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Tuesday, July 3, 2018
Question:
We have a solar powered lighting pole and the conduit in its concrete pole foundation meant for running ground wire from earth rod to inside of pole is blocked. So, can we have this grounding bare tinned coated copper wire installed as exposed and connect it 50 cm above ground? The size of wire is 25mm square. Or should we run it through a pvc conduit for mechanical protection. This lighting pole is located in the middle of road for road lighting.
Khider Alam
A
Answer:
Hey Khider thanks for your question. Using NEC Table 8 in Chapter 9, the 25 mm2 conductor is larger than 4 AWG but slightly smaller than 3 AWG. Grounding Electrode Conductors 6 AWG and larger can be run along a surface if not exposed to physical damage as stated in 250.64(B)(1). If exposed to physical damage they must be protected as stated in 250.64(B)(2) - which includes rigid polyvinyl chloride conduit (PVC). PVC conduit that is exposed to physical damage must be identified for that use (Schedule 80) as stated in 352.10(F) and explained in the Informational Note.
The pole you describe is probably located in a median between roads because if it was in the middle of the road we have much bigger problems. Grass covered medians are often mowed using large mowing equipment which can be a physical damage concern. If spraying for weed control or other reasons is also done there might be a concern about corrosion. The entity responsible for the roadway might also have additional requirements.
So it seems given all the possible conditions that could exist using Schedule 80 PVC conduit as a minimum would be prudent. It is a judgement decision by the AHJ if a different wiring method, or other means of providing physical protection is necessary.