A generator without automatic control needs a person: someone must notice the outage, reach the set, start it and transfer the load. On many sites that is perfectly acceptable. On others, those minutes are the whole problem — and that is what an automatic transfer switch removes.
What the device actually does
An ATS continuously monitors the mains supply. When it disappears or drops out of tolerance, the controller starts the generator, waits for it to stabilise, and transfers the load across. When the mains returns and holds steady, it transfers back and shuts the set down after a cooling run.
It also guarantees something less visible but critical: the facility is never connected to both sources at once. Back-feeding a dead grid is dangerous to line workers and destructive to equipment, and preventing it is a mandatory function, not a convenience.
Seconds, not instant
An ATS is not an uninterruptible supply. The transfer takes seconds — the engine must start and reach stable operation. For lighting, heating, pumps and most machinery this is invisible. For servers, medical equipment and anything that must not lose power for even a moment, the correct arrangement is a UPS covering the gap and the generator carrying the load afterwards.
This is the most common misunderstanding in specifying a system: an ATS answers how long, a UPS answers how immediately. Facilities that need both, need both.
When you need one
- The facility works round the clock and no one is permanently present at the generator.
- Outages are frequent, and manual starting becomes a daily duty someone will eventually skip.
- Processes cannot pause: refrigeration, heating circulation, ventilation, security systems, communications.
- The generator stands at a distance from where staff work.
- Unmanned sites — pumping stations, transmitters, remote infrastructure.
When manual is honestly enough
A site with people always present, tolerant of a few minutes without power, and using the generator rarely, does not need automation. Adding it is money spent on a problem that does not exist. We say so when that is the case.
What to specify when ordering
- Whether the generator is prepared for automatic start — not every set is.
- The load being transferred: the whole facility, or an essential circuit only.
- Acceptable transfer time, and whether a UPS is required alongside.
- Where the switchgear is installed and how it connects to the main distribution board.
- Battery maintenance charging — an automatic system is worthless if the starter battery is flat.
- Testing after commissioning: an ATS that has never been tested under a real outage is an assumption, not a system.
We supply generating sets together with automatic control and commission them on site, including facilities where a failed start is not an option: 26 generators of 120 kW for humanitarian operations and 35 sets securing railway stations. Describe the facility — we will propose the configuration.