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THHN conductor sizing & Meter base grounding

Question asked by Chester rmstrong on May 25, 2018
Latest reply on May 31, 2018 by Nick Sasso

Greetings, my question deals with a Sub feed conductor sizing and also meter base grounding requirements.

I am a first year licensed Electrical Journeyman and am working in the Heavy Industrial field under my companies Renewable energy group. Specializing in Solar facilities. One of our smaller newly constructed facilities (96Mw DC) has very minimal O&M building requirements due to off site SCADA monitoring. Basically, the building is air condition office trailer with a pre installed 100A Panel. I have been tasked to set up the permanent power for this building. Unfortunately the customer down graded this building. 3 times now, from what was originally planned and thought to be either 150A or 125A requirement. I installed the 200A Meter which is a BT thus allowing me to Sub feed off a 100A breaker at the meter. My question about the conductor sizing is: I had planned on running 3-3-3 w/G THHN copper in PVC a span of 45' from Meter to service entrance. Now, I've learned to lean on the resources within my company. In this case verification. A second set of eyes never hurts. During a phone conversation with one of my most trusted mentors and now colleague. He was insistent that I use #1 instead of #3 and I cannot understand why. Have I missed something that would call for the up sizing of this wire? Temp is not a factor nor is V-Drop. I wonder if is simply miscommunication on my part. The whole installation is quite simple. Or am I under thinking this and have not considered all factors? Out of pride when Inspected I want it to be perfect. Which leads to my second question. According to a local Electrician, the grounding conductor installed #6 SOL coming off a 10' ground rod may not meet the service providers requirements. according to the local, a #4 is "preferred". (would have been nice to know a month ago) To the best of my knowledge #6 is up to code. My question is if the NEC is the national standard, do providers have a legally enforceable right to raise those standards at their discretion? Not that it matters. If the tell me to change it I absolutely will. Just curios.

Sorry so long winded. I am a new member here and feel the Xchange can and will be a useful tool in my career development.

Thank you

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