There has been a lot of talk about solar and photovoltaic systems of late, mainly because of Government incentive packages for the installation of these systems in homes coming to a close.

The abolition of grants for solar panel installations and the fact that credits paid to home owners have been reduced mean that home owners are currently reassessing their need for a solar system at home.

Up until the start of 2010, photovoltaic (PV) systems could be fitted by any person, whether skilled or not, with an electrician only required to make a connection to the meterbox and thus into the grid.

This has since been changed because some installations have simply not been safe. And, as a result of this, regulators now require the electrician that installs the system and makes the connection to the grid to be accredited by the Clean Energy Council (CEC).

Essentially CEC accreditation is necessary so that Renewable Energy Certificates (RECs) can be claimed. While that makes you think, it’s not the reason for this article…

As a member of an electrical trade, you need to ask: What are my customers getting from installing a solar system? And what are the issues from a safety and performance point of view?

Well, beware! If you play with snakes you could be bitten.

Solar panel systems are probably one of the most dangerous systems that can be installed at a residence, particularly if due care isn’t taken.

Let’s look at some of the reasons why:

Wiring of the isolators in the correct polarity
Polarised and non-polarised isolators, or circuit breakers for the isolation of the solar panels, are quite legal and legitimate to use. But there are issues here that can lead to very dangerous situations.

A polarised circuit breaker or isolator requires that the current flows in a certain direction within the unit. This is because a magnet is used to draw and extinguish the arc from the contacts upon disconnection. If you run the current in the opposite direction the magnet does nothing to extinguish the arc and the result is a fire within the isolator or circuit breaker, regardless of being switched off manually or whether there is an overload and subsequent disconnection.

A non-polarised circuit breaker or isolator does not have this problem and would be preferred by the installer. Either way the installer should follow installation instructions to ensure they work safely.

What exactly is isolated?
In all States there is a requirement to place the DC isolator or circuit breaker at the inverter. In selected States there is the additional requirement of placing a DC isolator at the solar panels.

Considering that the solar panel creates DC power as long as the sun shines, if you switch the isolator off at the inverter there is still a live current in the solar panel and, as a result, in the cable from those panels to the isolator at the inverter. Any problems that occur, for example the cutting of cable, means the possibility of an electric shock at the panels or in the cable.

Where there is an isolator at the solar panel that is switched off, the cable to the inverter is isolated but the panels are still producing power and are live. This means there is still a possibility of electric shock at the panels.

As yet there is no satisfactory way of shutting down the panels and making them safe.

A DC isolator can be a circuit breaker or an isolator unit
This is causing much angst in certain parts of the country for installers. An isolator can be a DC circuit breaker fitted into an appropriate enclosure or a complete DC isolator assembly. Circuit breakers are approved as a switching device for isolation.

NOTE: A DC isolator must be able to handle 1.2 times the voltage in the string.

This is a really easy calculation for the installer where you add up the voltages in the string and then multiply them by 1.2. The result is the string array voltage and the isolator must be able to carry this voltage. So, if this calculation works out to be 415V DC, then the array should be isolated using a 500V DC isolator.

Fires
If a fire starts within the panel then it will continue to burn during the daylight hours because electrical power is still being generated. It will only stop at night.

Unfortunately, that fire will start again as soon as the sun rises the next day.

This has been a real issue in Europe and has been seen within Australia. Dealing with these fires is of real concern to our local fire brigades and you will find that in some areas the fire brigade will not be able to do much about it because the panels are live and could be of a very high DC voltage and dangerous to work around.

Earthing of PV systems
The revised AS/NZS 5033 Standard, Installation of photovoltaic arrays, will say that there are three reasons for earthing the exposed conductive parts of a PV array:
•    Protective earthing to provide a path for fault currents to flow.
•    Lightning protection.
•    Equipotential bonding to avoid uneven potentials across an installation.

NOTE: Exposed conductive parts are used here in the same way as “exposed metal” is defined and used in AS/NZS 3100.

Recently there has been a requirement for PV systems to be earthed when connected to a transformer-less inverter. This means the frames supporting the solar panels are to be connected to an existing earthing system. This is to ensure that there is no isolation between the existing earthing system and the PV system on the roof. With an inverter that uses a transformer there is segregation between the two systems and hence no need to earth the frames.

Damage to PV modules can result in under-performance
Any dents or knocks to the front or rear of a solar panel during installation can result in under-performance, which could result in call backs from customers when expected monetary gain or savings are not achieved.

Replacement of modules
In the event that a solar panel needs to be replaced it should be with a panel of the same characteristics in regard to voltage output and performance or there is a high risk that the system will be under-performing and the subsequent call back from your customer will be a real pain in the back pocket!

Water damage to connections
One of the biggest problems has been the poor standard of installing weatherproof isolators, or enclosures housing the DC circuit breakers, in the vicinity of solar panels. It seems that someone has forgotten to mention to some installers that the Wiring Rules requires due care to be used when fitting cable to these enclosures.

In most instances these enclosures have screwed conduit entries or cable glands for cable entry. Review the provision and ensure that you create watertight seals, even if it means using silicone. Any ingress of water will mean a failure of the isolator within so use a reputable manufacturer’s enclosure and abide by their instructions.

Systems need to be structurally connected to the roof structure
Another issue has been the poor fixing of systems, panels and supports on to the roof structure. The terrible practice of screw-fixing the supports on to galvanised roofing iron, for example, has been seen and you can imagine how dangerous this would be in the event of high wind. That’s why it’s imperative to ensure that all supporting members of the system are structurally connected to the roofing structure itself so that the system becomes part of the structure of the house.

Make the most of the sun
It is vital that the installation provides the best possible access to the sun throughout the day. Any shading from trees or buildings will result in under-performance and that may result in unhappy customers and that dreaded call back. Invest in devices that can measure the sun’s position relative to the location and provide the necessary angles of setup for maximum power generation.

Inverters feeding into the grid
This issue is directly related to the quality of the inverters installed in the system. Many of the lower quality, and often lower priced, inverters on the market are putting excessively high voltage into the grid.

Also of concern are the poor harmonics of that signal. High voltages can play havoc with electronic devices and possibly damage or destroy them. Poor harmonics may also cause a problem in regard to performance of the electronics within any device.

So, as you can see, my reference to playing with snakes is pretty apt. If you don’t know what you are doing you are likely to be bitten.

If you don’t know what you are doing with solar systems then leave them alone.