Regional, Blog
FAT Passed. Site Failed. The Commissioning Gaps That Still Cause Downtime
9 April 2026
A signed FAT certificate is a meaningful milestone. It confirms that a piece of equipment was built to specification, performed under controlled conditions, and met the manufacturer's defined test criteria. For complex power systems — generators, UPS, DRUPS, switchgear — that is not a small thing.
But it is not the same as site readiness.
The gap between equipment-level performance and system-level commissioning is where projects in Southeast Asia still run into trouble — not because the equipment was wrong, but because the conditions, interfaces, and integration that only exist on site were never fully tested before handover.
This article covers five commissioning gaps that appear repeatedly across data centre and critical infrastructure projects in Singapore, Malaysia, Indonesia, and beyond — and why they tend to emerge even on well-managed projects.
Related resource: Critical Power Tender Documentation: A Readiness Guide for SEA Projects
Why a Successful FAT Doesn't Guarantee Site Readiness
Factory acceptance testing is designed to verify individual equipment performance under controlled, repeatable conditions. The environment is stable. Variables are managed. Load profiles are simulated. The test proves that the unit works as designed.
What it does not prove is that the equipment will behave correctly when installed within a larger system — connected to site infrastructure, interfaced with third-party controls, and commissioned under the actual loads and sequences that the facility will operate under.
Site conditions introduce variables that no factory test can fully replicate: actual cable lengths and their impedance profiles, real load behaviour from mixed equipment types, interface signals passing between vendors who may not have coordinated their configurations, and physical installation details that directly affect how a system performs. These are not edge cases. They are the normal reality of site commissioning.
A factory pass is a prerequisite. It is not a guarantee of system readiness.
The 5 Commissioning Gaps That Still Cause Downtime
The following gaps are not theoretical. They reflect patterns that appear across real critical power projects — across different equipment types, project scales, and market conditions in the region.
When Site Interfaces Are Connected But Never Actually Verified
When Control Logic That Passed in the Factory Behaves Differently on Site
When Transfer and Failover Sequences Have Never Been Run Under Real Load
When No One Can Agree on What "Pass" Actually Means
When Documentation Is Still Being Written During Handover
Why These Gaps Are So Often Missed on Real Projects
These gaps do not typically appear because project teams are careless. They appear because of how commissioning tends to be positioned and resourced within a typical project structure — and because of pressures that are common across the industry.
When the factory acceptance test becomes the defining event of a project, everything that follows — site installation, interface verification, integrated testing — gets compressed into a smaller window with less scrutiny. A clean FAT certificate creates confidence that has not yet been earned at the system level.
Commissioning is often the last planned activity and the first to lose time when earlier phases overrun. The result is a compressed window where teams are executing tests and chasing documentation simultaneously — under pressure to hand over on a date that was set before the site realities were fully understood.
When multiple vendors, subcontractors, and site teams are involved, commissioning tasks can fall between ownership gaps. Each party assumes another has covered a step. Interface points between systems — which require coordination across scopes — are particularly vulnerable to this pattern.
Outstanding items — punch lists, unresolved RFIs, configuration changes — are carried into the commissioning phase rather than resolved before it begins. When issues surface during testing, the team is simultaneously trying to close earlier actions and validate the system, which compromises the reliability of both.
Test records, as-built drawings, and handover documents are often treated as a post-commissioning task rather than something built concurrently with the project. When documentation is assembled at the end, errors, substitutions, and gaps in the evidence trail become difficult to reconstruct accurately under time pressure.
What a Thorough Commissioning Process Should Actually Cover
Addressing these gaps does not require a fundamentally different approach to commissioning. It requires that certain fundamentals are agreed, documented, and in place before testing begins — and applied consistently across the full scope of integrated systems, not just the headline equipment items.
Clear witness points
Hold and witness gates defined before testing begins — so every sign-off is planned, not negotiated on the day of the test.
Agreed pass/fail criteria
Acceptance standards written down and agreed by all parties before testing starts — not interpreted differently at sign-off by different stakeholders.
Integrated system testing
Systems tested together — not in isolation — under conditions that reflect real operational sequences, including transfer, failover, and restore scenarios with actual connected loads.
Evidence tracking throughout
Test records built concurrently with commissioning activities — not assembled retrospectively under time pressure at the end of the project.
Handover document control
As-built drawings, O&M manuals, test reports, and close-out documentation prepared and reviewed before the handover date — not issued as a post-commissioning chase.
At PPG, every commissioning process is tailored to the specific project — because requirements, interfaces, and acceptance criteria are never identical across two sites. What remains consistent is the discipline: testing evidence is built alongside the project, not assembled at the end of it.
Need a more structured way to review commissioning readiness?
We have developed a practical toolkit covering the full commissioning evidence cycle — from FAT witness checklists and SAT site verification through to integrated system testing, evidence tracking, and handover document control.
- FAT witness checklist and sign-off gates
- SAT site verification framework
- Integrated system testing (IST) evidence tracker
- T&C sign-off and handover document control
A Pass Should Be the Start of Confidence — Not the End of Questioning
A successful FAT tells you something important. It confirms the equipment was built correctly and performed under verified conditions. That matters — and it is a standard PPG upholds as part of every project, including bringing clients to witness testing at the manufacturer's facility.
What a FAT does not tell you is whether the system is ready — ready to transfer under real load, ready to interface reliably with every connected component, and ready to be handed over with documentation that the operations team can actually use from day one.
The projects that avoid commissioning surprises are not necessarily the ones with the most rigorous factory testing. They are the ones where site readiness is treated as a separate, structured process — with its own witness points, its own evidence trail, and a shared definition of what passing actually means before the first test is run.
Every project is different. The standard for readiness should never be.
-
Share
