We have an existing 3-phase 208v service with an on premises outdoor transformer. X0 at the transformer is bonded to ground (a counterpoise) as required by 250.24(a)(2). There was no main bonding jumper installed at the service disconnect, a 300 amp distribution panel. The service lateral is run in RGC and the grounding conductor run in it and connected to X0 as well. Neither the ground bar or the neutral bar in the service are connected to the counterpoise.
One side of the discussion maintains that no bonding jumper is needed at the service disconnect because of the connection at the transformer and because installing one would put the grounding conductor in parallel with the grounded conductor thereby putting objectionable current on the grounding conductor. The other side maintains there should be a bonding jumper installed in the panel per 250.24 (1) and it should connect to the counterpoise.
As I look at the illustration in the handbook, Exhibit 250.7, I notice that this example shows the service lateral as underground cable which would not have a separate grounding conductor and so there is no direct connection between ground at the service and ground at the transformer and I wonder if this is the situation that the Code committee had in mind and if that should make a difference in this case.
One side of the discussion maintains that no bonding jumper is needed at the service disconnect because of the connection at the transformer and because installing one would put the grounding conductor in parallel with the grounded conductor thereby putting objectionable current on the grounding conductor. The other side maintains there should be a bonding jumper installed in the panel per 250.24 (1) and it should connect to the counterpoise.
As I look at the illustration in the handbook, Exhibit 250.7, I notice that this example shows the service lateral as underground cable which would not have a separate grounding conductor and so there is no direct connection between ground at the service and ground at the transformer and I wonder if this is the situation that the Code committee had in mind and if that should make a difference in this case.