Installing your own Solar System
We strongly recommend that you have your solar system installed by an accredited solar installer. If this is not possible and you wish to install it yourself or with a friend, the following article gives a brief overview of some general wiring principles. If in doubt seek professional advice!
The following suggestions are offered:
There are now several hundred pages of standards that apply to solar and extra low voltage- electrical installations. The applicable primary standards are:
- AS 4509 Stand-alone Power Systems
- Part 1 Safety requirements
- Part 2 Design guidelines
- Part 3 Installation and maintenance
- AS / NZS 5033: 2005; Installation of photovoltaic (PV) arrays
- AS 4086 Secondary batteries for SPS Part 2 Installation and maintenance
Other relevant standards include:
- AS 3000 Electrical Wiring Rules
- AS 1768 Lightning Protection
- AS 1170.2 Wind Loads
- AS 4777 Grid Connections of Energy Systems via Inverters
- AS 3001 Electrical wiring rules for mobile applications
A common fault is using undersized cables. Cables should be sized so that the voltage drop is not greater than 5% - e.g.: 0.6 Volts for a 12V system. See our handy table on 12 and 24 Volt voltage drops.
Note that we use sq.mm. to refer to our cable sizes - some suppliers and manufacturers use mm when selling their cable. Cables should be protected in conduit if exposed to the elements, risk of mechanical damage or attack by rodents. Your 12/24 Volt cables should be physically separated from 230 Volt wiring and never use 230V type power points for 12 or 24 Volts!
Every circuit should be protected by a fuse or circuit breaker. The main leads to the battery should be protected by an HRC type fuse, installed below the vent level of the batteries. Where a smaller cable is connected to a larger cable the fuse should be sized to protect the smaller cable. Read more about fuse sizes.
Label your breakers so you can identify them in the future.
According to Australian Standards batteries are to be inside a ventilated, lockable and vermin proof box. The terminals should be protected with terminal covers so that explosions won't occur if an screw driver or something falls across them. Flooded wet cell batteries should also be installed on a battery tray (to contain acid leaks).
There should only be one cable going to each battery terminal. Spaghetti junctions at the terminals should be avoided. Multiple connections should be made using links in the distribution box. Read more about Battery Enclosures.
a) These should point north (in the Southern Hemisphere) at an angle suggested by your solar designer. This will generally be at a 'best yearly average'. However, depending on your loads you may wish to maximise your solar input for either summer or winter conditions. You can get some idea of suitable angles for Australia by looking at the solar radiation figures for some selected locations in the drop down menu for Solar Radiation Figures.
b) Make certain that water won't creep along your cable to your solar panels into the J box at the back. If the cable is coming above or horizontal to the J box have it loop down first below the J boxes so water can drip off it first.
c) Make certain your panels are securely bolted or fixed to your roof or other structure so they don't blow away in the first storm. If possible leave a 50-100 mm gap between the modules on the frame to reduce the wind loading.
d) You might like the appearance of your panels flat on your roof. We generally prefer to see them at least 150-200mm above the roof to help keep them cool and to avoid any build up of leaves or vermin under them. Remember, one day you may need to access the wiring for service or testing purposes. More information on mounting & ventilation of solar panels.
e) Your panels, like all other circuits, should be protected by fuses or circuit breakers. One day in the future you will probably notice a decrease in solar input performance. This will probably be due to a poor connection or failing batteries. In very rare circumstances a solar panel could develop a problem. Fault finding when there are multiple panels can be a time consuming task. We suggest you have at least a separate circuit breaker for each half of your solar panel array. If you have many solar panels, we suggest you have a separate breaker for every two or at most four panels. By installing extra circuit breakers you can turn off sections of your array and observe the difference it makes to your solar input Amps. If there are no observed differences, any performance decrease is now most likely to centre around the battery connections. The new Australian Standard 5033 specifies lots of breakers on longer arrays- 70 pages of PV cable protection!
f) Check your wiring first with a voltmeter before turning your circuit breakers and appliances on. The open circuit voltage of solar panels connected in parallel for 12V should be 18-20V or double that for a 24V system. Connected to a 12V battery you would expect a voltage of 12-15 Volts depending on your battery state of charge. If the voltage appears to be correct, slowly turn on your lights and other loads. If some lights go dim when other loads are turned on this is probably an indication of poor connections, undersized cables or poor battery condition.