We're installing an auto transfer switch ahead of an existing main service panel. The 2 feeds will be from separate pad mounted transformers on different distribution systems. The neutral conductors would normally be grounded in the transformers. The plan is to install service entrance disconnects between each transformer and the ATS. It seems the neutrals should be grounded and bonded in each new service disconnect (correct?) but would there need to be changes made in the existing service panel too?
thanks
A hospital? ISP Server center?
Much depends on where the utility stops, and the customer begins, if this is being installed by the utility, and they own it, then the NEC might not apply, and the existing service panel stays as just that.
Basically you have two redundant utility services, each new disconnect will require a MBJ, after this point the grounding and grounded conductors must be kept separate including at the ATS, which will mean at the existing panel, if the grounding conductors were landed on the neutral bar, they will have to have a bar of their own and the MBJ in the existing panel will also have to be removed, now as for the grounding electrode conductors, they also will have to be moved to the new MBJ point, which is these disconnects, I would say running them to one disconnect then tap to the other, but at least one GEC in each would have to be continuous?
Roger on here does hospitals so maybe he can chime in?