Feedback received from ECA WA members engaged in the solar industry indicate that there are a significant number of roof-top fires occurring throughout Australia caused by the failure of roof mounted DC isolators. ECA WA has raised its concerns to Building and Energy who are also aware of this problem.
Although the DC isolator is approved and, in most cases, installed correctly, when up to 700 volts DC (residential) passes via a switch exposed to the elements, the risk rate is always going to be high. A small amount of condensation within the switch enclosure due to changing temperature extremes, or moisture over time entering through a damaged seal, will result in arcing. On high DC voltages this arcing is very severe and will cause a fire, which will continue to burn regardless of what additional measures are put in place.
The question needs to be asked as to what the benefit of these roof top mounted isolators is, and, can we eliminate the risk, rather than just compounding it by introducing more onerous regulations. Most countries throughout the world, including New Zealand, have removed the obligation to fit roof-top DC isolators, however we continue to enforce their installation in Australia.
ECA WA believes that the original intent of the roof-top DC isolator was to enable emergency fire personnel to isolate the solar PV unit in the event of a fire, however in reality it is unlikely that fire officers will climb onto a roof in thick smoke in order to locate the isolator.
ECA WA’s view is to eliminate the root cause of the problem by removing the obligation to install roof-top mounted solar unit DC isolators, as they have done elsewhere. If a DC isolator is required, then a much safer option is to have it adjacent to, or incorporate it as part of, the inverter.
We will continue to update members on further developments in this area.