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Changes NEC 690.12, Solar Photovoltaic Systems

04/05/2014 5:22 PM

Changes are being made soon, 2014, in the National Electrical Code, NEC 690.12, Solar Photovoltaic Systems. These changes are primarily to require for much quicker shutdowns of the system to facilitate firefighting and less risk maintenance. There have been several threads on the subject of solar panels recently but very little that included this specific information on the subject of firefighting. The following articles describe the changes in detail. Please read them before posting. What are your thoughts on this movement?

Disclaimer- I have no monetary or otherwise connections to this article. I am a firefighter and have been involved with several of these types of fires, including the complete loss of a residential structure. I have attended numerous training sessions on this subject. I would like to get others view points on this sometimes contentious subject.

http://ecmweb.com/fire-amp-security/solar-under-fire

http://ecmweb.com/fire-amp-security/solar-under-fire?page=2

Good Luck, Old Salt

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#1

Re: Changes NEC 690.12, Solar Photovoltaic Systems

04/05/2014 10:36 PM

I didn't bother to read any of that, because it required me to register. Perhaps you could quote whatever matters.

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#2
In reply to #1

Re: Changes NEC 690.12, Solar Photovoltaic Systems

04/05/2014 10:59 PM

Tornado-

Thanks for the heads up! I have abridged the article and hopefully included the major points of it. The orginal 1st citation was 5 pages including pictures. The thread of the article is what the new code additions/changes will do to make it safer for fire fighters and maintenance personnel vs. the solar cell industry.

Here goes:

Festering fire service worries over the hazards of working around rooftop photovoltaic (PV) installations are beginning to see the light of day. They're being reflected in notable revisions to the National Electrical Code (NEC) and a renewed push by state and local authorities for laws addressing the design, operation, and installation of the increasingly popular renewable energy technology.

In a major change spearheaded by firefighter interests, the 2014 edition of the NEC now includes a new rapid shutdown provision. Wording in Sec. 690.12 spells out requirements for de-energizing PV system conductors to a point where the voltage is at a level generally considered to be safe.

But as they celebrate victories they claim will increase the margin of safety for those forced to navigate rooftops clogged with energized PV arrays, some PV industry interests are sulking. Some in the system and components design, manufacturing, and installation sector complain the new regulations were hastily drawn up. New requirements criticized as vague, unclear, and difficult to implement quickly, they complain, could throw formidable roadblocks into solar's path. Critics concede safety is a valid and important concern, but they charge the risk-benefit trade-off hasn't been fully explored.

Yet recent fires involving structures with rooftop PV arrays have helped vividly illustrate the potential dangers and how the mere presence of PV systems can affect firefighting tactics.

For instance, a rooftop PV array consisting of some 7,000 panels likely hampered efforts to fight a warehouse fire in Delanco, N.J., last September. Responders chose not to follow the standard protocol of rooftop venting and other procedures, fearing the energized panels and factoring in the already-heavy involvement of the roof when they arrived on the scene. Firefighters ended up fighting the blaze, which destroyed the building's contents but claimed no lives or injuries, for more than a day.

The quickening pace of PV installations on houses and buildings raises the likelihood that similar scenarios are bound to be repeated. Those with a stake in the safety of firefighters and their ability to fight fires with a full arsenal are responding more aggressively.

In Stamford, Conn., city officials are considering regulations that would require rooftop panels to be spaced in a fashion that would give firefighters room to safely move around a structure's roof. Wider pathways between arrays would allow firefighters to steer clear of energized panels and leave room for venting.

Meanwhile, fire service-safety advocates, particularly those in regions where PV systems are more commonplace, have been working to address the problem with wider dissemination of educational and training resources to fire personnel.

The noteworthy addition to the 2014 NEC (Sec. 690.12) mandates that PV system circuits in or on buildings incorporate a function to reduce voltage to 30V and 240VA within 10 seconds of activation. Only conductors more than 5 feet in length inside a building or located more than 10 feet from an array are affected. It also requires that equipment performing the rapid shutdown must be listed and labeled.

The new "Rapid Shutdown of PV Systems on Buildings" requirement was inspired by the desire to give fire responders - or anyone else for that matter - a quick and reliable way to bring DC power residing in the PV system down to a level considered safe enough to work around. The standard recognizes that DC ranging from 300VDC to 600VDC is typically present in array wiring, combiners, and other exposed system components even after a building's main AC power is shut down. It's that electricity, generated by the solar panels and transformed to usable AC through inverters, that could badly shock firefighters as they walk on or hack through roofing in close proximity to panels and associated wiring and components.

Solar industry interests effectively pushed back against that proposal, citing the prospect of prohibitively higher costs for designing and building systems on a much more "micro" level. But the price for its defeat was output-circuit shutdown.

He cites a previous Code change dealing with AC arc fault branch circuit protection that was post-dated in the NEC to allow time to adapt. With the new rapid-shutdown change, it also may take time to develop equipment that meets the standard. In the meantime, inspectors following the Code might be forced to hold up approvals for systems that might otherwise sail through or reject installed systems.

"The problem is that there's no 'listed' way to meet the new requirement now for string and central inverter systems," he says. This could severely limit the feasibility of using one popular new SMA string inverter that produces backup power without batteries.

This, he says, may also present a problem for large arrays and difficult roofs, which now might need to have a microinverter under each module or require the use of AC modules to meet the new requirement. Inverters are far more likely to fail than modules, so designers often prefer not to use microinverter technology where access is difficult.

Good Luck, Old Salt

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#3
In reply to #2

Re: Changes NEC 690.12, Solar Photovoltaic Systems

04/05/2014 11:06 PM

Thank you. How about "Knox Box" technology for this, or similar?

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#7
In reply to #3

Re: Changes NEC 690.12, Solar Photovoltaic Systems

04/06/2014 9:40 PM

The "Knox Box" system, where a key storage box is remotely controlled, certainly will help in one aspect of the system. A key could be stored there, access remotely given and the key used to lock all necessary enclosures that control the system. The biggest problem then would be how is the power generated by individual panels or groups of panels brought to zero so work activities can be started in that area. Knox Box is part of the solution, a very good one for that segment, but what about the other problem functions and areas?

Last week I attended another briefing on fire fighting where there is solar panels, given by the state's largest power supplier. Their message was that until more improvements are made and proven safe, if there is any doubt- stay off, stay out, stay away and keep water off the panels. Their premises for those are these items can kill you without you knowing it is going happening.

Thanks for the good idea. I will be certain it incorporated in our pending GOG for PV Solar Panels.

Good Luck, Old Salt

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#4
In reply to #2

Re: Changes NEC 690.12, Solar Photovoltaic Systems

04/06/2014 10:18 AM

Thanks. It is a very good point you shared with us.

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#14
In reply to #2

Re: Changes NEC 690.12, Solar Photovoltaic Systems

04/09/2014 11:08 AM

Thank you all for your obviously very intelligent and well thought out answers.

As some of you have stated, this is a subject that must be resolved by all those involved with the situation. It isn't just the fire fighters well being that must be considered but also the maintenance personnel, the owners, the manufacturers, the installers, inspection personnel and several others.

Ironically, yesterday I saw an old friend who had been a volunteer firefighter and a finishing carpenter. He is now an installer of solar systems. He is no longer involved with fire activities but his concern for the systems and the problems they are confronted with in maneuvering around them during installation and maintenance has become forefront in his mind. He had no all inclusive answer but has great concern about his health and safety while working up on a crowded roof.

Not until every function involved realizes that they need the support of all others, including compromises, to bring together a safer system and procedures will this become a "safe" subject. It has been done in other industries, the time is now for PV solar panels.

Good Luck, Old Salt

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#15
In reply to #14

Re: Changes NEC 690.12, Solar Photovoltaic Systems

04/09/2014 11:12 AM

Here, here

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#16
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Re: Changes NEC 690.12, Solar Photovoltaic Systems

04/09/2014 11:15 AM

The expression is, "Hear, hear!"

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#17
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Re: Changes NEC 690.12, Solar Photovoltaic Systems

04/09/2014 11:19 AM

is it really? Honestly, I use it rarely, and it never occured to me. Have a great day!

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#18
In reply to #2

Re: Changes NEC 690.12, Solar Photovoltaic Systems

04/22/2014 4:29 AM

Tornado,

The electrical safety issue for firefighters is also considered in other country that USA and is included inside German (VDE) and French (UTE) PV installation guides.

For that need, Mersen has developped a PV module level safety switch which allows to shut down individualy each PV module in case of emergency. This reduces to zero volt the DC voltage on any point of the PV roof.

You can find more info on this system on:

http://ep-us.mersen.com/products/catalog/line/greeneye-greenbrain/

This system is now in test in several countries and should be soon certified for USA.

Let me know if you need more infos.

tarn

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#5

Re: Changes NEC 690.12, Solar Photovoltaic Systems

04/06/2014 5:37 PM

Mr. Old salt,

Since the PV power output is directly proportional to the amount of light it receives, cutting off the light source or limiting its exposure to sunlight will also cut off the PV's power output to the minimum or safe level.. By having a black or dark colored chemical foaming fire suppressants sprayed on those PV panels may facilitate disabling of those panels, thus improving the safety aspects for the responding firefighters..

Just another thought...

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#6
In reply to #5

Re: Changes NEC 690.12, Solar Photovoltaic Systems

04/06/2014 9:28 PM

Yes, the objective of the changes are to make it safer for firefighters to work at structures with PV panels. I know of no suppressing foams that are other than white when applied. A dark color would also hide the area that they were working in, such as a roof with panels, making it more dangerous to be there. Also when foams are applied initially they tend to run down the surface thus decreasing their effectiveness in blocking light. This would make it more dangerous for the firefighters. How would it be possible to cover all panels at one time and to maintain that light blocking property to keep the power off initially?

The original article had this picture:

In it firefighters are using tarps with very low light transmittal to cover the panels. The primary problems with this are those in the picture only have about 10-15 lbs of gear on. A full equipped fire fighter has over 70 lbs on plus then the tools (axe, haligan tool, saw, hand light) adds up to over 100lbs. Add to that the weight of the tarps and its a very heavy load especially for a 150 lbs person. Another problem is footing on the roof that is almost completely covered by panels, where do you walk or stand? How long will it take to put the tarps in place and secure them? What is done if the fire is below the panels and a hole needs to be cut in the roof below them for venting purposes?

I don't know the answers to all these questions. That's why I posted this subject. I greatly appreciate your input. Having been involved with these I am aware that much needs to be done about the panels and their systems, for the user, the maintenance personnel, the owners, the manufacturers of the systems, the installers and the fire fighters.

Good Luck, Old Salt

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#8

Re: Changes NEC 690.12, Solar Photovoltaic Systems

04/06/2014 10:57 PM

Old salt how about marking the voltages on the system in question, with a cut out switch at ground level in a Knox box controlled switch. Just saying most, not all of the systems that I have seen have all been 12,24, or 48 V DC. Is this a viable solution or not. Duke

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#9
In reply to #8

Re: Changes NEC 690.12, Solar Photovoltaic Systems

04/06/2014 11:14 PM

The Knox Box is a good idea for the controls. Unfortunately many of the newer installations operate at higher dc voltages. The unabridged article mentioned:

The standard recognizes that DC ranging from 300VDC to 600VDC is typically present in array wiring, combiners, and other exposed system components even after a building's main AC power is shut down. It's that electricity, generated by the solar panels and transformed to usable AC through inverters, that could badly shock firefighters as they walk on or hack through roofing in close proximity to panels and associated wiring and components.

In many systems the panels are connected in series and then these sets connected in parallel to each other. Combine that with the lack of walking space between powered, or potentially powered, panels and the often times wet conditions sets up a potentially fatal incident if someone fell onto a panel. Also water can't be applied to these panels without the danger of a shock, just like putting water onto a live electrical wire.

Still open to many more suggestions. Keep them coming!

Good Luck, Old Salt

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#13
In reply to #9

Re: Changes NEC 690.12, Solar Photovoltaic Systems

04/07/2014 1:39 PM

Thanks so much for this discussion. A few notes. We are building systems now that are nominal 1000VDC systems. There could be consistant votages at 850VDC common in these systems.

Danger to firefighters from these PV systems is DC only. It could be from module output in serial and or parallel configrations to step a 40V module up, but also from some internal inverter components that can remain energized for up to five minutes after the power supply (either grid or PV ) is disconnected. However, the danger on the roof is all DC, even if the inverters are roof mounted, if ff have killed the grid. I am assuming that ff always kill the grid before they fight a burning structure. Is this correct?

All inverters in the US are UL1740, which means, in the event of a fire, when a ff pulls a grid supply primary meter head or disconnect, all inverters are disabled on the AC output side. By definition, it opens the circuit on the DC conductors supply side, but a short on the PV array could close that circuit, leading to ff danger when working around potentially damaged modules and wiring, as would be the case in a fire. So the proposed solution, the ten foot emergency shutdown rule, may decrease the amount of potentially live circuits, but does not solve the problem. The PV array (and associated grounded array racking) is still a potential short. In this case, the equipment ground actually increases the danger.

Falling onto a module may be hazardous, because it is possible that you could create a good solid path to ground, but I think that is not the primary danger. Hacking through a metallic conduit that has 20 amps at 850V could be tragic.

NEC 2014 705 has good requirements to deal with equipment crowding on the roof. Roof corridor creation is just common sense. It even requires (suggests) f marshall approval in some scenarios, a very good thing. Most ff I have met don't want to be on a roof, period. They want to eradicate the fire from a stable remote platform. If it's an industrial facility that cannot be controlled from these platforms, I have serious reservations about trying to imply that we can , as an industry, make them safe to work around if they have power generating systems that are active. Is it safe to fight a fire that is adjacent to a fuel tank? Maybe we should give ff's more information about the structures they are protecting.

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#10

Re: Changes NEC 690.12, Solar Photovoltaic Systems

04/07/2014 7:57 AM

Having recently attended a conference on 2014 NEC code changes for PV systems, I came away with a distinct feeling that changes required to make firefighting more safe around PV systems are feasible. It is unsafe to fight a fire. It is even more unsafe to get on the roof of a building that is on fire. I got the feeling that the public nature of the NJ fire (which we discussed at length, and agreed that any of the proposed changes would not have prevented that fire) has led some to believe these changes will both reduce property losses, while reducing firefighter risk. FF fight fires first to protect lives, second to protect property. If protecting there own lives simply requires them to not get on roofs that are on fire if they have PV, it seems to me a similar piece of logic that keeps ff away from propane tanks in a fire.

Specifically, remote shutdown, even if it takes place within 10 feet of the array output (which could be 300 feet away from a PV Panel that is part of the energizing string, still does not protect a ff from electric hazards if he is in the wrong place when the physical connections are shorted. The only realistic way to de-energize a PV Panel in the light is at the module box itself. An internal, remotely controlled disconnect is entirely possible, and would cost on the order of 25$ per panel (ablout 6-8%). Is it reasonable? possibly.

It would be much more reasonable to require buildings with PV to be sprinklered, thereby reducing the risk of requiring a ff on the roof to nearly zero.

It would be more reasonable to not allow ff on burning structures with PV in the daylight.

That was the consensus, IMHO, in a room full of 125 PV professionals.

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#11

Re: Changes NEC 690.12, Solar Photovoltaic Systems

04/07/2014 9:37 AM

Thanks for the discussion.

On another note, I am aware that NAVFAC and San Diego FD have raised concerns of overcrowding a roof top to maximize PV collection to the point that roof access for HVAC maintenance or fire fighting is impossible.

Solar designers need to be made aware of these issues before the panels are installed, and maintenance and fire fighting personnel need to be aware of the risks around solar panels. The only safe way to kill the power is to cover the PV panels so they do not generate power, but during an emergency this is very limited in practicality.

I do not have a simple recommedation to solve this issue, aside from educating designers, owners, maintenance, and fire fighters of the hazards from solar equipment on rooftops.

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#12

Re: Changes NEC 690.12, Solar Photovoltaic Systems

04/07/2014 11:33 AM

This brought up some interesting things that just control systems can not address. We are a commercial refrigeration company, so we are on roofs to work on equipment regularly. As the use of PV grows, having adequate walking and working area will be an important issue. Thanks for the 'Heads Up!'. Maybe by the time this equipment gets to the smaller buildings we usually are on, there will be standards to help us move around safely. -- JHF

P. S. - Thank you for your service as a firefighter.

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