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Installation & switching

Generator Automatic Transfer Switch

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An open grey automatic transfer switch panel on a garage wall beside a distribution board, with neat cable entries
IN-02
Rated output
5 to 1,000 kVA
Fuel
Diesel, petrol or LPG with electric start
Output
Single phase 230 V or three phase 400 V
Service
Test the transfer sequence every 3 months
Turnaround
Supplied in 2 to 10 days, fitted in 1 day for homes

An automatic transfer switch (ATS) watches the mains supply, starts the generator when it fails, moves the load across, and switches back once the power has been stable for a few minutes. GeneratorRepair.co.za passes your request for a generator automatic transfer switch to independent electricians and generator installers nearby, and they quote you directly. We do not supply or fit ATS panels, and the request is free. An ATS only works with a generator that has electric start and an auto start controller, so the set and the panel must be matched.

How a generator automatic transfer switch works

The ATS controller senses voltage on each phase. On mains failure it waits a few seconds to ignore short dips, sends a start signal, waits for the generator to reach stable voltage and frequency, then closes the generator contactor. When the mains returns it waits again, usually two to five minutes, transfers back and lets the set cool down before stopping. Mechanical and electrical interlocks make it impossible for both sources to be connected at once, so the generator cannot back-feed the grid and endanger municipal and Eskom linesmen.

Choosing an ATS automatic transfer switch

  • Rating: matched to the main breaker or generator output, for example 63 A single phase for a home or 100 A to 1,600 A three phase for commercial sites
  • Single or three phase: a three phase ATS should also detect a lost phase, common after cable theft
  • Contactor or motorised switch: contactor panels suit most homes, motorised changeover switches suit larger loads
  • Neutral switching: the installer decides whether the neutral is switched, which affects earth leakage protection on generator power
  • Extras: exercise timers, load shedding of heavy circuits and remote alerts

Backup generator ATS with inverters and solar

Many homes already have a battery inverter. A backup generator automatic transfer switch can feed the inverter's AC input so the generator charges batteries during long outages, or it can sit upstream of the whole board. The layout has to suit the inverter's earth and neutral design, which is a job for an electrician who knows both. For a cheaper option without auto start, see our generator changeover switch page.

ATS prices, installation and CoC

As a guide, a single phase home ATS panel supplied and fitted costs R6,500 to R18,000, and a three phase diesel generator automatic transfer switch for a business R18,000 to R60,000, more for very large sets. Adding an auto start module to an older generator costs R2,500 to R8,000. Installation takes a day for most homes and must be done by a registered electrician who issues a Certificate of Compliance under SANS 10142-1. A full generator installation can include the ATS in one quote.

What to include in your request

  • Give the generator kVA and whether it has electric start
  • Say whether the supply is single or three phase
  • Note the main breaker size on the board
  • Mention any inverter or solar system already fitted
  • Send a photo of the distribution board

Automatic Transfer Switch for different sites

  • Homes: a single phase ATS that starts the standby set during load-shedding while you are out
  • Estates and complexes: an ATS keeping gates, lifts and booster pumps running for every unit without a caretaker
  • Farms and smallholdings: automatic start for borehole, dairy and cold room loads when the rural line trips
  • Shops, offices and restaurants: a three phase ATS that keeps tills, servers and fridges on supply within seconds
  • Factories, mines and sites: large motorised transfer switches with phase failure detection and load priority
  • Lodges, venues and events: unattended changeover at lodges and guesthouses so guests barely notice an outage
  • Clinics, schools and towers: fast, logged transfer for clinics, cell towers and pump stations that cannot stop

Frequently asked questions

Who supplies and fits the automatic transfer switch?
Independent electricians and generator installers do, not GeneratorRepair.co.za. We are a free matching service that forwards your request to installers near you. Each sends their own quote for the panel and fitting, you choose one or none, and you pay them directly. Using us is free.
Can I fit an ATS to my petrol generator?
Only if it has electric start and either a built-in auto start port or room for an add-on auto start module. Pull-start sets cannot start themselves, so they need a manual changeover switch instead. Send the model and rating plate photo so installers can check.
How long is the break in power with an ATS?
Typically 10 to 30 seconds: a short delay to confirm the failure, the start and warm-up, then transfer. Computers and alarms need a small UPS or the inverter to ride through the gap. Returning to mains causes only a brief flicker.
Does an ATS need maintenance?
Yes, a little. Contacts, relays and the controller battery should be checked, and the full mains failure sequence tested every few months. It is usually included in a generator maintenance contract along with the generator's own exercise runs.

Automatic Transfer Switch by province and city

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