Understanding the NEC Rules for
Backup Power Systems 2008 Edition – Part 4 of 4
We at Mike Holt Enterprises try to provide as much as we can to the industry at no charge. For this reason we’ve created a free Understanding the NEC Rules for Backup Power Systems textbook. The material in this textbook was extracted from Mike's Understanding the 2008 NEC, Volume 1 textbook.
Because of the size of the textbook we’ve decided to make it available in four parts. Over the last 3 months we sent Parts 1 - 3, and now here is the final Part 4.
Scope of Part 1 of 4 - Articles 90 and 110
Scope of Part 2 of 4 - Articles 220, 230 and 240
Scope of Part 3 of 4 – Article 250
Scope of Part 4 of 4 - Articles 300, 310, 312, 408, 700, 701, 702
Click here or on the image above to download Part 4 (7.32 MB), but be advised that this may take a few minutes to download depending on your internet connection speed. If you encounter a problem opening this file, be sure you have the latest version of Adobe Acrobat installed on your system (click here).
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I have a ponderance to back-up power. Should the grounded conductor be connected to the grounding conductor at the generator and the first means of disconnect(Panel). 120-208 1phase with two wire disconnect main breaker. I am working in Iraq where the neutral is disconnected.
Reply from: Mike Holt
My answer is based on the following conditions (Iraq): The generator supplies power to the building without any utility service, meaning no transfer switch is needed/provided.
Answer: The neutral conductor must be connected to the metal frame of the generator (system bonding jumper-250.2) and not the metal frame at the panel [250.24(A)(5)], since the generator has a main breaker. Doing so would create a parallel path for neutral current violation of 250.6.
You must have an equipment grounding conductor between the generator metal frame and the metal frame of the panelboard in accordance with 250.4(A)(4) and 250.118. This conductor serves as the low impedance path necessary to clear a ground fault on the premises.
Reply to Mike Holt
Long time subscriber to Mike's excellent newsletter. I just had to comment on the irony of getting his latest e-mail (and generously making his backup power materials avaialbe for free) as I sit here in dark waiting for the transformer down the street to be replaced...
Anyway Mike, thanks for all you do!
Reply from: David Engelhart
Classic!
Reply to David Engelhart