Air Terminal lightening protection?

[gmanInPA]

Is there any recommended or required practice of using air terminal lightening protection on roof-mounted solar arrays? If not, does anyone have strong opinions about the usefulness of such? Would there be any benefits to doing so?

Disclaimer: I'm not an electrician. I'm not an EE. I don't have the NEC memorized like many here.. Our solar installation was done by a reputable, licensed local electrician. Before flaming me for not having an solar installer do my installation, understand that I pursued several companies, three or more in our area have gone out of business. Everyone felt that were too far away or were not interested in installing systems they didn't sell.

[sensij]

See NFPA 780. If a direct lightning strike is a risk you want to mitigate, air terminals can be a part of it. If indirect light damage is the concern (surges, etc), there are other mitigation techniques. NEC does not require any lightning protection, and conventionally, no protection is installed in areas that are not extremely lightning prone.

[Sunking]

NFPA 780 is the Bible of LPS. It is not DIY. In reality adding Air Terminals and LPS makes you a target. When it come to Ground Strikes is a misnomer. Lightning does not strike the ground. The Ground strikes the cloud.

To make an effective LPS requires a professional designer qualified for UL Master Label UL96A certification. It allows you a big discount on your home insurance policy. It is a very expensive program. Telecom, Military, High Rise Building, and Emergency Communications all use UL96A certifications using NFPA 780

[gmanInPA]

NFPA 780 is the Bible of LPS. It is not DIY. In reality adding Air Terminals and LPS makes you a target. When it come to Ground Strikes is a misnomer. Lightning does not strike the ground. The Ground strikes the cloud.

To make an effective LPS requires a professional designer qualified for UL Master Label UL96A certification. It allows you a big discount on your home insurance policy. It is a very expensive program. Telecom, Military, High Rise Building, and Emergency Communications all use UL96A certifications using NFPA 780

Hey Sunking - I got the idea from the Mike Holt video about the auxiliary grounds (that you mentioned being in actually). He references a simple diagram where he seemed to explain that the LPS at the roof peak and at the eaves essentially created a "ceiling" of sorts over the area containing the array. I certainly don't want to draw a lightening strike by having one. Do you see any merit in such a system to protect a roof-mounted array from a direct strike, or is that really overboard for residential protection? Of course, it's not just the array I want to protect - it's the whole building (a metal pole barn) that also contains my office and all my solar equipment. I don't have any issues with having a professional design and install the service - but if it is largely unnecessary, I wouldn't pursue further. My HO insurance is pretty affordable already, but a discount would never hurt I suppose.

OAN: I was under the impression - mostly from wunderground maps that lightening strikes could be ground to cloud, cloud to ground, and cloud to cloud.

[Sunking]

gman you have to decide. Answer a few simple questions:

Do you live in an area where lightning strikes are common?
Is your home open, exposed, and the tallest structure immediately around you?
Does your Insurance Carrier offer a discount?

If you answered yes to at least two of those questions, you might seriously consider it. Consider this. If you properly bond the panels, run down conductors to a code compliant Ground Electrode system is just as good as Air Terminals. In any LPS everything on the roof and metallic object is bonded to the Air Terminals including solar panels. All the AT's do is present a target to lightning rather than a direct hit on the panels.

Keep in mind Mike, I know him personally and a moderator on his forum, is a professional talking to professionals. Yes you are correct Lightning can strike in 3 modes. In a Ground Strike Lightning is looking for Earth Potential. When you put panels on top of your home, you have elevated Earth. The best protection you can have from Lightning is having your house surrounded by large trees, or a tall Flag Pole in which puts your home under the CONE OF PROTECTION. Mike did not go that deep, but with Air Terminals there must be enough of them and high enough to put everything on your roof under a Cone of Protection.

Personally unless you live in an area known for Lightning like Florida or Tornado Alley, there i snot much risk. Bond the panels together and you are good. If the risk were high, NEC would require LPS. Fact is NEC does not require it. 690.47 was a huge error put in by Special Interest Minority Activist in an attempt bring down installation cost at the cost of property damage and life safety. That is what the Green Mafia does. 690.47 is amended out of most cities who have adopted 2014 Code Cycle. It is dangerous and will be removed in 2017.

[gmanInPA]

Thanks Sunking. I live on a small mountain side, so there are plenty of things taller than my home and barn in the immediate vicinity. PA is not exactly like FL when it comes to lightening, but we get our fair share of T-storms. My panels are all bonded together and that ground carries all the way through the combiners to CCs to power panel and back to a single ground where my grid service is grounded. There are no neutrals bound to common anywhere but my main panel (I had corrected all of those when I set all this up) and I have no other auxiliary grounds in my electrical system. I do however have a metal building and metal panels on metal racking, so though not planned or intended as a ground, electrically, it is still a possible, and perhaps a preferred path to ground than my utility ground if that building were struck. If a well-placed flagpole would do similar to the air terminal, that might be a preferred approach - especially if such systems are intended to work in a "hey, over here, hit me first" approach. Really appreciate the response and feedback.

[sensij]

I do however have a metal building and metal panels on metal racking, so though not planned or intended as a ground, electrically, it is still a possible, and perhaps a preferred path to ground than my utility ground if that building were struck. If a well-placed flagpole would do similar to the air terminal, that might be a preferred approach - especially if such systems are intended to work in a "hey, over here, hit me first" approach. Really appreciate the response and feedback.

I hope that the conversation has not dissuaded you from reading NFPA 780. I'd suggest that you start with Annex B for an overview (and eventually chapters 4 and 12 if you want to see the technical requirements). It is freely available to anyone who would like to view it, not restricted to pros only. I would not suggest you try to go out and DIY a system without help, but there is a lot in there that may help you understand how to assess the risk and inform your questions if you choose to work with a professional on a design. The advice you can get on a forum may be well intentioned from someone who is well qualified, but who also bears no responsibility for the costs and consequences of your decisions.

[SunEagle]

Thanks Sunking. I live on a small mountain side, so there are plenty of things taller than my home and barn in the immediate vicinity. PA is not exactly like FL when it comes to lightening, but we get our fair share of T-storms. My panels are all bonded together and that ground carries all the way through the combiners to CCs to power panel and back to a single ground where my grid service is grounded. There are no neutrals bound to common anywhere but my main panel (I had corrected all of those when I set all this up) and I have no other auxiliary grounds in my electrical system. I do however have a metal building and metal panels on metal racking, so though not planned or intended as a ground, electrically, it is still a possible, and perhaps a preferred path to ground than my utility ground if that building were struck. If a well-placed flagpole would do similar to the air terminal, that might be a preferred approach - especially if such systems are intended to work in a "hey, over here, hit me first" approach. Really appreciate the response and feedback.

Yes we get a lot of lightning here in FL. Although while it can easily hit the highest point it also hits the ground and bypasses the tall structure or tree. I am not sure why except for "the path of least resistance' comes to mind. We also have all of the power lines in my area underground which eliminates some of the attraction to lightning.

I have lost a few items (tv, telephone answering machine, clock radio) due to lightning strikes close to my home. But they seem pretty random in what it strikes and what it bypasses.

I did have my POCO install an isolation device on my power meter so that any surges coming from them is hopefully stopped at the meter and does not get to my electrical loads.

[gmanInPA]

I hope that the conversation has not dissuaded you from reading NFPA 780. I'd suggest that you start with Annex B for an overview (and eventually chapters 4 and 12 if you want to see the technical requirements). It is freely available to anyone who would like to view it, not restricted to pros only. I would not suggest you try to go out and DIY a system without help, but there is a lot in there that may help you understand how to assess the risk and inform your questions if you choose to work with a professional on a design. The advice you can get on a forum may be well intentioned from someone who is well qualified, but who also bears no responsibility for the costs and consequences of your decisions.

Hi sensij - not, it's not persuaded me not to read it - it's just persuaded me primarily that my system is not out of compliance (though I would have hoped that the electrical inspector would have said so) and that an LPS is not an imminent need. I'll heed your advice to seek professional help if I do go that route.

[Sunking]

Hi sensij - not, it's not persuaded me not to read it - it's just persuaded me primarily that my system is not out of compliance (though I would have hoped that the electrical inspector would have said so) and that an LPS is not an imminent need. I'll heed your advice to seek professional help if I do go that route.

IMO, it is not worth it, and you would be one of the rare birds if you did it. I already gave you a link to NFPA 780 if you want to read it. Lastly if you are concerned, I would not advise Air Terminals. I would recommend to use just a simple Down Conductor from the panel frames straight down the side of the structure to a 8 foot long 5/8 copper clad steel ground rod. However if you do that be sure to trench a bonding conductor from the Down Conductor Rod to the building GES. That is what is required even with Air Terminals. Does the exact same thing Air Terminals would do.

Keep in mind a direct strike is going to take out your equipment regardless if you have LPS or not. They are not intended to protect the equipment. They are designed to provide a safe path for lightning fault current to find a way to earth to prevent flash overs and starting a FIRE and protect life safety. So don't fool yourself into thinking it will save the equipment because it is not intended to do that. It can only protect the equipment from a near by strike, not a direct hit. Think of it like a bomb shelter. It will protect you from nearby bombs, but not a direct hit.

[sensij]

I already gave you a link to NFPA 780 if you want to read it.

You linked UL's lightning protection guide, and mislabeled it as NFPA 780. It happens. The substance is the same, but there is a substantial difference in how it is written and presented. Reading both is probably worthwhile for those who really want to understand the basis of some of your advice and recommendations.

[Sunking]

You linked UL's lightning protection guide, and mislabeled it as NFPA 780. It happens. The substance is the same, but there is a substantial difference in how it is written and presented. Reading both is probably worthwhile for those who really want to understand the basis of some of your advice and recommendations.

You are right, my bad. Here is a Link to a Free Download. You will have to register. Use to be easy to get older copies.

[gmanInPA]

Thanks everyone for the insights and links. I will read these cuz I'm nerdy like that. I do have fire protection as a primary goal - but so was equipment protection based (wrongly) on the brief introduction in Mike Holts video.

[Sunking]

Thanks everyone for the insights and links. I will read these cuz I'm nerdy like that. I do have fire protection as a primary goal - but so was equipment protection based (wrongly) on the brief introduction in Mike Holts video.

If you know where to look on MH video, I am in it on the side with others. We are feeding him info via laptops. I and the others in the Video are all Moderators on MH Code Forum.