Wrenches:
Here is a question that has bothered me for some time: If one is using a GFD (ground fault detection) breaker on a PV feeder(s) to a battery inverter system, the state of the industry is to use a breaker with an extra 0.5 or 1 amp pole. This section of the breaker connects, or bonds the DC negative, or grounded conductor, to the grounding system. In order for the GFD breaker to work one needs to isolate the grounded bus bar (negative). If there is a ground fault the breaker opens and breaks the bond. This goes very much against my conceptualization of how a bonding system should work. The bond should never be broken, particularly when there is a fault in the system. When this breaker opens, either manually or by an overcurrent condition on any pole, the DC bond is removed for all portions of the DC system. There is a prominent personality in the industry that often presents academic opinions on solar related electrical issues in articles and in seminars. This person claimed to have invented this GFD system, but when pressed to comment on the concerns mentioned above, changed the subject. I believe ground fault protection is important. I just don’t believe the method the industry has offered is really effective in solving the issues presented in a ground fault scenario. I believe similar issues present on non-battery PV systems with the simple fuse in the ground system found on many inverters. I know some troubleshooting guides warn of energized parts in ground fault conditions. Have any of you thought about these concerns? Are my concerns valid? What are your policies on this subject? Thanks in advance for any insight. William Miller Miller Solar 17395 Oak Road, Atascadero, CA 93422 805-438-5600 www.millersolar.com CA Lic. 773985 Quote of the month: “As they age, batteries transition from energy storage devices to energy consuming devices.“ W. Miller
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