ER in conduit with a seal through the wall (I believe this meets NEC requirements)
    • Option 2 for passing through the wall between the C1D2 and non-haz locations: route the PLTC-ER through a fire rated passthrough through the wall
      • The gas cannot be transmitted through the cable and into the PLC enclosure because of the listed connectors, so I believe this meets NEC requirements; however, it also means that there is a way for gas to leave the room, in general. I believe this would (or could) result in a small classified area outside of the room per NFPA 497. The AHJ signed off on this, FWIW, and I would like to get some feedback here.
PLTC-ER good stuff, but listed connectors do not necessarily render the cable incapable of transmitting gases through the core. See Section 501.15(E) in general and 501.15(E)(3) specifically as it applies to PLTC-ER. NOTE: Section 501.15(E)(2) doesn’t apply to any cable except to MI and it has its own rules for installation.

The other options for sealing at the wall may or may not be necessary depending on reviewing the area classification envelopes and how they were determined; however, if they are necessary, they are fine.
 
rbalex said:
My first question would be, “How was the room determined to be Class I, Division 2 in the first place?” There are several things that need to be addressed for enclosed spaces.
Click to expand...
Mainly because the LPG is piped in there, used, and stored in that room. Yes, there are many other items that have been addressed because of this that are well covered in fire and building codes. I'm much more comfortable with those than the NEC.
 
rbalex said:
  • Intrinsically safe stuff (not used, but I understand that this is also an option along with purged enclosures and ex proof boxes)
Sure, OK - it’s just not as easy as you may think.

EDIT ADD: General Comment: IS is far more complicated than just installing per a control drawing. That’s why it has its own Article (504).
Purged/pressure even has its own Standard (NFPA 496)
Click to expand...
Agree. And that's why I didn't pursue IS equipment along with some other reasons on the control system design side of things.
 
rbalex said:
  • Use ex proof process control equipment -> conduit run to an ex proof junction box inside the classified area -> listed connectors in the classified area -> PLTC-ER cable route from the connector in the hazardous area to the non-hazardous area -> wire into the PLC enclosure in the non-hazardous area (I believe this meets NEC requirements)
    • Option 1 for passing through the wall between the C1D2 and non-haz locations: route the PLTC-ER in conduit with a seal through the wall (I believe this meets NEC requirements)
    • Option 2 for passing through the wall between the C1D2 and non-haz locations: route the PLTC-ER through a fire rated passthrough through the wall
      • The gas cannot be transmitted through the cable and into the PLC enclosure because of the listed connectors, so I believe this meets NEC requirements; however, it also means that there is a way for gas to leave the room, in general. I believe this would (or could) result in a small classified area outside of the room per NFPA 497. The AHJ signed off on this, FWIW, and I would like to get some feedback here.
PLTC-ER good stuff, but listed connectors do not necessarily render the cable incapable of transmitting gases through the core. See Section 501.15(E) in general and 501.15(E)(3) specifically as it applies to PLTC-ER. NOTE: Section 501.15(E)(2) doesn’t apply to any cable except to MI and it has its own rules for installation.

The other options for sealing at the wall may or may not be necessary depending on reviewing the area classification envelopes and how they were determined; however, if they are necessary, they are fine.
Click to expand...
Correct. For the specific ones I'm using, I have specific control drawings for them and how to wire them between classified and non classified areas. Maybe my terminology should have been more specific: they are more like a plug and receptacle. The receptacle is wired into the ex proof conduit to the field device, and the plug is wired to the PLTC-ER with proper hermetic seals.
 
dont_blow_up said:
Mainly because the LPG is piped in there, used, and stored in that room. Yes, there are many other items that have been addressed because of this that are well covered in fire and building codes. I'm much more comfortable with those than the NEC.
Click to expand...
Oddly enough, that particular description indicates to me that it may not be classified in the first place. Of course, I don’t know the full details so I’m not trying to classify it for you.
 
rbalex said:
Oddly enough, that particular description indicates to me that it may not be classified in the first place. Of course, I don’t know the full details so I’m not trying to classify it for you.
Click to expand...
Again oddly enough, if it weren’t unclassified, it would probably be Division I

Edit Add: If you classified the location, I would seriously consider reviewing NFPA 497.
 
rbalex said:
Again oddly enough, if it weren’t unclassified, it would probably be Division I

Edit Add: If you classified the location, I would seriously consider reviewing NFPA 497.
Click to expand...
Definitely div 2, not div 1. Not only was it our interpretation of the NFPA 497, but also the AHJ. Additionally, I've done many similar classifications based on NFPA 497 for other jurisdictions that look very similar to this particular setup. I'm quite confident about the classification here.
 
rbalex said:
There are a few misconceptions, so I’m going to deal with Scenario 2 first: See Section 590.2(A). “Temporary” means very little in Classified locations. Be sure to review Section 501.140 carefully.
Click to expand...
The idea is that I want to make it more permanent. I'm having trouble finding anything that can be installed permanently yet also support multiple engines coming in and out of the chamber on a regular cadence. And the fact that it needs a ridiculously high current at 24V.
 
dont_blow_up said:
Definitely div 2, not div 1. Not only was it our interpretation of the NFPA 497, but also the AHJ. Additionally, I've done many similar classifications based on NFPA 497 for other jurisdictions that look very similar to this particular setup. I'm quite confident about the classification here.
Click to expand...
As I said, I’m not trying to classify the location for you. I do not know enough about the installation. Most of my previous comments were based on assuming a Division 2 location.
 
dont_blow_up said:
The idea is that I want to make it more permanent. I'm having trouble finding anything that can be installed permanently yet also support multiple engines coming in and out of the chamber on a regular cadence. And the fact that it needs a ridiculously high current at 24V.
Click to expand...
This is why I suggested reviewing Section 501.140. It addresses using flexible cords in temporary applications.
 
dont_blow_up said:
But what if I can't comply with 501.140(B) because of the design of the engine?
Click to expand...
Please explain why the engine design would be prohibitive for connecting to the instrumentation through temporary cords. Remember, we can’t do your detail design either; especially when we don’t know the details of the installation.
 
rbalex said:
Please explain why the engine design would be prohibitive for connecting to the instrumentation through temporary cords. Remember, we can’t do your detail design either; especially when we don’t know the details of the installation.
Click to expand...
The way I read 501.140(A), it doesn't comply because the connections to the engine are not listed type connections, of course. On the test chamber side of the connection, I'm not sure what sort off connection to use. I'm having a hard time finding anything that would meet code. I'm also not sure how to meet 501.140(B)(2) as well. The engine has its own separate grounding connection that isn't part of the 24V power supply to it. It's unclear to my reading of it if that's acceptable per NEC. It's also unclear to me how to properly seal these connections or if it's even required. I don't want them potted because the different engines get their electrical harnesses swapped out regularly, so I can't really pot them through conduit and the cables can technically pass gas through the connection at the engine to the non classified space.
 
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