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Electrical engineering

To connect a solar roof, you need an inverter that converts the direct current of the solar panels into 230V alternating current.


An inverter must be mounted in a well-ventilated room. For wall mounting, a space of 1.5 metres height and 1 metre width per inverter is normally sufficient. In the case of inverters of a different size, we will inform you of the dimensions. A ventilated technical room is often suitable for placing an inverter. If you use a casing, extra ventilation grids must be installed, both at the bottom and top of the casing. If the rear wall is not made of stone, a fireproof plate must be installed behind the inverter. Robisol can supply a Fermacel panel for installing the inverter. According to the Scope 12, you should install a smoke detector in the area of the inverter.

DC cabling

The PV installer is generally responsible for the DC cabling and commissioning of the inverter. For this purpose, it is desirable that the cable route is determined in advance. The roof gland is an important part of this. Please note that the plus and minus cables must be separated from each other. If you do not install the cable ducts yourself, we will be happy to provide you with information about this in advance and Robisol will supply and fit the ducts for the transit of cables from the roof to the technical room.

Earth leakage switch

The electrician is generally responsible for the AC cabling and the installation of earth leakage switches. Unfortunately, this sometimes goes wrong because the electrician is not used to only installing 30mA earth leakage switches in homes. Please bear in mind that an inverter must be fitted with more powerful earth leakage protection.

Robisol assumes that an inverter will always be fused to its own group:

Solar group Earth fault Minimum main fuse Inverter

1-phase 16A 100mA 1x25A Power up to 3,680W

3-phase 16A 100mA 3x25A Between 4,000 and 10,000W

3-phase 16A 300mA 3x25A Between 10,000 and 11,040W

3-phase 25A 300mA 3x35A Between 11,040 and 17,250W

3-phase 32A 300mA 3x40A Between 17,250 and 22,080W

3-phase 40A 300mA 3x63A Between 22,080 and 27,600W

3-phase 50A 300mA 3x80A Between 27,600 and 34,500W

IIf you have user groups of 25A, a maximum inverter power of 5,750W can be installed based on a single-phase connection. The earth leakage switch must be 100mA. Up to approximately 3,000 Watts, a standard 30mA earth leakage switch may be used.

If it is desirable to maximise the capacity of the PV installation on a main connection, Robisol generally opts for two separate inverters so that selectivity can be maintained. Robisol will of course ensure that the joint capacity of the inverters never exceeds the terminal value of the main fuse. With a single-phase 35A main fuse, the maximum inverter power with two inverters is 8,050W. With a single-phase 40A main fuse, the maximum inverter power with two inverters is 9,200W. With a three-phase 25A main fuse, the maximum inverter power with two inverters is 17,250W. With a 35A three-phase main fuse, the maximum inverter power with two inverters is 24,150W. When using two inverters, each inverter is placed on its own earth leakage circuit breaker. The fuse of the solar group remains 1.6 times smaller so that your main fuse is also safe in the event of a short circuit. With a total inverter power of up to 10,000 watts, a 100mA residual current device will suffice, with more inverter power, a 300mA residual current device must be installed.

AC wiring

The AC cabling is generally installed by the electrician. If Robisol takes care of commissioning the inverter, we assume that a fused AC cable is made available at the location where the inverter may be hung. YMVK cables are used as standard for connecting the AC side. For a single-phase inverter, use a three-core cable; for a three-phase inverter, use a five-core cable. We recommend that a maximum voltage drop of 1% be taken as the basis for the cable diameter required and that the following advice be given for the cable diameter:

Inverter phase cable length YMVK cable

2000W 1-phase 20m 3 x 2.5 mm2

3000W 1-phase 20m 3 x 4 mm2

4000W 1-phase 20m 3 x 6 mm2

5.750W 1-phase 20m 3 x 10 mm2

11.000W 3-phase 20m 5 x 2,5 mm2

17.000W 3-phase 20m 5 x 4 mm2

27.000W 3-phase 20m 5 x 6 mm2

44.000W 3-phase 20m 5 x 10 mm2


AC Circuit Breaker

The AC isolator, which is installed next to the inverter, generally forms the demarcation line between the electrician and the PV installer. It allows the AC voltage to be switched off directly next to the inverter. We consider this to be desirable for the safety of the user and also an excellent instrument to ensure that the installation warranty of the electrician on the group box remains separate from the installation warranty of the PV installer on the inverter. If required, Robisol can supply and install the AC isolator.

LAN cable or WiFi signal strength

To monitor the performance of your installation, the inverter must be connected to the internet. The inverter has a LAN or Wifi connector for this purpose. This differs per inverter. A Growatt inverter is supplied with a Wi-Fi connector as standard, a SolarEdge inverter is supplied with a LAN connector as standard. If Robisol is responsible for the installation and commissioning of the inverter, we request that you provide an available LAN cable or a Wifi network with sufficient signal strength, depending on the inverter. If we do not have access to your router during installation, we will assume that network access is activated by the customer. If you purchase a SolarEdge inverter but prefer a WiFi connection, a SolarEdge SE WiFi communication kit can be installed additionally for you. If you are buying a Growatt inverter, but prefer a LAN connection, a Growatt LAN module can be provided. In both cases, please let us know 2 weeks before the installation date if you would like to make such a change.

In basic terms, a solar installation consists of simple electrical components. As mentioned, it is desirable to pay some attention to the weight of the earth leakage switch, but apart from that it should not be a problem to deliver a well-functioning installation in cooperation with your electrician. If required, Robisol can also take care of a modification to the distribution board and an AC cable routing, but if you have an electrician, it is advisable to discuss this with him/her.

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