Factory Acceptance Testing (FAT) and Site Acceptance Testing (SAT) are two important but different stages of equipment verification. FAT provides an opportunity to identify major problems before equipment leaves the manufacturer, while SAT confirms that the delivered and installed equipment remains correct after transport, assembly, connection and site configuration.
Why FAT matters
Large UPS systems, switchgear, generators, chillers, control panels and other critical equipment can be difficult and expensive to modify after delivery. FAT allows the project team to inspect workmanship, verify configuration and perform selected functional tests in a controlled factory environment.
Prepare an approved test procedure
The FAT should follow a reviewed test script that identifies equipment, prerequisites, instruments, test steps, acceptance criteria and required records. The procedure should be agreed before the witness team arrives at the factory.
Testing without defined acceptance criteria often leads to disagreements at the end of the test.
Typical FAT scope
The exact scope depends on equipment. It may include visual inspection, nameplate verification, control wiring, protection settings, breaker operation, alarms, interlocks, communication points, functional sequences and performance tests that can be safely reproduced at the factory.
Witnessing and evidence
Witnessing should focus on critical functions and project-specific risks rather than simply observing routine manufacturer production tests. Records should include measured values, test results, settings, firmware versions, photographs where useful and identified punch items.
FAT does not replace site testing
Equipment can be damaged in shipping, assembled incorrectly, connected to the wrong source or configured differently on site. Interfaces with other systems usually cannot be fully proven at the factory.
For this reason, FAT should reduce site risk, not replace SAT or commissioning.
Site Acceptance Testing
SAT verifies the equipment after installation. Typical checks include shipping condition, assembly, cable or pipe connections, grounding, settings, local controls, alarms, communications and operation with actual site interfaces.
Repeat critical tests after delivery
Tests that depend on site wiring, protection, communication or mechanical connections should be repeated even if they passed at FAT. If the equipment was disassembled for transport, the commissioning team should verify all restored connections.
Manage punch items
FAT and SAT deficiencies should be recorded with clear responsibility and closure evidence. A minor cosmetic issue is different from a protection, control or capacity problem; the punch list should reflect risk and acceptance status.
Practical FAT/SAT controls
- Use approved procedures and acceptance criteria.
- Confirm calibrated test instruments.
- Record settings and software versions.
- Identify deviations from approved submittals.
- Track punch items to retest and closure.
- Repeat site-dependent tests during SAT.
- Preserve signed test evidence for handover.
Key takeaway
FAT and SAT are complementary. FAT prevents factory defects and configuration problems from reaching site, while SAT proves that equipment survived transport, was installed correctly and works with real site interfaces. Together they reduce commissioning risk and protect the project schedule.
References and Further Reading
- ASHRAE Guideline 0-2019, The Commissioning Process.
- ANSI/ASHRAE/IES Standard 202-2024, Commissioning Process Requirements for New Buildings and New Systems.
- Applicable equipment manufacturer factory and site test procedures.
