Reliable, quality breakers are an important part of a safe, professional Solar PV system. To ensure your safety and the longevity of your system, Greenforce Energy only use DC rated breakers from known brands such as ABB, Clipsal, Moeller and GE.
For home solar power in Sydney, it is normal to have a breaker or ‘twist knob’ isolator on the direct current (DC) circuit running from the panels to the input of the inverter. This is referred to as a Solar DC Isolator, a PV Array Main Switch or sometimes a solarswitch. The typical location for this is the left hand side of the inverter, usually towards the bottom (where there are sockets for the DC input cables). In some other states, there are also breakers on the roof, and a case can be made for both including that or excluding rooftop breakers (due to the possibility of water ingress).
It is important to note that due to the nature of DC electricity, AC circuit breakers cannot be used for solar PV circuits (exception: very small hobby situations). In addition, the DC breakers are often polarised, meaning that it matters which side of the breaker that the current enters the breaker; there are markings on the breaker that trained professionals can follow to ensure the breaker is wired correctly.
The reason for the polarized nature of the breaker is that extinguishing a DC arc is more difficult than breaking an AC circuit, and it requires a sophisticated approach to pull the arc aside using magnets as the circuit is broken – leading to a more compact size. Non-polarized breakers are also available, however these are usually larger in size or have shorter cycle lifetimes.
Because of the potential to select the incorrect breaker for the circuit, new installers and electricians without solar training are encouraged to review manufacturers documentation and consult widely with peers before working on circuits that require DC breakers. It’s important to note that in the Solar PV case, the positive marking is the point where the panel’s positive wire is to be connected, since the panels are the source.