An AMF (auto mains failure) panel senses a mains failure, starts the DG set, transfers the load, and reverses it all when the mains returns. A synchronising panel goes further: it lets multiple sets — or set and grid — share one bus. SITC — supply, installation, testing and commissioning — is how either arrives as a working system. Which panel you need, and what a proper SITC contract must contain, is what this guide settles.
TL;DR
- An AMF panel automates one set: sense the mains failure, start, transfer the load, retransfer when mains returns, cool down, stop
- A synchronising panel parallels multiple sources on one bus: voltage, frequency and phase must match before the breaker closes, then the controllers share the load
- One set carrying the whole load → AMF. Multiple sets, redundancy, stepped load growth, or a new set beside existing sets → synchronising
- SITC = supply, installation, testing, commissioning — and testing under a real load transfer is the part that separates vendors
- Recorded jobs behind this article: a 1500 kVA set onto a three-set bus at a Coca-Cola bottling plant, and a 1010 kVA Cummins synchronised to existing CAT sets
What an AMF panel actually does
AMF stands for auto mains failure. The panel exists so that nobody has to be standing next to the genset at 2 a.m. when the feeder trips — it runs the whole event, both directions:
| Stage | What the panel does |
|---|---|
| Sense | Monitors the incoming mains on all phases for failure, under- or over-voltage and phase loss. A short delay filters momentary dips so the engine doesn’t crank on every flicker |
| Start | Cranks the engine, with repeat attempts and a start-failure lockout if the set won’t fire |
| Transfer | Waits for the set to build stable voltage and frequency, then moves the load across through the changeover |
| Supervise | Watches the running set’s parameters — and keeps watching the mains |
| Retransfer | When the mains returns and holds steady through a delay, moves the load back |
| Cooldown | Runs the engine off-load briefly to shed heat, then stops and re-arms for the next failure |
The delays matter as much as the actions. Transfer too eagerly and the set cycles on every voltage dip; retransfer too eagerly and an unstable mains drops your load twice in five minutes. The specific timer values are engineered per site against how your supply actually behaves — which is a testing question, not a catalogue question.
This is also the default way rental sets run. Sets from our rental fleet run unmanned on AMF panels as standard — an operator is the exception, priced in only where the site demands one.
What a synchronising panel does
An AMF panel manages one source at a time: mains or set, never both. A synchronising panel manages sources together — two sets, five sets, or a set running in parallel with the grid, all feeding one bus.
Closing a breaker between two live AC sources is the one operation in LT work you cannot do approximately. Before the breaker closes, three things must match within tight limits: voltage magnitude, frequency, and phase angle. Get any of them wrong and the sources fight — at best a trip, at worst mechanical damage to an alternator. So the panel’s controllers nudge each incoming set’s governor and AVR until the match is made, a synchronising check confirms it, and only then does the breaker close. The first set onto a dead bus closes straight in; every set after it synchronises to the live bus.
Once paralleled, the job changes from matching to sharing. The controllers divide the real load (kW) and the reactive load (kVAr) across the sets so no machine hogs or loafs, and protections — reverse power among them — catch a set that starts motoring instead of generating. Our synchronising and PCC panels are built on Woodward or equivalent controllers, and because the controller talks to each set’s own governor and AVR, the sets on the bus do not have to share a brand or a vintage. We have paralleled new Cummins with existing CAT machines; the controller neither knows nor cares what colour the engines are.
One phrase from tender BOQs is worth decoding here, because it is exactly what it sounds like: an AMF cum synchronising panel is one panel that does both jobs. It senses the mains failure and auto-starts like an AMF panel — but instead of one set, it starts the bank, synchronises the sets onto the bus, shares the load between them, and sheds or stops sets as the load allows. When a BOQ line reads “AMF cum synchronising panel SITC,” that whole sequence — supplied, installed, tested and commissioned — is what is being bought.
AMF or synchronising: which does your site need?
| Your situation | The panel answer |
|---|---|
| One set, sized to carry the full load | AMF panel |
| Two or more sets sharing one load | Synchronising panel |
| Redundancy — the site must ride through one set failing | Synchronising, with spare capacity on a common bus |
| Load grows in steps over the years | Synchronising — add sets to the bus instead of replacing the set |
| New set beside existing sets, same brand or not | Synchronising, cross-brand controller integration |
| Set running in parallel with the grid | Synchronising — plus the distribution utility’s approval and whatever protections it specifies |
The single-set case is genuinely simple, and an AMF panel is the honest answer — nobody should sell a synchronising panel to a site with one generator. The moment there is a second machine, the question stops being “how does the set start” and becomes “how do the sets behave together,” and that is synchronising territory.
There is a pattern in our own project records worth naming: the synchronising work clusters at the top of the rating range. The new sets we have paralleled were 1010 and 1500 kVA machines. That is not an accident. At those ratings the load is usually too important to hang on one machine, too big to backfeed from a neighbour, and still growing — so plants build a bus. A synchronised bank also lets each machine run loaded in the healthy band of its prime rating instead of one oversized set loafing at a fraction of its capacity, and it lets you pull one set out for maintenance while the rest carry the site. Six 1010 kVA sets across the Reserve Bank of India’s three sites — Belapur, Kharghar, Nagpur — is what institutional standby looks like at this scale — delivered as turnkey installations, not a synchronised bus: six large machines across three campuses, with the control wiring engineered as part of the same accountable bill as the sets themselves.
What SITC means on paper
SITC is the contract structure most Indian tenders use for panel and genset work: supply, installation, testing, commissioning. Four words, four different obligations:
- Supply — the panel itself, built to the approved drawings and BOQ: breakers, controllers, metering, protection, busbar, the lot. This is the part every vendor can quote.
- Installation — the panel positioned, power cabling terminated, and the control wiring run between panel, sets and mains incomer. Control wiring is where installation quality shows: a synchronising scheme is only as good as the signals reaching it.
- Testing — proving the logic on the real site. Simulated mains failures. Live transfers and retransfers under actual load. For synchronising panels: the first synchronisation watched instrument by instrument, load sharing verified across the bank, and a deliberate trip of one set to prove the rest pick up the load.
- Commissioning — the system handed over live, with documentation: as-built drawings, settings records, test results.
Testing is the word that separates vendors, because it is the only one of the four you cannot see in a photograph. A panel can be supplied gleaming and installed neatly and still drop the load on its first real mains failure, because the logic was never proven against the site’s actual behaviour — its real voltage dips, its real motor inrush, its real retransfer conditions. Each unit testing OK on a bench is not the same thing as the site riding through. The failure that hurts is never inside a machine; it is in the changeover between machines, which is precisely the part only live testing exercises.
So when you compare SITC quotes, ask one question: what does your testing protocol contain, and will you run it in front of us? A vendor who tests will answer with a list. A vendor who doesn’t will answer with reassurance.
How a real SITC project runs
The sequence we run on panel projects, from the first visit to handover:
- Site survey and load study. What runs, what starts hardest, how the mains behaves, what exists already — sets, switchgear, cabling — and in what condition.
- Panel engineering. Single-line diagram, breaker coordination, controller selection, metering and protection scheme, all issued for approval before anything is fabricated.
- Manufacture and pre-dispatch checks. The panel is wired and function-checked before it ships — site is a bad place to discover a wiring error.
- Installation. Positioning, power terminations, and the control wiring between panel, sets and incomer — on brownfield jobs, sequenced around a running plant.
- Protection coordination. Settings on the new panel coordinated with the breakers upstream and downstream, so a fault trips the right device and only the right device.
- Live testing under load. Simulated mains failure, transfer, retransfer, cooldown. On synchronising jobs: first parallel, load-sharing verification, single-set trip test. The client watches.
- Documentation and handover. As-builts, settings, test records — the file your electrical auditor will ask for years later.
On brownfield sites, step 1 earns its keep. At a Coca-Cola bottling plant in Jabalpur, the new machine was a 1500 kVA set that had to join a bus with the plant’s existing 1250 and 500 kVA units — three generators of different vintages sharing one load, integrated around a running bottling operation. The survey and the controller engineering are what made that routine instead of dramatic.
The panels behind our project record
Where Power Solutions has actually done this, as recorded on this site: the Jabalpur three-set synchronised bus above, and a new 1010 kVA Cummins synchronised with existing CAT sets at Weikfield Foods — cross-brand paralleling through synchronising/PCC panels on Woodward or equivalent controllers. AMF panels, auto and manual changeovers, panel modification and shifting on live sites are the everyday layer beneath those headline jobs — including for every unmanned set in the rental fleet.
If you are holding a BOQ line for an AMF or synchronising panel — or a site with two generators that have never met — send it to us on WhatsApp. Panel scope, controller basis and a testing protocol come back as a written quote, and the UPS & LT panels page covers the full scope, with turnkey projects handling the jobs where the panel is one line in a larger installation.
Sources: Power Solutions project records and service scopes as published on this site — synchronising and PCC panel scope with Woodward or equivalent controllers (/services/ups-lt-panels/); the Coca-Cola Jabalpur three-set bus and the Weikfield Foods cross-brand synchronisation (/services/turnkey-projects/ and /projects/); the rental fleet’s unmanned-AMF standard (/services/dg-rental/). AMF sequencing and synchronising fundamentals are stated qualitatively as standard trade practice — set-specific timers, synchronising windows, relay settings and grid-parallel protections are engineered and documented per site, never copied from an article.