QAC 3/5 KW
Single-phase AC protection panel for 3 to 5 kW photovoltaic systems, 25 A 230 V. Integrates a 300 mA Class A RCBO and Class II SPD surge arrester 2P 230 V 15 kA.
12-module IP65 box with single-line diagram and declaration of conformity. It is a protection and disconnection panel: the interface protection remains the one integrated in the inverter.
The QAC 3/5 kW single-phase AC panel is the AC-side protection for the most common size in the Italian residential market: a 4-5 kWp system paired with a single-phase inverter. It is installed between the inverter and the main distribution board and provides isolation, overcurrent protection, residual current protection suitable for power electronics, and surge limitation.
Why 25 A
The output current of a single-phase inverter is calculated by dividing the AC power by 230 V. A 5 kW inverter delivers approximately 21,7 A at full power; a 4,6 kW inverter about 20 A. A 20 A circuit breaker would constantly operate at its limit on days of maximum production, with the risk of nuisance tripping in summer, when the temperature inside the panel reduces the effective current capacity. The 25 A rating provides the correct margin without increasing to a value that would no longer protect the cable.
The reverse reasoning applies upstream: the cross-section of the AC cable between the inverter and the panel must be selected for a current capacity at least equal to the 25 A of the circuit breaker, typically 4 mm² for short runs and 6 mm² when the distance exceeds 20-25 meters, to keep the voltage drop within the 1% required by inverter manufacturers.
QAC 3/5 kW technical specifications
| System power | From 3 to 5 kW |
| Grid type | Single-phase 230 V |
| Rated current | 25 A |
| Main protection | Residual current circuit breaker with overcurrent protection (IMTD) 25 A, 300 mA, Class A |
| Surges | Class II SPD surge arrester, 2P, 230 V, 15 kA |
| Interface protection | Not present (systems below 11,08 kW) |
| Enclosure | 12-module IP65 box, 115 x 220 x 200 mm |
| Documentation | Single-line diagram and declaration of conformity |
| Weight | 2 kg |
Selectivity with the home distribution board residual current device
A common mistake is installing a 30 mA residual current device downstream of the inverter in series with the one already present in the main distribution board. The result is that at the first fault both trip, leaving the user without power throughout the home, without understanding where the problem comes from. The choice of a 300 mA Class A residual current device on this panel is deliberate: it trips for solid faults and fire risk, leaves protection against direct contact to the home’s 30 mA device, and maintains selectivity between the two levels.
Frequently asked questions
Is it suitable for a 6 kW system?
No. A 6 kW single-phase inverter delivers approximately 26 A, exceeding the 25 A capacity of this panel. For that size, the 32 A version of the same series should be selected, which is fitted with an 8-module box and a properly rated residual current circuit breaker with overcurrent protection.
Should I install it indoors or outdoors?
Both solutions are possible: the IP65 rating makes it suitable for outdoor use. Outdoors, a shaded position or placement under a canopy is preferable, because direct sunlight raises the internal temperature and shortens the service life of the surge arrester and residual current device.
Is it needed even if I already have a DC panel on the string side?
Yes, they are two separate and complementary protections. The DC panel protects and isolates the section between the modules and the inverter; this one protects and isolates the section between the inverter and the grid. A professionally installed system has both.
Can I still access the tax deduction with this panel?
Yes. The AC panel is an integral part of the photovoltaic system and its cost is included in the eligible expense together with modules, inverters, and installation works, provided it is documented in the invoice and in the system declaration of conformity.
What documentation comes with the panel?
Single-line diagram of the panel and declaration of conformity of the panel itself. These are the documents the installer attaches to their own DM 37/08 declaration and to the connection application submitted to the distributor.