Changeover Panel (AMF)
A changeover panel transfers the facility's load between mains and generator; an AMF (auto mains failure) panel does it automatically — sensing outage, starting the DG, transferring, and reversing on mains return — with mechanical/electrical interlocks that forbid paralleling.
Why it matters on an MEPF project
The changeover is where backup either works or embarrasses: transfer logic (delays, voltage sensing, retransfer timing), load-shedding of non-essentials, and above all interlocking — grid and DG must never meet unintentionally. Backfeeding a "dead" grid through a sloppy changeover is a lineman-safety crime, not a nuisance.
Design choices scale with criticality: simple mechanical changeovers for small setups, motorised/contactor AMF for most industry, closed-transition or synchronising schemes only where brief paralleling is engineered deliberately (and cleared with the DISCOM). Whatever the tier, the panel deserves the same Form/Icw scrutiny as any switchboard — it carries everything, twice.
How it's specified in practice
| Parameter | Typical / working position | Governing reference |
|---|---|---|
| Manual changeover | Operator-switched; small facilities | interlocked switch assemblies |
| AMF panel | Auto start + transfer on mains failure | panel design (IEC 61439 context) |
| Interlocks | Mechanical + electrical; paralleling impossible by construction | safety requirement |
| Synchronising schemes | Only as engineered systems with protection + DISCOM clearance | protection design |
Common mistakes
- Field-improvised changeovers with plug/socket "arrangements".
- Retransfer set instant — the set drops load on the first grid flicker back.
- AMF batteries dead, discovered during the outage.
- No annual full transfer test under load — the panel that only ever worked in theory.
Related on this site
One of 68 working definitions in the MEPF & solar engineering glossary. The buying side of the same decisions is in the buyer's guides; the numbers are in the calculators.
Frequently asked
What is AMF exactly?
Auto Mains Failure: the panel senses supply loss, cranks the DG, transfers load when the set stabilises, and retransfers + cools down when mains return — no human in the loop, interlocks throughout.
Can my DG parallel with the grid for peak shaving?
Only through a deliberately engineered synchronising scheme with protection and DISCOM consent — never through a changeover shortcut. For most factories the honest answer to peak shaving is solar + storage, not paralleling.
Standards referenced: IEC 61439 (assembly context) · CEA (Safety) Regulations 2023