FAT and SAT are two different stages of verification for a data center E-House. A Factory Acceptance Test (FAT) is performed at the manufacturer’s facility before shipment to check the supplied equipment and agreed functions under factory conditions. A Site Acceptance Test (SAT) takes place after delivery and installation to confirm the E-House works correctly with site utilities, connected systems, and project interfaces. In short, FAT checks what can be verified before dispatch; SAT checks the installed system in its actual operating environment.
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A FAT is a planned inspection and test of an E-House, its installed electrical equipment, and any included control or auxiliary systems before release for delivery. Its scope depends on the purchase specification, approved drawings, equipment supplied, and agreed inspection and test plan. Typical checks may include visual inspection, nameplate and component verification, wiring checks, and functional tests of control circuits or alarms. Where applicable and agreed, the FAT may also include checks of switchgear, protection functions, HVAC controls, lighting, or fire and safety interfaces.
The factory environment offers an important practical advantage: equipment and wiring are generally more accessible than after the E-House has been installed and connected at the project site. The buyer, an appointed inspector, or a commissioning representative may witness selected tests if the contract and schedule provide for it. A FAT report records the checks performed, results, observations, and any outstanding items. It does not, by itself, prove that the unit will operate correctly after transport, installation, and connection to site systems.
A SAT is performed at the installation site after the E-House has been delivered and relevant installation work is complete. It checks that the equipment has arrived in acceptable condition, has been installed as intended, and can work with the site’s power supplies, grounding, communications, and external equipment. Depending on the project, site tests may cover cable terminations, phase sequence, control and communication links, interlocks, alarms, and agreed operational sequences. The test plan should identify which checks are safe and feasible with the facility in its current state.
Unlike the FAT, a SAT depends on project readiness. The required utilities, upstream and downstream equipment, communication networks, permits, and qualified personnel may need to be available before integrated tests can proceed. If a site interface is not ready, the team should document the limitation and agree whether the relevant test will be rescheduled, witnessed through an alternative method, or recorded as an outstanding item. SAT results should distinguish completed tests from checks deferred because of access, safety, or commissioning constraints.
| Comparison point | FAT | SAT |
|---|---|---|
| When it takes place | At the factory, before shipment | At the project site, after delivery and installation |
| Primary focus | Equipment build, factory wiring, and functions that can be tested before dispatch | Installation, field connections, site interfaces, and agreed integrated operation |
| Test environment | Controlled factory conditions, often with access to the E-House interior | Actual site conditions, with tests dependent on project readiness |
| Typical constraints | Some external systems or real site loads may not be available | Access, permits, operational restrictions, and unavailable interfaces may limit testing |
| Main record | FAT procedure, inspection records, results, and open-item list | SAT procedure, site test results, integration status, and remaining actions |
FAT is suited to checks that can be completed using the factory-installed equipment and available test facilities. Examples include confirming component identification against approved drawings, checking accessible wiring and terminal connections, and demonstrating agreed control sequences. A project may also specify simulated inputs to verify that an alarm or interlock responds as intended. For example, a 400 V AC supply or a 50 Hz system may appear in a project specification, but these are illustrative values rather than universal E-House requirements; the approved design determines the actual ratings.
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SAT is suited to confirming conditions that cannot be fully established at the factory, especially those involving site installation or external interfaces. These may include verification of field cabling, grounding connections, communication paths, and coordination with upstream power or control systems. Where the approved plan requires it, teams may test agreed operating sequences with connected equipment under controlled conditions. Any numerical limits, such as an acceptable response time in milliseconds or a temperature limit in degrees Celsius, must come from the project documents and applicable requirements rather than being assumed across projects.
FAT and SAT have different schedule dependencies. Factory testing must be coordinated with manufacturing completion, inspection availability, and shipment planning, while SAT depends on delivery, installation, site access, and the readiness of connected systems. Identifying witness requirements early can help buyers and suppliers plan attendance, test equipment, and documentation without implying a fixed lead time. The actual schedule should be agreed for each project.
Testing can also affect cost, but there is no universal price difference between FAT and SAT. Costs depend on test scope, witness arrangements, travel, specialist labor, required equipment, and whether testing or retesting is needed. A clear test plan can reduce ambiguity by specifying who supplies test instruments, who provides safe access and utilities, how deviations are recorded, and how retests are handled. Buyers should compare the included scope—not just a line-item price—when reviewing supplier quotations.
Neither test is universally more important because they address different risks. FAT is especially useful when buyers need to review factory assembly, confirm agreed functions, and document issues before shipment makes access more difficult. SAT is essential for checking installation and site integration that cannot be confirmed in the factory. For a data center E-House with multiple external interfaces, the project team should give particular attention to interface ownership and the conditions required for integrated testing.
Before placing an order, ask the supplier to define the FAT and SAT scope, test procedures, acceptance criteria, witness arrangements, required project inputs, and report format. Confirm which tests are included in the quotation and how incomplete or failed checks will be managed. Pushen can discuss E-House project requirements with buyers and coordinate the proposed inspection and test documentation around the agreed supply scope. Share your technical specification and project interfaces to start a practical FAT/SAT discussion.
The difference is primarily timing, location, and purpose: FAT verifies agreed equipment and functions at the factory before shipment, while SAT verifies installation and site-dependent operation after delivery. A sound acceptance plan uses both where appropriate, with clear criteria and documented results rather than relying on assumptions or generic checklists. For your next step, align the test scope with the E-House specification, identify interface responsibilities, and confirm the schedule and acceptance process with your supplier before manufacturing begins.
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