I am currently building a new building. We as the owners have decided to install a diesel back-up generator unit with auto transfer. The building uses well water and therefore requires a water storage tank for the fire suppression sprinkler system. It also will be using a 100 hp 480 volt 3 phase fire pump. The building as designed currently has 800 amp 277/480 3 phase service. The fire pump requires a separate service and meter completely independent of the 800 amp main service. How do I install the auto transfer switch to supply power to both the fire pump and main service? There is a electrical utility pad and transformer within 5 feet of the main switchgear inside the building. The genset is a 500 kw unit 277/480 3 phase. How much amperage will I get from it? Can the transfer switch be rated at 800 amps or do I need it rated for the combined main service and fire pump amperages? The building is a trucking terminal and 800 amps is probably overkill but I have 74 dock doors with a 20 amp 120 volt outlet for each door to plug in block heaters (typically 1000-1500 watts each) for the trucks. If it matters, I am in unincorporated cook county in Illinois... thankx for the help... mike
p.s. the indoor switch gear will use current transformers with outside mounted meters.