Installation Of Fronius System By Inverex


To install Fronius symo 5.0-3-s grid tie inverter in RASHIDABAD existing solar project.


During the planning stage of Rashidabad’s solar project the inverter was under sized because of which only two strings were connected. That’s why the third string was remain unused since the installation time. And we were unable to achieve maximum percentage of efficiency.

Following data were observed by interns phase 3 to decide the new size of inverter.

• Outback’s inverter capacity: 7 KVA

• Production by a single solar string: 3.6 KWH

• Production by two solar string: 3.6*2 = 7.2 KWH

• Production of all three solar strings: 3.6*3 KWH = 10.8 KWH

So, according to the above mentioned specifications. We can observe that the inverter is undersized. It can only bear upto 7 KVA which means only two solar strings can be connected to that inverter.

We were in need of another inverter of size greater than or equals to 3.6 KVA to utilize maximum production of solar by connecting third string.


So, for optimizing the system, Interns phase 3 decided to install a new inverter to obtain maximum efficiency from the installed system. For this purpose instead of using hybrid system we proposed on grid system to utilize the energy of third solar string. On-grid or grid-tie solar systems are by far the most common and widely used by homes and businesses. These systems do not need batteries and use common solar inverters and are connected to the public electricity grid. For this new installation, we hired a local vendor inverex and choose Fronius symo grid tie inverter.

The reason of choosing on grid system:

• The on grid solar power systems will reduce the electricity bills. (Currently, RASHIDABAD system is not working on net metering method. But it can be applied in future),

• This is an investment on return. If you invest in on grid solar power plant you will get returns for sure.

• The lifespan of on grid solar power systems is more. You can use it for a long period without any damage.

• This system will reduce the carbon footprint. Thus help our environment pollution free.

• There is no need of expensive batteries to store the electricity.


4.1. Fronius symo 5.0-3-s:

Fronius symo is 5 KW grid tie inverter which coverts DC power of solar into AC and supplies AC power to the load.

• If solar generation is greater than load demand: If the solar is generating more power (generally, in peak hours of the day) and supplying to the load while producing excess energy than in this case Fronius symo inverter will feedback AC power to the grid.

• If solar generation is less than load demand: When solar system is not operating, or load is using more electricity than the system is producing, the load will start importing or consuming electricity from the grid.

What if we don’t want to feedback to the grid?

The existing system in RASHIDABAD is implemented as a so-called export limitation scheme (zero feed-in / zero export) whereby either the energy generated is consumed by the producer (100 % consumption) or the PV systems power output is limited but will not feedback to the grid.

4.2. Smart meter (50 KA):

A smart meter is an electronic device that records consumption of electric energy and communicates the information to the electricity supplier for monitoring and billing. Smart meters enable two-way communication between the meter and the central system. The Fronius Smart Meter is a bidirectional meter that optimises self-consumption and records the household’s load curve

4.3. Communication Cable:

To connect Fronius inverter which is installed in the control room (third floor of hospital) to the smart meter (installed in generator room), a communication cable is pulled from generator room to the control room.

4.4. Surge protection device (SPD):

Surge protection should ensure that surge voltages cannot cause damage to installations, equipment or end devices. This device is connected in parallel with the 4 pole circuit breaker. As such, surge protective devices (SPDs) chiefly fulfil two tasks:

• Limit the surge voltage in terms of amplitude so that the dielectric strength of the device is not exceeded.

• Discharge the surge currents associated with surge voltages.

4.5. 4 pole circuit breaker:

4pole MCCB for 4 wires connections, the one additional 4th pole for neutral wire connection so that between neutral and any of the other three will supply. It is used where is the possibility of high neutral current (due to unbalance loads and /or 3rd and multiple of 3rd harmonics current etc) and Neutral / Earth Protection is provided on Neutral.

4.6. Ceramic fuse:

Opaque and metal tipped, a ceramic or sand fuse is fairly common. A ceramic fuse is built to withstand high temperatures. The more thermally stable fuse is typically filled with sand in order to prevent. the conductive film from forming. The film is formed when a short circuit melts the fuse element, causing a deposit to be seen on the inside of the fuse barrel as a film.

4.7. Connecting cables:

Connecting cables are used to connect breakers with SPD in parallel.

4.8. AC cable 60 ft:

From generator room, right after the main grid supply DB, AC cable is pulled to the control room (third floor of hospital) which is bidirectional. This is connected to the 4 pole circuit breaker of inverter. It is noted that the AC cable of the inverter should be connected to the main supply from grid. The problem encountered during the installation was that the AC cable of the inverter was first connected to the basement DB which is the incoming supply of hospital. But it is clearly mentioned in the user guide manual of Fronius inverter that the AC cable should be connected to the main grid supply DB. Main grid supply DB is situated outside the hospital in the generator room. So, the AC cable was first disconnected from the basement DB of the hospital and then connected to the main grid DB of the generator room.


final picture of fronius system