FAT · Handover
Common causes of FAT and handover delays — and how to remove them
· 5 min read
It's a frustrating way to miss a date: the panel is built, wired and tested, but the handover pack isn't ready, so it sits while someone assembles paperwork from wherever it happens to live.
The engineering is rarely the problem. The panel passes its dielectric and functional checks. What holds it is the pack — test records, as-built drawings, the O&M documentation, evidence that every inspection was signed off. When that gets left to the end, FAT and handover slip on collation, not on build quality.
Handover should be the natural close of the build, not a separate scramble. Most delays trace back to a handful of avoidable causes. Here they are, what good looks like instead, and a FAT-readiness checklist you can run before you book the customer's witness.
The pack is assembled last-minute
The biggest cause is leaving the pack to the end. Test certificates, inspection records, drawings and O&M documentation get pulled together the week the panel is due, by someone hunting through folders and inboxes. If those records were captured against the job as the build progressed, most of the pack would already exist when the panel is finished.
The verification a panel needs under BS EN IEC 61439 — the routine tests, the design checks — produces evidence at the point each step is done. Leave it uncaptured and you pay for it twice: once doing the work, again reconstructing proof it happened.
Records are scattered
Even when the evidence exists, it's spread across people and places — a test sheet on the bench, a photo on someone's phone, a certificate in an email, the latest drawing on a laptop. Assembling the pack becomes a hunt, and a hunt loses things. Hold inspection records, test sign-off and documentation against the job in one place and assembly is collation, not detective work.
Wrong-revision documents
A panel built or checked against a superseded drawing is a delay waiting to surface at FAT. The GA shows a device that isn't fitted; the schematic predates a change the customer signed off; two people worked from different copies of the same wiring diagram. The witness spots it, and the panel is held while the drawing set is corrected and re-checked. Control the revision — one current drawing per document, clearly marked — and the as-built matches what's in front of the customer.
Open NCRs at test
Walking into FAT with non-conformances still open is asking for a re-test. An unresolved defect either fails the witness outright or forces a caveated sign-off and a return visit. Every NCR raised during the build needs an owner and a closed status before test — with the corrective action recorded — so the panel arrives at FAT clean rather than carrying known problems into the room.
Missing test evidence
No clear record that FAT and routine tests were signed off means the panel can't ship with confidence, and chasing that confirmation after the fact costs days. Continuity of the protective bonding, insulation resistance, dielectric withstand, functional operation — under BS EN IEC 61439, with BS 7671 governing the installation it feeds — each needs its result captured against the job, with who signed and when. Verbal assurance that testing was done is not evidence at handover.
What good looks like
In a shop that hits handover dates, the pack assembles as the build progresses rather than at the end. Nobody sits down to build it, because it's been building itself.
Each stage produces its evidence at the point it's done. Kitting confirms the right parts against the current BOM. The wiring inspection is recorded when it's checked, at the correct drawing revision. Routine tests are signed off on completion, against the job. NCRs are raised, owned and closed as they arise, so none are open at test. By the time the panel is finished, the O&M pack, the as-built set and the test records are already sitting together — because they were captured together.
Keep one current drawing per document and the revision problem goes away. Hold evidence against the job rather than across inboxes, and nothing is scattered to chase. By the time the panel is finished the pack is already there — so booking the customer's witness is a decision about the calendar, not a race to finish the paperwork.
FAT-readiness checklist
Run this before you book the witness. If any line is a no, the panel isn't ready:
- The BOM is confirmed against the current revision and every fitted device matches it.
- As-built drawings — GA, schematics, wiring — are at the correct revision and match the panel.
- Routine tests are complete and signed off against the job: bonding continuity, insulation resistance, dielectric withstand, functional checks.
- No NCRs are open on the job, and each closed one records its corrective action.
- Inspection records for each build stage are captured and stored against the job.
- The O&M documentation pack is assembled and current.
- A named person has signed the FAT sign-off, with the date.
- The customer's witness slot is booked against a pack that is complete, not one still being gathered.
A worked example
Take a shop building 30 panels a month. On the old way, evidence lands wherever it's created — test sheets in a folder, photos on phones, drawings on a shared drive that isn't always the latest. Handover starts when the panel is finished: someone spends most of a day per job chasing certificates, matching drawings to what's actually fitted, and confirming tests were signed. Two jobs in five throw up a surprise at that point — a superseded GA, an NCR nobody closed, a missing insulation-resistance result — and each surprise costs a day or more while it's chased down or, worse, surfaces in front of the customer's witness.
Change one thing: capture the evidence against the job as each stage completes. Kitting signs off the BOM at the current revision. The wiring inspection is recorded at check, against the right drawing. Routine tests are logged on completion. NCRs are closed before test. Now handover is a review of a pack that already exists — minutes per job, not most of a day. The FAT surprises largely go away, because the wrong-revision drawing and the open NCR were caught weeks earlier, when there was still time to fix them cheaply. The panel ships on the promised date because nothing was waiting on paperwork.