ATS PDU Guide: Redundant Rack Power

An ATS PDU can transfer connected equipment to an alternative source when the selected supply becomes unsuitable. For example, designers often consider rack ATS units for equipment with a single power input.

Equipment rack with network cabling for an ATS PDU installation plan

What an ATS PDU does

An ATS selects between its inputs; it does not create battery backup. If both sources fail, it has no source from which to power the load. Specify the role of each UPS or supply feeding the arrangement.

However, two input cords connected to the same vulnerable supply do not establish independent power paths. Draw the upstream connections and identify the failures the proposed system is intended to tolerate.

Check ATS PDU transfer compatibility

Next, request the model’s transfer behaviour, transfer-time specification, input requirements and compatibility with the connected equipment. Avoid assuming that every ATS offers zero transfer time or that every load will tolerate its changeover.

Each intended surviving source and the distribution path must support the load after a transfer. Review ratings at the inputs, outlets and any protected groups, as well as the upstream equipment.

Separate single-input and dual-input equipment

Equipment with redundant power supplies may use separate A and B feeds according to its manufacturer’s design. Single-input equipment may need an ATS PDU to access alternative sources. Ask the designer to document both cases rather than applying one wiring pattern to everything.

Define the operational plan

For a quotation, provide the load list, equipment inlet types, the two proposed sources and the intended failure scenario. Also ask which monitoring functions the model includes and how preferred-source settings and return-to-source behaviour work.

Agree a controlled commissioning and maintenance procedure with the installer. Document input and output labels, the permitted load and what should happen during the planned checks. Distinguish an automatic transfer unit from a manual maintenance-bypass arrangement.