I want to start discussion concerning proper SDS grounding, specifically transformers. I hear a lot of different opinions from PE?s, electrical engineers, inspectors, and electricians about the proper terminating point for the GEC in step-down/isolation transformers.
The differences of opinion arise in the interpretation of 250.30 (A)(2) where it says except as permitted in 250.24(A)(4). Some say you can land the GEC on either the Xo terminal or ground bus in the transformer, or at the neutral or ground bus in the first disconnect.
I will stick my neck out first and say my interpretation is the GEC should be landed on the Xo terminal at the transformer, or on the neutral buss in the first disconnect. If the transformer is part of the ?service equipment? then the exception of 250.24(A)(4) would permit the GEC to terminate to either the Xo or ground bus provided the MBJ is a wire or bus-bar and is installed from the neutral bus to the equipment grounding terminal.
Don?t be shy. I am not looking to prove anybody right or wrong, just wanting to know how you interpret the code.
The differences of opinion arise in the interpretation of 250.30 (A)(2) where it says except as permitted in 250.24(A)(4). Some say you can land the GEC on either the Xo terminal or ground bus in the transformer, or at the neutral or ground bus in the first disconnect.
I will stick my neck out first and say my interpretation is the GEC should be landed on the Xo terminal at the transformer, or on the neutral buss in the first disconnect. If the transformer is part of the ?service equipment? then the exception of 250.24(A)(4) would permit the GEC to terminate to either the Xo or ground bus provided the MBJ is a wire or bus-bar and is installed from the neutral bus to the equipment grounding terminal.
Don?t be shy. I am not looking to prove anybody right or wrong, just wanting to know how you interpret the code.