The power for such services is normally provided from a separate MV/LV transformer via its own LV switchboard and in turn distributed to the loads. Even “non-essential loads” need some reliability of power supply in order that the air conditioning can run in the event of a complete mains failure. Should such a mains failure be more than a few minutes then the chilled water air conditioning used in most modern data centres will not be able to deal with the heat being generated in the data halls resulting in loss of service of the computer equipment.
It is therefore usual to provide diesel generator back-up to the non-essential services. The diesel generators are arranged to start up automatically in the event of an electrical mains failure. This normally takes only a few seconds which is acceptable to the load. The non-essential LV mains switchboard will have incorporated mains failure detection and power changeover switchgear.