Solar fire raises questions about panel safety

[e57]

Looking over some of the posts in this thread, I'd like to point out something. Just like there are hack electricians, there are certainly hack solar installers. (They seem to be coming out of the wood work these days).

I beg to differ - the back woods personnel dominating the solar PV industry are the actual "pioneers" in the industry unfortunate to say - (At least in CA) Back woods green types and off the grid types are unfortunately very well established in the solar market - what the problem is - the methods and education they have been allowed for the last 20 years are not acceptable for most urban or suburban areas away from camp sites.... Only recently have they been reminded that they are doing "electrical" work... And the scale has changed exponentially... One should note - most of the PV solar installs in this state - are not done by "electricians"... Not that I'm a huge fan of our state laws on apprenticeship, and certification of electricians - but these guys are not subjected to them... And IMO they need to be...

The solar industry in the last 5 years in CA has changed pretty radically. Many of the items people mentioned have been addressed by code sections, knowledgeable inspectors and manufacturers updating there products . (I.e. Modules use USE-2 wire which is Sunlight resistant, Conduit is required where exposed to physical damage).

Additionally legit solar installers just like electricians understand that a product must not only be listed but must be used as listed. Homemade combiners are hack or homeowner installs.

It's changed - and IMO not enough - but due to licensing, and more stringent inspection and criticism.

Most of the listed items used with solar are new products, and previously where 'made' - and some cases still 'made' due to non-availability Of the topic of combiner boxes - I had a conversation with a solar guy on one job about his 'listed' box... It was listed - as a NEMA 3 box... Which is what everything was installed in... A few buss bars, and some labels... It's still a j-box.

I was talking with my boss about the particular installation mentioned in the article. It seems like a listed flush roof mounted fused DC combiner would be the simplest solution. It would protect against DC faults inside a structure.

Fuses - may protect against short circuit but not 'every' fault. Carbonized wood becoming a current path due to cuts in insulation, water paths of current. Fuses, and even the location of fuse may have little or no effect for that situation.

The article - the fire was it seems like it started in what looks to be one of if not both inverters by wiring that is no longer in the enclosure...
http://www.nctimes.com/business/article_8a32fb03-9e3f-58ca-b860-9c7fe1e28c7e.html?mode=image&photo=2
Much of this seems to be without OCP at all - or means of disconnect.
http://www.nctimes.com/business/article_8a32fb03-9e3f-58ca-b860-9c7fe1e28c7e.html?mode=image
(Yes that's an aluminum ladder there in the picture...)

(Fusing) While this would not provide a Firefighter the ability to "Disconnect" the system, an array could "disconnect" itself if compromised. As far as I am aware this is not currently required by any NEC code section.

I doubt it would disconnect itself in many of the fault types that would present a hazard, and certainly not render the system safe enough to conduct fire fighting operations with say water... On the structure, and unless the voltage and capacity is reduced it would be a hazard to personnel.

As far as the NEC/CEC

690.5 Ground-Fault Protection.

Roof-mounted dc

photovoltaic arrays located on dwellings shall be provided
with dc ground-fault protection to reduce fire hazards.
(A) ​

​

Ground-Fault Detection and Interruption. The

ground-fault protection device or system shall be capable
of detecting a ground fault, interrupting the flow of fault
current, and providing an indication of the fault.
(B) ​

​

Disconnection of Conductors. The' ungrounded

conductors of the faulted source circuit shall be
automatically disconnected. If the grounded conductors of
the faulted source circuit are disconnected to comply with
the requirements of 690.5(A), all conductors of the faulted
source circuit shall be opened automatically and
simultaneously. Opening the grounded conductor of the
array or opening the faulted sections of the array shall be​

pennitted to interrupt the ground-fault current path.
​

​

​

​

​

The code should IMO elaborate on where this GFI device is located... That fire article didn't look like it had any.... And if it's contained in the inverter - that's the last point for it and does little to protect much would it...

And as far as disconnects - the more I look at 690 - the more I think that they are already required... I'd like to see if some more forum members with more experience in 690 have any opinions on that?
​

 

[ty]

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.

Yeah, I'm not looking at the book, but I believe it refers you to 240. (in 2008NEC)

240.15
Is for 2008. It clearly states fuses or over current protection is required for ungrounded conductors. We are currently using the 2005 NEC in CA. But I am certainly making a list of changes for the adoption of 2008 so this is good to know. It does not however mention it being required at roof level.

like I said, I don't think it is stated easily.
I'm shooting from the hip, so correct me if I'm wrong, but I also believe in 690 it states that anything over 150v to ground, in dwelling source circuits, shall not be accessible to other than qualified persons while energized. The most logical place would be in the combiner box on the roof.

690.18
Just says cover modules when installing or servicing. I am assuming you mean the Staff notes when you say "3 possible solutions". There are probably more, staff notes are not code requirements.

Actually, it says open circuiting or short circuiting or covering.
The Fine Print Note states, for the most part, modules are energized when exposed to light and could expose one to electrical shock.

I was stating this, because, I don't think ALL Firemen are Electricians.

Maybe, Don resqcapt, could shed some potential light on Firefighter safety training on structures with PV arrays.

 

[ty]

The GFDI is part of the inverter controls.
It is one of the things the inverter checks before allowing power to 'transfer' to the AC side.
If a DC ground fault occurs, it disconnects both conductors.

 

[e57]

The GFDI is part of the inverter controls.
It is one of the things the inverter checks before allowing power to 'transfer' to the AC side.
If a DC ground fault occurs, it disconnects both conductors.

Well it did very little good there did it?

 

[ty]

Well it did very little good there did it?

Yeah, and I'd like to state again, I would question the Installation, not necessarily the equipment. Not that equipment can't and/or doesn't fail. just sayin.

 

[e57]

Yeah, and I'd like to state again, I would question the Installation, not necessarily the equipment. Not that equipment can't and/or doesn't fail. just sayin.

Thats like having a GFI ptrotected hairdryer - with that GFI protection INSIDE the hairdryer - has little effect in way of intent of the requirement when the cord feeding it is in the tub with you... So in this case - If you say that GFI protection was in the invertor enclosure - what did it protect? The invertor circuit and the few inches of conductor leading to that circuit? While the fire the fault created is already in the enclosure...

 

[SeanD]

E57

It is hard to tell from the photos but I would hardly classify it as a back wood self install. It looks to be a urban or suburban residential install. Comparing the 2 is like comparing apples to oranges.

Fuses - may protect against short circuit but not 'every' fault. Carbonized wood becoming a current path due to cuts in insulation, water paths of current. Fuses, and even the location of fuse may have little or no effect for that situation.

[/LEFT]

If an install is code compliant when will the DC conductors come in contact with wood.

Like Ty said, I question the installation. I would also look at the inverter type for known issues. It's not an inverter I am familiar with.

 

[e57]

E57

It is hard to tell from the photos but I would hardly classify it as a back wood self install. It looks to be a urban or suburban residential install. Comparing the 2 is like comparing apples to oranges.

You'll have to excuse my rather punchy "back woods" comments I was referring to the overwhelming amount of C-46 contractors with very little if any electrical experience - not specifically the installation in the article at that moment - But on the serious side the PV solar market while it has been around for some time has not been addressed by the code or the licensing and inspection entities in full or on the scale it will be in the future. And changes will need to be made and problems addressed. The situation in the article is one of them... As far as C-46 - they have in the last few years gone from installing really small low voltage, low amperage systems - but the methods they used did not change - just bigger... Some of them are bizarre... Things a C-10 could have trouble coming up with - never mind get away with. Granted - not many of us C-10's are doing or getting into solar for reason of competition with the C-46's. (The pay is pretty low for an electrician to go work for them... I have spoken to a few recently who's only interest is 'renting' my license to pull permits. So yeah it does kind of tick me off - sorry if it seems I'm taking it out on you - or this topic...)

If an install is code compliant when will the DC conductors come in contact with wood.

Like Ty said, I question the installation. I would also look at the inverter type for known issues. It's not an inverter I am familiar with.

They do not necessarily come in contact with anything to be, or create a hazard. And fusing or inappropriate GFI device location won't solve the issue.

What I was trying to get at is an issue that could be created by a fault - pyrophoric-carbonization. (An example) Since the conductors on the roof are often exposed, and exposed to the elements - they are not free from physical damage. If a fault occurs -the path of that fault may not be to a grounded surface or EGC it may be through all kinds of things, roofing materials, nails, and rain gutters not excluded. And a small nick in insulation may pose a hazard - only when it rains... It does rain of roofs...

Besides that - Any fault condition that happens on unprotected conductors could cascade affecting other conductors and cause further damage - most likely in a location where those conductors too are unprotected - No means of disconnect, and location of GFI protection where it is least effective if at all.

IMO It's a rather large hole in the fabric of electrical and fire safety. I assume only time will tell.

 

[e57]

I was trying to look and see if the invertor in the article could be identified (Not sure if this is that one) - but came across this. It would seem to me that the manufacturer is aware of issues, but also that they are fitting the letter of the code, maybe not the intent.

 

[SeanD]

This post is starting to remind me of thread titled: What I have learned from being a member of Mike Holts forum?

E57

Last time I checked we were talking DC PV Source circuits Your example is AC.

I imagine that makes a difference.

My guess the reason starting out as an electrician with a C-46 pays less than you expect is the training involved.

But at least I think we can agree on one thing, your response to the guys looking to "rent" your license. :grin:

 

[SeanD]

I was trying to look and see if the invertor in the article could be identified (Not sure if this is that one) - but came across this. It would seem to me that the manufacturer is aware of issues, but also that they are fitting the letter of the code, maybe not the intent.

Those are not Xantrex inverters. In the models I am familiar with there is only a single disconnect for both AC and DC.

 

[220/221]

I've always felt that the panels should be fused and switched.

A real firefighter would have just taken his axe to the rooftop jbox

 

[dbuckley]

The thing worth remebering about solar panels (and fuses) is that the panels are not a supply of power with utility level stiffness, and the short circuit current out of a panel is not necessarily much more than its normal output. So even if you short the output of a panel (or an array of panels) the fuse wont necesarily blow, or may take some time to blow.

Its not so long ago that pretty much all PV installs used shunt regulators, which basically put a transistor (or several transistors) across the output of a panel and the transistor acted as a variable resistance across the panel to load the panels down to prevent excess voltage. Sunlight to electricity to waste heat. Of course now we have cleverer electronics, that keep the panels at the optimum voltage / current crossover point, but I bet there lots of old shunt regs still doin' service...

 

[e57]

This post is starting to remind me of thread titled: What I have learned from being a member of Mike Holts forum?

Note in my own post in there I mentioned nothing about my hard head...

Last time I checked we were talking DC PV Source circuits Your example is AC.

I imagine that makes a difference.

Last I checked my arc welder puts out 33V DC at 175A max. - makes a nice white light that melts metal in controlled situations. Jumps small gaps...

So where do you see the safety threashold for DC voltage or current - vs capablity to produce heat or potential hazard?

My guess the reason starting out as an electrician with a C-46 pays less than you expect is the training involved.

But at least I think we can agree on one thing, your response to the guys looking to "rent" your license. :grin:

Yep - and some of them are right off the street, former roofers or plumbers and pool contractors. Since the main stay of 'solar' for a long time was hot water for pools... Basically they'll hire anyone they can get on a roof...

 

[SeanD]

Last I checked my arc welder puts out 33V DC at 175A max. - makes a nice white light that melts metal in controlled situations. Jumps small gaps...
So where do you see the safety threashold for DC voltage or current - vs capablity to produce heat or potential hazard?

Voltage varies but typically we are seeing 250-600v. Max Amperage will vary per the size of the system. Residential systems would be between 5 to 40amps. I don't define the safety threshold. The NEC does. What exactly is your issue with the code requirements? DC on the roof. DC inside buildings. DC period.

Yep - and some of them are right off the street, former roofers or plumbers and pool contractors. Since the main stay of 'solar' for a long time was hot water for pools... Basically they'll hire anyone they can get on a roof...

Or maybe your issue is the perception that C-10's aren't doing all the work

 

[e57]

Voltage varies but typically we are seeing 250-600v. Max Amperage will vary per the size of the system. Residential systems would be between 5 to 40amps. I don't define the safety threshold. The NEC does. What exactly is your issue with the code requirements? DC on the roof. DC inside buildings. DC period.



Or maybe your issue is the perception that C-10's aren't doing all the work

I think i have been very clear about my opinions of the location of the disconnecting means, GFI location and OCP. I would feel the same it were AC.

And yes - while few C-10's in my area can compete with C-46 on solar - what bothers me is the two different standards of licensing (which recently and fortunatley has gotten better) and certification of employees - who are held to two vastly different standards.

 

[e57]

SeanD -

I just want to let you know - my opinion of the C-46 v. C-10 license is neither new - or obsolete. It has been an issue for quite some time...

An article from '06

In other words, licensing issues have not gone away but rather are very much in play.

"One thing I think will be very interesting to see played out is this licensing issue. I'm not surprised this was pushed out of the bill," said Aaron Nitzkin, VP of Solar Operations for Old Country Roofing, who recently joined Old Country Roofing to incorporate solar PV into their roofing business.

Nitzkin comes down somewhere on the middle of this debate. He acknowledges it will be a major issue, likely a traumatic one, if there's a push to require a full electrician's license (C-10) for all future California solar work. On the other hand, he feels the barriers to entry on the C-46 license are too low.

Someone like Chris Anderson, Chief Operations Officer at Borrego Solar, a bay-area solar contractor, thinks they're just fine.

"A lot of solar contractors only have the C-46 and many came from the solar thermal side. But the C-46 exam truly addresses both thermal and PV," Anderson said. "And the C-10 I took in 2005 had not a single question related to PV."

For the record the C-10 and C-46 have the same amount of questions less than 50% of which are trade related - most of the questions are contract law... To become a C-10 or 46 also requires affidavit from someone to verify experience in a related trade... For a C-10 that would be an Electrical Contractor, for a C-46 a roofer or plumber... Yet solar PV is >50% of their market now... Yet most do not know what the NEC/CEC is or that it pertains to them - some feel they need not be inspected or require permits either...

To work for a C-10 you must be certified by the DAS requiring apprenticeship and CEU's - to work for a C-46 you need to have a grasp on your fear of heights or at least sober for the moment. :roll: