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Solar Insiders Podcast August 23

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Is your rooftop solar system a fire risk? It seems the biggest risk of household fires from rooftop solar PV may be due to a standard imposed by fire authorities in Australia nearly two decades ago.

Nigel Morris, from Solar Analystics, joins RenewEconomy and One Step Off The Grid editor Giles Parkinson to discuss the fire risk issues in our regular fortnightly podcast on the solar industry, Solar Insiders.

The issue is not just DC Isolators, often cited as the major culprit, but also the use of high votage DC equipment. Morris describes how this came about and what could be done.

Also on the agenda are some more dodgy sales practices, with one installer being sprung by the regulator, and another under scrutiny over letters sent out to solar households about so-called battery storage “discounts.”

Thanks to all those who gave us great feedback on the first podcast, and please give us your feedback, leave a review on iTunes to help more people find it.

You can find the back catalogue of Solar Insiders and Energy Insiders podcasts here.

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Solar Insiders is sponsored by Solar Analytics

 

  

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  • Bill Holliday

    I was disappointed to hear Nigel attributing cable protection as a reason for fitting rooftop panel isolators. Solar panels are inherently current limited and the current at maximum power point is not much less than this current limit value so the cabling would be rated at this value or greater.

    I was also a little disappointed to hear 240v AC micro-inverter systems being described as a way of reducing cable current. This may be true when talking about low voltage (12V, 24V or 48V DC arrays) but not true when talking about the typical high voltage string of 400V or more.

    I was under the impression that DC rooftop isolators were there to allow maintenance people to isolate the cable from the panels. If 38% of fires are caused by rooftop isolators with perhaps all of these fires resulting from water ingress to the supposedly water proof isolator enclosures then one must ask whether it would be less safe to isolate the panels using a (suitably rated) semiconductor isolator than a damp mechanical one or to reduce the panel output by covering them and then shorting out the remaining (small) DC current.

    Alternately, the isolators could be housed within an enclosure within another enclosure, the outer one possessing a suitable drain hole. One might also ask whether rooftop isolators should be used at all, considering that they are often hard to access (rooftop) and that there are isolators at the DC input to the string inverter.

    • Alan

      The isolator at the inverter only isolates the tiny bit of cable up to the inverter. It’s still live from the panels all the way to the isolator which is the problem.

    • Nigel Morris

      Thanks Bill, yep, I apologise for that. In the early days CBs and fuses were used but i agree it’s only an isolator today. What I meant was it offered protection for someone wanting to do work on the cables, if switched off but I muffed the description and i’m still getting used to the rapid fire pace of the “Ad lib” conversation with Giles. Ill correct it next episode!

  • Steven Zilm

    I have just had a listen to the first 2 podcasts…. Interesting…. keep up the good work!…. Now, in the interest of clarity, just a quick definition for you both remember… In Australia, high voltage or HV, in relation to electricity, means electricity at a voltage exceeding 1,000 volts alternating current (ac) or 1,500 volts direct current (dc);
    We do not have high voltage solar! Simple!
    DC rooftop isolators are only part of the roof top problem, mismatching DC plug and sockets are as big a problem or fire risk.
    There is nothing wrong with a correctly installed rooftop isolator, although it can lure the uneducated into believing there is no voltage when it is switched off…

    • Nigel Morris

      Thanks Steven – several people have corrected me on this so my apologies. Ill correct in our next episode! Completely agree on connectors, they were the root cause of fires in the BP recall. However, way too many isolators are failing despite many attempts and setting standards.

  • Solar PV Expert

    As another commenter has astutely pointed out, the cause of the disproportionately high number of solar-related fires in Australia could not possibly be “high
    votage (sic) DC equipment” because solar systems do not use any
    such thing anywhere in the world, including in Australia. However, if
    we assume that by “high votage (sic)” they mean low voltage, then
    one is still left to wonder why Australia leads the world in solar
    panel fires when every place else uses the exact same equipment. If we
    go ahead and look at the evidence, then we indeed find that DC switch
    disconnects are a primary cause of faults, failures, and even fires
    everywhere they are used, even when they are not used on a rooftop. This has to do with the nature of DC electricity. Indeed, the European PV installation standard does not call for switch-type DC disconnects at all–too risky. Again, looking at the evidence, one finds that the leading cause of fires in Australia is, by far, the rooftop DC
    isolator. Given that this requirement is uniquely Australian, while low voltage DC equipment is not, it is not surprising to find that Australia, with its fire-causing rooftop
    DC isolator requirement, is #1 globally in solar fires.