With record-breaking heat and bushfires raging across the country, times like these are a sobering reminder of why we need more solar energy – and also a reminder that those of us living in vulnerable areas should adequately prepare and maintain our rooftop PV systems.
I recently heard a conspiracy theory supposedly coming from the US about how Australia made the California fires a million times worse. However, this is not the usual argument about our massive fossil fuel exports and world-leading carbon pollution.
The Americans have found out that we have planted arsonists all over their country.
We already know, but after more than a century of sowing, Californians have discovered that eucalyptus trees are flammable. Without native pests, rubber trees thrive really well in a Southern California climate. I’ve seen firsthand that they actually grow taller than the trees you know here.
I’ve also seen firsthand the crazy wood shingle roofs they use, but the point is that we all need to be careful about how we build and maintain our homes.
BAL is the new black
Bushfire Attack Level (BAL) is the planning jargon that describes how you should build a new home if there is a chance it could be at risk of fire. On the whole, the deeper into the bush you build, the stricter the rules are, and justifiably so.
When working on homes that meet the highest standards, the golden rule is to achieve everything to the millimeter. When finished there should be a gap of no more than 1mm in each finished surface and behind that a mineral fiber insulation (rock wool) will fill the voids.
There aren’t much differences when it comes to installing solar on your roof than the average suburban home, but there are three details that are really worth getting right.
This array had a number of problems, but leaves were one of the worst problems.
Penetrate the roof
Running DC wiring from the roof to your inverter requires mechanical protection in accordance with the Australian Solar Standard (AS 5033). For a BAL rated installation, this means using what is known as an “anaconda,” a flexible metal conduit in a protective plastic casing.
The hole in the roof must have a tight tolerance to meet the 1mm gap requirement. The best course of action in our opinion was to install the plumbing, wiring, and weatherproof rubber sheathing (often referred to by the trade name Dektite) with urethane sealant.
The black plastic jacket prevents corrosion of this flexible metal pipe.
The next day we stretched the flashing enough to attach a caulk gun to the outside of the pipe, then pumped foaming sealant into the cavity between the flashing and the roof.
This “fireproof” caulk is not a good glue or sealant – it’s difficult to use because it doesn’t stick anything together, but it fills gaps so the caulk still provides some protection even if the rubber seal has burned off.
If you really want a bombproof system and care about an industrial aesthetic as much as I do, the best idea is to run the DC wiring in a metal conduit and run it outside the building.
This bush home has copper pipes used for a fire sprinkler system. (highlighted in green) To avoid drilling the asbestos eaves and roof, the DC line is routed externally.
Mounting on vertical rails
Keeping the roof clean is crucial and it is easier if the mounting rails run parallel to the roof rather than across it.
Average houses have a roof pitch of 22.5° and anything higher than that will cause rubbish and wildlife to slide off immediately.
Solar regulations require a 4mm² ground wire for mechanical strength. This provides good support for DC cables, but even better is using a plastic-coated steel support cable.
In my experience, cobwebs are the biggest problem when cleaning under solar panels at relatively low altitudes.
Not even a gasoline-powered garden blower can break the silk threads that entangle leaves and bark. So you’ll need some sort of broom to move everything along. It’s slow, tedious, fiddly and awkward, even taking the roof angle into account.
If your array is on horizontal rails and is more than a few feet long, it will be impossible to clean without dismantling parts.
Modern panel frames are often only 30mm deep, making it difficult to run cable ducts or ground wires (arrow) on top of the frame. If you can find 35mm frames, they offer more options for neat cabling
Cable management is crucial
If the AI hype of the last few years has taught me anything, it’s that the word “crucial” has been overused.
However, I’m really serious here. If there are any obstacles, leaves or branches under your solar system will get stuck and it only takes one to cause a cluster of others. This is why Australian standards insist that none of your array cabling should hang down and touch the roof.
Ground connections must be sprayed with cold galvanizing paint to prevent corrosion.
It really does take some planning and some pride to get a good result, but you really need to make it clear to your installer that dangling cables are not acceptable. They are often very reserved when it comes to making the top aesthetically nice and straight, but the functional cable management that you can’t see is more important.
While this line is good practice, it runs under the rails near the roof, making it easy for trash to get caught there.
One of the best ways I know is to run support cables across the array frame before the modules fall down. This gives your electricians a nice, narrow path for the cables to run safely.
If you look up from the bottom and can see straight through, you can easily check and clean it
While this isn’t always possible, one of the cleverest ideas I’ve seen for solar maintenance was simply a very long broom that could be used to easily sweep the roof from the ground. The biggest trick was making sure the wiring wasn’t broken in the process.
It should be noted that not all parts of the array are the same and the connection point of the wiring may be a bit messy
For guidance on what to do with your solar system and battery if you need to evacuate due to a bushfire, see my detailed guide.
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