Grounding for Rooftop system

[ButchDeal]

I'm late to the party on this thread, but I am curious what the difference is between the SE7600-USS and the SE7600-USS2.

The latter is the StorEdge and capable of supporting a battery in bimodal mode.

[Relaxedchap]

I'm late to the party on this thread, but I am curious what the difference is between the SE7600-USS and the SE7600-USS2.

[Sunking]

I've also seen some city inspection guidelines (not San Diego) state that if an auxiliary electrode is provided to ground the array, it *must* be bonded to the service electrode, without bothering to actually write or amend any codes to support it. At some level, since the AHJ is always right, the inspection checklists are as powerful as code.

That is the way it should be done.

Again, tying this back to the OP's question, neither the NEC, the CEC, nor Walnut Creek's city code prescribe lightning protection for PV systems, just ground fault protection. If the OP is concerned about lightning, it is probably an add-on to the existing contract, or at the very least, is a consideration to be weighed against the aesthetic desire for interior conduit runs.

Np problem there, no LPS is required or needed. If you properly bond the frames, and take a down conductor to the building Ground Electrode System, is as good as it gets. Adding LPS does not gain you anything as the are almost the exact same thing without Air Terminals. You want an Air Terminal. put it on a Solar Panel Frame along with a Bulls Eye.

If it were me and I was really concerned about lightning, bond it to code and buy the best TVSS/SPD money can buy to put on the roof and at the AC Service Meter.

[SunEagle]

Exception 2 can be interpreted in a way that means an additional electrode is not required for rooftop systems. That significantly reduces the number of systems subject to the unsafe rule, and for ground and pole mounts that remain, there are other ways to deal with it. Perhaps that is why the CEC left that code section alone, but I don't know. I've also seen some city inspection guidelines (not San Diego) state that if an auxiliary electrode is provided to ground the array, it *must* be bonded to the service electrode, without bothering to actually write or amend any codes to support it. At some level, since the AHJ is always right, the inspection checklists are as powerful as code.

2017 NEC helped, by no longer *requiring* that auxiliary electrode for any system, but it still allows it, and still allows it to be unbonded to the GES. So, for someone who really wants to create the hazard of potential between two otherwise unbonded electrodes that will drive current through the EGC, they are allowed to do it.

Again, tying this back to the OP's question, neither the NEC, the CEC, nor Walnut Creek's city code prescribe lightning protection for PV systems, just ground fault protection. If the OP is concerned about lightning, it is probably an add-on to the existing contract, or at the very least, is a consideration to be weighed against the aesthetic desire for interior conduit runs.

A better way to help reduce lightning damage is to install a high pole or tower with a rod or Linear Dissipater Array connected to a down wire to direct a strike away from your roof. It creates a "cone" protection roughly having a diameter on the ground about the height of the pole. This type is used at POCO switch-yards and can cover a much bigger area then just putting individual rods along the roof ridge or edge.

Of course a HOA might not like a tall pole.

[sensij]

690.47(D) is the only code written known to be dangerous to public safety. That is what happens when you let advocates get involved with something. In thi scase John Wiles from NMSU and Sandia National Labs. John pretty much srote 690. Anyway 690.47(D) intention is to save the homeowner significant installation cost. That is it plain and simple. If that option is used just makes the system extremely dangerous. We are talking major property damage, fire, and death dangerous. Most Jurisdictions arre aware of the Danger and have amended 690.47 out of local codes because they know it is dangerous.

That is why I was surprised, especially a city the size of San Diego left it in.

Exception 2 can be interpreted in a way that means an additional electrode is not required for rooftop systems. That significantly reduces the number of systems subject to the unsafe rule, and for ground and pole mounts that remain, there are other ways to deal with it. Perhaps that is why the CEC left that code section alone, but I don't know. I've also seen some city inspection guidelines (not San Diego) state that if an auxiliary electrode is provided to ground the array, it *must* be bonded to the service electrode, without bothering to actually write or amend any codes to support it. At some level, since the AHJ is always right, the inspection checklists are as powerful as code.

2017 NEC helped, by no longer *requiring* that auxiliary electrode for any system, but it still allows it, and still allows it to be unbonded to the GES (except through the EGC). So, for someone who really wants to create the hazard of potential between two otherwise unbonded electrodes that will drive current through the EGC, they are allowed to do it.

Again, tying this back to the OP's question, neither the NEC, the CEC, nor Walnut Creek's city code prescribe lightning protection for PV systems, just ground fault protection. If the OP is concerned about lightning, it is probably an add-on to the existing contract, or at the very least, is a consideration to be weighed against the aesthetic desire for interior conduit runs.

[Sunking]

Remember the two rules. Still, if I ever thought something an inspector said or wanted changed produced a dangerous situation, and we couldn't work it out, I'd start climbing the chain of command after advising the inspector of my intentions. Done that a couple of times, both of which were for pressure vessel equipment designs requiring nuclear stamp. I batted 0.500 in that league.

Not so much talking about a person. Local Jurisdictions, say San Diego, can accept or reject any NEC codes. They can even make up their own rules as many cities like Chicago do.

690.47(D) is the only code written known to be dangerous to public safety. That is what happens when you let advocates get involved with something. In thi scase John Wiles from NMSU and Sandia National Labs. John pretty much srote 690. Anyway 690.47(D) intention is to save the homeowner significant installation cost. That is it plain and simple. If that option is used just makes the system extremely dangerous. We are talking major property damage, fire, and death dangerous. Most Jurisdictions arre aware of the Danger and have amended 690.47 out of local codes because they know it is dangerous.

That is why I was surprised, especially a city the size of San Diego left it in.

But yeah I remember the two rules well. I have gone to battle twice. won one war, lost another. The one that I won was in King of Prussia Pennsylvania on a large data center we built. The Inspector wanted a Emergency Power Disconnect Button at every egress point. We call those disgruntled Installer Button. So as you walk out the door, hit the button and the room goes ark and quite along with knocking out all communications in a city. Anyway there are some leniencies in the code that allow you not to use Emergency Disconnect. That little button he wanted was a $3 million dollar button.

[J.P.M.]

Wow your local AHJ did not amend 690.47 out of the local code?

First AHJ I have heard that will let you use EGC. That is flat out dangerous, not to mention stupid. .

Remember the two rules. Still, if I ever thought something an inspector said or wanted changed produced a dangerous situation, and we couldn't work it out, I'd start climbing the chain of command after advising the inspector of my intentions. Done that a couple of times, both of which were for pressure vessel equipment designs requiring nuclear stamp. I batted 0.500 in that league.

[Sunking]

If you are worried about lightning, I would NOT run (invite the lightning path) the conduit inside the building envelop.

Ditto, you just sat out the Welcome Sign for Lightning to come on in and make yourself at home.

[Sunking]

How the requirement is interpreted will vary from one AHJ to the next. Around here, the interpretation of 2014 690.47(D) for roof mounted arrays seems to be that exception 2 allows the EGC from the array to the inverter to serve all grounding needs if it meets GEC standards. This didn't change much in 2017 NEC, again with only the EGC for fault protection required, and an auxiliary electrode (and conductor) being permitted by 690.47(b), but not required..

Wow your local AHJ did not amend 690.47 out of the local code?

First AHJ I have heard that will let you use EGC. That is flat out dangerous, not to mention stupid. .

[Mike90250]

....
I'm also requesting the conduit be run inside the attic space below the upper roof where the panels will be installed, down a chase way over the garage and out to the subs and main panel... any concerns regarding the conduit runs inside the house instead of over the roof, through the eave, and down along side of the house (which I consider unappealing) ?.........

If you are worried about lightning, I would NOT run (invite the lightning path) the conduit inside the building envelop. Think of lightning like a Slot Car (remember them?) You want smooth easy routing from the roof to the ground rod. Where there is a sharp bend, the charge will ignore it (cable bends are "inductors" at high frequencies) and "jump the track" and continue to Earth the way it wants to.

[sensij]

Your Installer will provide a Down Conductor(s) to bond the frames with and run them outside the house to your utility service ground. By installing to code is more than sufficient protection against lightning.

How the requirement is interpreted will vary from one AHJ to the next. Around here, the interpretation of 2014 690.47(D) for roof mounted arrays seems to be that exception 2 allows the EGC from the array to the inverter to serve all grounding needs if it meets GEC standards. This didn't change much in 2017 NEC, again with only the EGC for fault protection required, and an auxiliary electrode (and conductor) being permitted by 690.47(b), but not required.

If the OP wants a short, fat, straight down conductor, outside the structure, it is not safe to assume the installer will put one in, especially since the home run (including the egc) is being run through the attic and the walls.

[bcroe]

One other thing. A few grounded sharp points will tend to spray off some charge before a direct
strike occurs. They tend to "neutralize" the potential nearby, though that is no guarantee. Bruce Roe

[Sunking]

SLightning rods work because they provide a lower resistance means of conducting the current of opposing ions from cloud to ground and ground to cloud versus the other building materials (wood, plastic, brick). Thus lightning rods reduce the localized likelihood that the structure itself serves as the conductor which can often result in a fire. So, given the likelihood of your roof to get struck by lightning, in general, if a PV system is present, it stands that it is more likely to hit (or hit proximal) to your PV system, than say your un-grounded chimney or a PVC sewer vent.

That is about half true, and you seem to know more than most. While true if you put up a Lightning Rods on a framed house, you have given Lightning a Planned Path to earth and out away from the protected structure. But in doing so you just greatly increased your chances of a Strike. Depending On how the house is constructed. there was likely no conductive surfaces referenced to earth before you put up the rods.

Rods are not going to buy you anything with panels on top, unless you now how to position each rod to put the whole structure under a Cone of Protection to ensure the rods are hit and not any point below them. But again gains you nothing with panels on top. You should be asking why?

Because when Rods are installed, they are Bonded to any thing conductive on the roof like Solar Panels, Raceway, Junction Boxes, Utility Cabinets, and the list goes on. So if a Rod is hit, everything on your roof is hit. However that is not much of a problem.

OK now let's look at the Big Picture. If you Install Solar Panels on the roof, code is going to require you bond them together, everything up there, and run Down Conductor to AC Service Ground. So if lightning strikes a Frame it has a planned path to earth outside your home. See that picture in your head?

OK forget solar get that out of the picture. Let's build a LPS. After we look, it will take 6 air Terminals and use 1 down conductor directly above you AC Service Meter We put all the Air Terminals at all the high points of the roof. We bond them together and run a Down Conductor to the AC Service Ground. Got that picture.

Now go back a grab the solar panel picture and compare it to the LPS. What do you see? A mirror image right? Why would you want to put up LPS with Solar Panels? All it does is make your wallet lighter.

Almost forgot. Those Cell Towers, tall buildings, trees, and such get hit by Lightning because they are the closet to the clouds, not so much because they are metal and grounded. That goes back to Cone of Protection. Put up a Tall Flag Pole away from the house and give lightning a diversion target.

I was fortunate in college in the late 70's. I did a Internship at Disney World in Lake Buena Vista Fl. I was a grad EE student and got in on construction of the Magic Kingdom and worked on the LPS Disney designed and installed. To this date is known among peers is still the countries best and proven LPS. Pretty slick system using Cathodic Protection of the Ground Electrodes. I really enjoyed it and got to see what no one else has seen since completion before they covered all the buildings with pavement and earth. What you see as a Park is the roof of a building under ground, or I should say a number of buildings.

[Sunking]

LPS is not required, and in your case you do not want it. Use a Electrical Contractor who knows the codes and has experience installing Solar GT Systems. As a DIY you really do not stand a chance of installing a system correctly and up to code.

An LPA is not going to gain you anything, just increase your chances of being struck. Your Installer will provide a Down Conductor(s) to bond the frames with and run them outside the house to your utility service ground. By installing to code is more than sufficient protection against lightning.

If you are that worried about, install a tall Flag Pole or Tower out away from your home to give lightning target practice.

[max2k]

Back to my original question, what should I install/connect/ask to be done in order to protect my house, equipment, etc... from lightning strikes.
I think its safe to assume it will attract lightning based upon the least resistance to ground... Ideally I should have both, Ground Fault Protection and Lightning - No ?
<for the record, I completely rewrote the T&Cs prior to signing and ask them (politely) to sign based upon mine plus the forums outrage as to what was listed., and they did - I guess they are hungry for market share and agreed to all my changes, except for removal of the mechanics lean.>

as sensij pointed out lightning protection is not enforced therefore it will most likely cost you extra.

I personally left #6 gauge running outside conduit from the array to the house grounding rod in hope to provide less resistance path for induced currents from nearby strikes. My understanding is in case of direct strike my equipment will be toast anyway.

The array presence on the roof increases probability of the strike- any sharp 'pointy' conductive object increases electrical field intensity due to small radius of its sharp end as a result greatly decreasing voltage difference the air can sustain before the strike actually happens. In other words corners of your panels do 'invite' lightning to some extent.

Apparently the increase in probability of the strike is not that great otherwise some rules would already be in place as PV arrays are up there for at least last 10 years. My inspectors had no comments on the subject and ignored my grounding wire.