Odd claims, some electricians warning about using DC isolators with PV

[AlaskanNoob]

Apparently, at least in the UK, there is some concern about using DC isolators with solar panels as a fire risk despite isolators being required. Haven't looked much into this new development. I guess there has been a rash of fires lately and this is one of the new recommendations, to not have an isolator unless it's built into your inverter.

Or so says this video anyway.

 

[OffGridForGood]

I didn't hear any clear connection between the fires and the DC disconnects.
That said, I don't put much faith in those typical plastic rotatary DC disconnects - and I am not allowed to use them in Canada anyway.
I needed a metal case, double pole fast acting (snap open) dedicated disconnect, and I have checked it under full PV load - no arc.
If you want to work on your inverter, during the day, and don't have a PV disconnect, sounds like a worse safety issue.

 

[Danke]

Solar kills.

 

[profesor79]

interesting...
just did some googling and found this: https://worksafe.nt.gov.au/forms-an...tallation-increases-risk-of-dc-isolator-fires
They pointing that source of fire is rather in wrong montage, than the isolator itself.

 

[upnorthandpersonal]

I didn't hear any clear connection between the fires and the DC disconnects.

Incompetent installers.

 

[SupraSPL]

When there's a long sunny day, I notice a bit of heat buildup in my DC breaker box with 6 breakers, 6 strings of 8 gauge THWN carrying 20 amps each. It's hard to measure the voltage drop because the PV voltage is always bouncing around but yeah ironically safety devices are expensive to do right and add complexity and potential points of failure to any system.

 

[OffGridForGood]

Incompetent installers.

DIY - the only safe way to do it!

 

[AlaskanNoob]

That DC isolator is the most concerning part of my install. Because I am, most definitely, an incompetent installer. I put two arrays into one of those isolators and it was a bit of a cramped space to work in. I'd hate to find out one of the wires wiggled loose in there.

I'd almost rather forego the isolator and just go unplug one of the connections at the panels themselves to isolate it.

 

[timselectric]

DIY - the only safe way to do it!

At least you won't have anyone else to blame. lol

 

[wattmatters]

Rooftop DC isolators have been the cause of more than half of the fires related to rooftop solar PV in Australia. It's not a lot of fires in total but the issue is usually isolators getting damaged in the sun and water ingress, causing corrosion, poor contacts, heat build up.

Rooftop isolators since 2014 were required to have additional protective covers and more recently their requirement has been abolished if alternative safety measures can be implemented (not always possible so rooftop isolators still get installed here).

The irony is the requirement for rooftop isolators was insisted on by the fire fighting authorities - yet they were the most likely cause of PV fires and are rarely if ever actually used.

As to isolators on a wall near an inverter - the main thing to check is the quality of the isolator, and ensure it is well protected from water ingress. Avoid top entry conduit/cables for instance, and drip control for any condensation inside PV conduit. Also avoid using them when generating, best to shut down the inverter first, then do the DC disconnect. Only in an emergency would I consider switching a DC isolator when a system is generating. Obvious not a concern at night.

I like to get my rooftop isolators checked every so often.

 

[timselectric]

The irony is the requirement for rooftop isolators was insisted on by the fire fighting authorities - yet they were the most likely cause of PV fires

Job justification? lol

 

[SparkyJJO]

At least you won't have anyone else to blame. lol

Been there done that when doing DIY.

At least I learned something NOT to do...

 

[SupraSPL]

Rooftop DC isolators have been the cause of more than half of the fires related to rooftop solar PV in Australia. It's not a lot of fires in total but the issue is usually isolators getting damaged in the sun and water ingress, causing corrosion, poor contacts, heat build up.

The irony is the requirement for rooftop isolators was insisted on by the fire fighting authorities - yet they were the most likely cause of PV fires and are rarely if ever actually used.

???

Avoid top entry conduit/cables for instance, and drip control for any condensation inside PV conduit.

Good point. I have top entry above my DC breakers so I put a drip hole in the horizontal before the box.

 

[OffGridForGood]

Interesting, in this case you are talking about isolators at the PV panel array - up on a roof.
In my case, the disconnects are specifically to be at ground level (accessible), exterior rated, metal 2P, DC snap-action disconnects. I mounted them on the wall, and I have checked on them from time to time, no corrosion in the boxes. Point taken to keep checking once or twice per year.
Inside I have a second set of disconnects interior before the Inverters on each string, these are fused. I have again metal boxes, snap-acting disconnects, I find myself using these once in awhile to safetly do work on my system with the PV isolated.

 

[wattmatters]

Interesting, in this case you are talking about isolators at the PV panel array - up on a roof.
In my case, the disconnects are specifically to be at ground level (accessible)

We are required to have DC isolators at the inverter as well. Some inverters have it built in.

Mine at the inverter:

While that's an exterior wall, it's under a 2m wide eave and well protected from the elements.

 

[OffGridForGood]

yes, if my inverters had their own integrated isolator switch, then I wouldn't need the interior disconnects.
Those plastic rotary switches like in your photo - I am sepcifically not allowed to use. This bothered me at the time, since the required disconnects were far more expensive, and I needed four. Today I feel like maybe there are reasons for the code requirement on these. Like yours, my exterior ones are under a roof eave.

 

[wattmatters]

Job justification? lol

Done with good intentions but with unintended and counterproductive consequences.

 

[wattmatters]

Those plastic rotary switches like in your photo - I am sepcifically not allowed to use. This bothered me at the time,

Yes, but also note the "SHUTDOWN PROCEDURE" label on the inverter. That's also a requirement.

 

[OffGridForGood]

Our exterior disconnects are intended for Fire Fighter use, prior to entry to the building. No 'shutdown procedure' will matter. If they are in a hurry they will use an Axe instead of the disconnects LOL!
{actually not, because I live off the beaten path by a good margin, the only firefighters will be the local volunteer group, they even asked if I would join since I have that training from my younger days. I figure I will be the only firefighter involved, unless the water bombers are called in...!}