Factory Acceptance Testing (FAT) and Site Acceptance Testing (SAT) are two different checkpoints for a data center E-House. FAT is performed at the manufacturing facility before shipment to verify the assembled package against agreed project requirements; SAT is performed after delivery and installation to check the E-House and its interfaces under site conditions. FAT can identify factory-stage defects before transport, while SAT helps confirm that installation, connections, and integration are ready for the next commissioning steps. The tests are complementary, not interchangeable, and their exact scope should be defined in the project specifications and approved test procedures.
Please visit our website for more information on this topic.
The simplest distinction is where and when each test occurs. FAT examines the E-House as a manufactured assembly, while SAT examines the delivered installation in its actual project environment. Some checks may appear in both plans, but the test conditions and purpose differ.
| Comparison point | FAT | SAT |
|---|---|---|
| Location and timing | At the factory, generally before shipment | At the project site, after installation and before the relevant handover or commissioning milestone |
| Main focus | Manufacturing quality, assembly, and agreed equipment functions | Installation quality, site services, interfaces, and integration |
| Typical participants | Manufacturer, purchaser or representative, and other agreed stakeholders | Owner, contractor, commissioning team, manufacturer, and interface vendors as required |
| Typical evidence | Approved FAT procedure, inspection records, test results, and punch list | Approved SAT procedure, site test records, interface checks, and closeout items |
An E-House, or electrical house, is a prefabricated enclosure that can contain electrical equipment such as switchgear, motor control centers, transformers, protection and control panels, or auxiliary systems. Its configuration depends on the project, so a FAT should be based on the approved drawings, equipment schedules, data sheets, and contract requirements for that specific package. It is not a generic test that proves every aspect of the future site installation.
FAT activities may include visual inspection, verification of equipment identification, checks against approved layouts, and confirmation that supplied components match the agreed scope. Electrical checks can include control wiring continuity, functional operation of specified devices, and review of protection or control settings against approved documents. Where applicable, the test plan may also cover alarms, interlocks, metering, and communication functions.
For example, a project test matrix can call for checking 100% of the agreed critical alarm and trip signals. That is a useful way to make the scope measurable, but it is not a universal requirement for every E-House. The buyer and supplier should identify which signals are included, what constitutes a successful result, and how any exceptions will be recorded.
FAT can also reveal issues that are easier to correct before shipment, such as a labeling discrepancy, a wiring error, or a mismatch between the approved drawing and the assembled equipment. However, factory testing cannot confirm that site cabling, foundations, earthing connections, or external utility services will be correct. Those items require site verification.
SAT begins after the E-House has been delivered and positioned, and after the relevant installation work is sufficiently complete for safe testing. Its scope depends on what has been installed, what site services are available, and which interfaces the responsible teams are ready to verify. The test procedure should make clear which work is the supplier’s responsibility and which work belongs to the owner, EPC contractor, or other vendors.
Site checks may include inspection for transport or installation damage, confirmation of the installed location and orientation, and review of cable termination and earthing arrangements. Teams may verify auxiliary power, ventilation or cooling interfaces, fire and alarm connections, and communications with upstream or downstream systems where these are part of the contracted scope. Functional checks can then confirm that selected equipment and signals operate correctly in the installed configuration.
For instance, if an auxiliary circuit is specified as 400 V AC, the team can verify the supplied voltage against the approved design and equipment requirements before energizing it. The value is an example only; actual voltage, frequency, and testing methods must follow the project documents and applicable safety procedures. Site conditions can also affect test readiness, so the SAT plan should state prerequisites such as available power, completed terminations, and approved access.
Pushen are exported all over the world and different industries with quality first. Our belief is to provide our customers with more and better high value-added products. Let's create a better future together.
SAT does not automatically mean that the entire data center is commissioned or ready for service. It verifies only the defined site acceptance scope, and broader integrated systems testing may be a separate project stage. Likewise, successful FAT results do not remove the need to check site-dependent connections and interfaces.
FAT and SAT form part of a wider quality and commissioning process. A practical sequence is to agree the requirements and test procedures, complete factory inspections and tests, resolve or document factory findings, ship and install the E-House, and then execute site checks before the applicable handover milestone. The project may add equipment-specific tests or integrated testing depending on its design and acceptance plan.
Before FAT, the buyer and supplier should align on the test agenda, approved drawings, inspection points, equipment settings, witnessing arrangements, and required records. The procedure should identify pass criteria, instruments or methods where relevant, and how deviations will be handled. This reduces the risk of disputes caused by different expectations during a witnessed test.
Before SAT, confirm installation completion, safe access, permits, available site services, and the status of connected systems. A responsibility matrix is especially helpful when several contractors provide equipment or cabling. It should show who prepares, performs, witnesses, and signs off each test.
These risks can affect schedule, rework, and acceptance, but their impact depends on the project scope and execution. A clear test plan does not eliminate every issue; it helps teams identify responsibility and make decisions with documented evidence. Buyers should also agree whether unresolved non-critical items can be carried forward and under what conditions.
Neither test is more important in every situation. FAT is particularly valuable when the E-House contains complex assemblies or control functions that can be inspected and demonstrated at the factory, before shipment makes access more difficult. SAT is essential for verifying site-dependent work and confirming that the delivered package connects as intended to the project infrastructure.
For a straightforward package with limited interfaces, FAT may focus on assembly checks and specified functional demonstrations, while SAT concentrates on installation and connection verification. For a package with multiple control, protection, or communications interfaces, both stages may require more detailed test matrices and participation from relevant vendors. In either case, the level of testing should reflect the actual design and agreed acceptance criteria rather than assumptions based on another project.
FAT is the factory-stage verification of the manufactured E-House; SAT is the site-stage verification of the installed package and its defined interfaces. FAT helps identify manufacturing or assembly issues before delivery, while SAT checks conditions that cannot be confirmed until installation. Together, they provide distinct evidence for project acceptance, but neither should be treated as proof of work outside its documented scope.
Before placing or finalizing an order, ask your supplier to provide a project-specific FAT and SAT outline, including test boundaries, acceptance criteria, witness points, prerequisites, required records, and responsibility assignments. Review the plan against your electrical design, interface list, and commissioning schedule, then confirm how findings will be tracked and closed. Pushen can discuss E-House configuration, project documentation, and test planning with your team so the proposed package and acceptance process are aligned with your requirements.
Are you interested in learning more about FAT vs SAT for Data Center E-Houses: What Is the Difference?? Contact us today to secure an expert consultation!