I have submitted code questions in the past and very much appreciate the service that you provide the industry.
I have been asked to install an isolation transformer in line with a feed to an existing panelboard. The panelboard is a 250-amp main lug only, fed from a 250-amp circuit breaker in a switchboard in the same room. The system is a 240/120-volt, 3-phase, 4-wire, Delta B-phase high leg. The isolation transformer is a 240-volt primary and secondary, and as such the neutral will be established on the secondary side of the transformer. This is not an industrial facility and the secondary conductors will be approximately thirty feet. My question is does the existing panelboard now require a main circuit breaker?
Thank you, Dennis DiPasquo