And from the comfort of my chair - well this flash light too... I can see a solution... Although a tree pruner may have been put artfully to effect in the situation. The real tool would be standardization of the solar industry, and yes - some standards for disconnecting means of multiple sets of series panels...Sue Kateley, the executive director of the California Solar Energy Industries Association, a trade group, said DC cutoffs create danger because they mislead firefighters.
The solar panels remain energized as long as the sun is up, and they even retain some electricity when it's dark. Putting a cutoff on the roof only neutralizes the wire running from the panels to the inverter box, but it doesn't eliminate the danger to firefighters.
"It's that perception of safety we want to avoid; they think they're safe, when there's potential from getting a shock, and falling off the roof," she said.
How many tarps do you expect them to carry?Rather than requires a disconnect why not show fire fighters the faster way to cut power to a PV panel.... put a tarp over them.
Cover panels.... disconnect AC main... no power coming in
Just a thought rather than requiring a DC disconnect that would still not truely kill the power coming from the panels.
As would I. My thoughts in looking at the photo: What a mess. Where was the company that installed the system? We have really only had one emergency call but we were there ASAP. (Corroded meter socket, which failed when the utility changed the meter)I would question the actual installation of this system.
This type of fire is rare, but can happen.
And, if there are more than two source circuits, there must be fuses on the roof for each string.
Personally I would be wondering why these systems are catching fire not so much as to installing some cutoff switch.Valid point on commercial systems... I was thinking of residential.
Granted most large commercial installations have DC combiner boxes with disconnected on the roof with the panels already.
Besides a micro-inverter system I doubt that we will see PV panels with disconnected built into the panel.
Hook stick operated plug at each set of panels... (That was my first idea - short of a tree pruner... )The connectors seem so cheap to me.
You're right! The fire Dept should not have to be trained in figuring out the fault - they should also not have to be subjected to a source of energy that lacks a disconnect or means of de-energizing. Nor should the owner of said system. It should be installed with a means if not to completely de-energize - isolate. Think big red button - or handle - 'break glass in case of emergency' etc.Some roof top commercial systems can be pretty big. And asking the fire department to identify which array the fault is in is probably asking too much.
Residential systems vary. It maybe easy to throw a trap over the whole array or there could be multiply array's on a number of roof surfaces. On large high end houses, you could have an obvious array on the front of the house. Then another array on a section not obviously visible.
In my experience in talking to Fire Chiefs regarding safety and solar. They generally don't want to leave safety up to a firefighters critical thinking skills. In that first adrenalin filled moment when they show up the Chief wants them doing what they are trained to do.
I think the simplest solution would be some kind of disconnect in the module.
A prime example of standards & methods....I like the hook style disconnect. Sounds very practical.
Does not need to part of the panel just a part of the hook-up wiring.
I recently saw a install where the Solar installer just laid a nema 3r style junction box on it's back right on the roof. The wires leading through the roof and to the panel below went through the back of the 3R box. The slope was at least 4/12. I don't think that type pf box is rated for that position. The conductors cam right through the roof no conduit at all just romex. I think it was UF type though
Me neither - but one would assume a multi-pole disco at what the solar industry likes to call a "combiner box". Many of which look DYI - or made in someones back yard manufacturing and distrubution center...Not having installed any of these systems myself, how would you provide disconnects for the fancy shingle-style solar panels? Even covering them may not be possible as it may not be immediately obvious which section of roof contains them.
nicely worded, but I don't think it's as simple as "article xxx.xxx says two or more source circuits"As would I. My thoughts in looking at the photo: What a mess. Where was the company that installed the system? We have really only had one emergency call but we were there ASAP. (Corroded meter socket, which failed when the utility changed the meter)
What's the code section on the 2 source circuits? I wanted to re-read it again but I don't have my code book handy.
I don't see that as very plausable in the installation.What about having a standardized load-break elbow on each conductor located at the solar panels? I've never seen a solar panel install, but I imagine we're only talking two conductors unless they're really massive commercial systems.
Firemen carry hotsticks. This isn't medium-voltage. They can yank each elbow from a safe distance, totally isolating the solar panels from the rest of the electrical system.
690.9 covers PV source circuits, while I just scanned through it. To paraphrase, Protect the wire, modules and inverter terminals from DC short circuit currents (It can be done by design as well as overcurrent protection) I am pretty sure it doesn't mention requiring fuses (or overcurrent protection) at roof level.nicely worded, but I don't think it's as simple as "article xxx.xxx says two or more source circuits"
It would start with 690.9 and go to 240.15, i believe, going off of memory.
There is an exception in 690.9 about the short circuit currents. I believe the exception applies with 2 or less source circuits, basically by process of elimination. After that, I think the exception wouldn't apply.
As far as covering the array that was mentioned, 690.18 gives 3 possible solutions.