Does a PSA plant need a backup generator or UPS?

Why backup power matters

A PSA plant needs electricity to make oxygen. WHO interim guidance (April 2020) says PSA plants are designed to run 24 hours a day and must be connected to a reliable power supply with voltage stabilisation, and UNDP's requirements (effective 1 January 2025) say the plant requires reliable, continuous primary and backup power supply sources. The Open Critical Care encyclopedia entry on PSA plants, based on PAHO recommendations, says the power supply of every oxygen system must consider primary and secondary sources, such as a diesel generator as backup, because the oxygen supply has to be continuous 24/7.

The generator

• Size: the Global Fund PSA, VPSA and VSA note (March 2025) warns that large PSA plants can have high compressor in-rush currents and that the generator and switchgear must be sized for them. Global Fund commissioning guidelines check that backup power meets the plant's start-up and running loads and has the same phase rotation as the primary supply, and UNDP asks suppliers for an electrical requirements chart with starting current, minimum protection current and load curves.
• Restart: NHS England's HTM 02-01 (2026) asks for all PSA components to be connected to the essential electrical supply and for the operating system to be capable of restarting automatically when power is reinstated, and asks for compressors to restart in sequence, so that two or more do not start simultaneously, to avoid overloading the supply.
• Installation: UNDP asks for generators to be weatherproofed, sound-attenuated and located safely away from the PSA plant and oxygen sources and, where diesel generators are used, to come with spare part kits and maintenance services.
• Alternatives: Global Fund sustainability guidance suggests considering renewable power instead of generators; see can a PSA plant run on solar power.

The UPS and power quality

Open Critical Care, in an answer by Assist International, always advises a small 1 kW uninterruptible power supply feeding the control circuit and PLC, calling it inexpensive protection. Its guidance on power problems warns that unstable voltage can damage equipment, especially electric motors, that a UPS with online double conversion can also provide voltage stabilisation for sensitive equipment, and that the surge when power is restored can damage equipment, against which stabilisers or other protection devices help by delaying reconnection. It also notes that power frequency fluctuation can, over time, damage the large motors of PSA plants.

Backup power is not backup oxygen

PATH and CHAI (2021) say a backup supply such as cylinders is required to maintain oxygen flow in case of a power outage or mechanical failure, and WHO interim guidance (April 2020) calls cylinders best practice as a backup for a PSA plant. See what backup to keep with a PSA plant. ULTRAOX plants can be connected to a diesel-electric generator, according to the ULTRAOX datasheet (2022), and the customer provides the three-phase power supply.