I am involved with an installation that has a 3 phase mains supply to run a range of plant and electronic equipment. The site also has a generator which is used as a source of exhaust gases for scientific work, the fact that it also produces power is incidental.

It would be preferable to have the generator run under load as this would mean cleaner burning of the engine and a longer service lifetime, as well as making use of the otherwise wasted energy. Is it permissible to have two independent supplies installed in the same location (i.e. to the plant room) where some equipment can be run from the mains supply and other equipment from the generator supply? All equipment would be in reach of each other, there are already 400V warnings for the circuits on different phases of the main 3 phase supply.

The mains and generator earths would require bonding and need to post warning of multiple sources of supply. I cannot find anything in the regulations that rules this out, but it is not explicitly covered that I can find.