Rack is Done - or is it a lightning rod?

[Syberdog]

Thanks to all in my last post, who helped make my rack better with their suggestions.... it is ready to populate with dodads and string....
I used the No-Ox-ID on all the connection points and rail splice screws etc and the Nikel anti seize on all SS bolts. Rails are not torqued in place yet -waiting to space with panels.
I am working thru the electrical details, getting the boxes mounted and ready to pull the wire.
I have 20' of #4 as a EGC in the #2 ballast block (E=1, W=4) next to the inverter pole. I plan on running the additional #4 up the pole and perpendicular down the rails to ground the mounted equip. components.
I know grounding is a complicated issue, so I will have a lot of questions. I am reading thru the code several times. Even though we use NEC 2011 I have gotten APS engineering (who recently decided to look at my 3-Line again) to OK using NEC 2017 for my PV system since it is ungrounded DC and addressed better by 2017.



First question is: Do I have one big lightning rod sitting in my yard and how can I protect the PV system - or is the #4 connected sufficient. The local electric pole have strike devices at their tops - they are much higher than my rack and the closest are about 100' away - will that cover me?

Q2 - My inverter equipment ground... I had planned on just hooking it and the metal pole to the #4 that is running up the pole but 250.58 indicates I may have to tie back to the system ground at the house 70' away... but 250.54 confuses me on that point. APS is uncertain and will let me know next week - so what is your opinion? can just ground the inverter equipment jumper to the UFER- what is the danger of not bonding either of them back to the house ground?

Q3 - I am using the IronRidge microconverter/optimizer bonding T-bolt mounting kits to attach the optimizers to the rails. I seem to be reading a lot of other posts indicating intermittent or failure of optimizers to report, function etc. I'm thinking maybe their ground isn't as good as it should be and maybe I should run a ground wire between them as shown in the Solaredge tech note. But I don't want to be running exposed copper all over my nice aluminum frame, so i figure I could use insulated #10 and bare it at the connection points.... what say y'all?


Thanks
Al

[Mike90250]

how much rebar (and how well is it tied together) in each concrete base?

how well are your uprights bonded to the rebar? each base to the other bases?

how many thousands of volts will build between your house & array? (Wiles had a video on this, I cant find the link)

[sensij]

Farlander recently made a post that included a Mike Holt video, might be the one Mike is thinking about.

Q3 - The Ironridge bonding hardware provides a very good ground connection when installed properly. Adding copper isn't going to do anything to help. I'm not sure there is any evidence that the communication problems some have experienced are related to grounding, in any case.

[bcroe]

Your concrete should provide a better lightning ground than anything you can add. A
couple points added along the array top could direct any hit more into the frame than
the panels, if you consider a hit likely, like the utilities use. These actually reduce the
likelyhood of a hit, by bleeding off charge and reducing potentials nearby.

Keep the pictures coming. Bruce Roe

[Mike90250]

here's the name of the vid 2014 NEC - Grounding Electrode System [690.47] (26min24sec).mp4 on youtube

[Syberdog]

Thanks for the link-
Each block has 2-#5 x7' about 3" off the bottom and 6x6 wire mesh about 3" from the top and 4- #4x12" vertical square about 6" from each post. Because I didn't want the alum to react with the conc & steel and thus rot I painted the posts with asphalt and kept the rebar away from them, so essentially the posts are separated from from the conc by the thin layer of asphalt. I don't have anything connecting the ballast together, so I suppose the only connection into concrete is the #4 wire.

"how many thousands of volts will build between your house & array?" ....duh? first I've heard of this possibility.

Out here in the open valley during Monsoon season its possible lightning will come close- in the last few years I'd say the utility transformers got hit 2 or 3 times, so I'll look into how to reduce the risk..

After watching that video, it seems that I may need to either connect my inverter equipment ground back to the house and/or connect the bare #4 wire back to the main system ground at the house.

[DanS26]

................After watching that video, it seems that I may need to either connect my inverter equipment ground back to the house and/or connect the bare #4 wire back to the main system ground at the house.

Lightning is a strange beast and it is not well understood......IMHO having a large dia (ie #4 wire) as your EGC back to the house is not advisable. A smaller dia EGC, which still complies with NEC code is more desirable. Why?....because the resistance of a smaller dia EGC wire will help force a strike or nearby strike into the ground at the array rather that traveling all the way back to the house.

Of course you realize a lightning bolt after traveling many miles through air does not care what size wire you have......it will go where it wants to go. Hopefully you can direct it in some small insignificant way to protect your property. Maybe......maybe not.

[Syberdog]

I was thinking of something smaller for that length of run. A #10 if code lets me.
I'm more concerned about the problems created by 2 separate ground points not connected than the lightning- I can't do much about that except put up strike points - would they have their own separate ground wire and grounding electrodes or would they tie into the alum support posts (not the one with the #4. OTOH all of the rack is tied together so putting strike points on the rack seems like it woulddn't be effective where a separate pole say 10' away might work better- looks like more midnight reading....

[Mike90250]

watch the 30 min video, it covers dirt potential differences and the ways to join parts together.

since your racks ARE isolated from ground AND you have no exposed rebar to connect to, you have no usable UFER ground, and I'd sink a couple of strike points (Franklin Rods) just north of the array (so it won't shade it) and tall enough that the "Rolling Sphere" model will protect the array from direct hit. Maybe a couple of flagpoles?

[Syberdog]

Good Idea on the flag poles...
Are you saying the 20' of #4 in concrete is not usable for a ground ... rack, equipment or otherwise, because it is not tied to the rebar or posts??

[Mike90250]

Ufer ground requires 6" of a 20 foot stick of half inch rebar, be exposed to clamp the structure ground to. I don't know what happens to copper in concrete.

[Syberdog]

Maybe my use of the term UFER is incorrect, I'm referring to 250.52.A.3 Concrete Encased Electrode -A concrete encased electrode shall consist of at least 6m (20') of either #1 or #2
option #1. is for using rebar of a certain type, dia, length encased in the conc...
option #2 is "Bare Copper Conductor not smaller than 4AWG". It doesn't say anything about tying it to metal etc. So this is what I did and have an additional continuous 20' I intended running up the rack to use as equipment ground for the rack and rails. I thought I'd also use it for the Inverter EGC since it was within 1 foot - but now I'm starting to see I should tie the inverter equipment ground back to the house system ground.

[J.P.M.]

I don't know what happens to copper in concrete.

Not much if old radiant heating systems still going strong using copper tubing are any indication, provided chlorides are not present. Also a good idea to make sure stuff like fly ash, etc., isn't used in the mix and lower the Ph of the mix too much and possibly cause problems down the road.

[bcroe]

I painted the posts with asphalt and kept the rebar away from them, so essentially the posts are separated from from the conc by the thin layer of asphalt. I don't have anything connecting the ballast together, so I suppose the only connection into concrete is the #4 wire.

I doubt the asphalt would be much of a barrier to lightning. But if so, I'd fold up some rebar
on top and pour a couple more inches over it, before giving up on the concrete ground.
Bruce Roe