UPS installations and the services required to install an uninterruptible power supply in a server rooms and datacentre environment.
Some uninterruptible power supplies include a built-in UPS maintenance bypass for service purposes. This does not fully isolate the UPS but provides a safe working environment for the UPS engineer. An external UPS maintenance bypass switch allows the full isolation of the uninterruptible power supply which can be safely shutdown without interruption of power to the critical load which is then supplied by the mains power supply. The shutdown UPS system can then be removed and swapped out.
UPS below 3kVA tend to use power cords with a moulded plug. From 4-6kVA the UPS may use a 16A Commando type industrial socket (blue single phase or red three phase). Where the UPS does not have a plug the system is referred to as hardwired and will require electrical installation by a qualified electrical contractor working to the latest IEEE wiring regulations (currently version 18) and there may also be other on-site or local regulations to comply with.
This may be the case where the battery extension pack has its own built-in AC mains powered battery charger. UPS systems generally include a built-in battery charging circuit but this may not be sufficient for larger battery sets i.e. as more external battery extension packs are added.