Thomas Underwood
Member
TanMike,
Myself, an electrical engineer since 1986 and my 70 year old electrical engineer veteran colleague have the following question about NEC Handbook Exhibits 250.14 and 250.15 for separately derived systems:
1. The two Exhibits for separately derived systems described the two available grounding and bonding methods depending on whether the grounding electrode connection is made at the source (the transformer) or the first disconnect. Do these figures only apply to a service entrance? What about downstream transformer and subpanels downstream of the main distribution panel?
2. It is assumed that NEC Exhibit 250.14 would be used in very rare situations because when is a service transformer ever going to be located right nest to building steel?
3. In the course of every electrical engineering design we have ever seen, neither Exhibit is ever used. Grounding to the electrode is done at the transformer and at the main distribution panel with the main disconnect. The ground wire is not connected between the transformer and the main distribution panel to keep unbalanced currents off of it that kill people. Electrical Engineers still submit their packages with this ground wire included because they still have not figured this out. This ground wire is not connected between the transformer and the main distribution panel I don't care if you got a delta wye separately derived transformer service, a wye-wye non separately derived transformer service, a center tapped or corner grounded Delta separately derived transformer service. You agree with this paragraph?
Thank You,
Tom from San Diego.
Myself, an electrical engineer since 1986 and my 70 year old electrical engineer veteran colleague have the following question about NEC Handbook Exhibits 250.14 and 250.15 for separately derived systems:
1. The two Exhibits for separately derived systems described the two available grounding and bonding methods depending on whether the grounding electrode connection is made at the source (the transformer) or the first disconnect. Do these figures only apply to a service entrance? What about downstream transformer and subpanels downstream of the main distribution panel?
2. It is assumed that NEC Exhibit 250.14 would be used in very rare situations because when is a service transformer ever going to be located right nest to building steel?
3. In the course of every electrical engineering design we have ever seen, neither Exhibit is ever used. Grounding to the electrode is done at the transformer and at the main distribution panel with the main disconnect. The ground wire is not connected between the transformer and the main distribution panel to keep unbalanced currents off of it that kill people. Electrical Engineers still submit their packages with this ground wire included because they still have not figured this out. This ground wire is not connected between the transformer and the main distribution panel I don't care if you got a delta wye separately derived transformer service, a wye-wye non separately derived transformer service, a center tapped or corner grounded Delta separately derived transformer service. You agree with this paragraph?
Thank You,
Tom from San Diego.