Solar wiring standards to deal with water?

I had a fire in the DC isolator in my basement just past Xmas.  There was a faint smell of smoke when I got up in the morning.  I was directed to the basement where I could see flames coming from the DC isolator.



The fire was eventually extinguished by the crew of several fire engines, lots of CO2 and powder.
The power company guy went onto the roof to pull all the wiring from the solar panels as until then the firemen could not put the fire out with the fire being fed by the sun.

Anyway, water had got into the conduit and tracked right down directly into the DC isolator.  Another company came and replaced the cabling, and put grommets everywhere where there were none.  Another company had suggested a service loop be installed before the switch so that water could drop out of the conduit before it looped back to the switch but the repair guys said it was not necessary.  The water had entered the system not from the roof but where the cabling had penetrated the weatherboards.  An attempt had been made to waterproof it with silicon at that point but it clearly had not been successful.

What are the recommendations from the people here?  Should a low loop be installed before the DC isolator to stop any water from reaching the switches?

That's an unpleasant surprise, and a helluva mess to clean up.

I assume this is a grid tie solar installation? Lots of wattage involved, then.

I'm not qualified to make a pro recommendation, but "once bitten, twice shy" would be my philosophy. The wiring in a system like that should be equivalent to electrical code.

That said, it's amazing how much water can be diverted off of wiring by a few thoughtfully placed zip ties.

Yes, it's a grid tie system. On seeing the fire I shut down the DC isolator ( well, in retrospect that didn't do anything because it was shorting ), the inverter and the battery bank.
I managed to smother the fire with some cloth but then I could see it start up again so called the fire brigade.
They stood there and watched it get hotter and hotter even though they smothered it with CO2 and fire suppressant powder.  That's when someone got on the roof to disconnect the panels.
DC isolator fires have been the most common cause of rooftop solar fires in Australia as regulations mandated that the DC isolator was to be installed on the roof; where water got into them.
I believe they're changing that requirement now.

https://www.pv-magazine.com/2020/11/20/australian-rooftop-pv-safety-standards-under-fire-in-new-report/

The Clean Energy Council (CEC) is among those advocating for a rule change. A recent CER report identified water ingress in DC isolators is the biggest safety risk associated with rooftop PV. The CEC has said that including the DC isolator inside the inverter, rather than as a separate switch near the inverter, is the best solution.