1. What an ATS is
ATS stands for Automatic Transfer Switch. It has two inputs and one output: the Growatt output on one side, the grid on the other; the output goes to the house panel. The ATS connects the house to one source at a time.
2. Why it is used
With an ATS the system runs off-grid and the grid stays as backup. A source running in island mode must never be in parallel with the public grid: the ATS switches live and neutral together and never puts grid and inverter in parallel.
Another advantage: the grid only reaches the house, not the inverter input.
3. What is in the diagram
- Panels and CEG string box (fuses, SPDs, isolator). DC box
- Growatt SPF 6000 ES PLUS and CEG 51.2 V battery, with the battery breaker already inside the box.
- Grid side: meter, circuit breaker and RCD.
- ATS: input A from the Growatt (output protected by a 32 A breaker), input B from the grid.
- House panel.
4. How it works day to day
Normally the ATS keeps the house on the Growatt, which uses panels and battery. If the Growatt stops, the ATS switches the house to the grid; when the Growatt is available again, it switches back.
5. Mistakes to avoid
- Using a switch that only breaks the live and not the neutral.
- Connecting the grid directly to the inverter input when the diagram uses the ATS.
- Forgetting the 30 mA RCDs on house circuits: the input RCD does not replace them.
6. The detailed wiring diagram
The block diagram helps you understand how it works. The detailed wiring diagram, with terminals and connections, is reserved for those who bought through Carmine Energia Gratis: write to Carmine with your CEG pre-order number. Wiring and testing must be done by a qualified electrician.
7. Frequently asked questions
Can I lose power with an ATS?
There is a short interruption while switching from one source to the other. Otherwise the house is always powered, by the Growatt or by the grid.
ATS or contactors: what is the difference?
They do the same job. Two contactors with mechanical and electrical interlock are an alternative to the ATS: in the CEG diagram the KA relay gives priority to the Growatt.
Does it work with two Growatts in parallel?
Yes, with different ratings: at 12 kW the Growatt output goes on a 63 A breaker and cables go from 6 to 10 mm². The grid input breaker is chosen on the meter power.
Who installs it?
Wiring, testing and the declaration of conformity must be done by a qualified installer, according to the rules of your country.
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