Grounding and Bonding requirement C1D2 30VDC systems

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Hwill

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I have a quick question regarding bonding requirements in C1D2 locations where the source is a simple TEG or solar powered system. The application is a an RTU powered by a TEG or PV system outputting no more than 30VDC. RGS is ran from RTU to switch on top of a valve actuator that sits on a pipe (pipeline). The pipeline is CP protected, so typically we isolate the conduit with a phenolic coupling just before it terminates into the switch box on the pipe. Art 250.100 was brought to my attention as to why the phenolic would not be appropriate. Does art 250.100 apply in this case, given conductors are not being supplied by a service, and there is very limited risk in the non-current carrying metallics becoming energized?
Thanks.
 
See 501.30 (2014) which says the grounding requirements of 250 apply regardless of voltage of electrical system.
 
Thanks for your reply, but I'm still a bit unclear. If there is very limited or no risk of metallic parts becoming energized (due to the 2 wire less than 30VDC system), why ground, and therefore, why bond? Grounding/bonding is bit of a fuzzy area for me, so any insight you can provide would be great. Further, 250.100 refers to 250.92 which refers to service grounding/bonding, perhaps this is not literal, but since there is no neutral or return fault path on the 2 wire system (or is there???) then does this still apply?:?
 
nhee2 said:
See 501.30 (2014) which says the grounding requirements of 250 apply regardless of voltage of electrical system.
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Grounding and bonding is a bit of a fuzzy area for me, but the impression I get is that the risk of non-current carrying metallic parts being energized in a fault event is the biggest reason for grounding and bonding. Given that the source is a 27VDC TEG/battery 2 wire system, I technically do not even need to ground it (though I am putting a ground rod at the RTU for noise mitigation), and therefore not bond. If I'm not grounding, I shouldn't be bonding, then I'd suspect 250.100 would not apply, correct?
Further 250.100 refers to 250.92 (B) which refers to services, since there is no neutral here what would be the cause/risk of sparking?:?
 
Hwill said:
Thanks for your reply, but I'm still a bit unclear. If there is very limited or no risk of metallic parts becoming energized (due to the 2 wire less than 30VDC system), why ground, and therefore, why bond? Grounding/bonding is bit of a fuzzy area for me, so any insight you can provide would be great. Further, 250.100 refers to 250.92 which refers to service grounding/bonding, perhaps this is not literal, but since there is no neutral or return fault path on the 2 wire system (or is there???) then does this still apply?:?
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how does the voltage affect the risk of metal parts becoming energized?
 
Hwill said:
If voltage doesn't affect the risk of metal parts becoming energized, why does the NEC take exception to DC systems under 60V, and not necessarily requiring grounding at all?
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Before I comment further, I want to make sure we are talking about the same thing.

Grounding = electrical connection to earth.

This has nothing whatsoever to do with the risk of metal parts becoming energized.
 
250.4(B) provides the general requirements for grounding and bonding of ungrounded systems. Since 501.30 references all of 250 (not specifically 250.100), 250.4(B) would apply.
 
nhee2 said:
250.4(B) provides the general requirements for grounding and bonding of ungrounded systems. Since 501.30 references all of 250 (not specifically 250.100), 250.4(B) would apply.
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I agree that earthing, or grounding, in the case of 250.4(B) for the purpose of lightning protection (I suppose?) has nothing to do with becoming energized, but bonding does.
250.4(B)(3)states:Electrically conductive materials likely to become energized shall be connected together in a low impedance path for ground fault...
My point is with a 2wire dc system doesn't seem like much of a fault, if any to consider; therefore, metallic structures not likely to become energized.

My original question is basically if I need to observe the bonding requirements of the conduit running from the low voltage RTU to a hermetically sealed switch on a CP protected pipeline, in a C1D2 area? SSD or PCR seems like overkill, since there no AC grounding system.
 
It may seem like overkill but all wiring methods in classified locations including nonincentive and intrinsically safe must meet the requirements of Section 501.30.
 
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