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FAT and SAT — Factory and Site Acceptance Tests Every BMS Project Needs

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FAT and SAT — Factory and Site Acceptance Tests Every BMS Project Needs — infographic

An Erode Panel Factory, a Shipment to Pune, a Day-3 Surprise

Ranjini is a QA engineer at a panel-build factory in Erode. The factory ships a 28-controller BMS panel to a pharma plant in Pune. The shipment arrives Tuesday. Commissioning begins Wednesday. By Friday, three controllers will not talk to the front-end. The panel team blames the network. The customer blames the panel. Each side investigates independently. ``` Time on site to find each fault: Controller 7 BACnet device-instance conflict 2 hours Controller 14 Wrong baud configured at factory 1 hour Controller 22 DIP switch position wrong 30 minutes ``` Ranjini reviews the factory test logs. None of the three issues had been tested. The factory test had verified power-on, basic comms, and IO continuity — but had not run the controllers as a network with their actual configuration. ``` Cost on site: 3 fault diagnoses × 1 senior engineer day each = 3 senior-engineer days Customer's project schedule slip: 2 days Customer's frustration: substantial Cost if caught at factory: Same 3 faults, fixed at the test bench in 2 hours No site visit required Schedule slip: zero ``` Catching faults early is one of the highest-leverage things a BMS project can do. The earlier the catch, the cheaper the fix. Every single one of these problems has one solution — disciplined Factory Acceptance Tests (FAT) followed by disciplined Site Acceptance Tests (SAT).

FAT — Factory Acceptance Test

Where: At the panel manufacturer's factory, before shipment. When: After panel build is complete and before crating. Who: Vendor's test engineer + customer's witness representative. Output: Signed FAT report, photographs, configuration backups. ``` FAT scope (typical for a BMS panel):
  1. Visual inspection
- Panel construction matches drawing (size, IP rating, colour) - Component placement matches layout - Wiring tidy and labelled - Earthing continuity
  1. Power-on test
- Apply 230V or 24V as per panel design - Confirm no sparks, smoke, or alarms - Confirm SMPS output voltages within tolerance - Confirm fan/cooling operates if installed
  1. Controller boot
- Each controller boots to firmware - Each controller's device instance, IP, baud, MAC are verified against the configuration document - Each controller's PICS document or BIBB profile is verified
  1. IO point-to-point continuity
- Apply test signal to each AI input — confirm controller reads it - Toggle each DI input — confirm controller reads it - Command each DO output — confirm relay actuates - Command each AO output — confirm voltage at terminal - Document each verified channel in the FAT report
  1. Network communication
- Each controller is discoverable from the supervisor controller via BACnet - Each Modbus device is discoverable on its assigned chain - End-to-end ping from front-end to each controller
  1. Sequence sample
- For at least 3 controllers, simulate inputs and verify the FBD logic produces correct outputs - For 1 chiller plant: simulate full sequence (start, stage, trip, restart)
  1. Configuration backup
- Take JSON or vendor-format backup of every controller - Save to project folder, copy to USB for handoff
  1. Signed report
- Test engineer signs each section - Customer witness signs the report - Two copies retained — one with vendor, one with customer ``` A thorough FAT for a 28-controller panel takes 2-3 days. It catches 80-90 percent of configuration errors before the shipment leaves the factory.

SAT — Site Acceptance Test

Where: At the customer's site, after panel installation and cable termination. When: After all field wiring is complete and before handover. Who: Vendor + integrator + customer + (for regulated sites) consultant. Output: Signed SAT report, photographs, as-built drawings. ``` SAT scope (typical):
  1. Site visual inspection
- Panel installation matches design - Cable termination matches IO list - Cable routing matches drawing - Earthing tested at the panel
  1. Field-end IO verification
- Apply known input at the field sensor (heat the temp sensor, open the DPS, depress the limit switch) - Confirm the BMS dashboard shows the correct value - Repeat for every IO point — every one - Document each verified channel in the SAT report
  1. Sequence verification
- Run every sequence end-to-end — chiller staging, AHU start sequence, fire mode, occupancy mode, schedule transitions - Verify alarms generate correctly - Verify trends are recording
  1. Network verification
- Front-end discovers all controllers - Front-end can read and write every IO point - COV subscriptions function for high-priority points - BACnet routing works across all networks
  1. Failover and edge cases
- Trip the lead pump — verify lag promotes - Disconnect a sensor — verify alarm generates - Power-cycle a controller — verify recovery - Network cable disconnect — verify graceful degradation
  1. Operator training session
- Walk-through of front-end with operator - Alarm queue review - Trend access - Schedule modification (typical operator-allowed actions) - Emergency override procedures
  1. Documentation handover
- As-built drawings (red-marked from design) - IO list (final, including any field changes) - Sequence of operations - Alarm and event list - Maintenance schedule - Configuration backups
  1. Signed report
- Each section signed by vendor and customer - Open-issues list (anything not yet resolved, with timeline) - Final acceptance signed when open issues close ``` SAT for a 28-controller panel typically takes 3-5 days, depending on building access and customer availability. It catches the remaining 10-20 percent of issues that survived FAT.

What Pharma 21 CFR Demands From Both

For pharma sites, FAT and SAT take on additional regulatory weight: ``` Each test must: - Be witnessed by a qualified person (customer + vendor + QA) - Produce a signed, time-stamped record - Reference the URS (User Requirements Specification) - Be retrievable for FDA inspection up to 7 years - Have any deviations documented and resolved with formal deviation reports - Be tied to the validation lifecycle (URS, FDS, IQ, OQ, PQ) Pharma FAT usually adds: - Validation protocol verification - 21 CFR Part 11 audit trail testing - Electronic signature workflow testing - Data integrity testing (read consistency, no tamper) - Backup and recovery testing ``` The discipline of pharma FAT/SAT raises the quality of the whole industry — the rigour developed for pharma sites makes its way into commercial best practice.

How Ranjini's Factory Becomes a Better Factory

After the Pune incident, Ranjini reworks the factory FAT process: ``` Pre-FAT improvements: - Add a 3-day "system test" to the FAT scope - Test all 28 controllers as a network, with the actual BACnet device instances and Modbus addresses - Run sample sequences from the supervisor controller - Take configuration backups before shipment Process improvements: - Customer witness invited to every FAT - FAT report template extended to cover network and sequence tests - FAT signoff required before crating - JSON configuration backup attached to FAT report Six months later: - Site commissioning faults dropped from average 5 per project to 1 per project - Average commissioning duration shrank by 40 percent - Customer NPS for the factory rose noticeably ``` The factory's reputation became the reputation for clean, predictable, on-time delivery — because what shipped from the factory was actually tested, not just built.

The Core Discipline

``` FAT catches: SAT catches:
  • Wiring errors at the panel - Wiring errors at the field
  • Configuration mismatches - Sensor calibration drift
  • Firmware boot issues - Site-specific protocol issues
  • IO continuity failures - Network-routing errors
  • Network-discovery errors - Sequence integration failures
  • Sequence logic bugs - Operator training gaps
What both share: Documented test plans (not improvised) Pass/fail criteria for every test Witnessed signatures Retained reports Open-issues tracking Final acceptance only after all issues close ``` A project that runs both well produces a building that works on day one, not on day forty. FAT catches the factory's mistakes before they ship. SAT catches the field's mistakes before handover. Skipping either pushes the cost downstream — and downstream costs are always higher. The discipline is small. The savings are large. The customer relationship lasts.

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