Three-Phase UPS Commissioning Checklist: AS/NZS 3000 and AS IEC 62040-3

Commissioning a three-phase UPS is not a power-on-and-walk-away exercise. Done correctly, it is a structured sequence of electrical verification, functional testing, and documentation that confirms the system will perform under fault conditions, not just under normal load. Done poorly, it produces a UPS that appears operational but fails the first time the mains drops.

This checklist is structured for electrical contractors, commissioning engineers, and facility managers working on three-phase UPS installations from 10kVA upward. It aligns with AS/NZS 3000:2018 Wiring Rules and AS IEC 62040-3, which defines UPS performance classification and test methods.

Pre-Commissioning: Site and Documentation Checks

Before any electrical work begins, confirm the following are in place:

• Installation drawings approved: Single-line diagrams, cable schedules, and battery layout drawings should be reviewed and signed off before energisation.
• Equipment inspection: Check the UPS cabinet, bypass panel, and battery cabinets for transport damage. Inspect busbars, connections, and module seating. Document any damage before proceeding.
• Nameplate verification: Confirm the installed UPS matches the specification, including kVA rating, input voltage range, output voltage, frequency, and bypass rating.
• Cable sizing compliance: Verify input, output, and bypass cables are sized per AS/NZS 3000 Tables C1 and C7, accounting for grouping, ambient temperature, and installation method. Three-phase UPS installations frequently see undersized neutral conductors on the output side, particularly where non-linear loads produce high third-harmonic currents.
• Earthing and bonding: Confirm the UPS earth is connected to the main earthing system per AS/NZS 3000 Clause 5.5. Check that battery cabinet earthing is continuous and that any isolated earth configurations (relevant in some data centre designs) are documented and intentional.
• Protection coordination: Review upstream and downstream protection devices. Confirm that the input MCCB, bypass MCCB, and output distribution protection are coordinated so a downstream fault does not trip the UPS input before the load protection operates.

Electrical Safety Checks Before Energisation

These checks must be completed with the system de-energised and locked out.

• Insulation resistance testing: Test phase-to-phase and phase-to-earth insulation resistance on input, output, and bypass circuits per AS/NZS 3000 Clause 8.3.3. For 415V AC circuits, apply 500V DC test voltage. Record all readings; minimum acceptable is 1 MΩ, though values above 100 MΩ are typical on new installations.
• Battery string continuity and polarity: Before connecting battery strings to the DC bus, verify string polarity with a DC voltmeter. Reversed polarity on a single string in a parallel configuration can cause immediate and severe damage to the rectifier or battery fusing. Measure open-circuit voltage of each string and confirm it is within the manufacturer's specified range for state of charge.
• Battery fuse and disconnect verification: Confirm all battery fuses are rated correctly and seated properly. Verify that battery disconnect switches operate freely and that their positions are clearly labelled.
• Torque verification on busbars and terminals: Use a calibrated torque wrench. Loose busbar connections are a leading cause of thermal failures in the first 12 months of operation. Record torque values against manufacturer specifications.
• Bypass switch position: Confirm the manual maintenance bypass is in the correct position before applying mains power. Applying mains to a UPS with the bypass switch incorrectly positioned can result in mains appearing directly on the UPS output before the system is ready.

Energisation Sequence

Follow the manufacturer's commissioning procedure for the specific model. The general sequence for a double-conversion three-phase UPS is:

• Apply mains to the input circuit breaker with the UPS output circuit breaker open.
• Confirm input voltage, phase rotation, and frequency at the UPS input terminals. Phase rotation must match the UPS specification; most three-phase UPS systems require ACB or ABC rotation and will fault or refuse to start on incorrect rotation.
• Power on the UPS per the manufacturer's startup sequence. Allow the rectifier to charge the battery strings before proceeding.
• Verify DC bus voltage is within the specified float voltage range for the battery chemistry installed.
• Confirm the inverter output voltage, frequency, and phase rotation match the specification before closing the output circuit breaker.
• Close the output circuit breaker and verify output voltage at the distribution board terminals, not just at the UPS output terminals. Voltage drop across long cable runs is a common source of out-of-tolerance readings at the load.

Battery String Verification

AS IEC 62040-3 requires that the UPS be tested on battery to verify runtime and performance. Battery verification at commissioning should include:

• Float voltage per string: Measure and record the float voltage across each battery string and across individual batteries or groups where access permits. Values outside the manufacturer's tolerance indicate a charging fault or a defective battery.
• Battery internal resistance baseline: Use a battery impedance tester to record baseline internal resistance for each battery or block. This baseline is the reference against which future maintenance readings are compared. A battery with no baseline is essentially unmonitorable.
• Discharge test to AS IEC 62040-3: Perform a timed discharge at rated load (or a defined percentage of rated load using a load bank) and confirm the UPS sustains output for the specified runtime. Record battery voltage at start, mid-point, and end of discharge. The end-of-discharge voltage must not fall below the manufacturer's low-voltage cutoff before the specified runtime is reached.

Load Bank Testing

Load bank testing verifies UPS performance under controlled conditions before the actual load is connected. It is the only way to confirm that the system performs as specified without risking production equipment.

• Resistive load test at 25%, 50%, 75%, and 100%: Step the load bank up in stages and record input current, output voltage, output frequency, and UPS efficiency at each step. Output voltage should remain within ±1% for a well-configured double-conversion system.
• Non-linear load test: Many data centre loads are non-linear. Test with a load bank configured to draw current with a crest factor of at least 2.8:1, consistent with AS IEC 62040-3 test conditions. Verify that output voltage distortion (THDv) remains within the UPS specification, typically below 2% for double-conversion systems under non-linear load.
• Dynamic load step test: Apply a step load change of at least 50% of rated load and record the transient voltage deviation and recovery time. AS IEC 62040-3 Class 1 UPS systems must recover to within ±10% of nominal within 20 milliseconds. Confirm the installed system meets its rated classification.
• Overload behaviour: Apply a load exceeding the UPS rating (typically 110% to 125%) and verify the UPS transfers to bypass within the specified time without alarming incorrectly or shutting down the output.

Static Bypass and Maintenance Bypass Testing

Bypass operation is one of the most frequently untested aspects of UPS commissioning, and one of the most consequential if it fails.

• Automatic transfer to static bypass: With the load bank connected, simulate an inverter fault (via the manufacturer's test mode if available, or by triggering an overload condition) and verify the static bypass transfer occurs within the specified transfer time. For most double-conversion systems, this is less than 2 milliseconds. Confirm the load does not drop during transfer.
• Bypass synchronisation: Verify the UPS is synchronising its inverter output to the bypass source before transfer. A UPS that transfers to bypass without synchronisation will produce a voltage transient that can reset or damage connected equipment.
• Manual maintenance bypass: Operate the manual maintenance bypass switch through its full sequence and confirm the load transfers to mains without interruption. This procedure should be performed with the load bank, not with live production load, during commissioning.
• Return from bypass: Confirm the UPS returns from bypass to inverter operation correctly, including re-synchronisation and automatic transfer back.

Alarm and Monitoring Validation

Every alarm the UPS can generate should be tested and verified before commissioning is complete.

• Mains fail alarm: Disconnect the input supply and confirm the UPS generates a mains fail alarm via the front panel, relay contacts, and SNMP/network management card where fitted.
• Battery low alarm: Run the battery down during the discharge test and confirm the low battery alarm activates at the correct remaining runtime threshold, typically 2 to 5 minutes depending on configuration.
• Overtemperature alarm: Verify the alarm is configured and that the relay output activates. Physical simulation is not always practical, but the alarm contact can be verified through the UPS test menu on most modern systems.
• Bypass active alarm: Confirm the alarm activates during bypass testing.
• SNMP and BMS integration: Where the UPS is integrated into a building management system or data centre infrastructure management platform, verify that all mapped alarms appear correctly at the monitoring endpoint. Test each alarm point individually and document the mapping.
• Relay output wiring: Verify relay output contacts are wired correctly and that normally open and normally closed contacts are used as intended. Reversed relay wiring is a common fault that produces a silent failure, where the monitoring system shows normal when the UPS is in alarm.

Common Commissioning Failures

The failures seen most often during three-phase UPS commissioning are predictable and avoidable:

• Incorrect phase rotation: Caught by measuring rotation at the input terminals before startup. Not caught, it prevents the UPS from starting or causes a rectifier fault.
• Battery strings connected with reversed polarity: Prevented by measuring string polarity before connecting to the DC bus. This step is skipped under time pressure more often than it should be.
• Undersized neutral conductor: The output neutral on three-phase UPS systems feeding IT loads must be sized for the expected harmonic current, often 1.7 times the phase conductor rating. AS/NZS 3000 Clause 3.5.1 addresses this, but it is frequently overlooked at the design stage and not caught until the neutral overheats.
• Bypass not synchronised: Discovered during bypass transfer testing. If the UPS is not configured to synchronise to the bypass source, the transfer will produce a transient. This is a configuration parameter in most modern UPS systems and must be verified.
• Alarm relay contacts wired in reverse: Found during alarm validation. The fix is straightforward, but if alarm testing is skipped, this fault remains undetected until a real event occurs.
• No battery baseline recorded: Not a failure that causes an immediate problem, but it means the first maintenance visit has no reference data. Battery health trending requires a baseline.

Documentation and Handover

Commissioning is not complete until the documentation is finished. The handover package should include:

• Completed commissioning checklist with measured values (not just pass/fail ticks)
• Insulation resistance test results
• Battery string voltage and impedance baseline readings
• Load bank test results at each load step
• Discharge test results with battery voltage profile
• Alarm test record
• As-built drawings reflecting any field changes
• UPS configuration file backup where the system supports it

Facility managers should retain this documentation and make it available to maintenance technicians at each subsequent service visit. A commissioning record that sits in a filing cabinet and is never referenced again provides no value.

For three-phase UPS commissioning across Brisbane, Sydney, and Melbourne, UPS Services Australia carries out full commissioning programmes aligned with AS/NZS 3000 and AS IEC 62040-3, including load bank testing, battery baseline recording, and alarm validation. Details are available at [ups.services](https://ups.services).