Factory Acceptance Testing (FAT) checks a data center E-House at the manufacturer’s facility before shipment; Site Acceptance Testing (SAT) checks it after delivery and installation at the project location. FAT focuses on whether the equipment and agreed functions meet the approved drawings and specifications, while SAT focuses on installation, site interfaces, and operation under project conditions. Both are useful because a successful factory test cannot verify every cable connection, utility interface, or operating condition at the site. The test scope should be agreed by the buyer, supplier, and relevant project stakeholders before equipment manufacture.
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| Comparison point | FAT | SAT |
|---|---|---|
| When it happens | At the factory, before dispatch | At the project site, after delivery and installation |
| Main focus | Build quality, equipment, wiring, and agreed functional checks | Installation, site connections, interfaces, and integrated operation |
| Typical participants | Manufacturer, buyer or representative, and other agreed parties | Owner, installer, commissioning team, manufacturer, and relevant site teams |
| What it cannot fully prove | Performance of site-dependent connections and operating conditions | That every manufacturing-stage inspection was completed before shipment |
An E-House is a prefabricated electrical building or enclosure that can contain electrical distribution and control equipment. Its configuration varies by project, so the FAT is not one universal test: it is a planned set of inspections and checks based on the approved design, purchase specification, and agreed inspection and test plan. The purpose is to identify issues while the unit is still accessible at the factory. This can make correction and documentation review more manageable before transport.
Buyers commonly use FAT to review the equipment against approved drawings, bills of materials, nameplates, and project requirements. The agreed checklist may cover visual condition, enclosure construction, internal wiring, equipment identification, and selected electrical or control functions. For example, if a project specifies a 400 V AC distribution system, the buyer should confirm that relevant equipment ratings and documentation align with the approved design rather than assuming that voltage is standard for every E-House. The test plan should state what will be inspected, how results will be recorded, and which items require buyer witness or approval.
Where control systems are included, the FAT may also include checks of alarms, interlocks, metering, or communication signals. The exact extent depends on the supplied scope and on what can be simulated at the factory. A factory test may demonstrate a signal path using test equipment or simulated inputs, but it cannot automatically establish that the complete site network or upstream equipment will communicate correctly. Ask the supplier to identify each simulated condition and any test that must be repeated on site.
SAT takes place after the E-House reaches the site and is installed or connected in accordance with the project plan. It verifies conditions that FAT cannot fully reproduce, including site cabling, grounding connections, utility supplies, external control interfaces, and coordination with other installed systems. Site teams may also confirm that the equipment is positioned and connected according to approved project documents. SAT results depend on the readiness of the site and the availability of required utilities and interface equipment.
The SAT checklist should reflect the actual installation and the boundaries of the supplier’s scope. It may include inspection of transport or installation condition, confirmation of field connections, checks of control and communication interfaces, and agreed functional tests with connected equipment. If the E-House is designed for a 50 Hz or 60 Hz system, for example, verify the project’s selected frequency and compatible equipment against the approved documentation; do not treat either value as universal. Record deviations and assign responsibility for resolving them before the system is accepted for its intended use.
Some projects include integrated or endurance-style checks, but the duration and acceptance criteria must be specified by the project team. A 24-hour operating observation, for instance, should be treated as a project-specific requirement only when it is agreed in the test plan, not as an automatic FAT or SAT standard. Likewise, the presence of a passed SAT does not replace the need to close open punch-list items or retain required commissioning records. Define what “accepted” means contractually before testing begins.
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FAT and SAT are complementary stages rather than alternatives. FAT provides an opportunity to review equipment and functions before shipment, while SAT confirms that the delivered E-House is properly integrated into its site environment. Passing FAT does not guarantee that site installation is correct, and passing SAT does not prove that every factory-stage check was performed. Buyers should therefore connect the two stages through shared equipment tags, consistent test records, and a controlled list of outstanding items.
FAT can reduce the risk of discovering build or documentation issues after shipment, when access and correction may be more difficult. However, a broader FAT requires time for test preparation, equipment availability, buyer attendance if required, and correction of findings. SAT also needs coordination with site work, utilities, commissioning personnel, and connected systems. Neither test has a fixed duration or cost across all projects; scope, complexity, travel, witness requirements, and retesting arrangements affect the effort.
For procurement, define whether FAT attendance, travel, test equipment, reports, and retests are included in the commercial offer. Clarify whether SAT support is included, available as an optional service, or assigned to another contractor. Buyers should also confirm how shipment release relates to FAT approval and how unresolved items are handled. These details help prevent misunderstandings between technical acceptance and commercial acceptance.
For a data center E-House with complex controls, multiple interfaces, or project-specific electrical configurations, buyers should define both FAT and SAT early and link them to the contract documents. FAT is especially valuable for verifying factory-built equipment and agreed functional checks before dispatch. SAT is essential for confirming installation and site-dependent integration after delivery. If project time or access is limited, prioritize tests by risk and document any checks that cannot be completed at the planned stage.
FAT is the factory-stage verification before shipment; SAT is the site-stage verification after delivery and installation. The main difference is the environment being tested: factory-built equipment and agreed functions during FAT, versus installation and real project interfaces during SAT. Neither stage replaces the other, and each is only as useful as its agreed scope, acceptance criteria, and records. As a next step, prepare a project-specific test matrix and confirm responsibilities, witness points, schedule, and closeout rules with your E-House supplier.
At Pushen, we recommend aligning the test plan with the E-House configuration, approved drawings, and project interface requirements before production and shipment. Share your electrical scope, control requirements, and site conditions with our team to discuss how FAT documentation and SAT support can be defined for your project.
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