Ground mount array - Grounding, Bonding and Lightning Protection

[kenyoncad]

Hi All.


I'm a newby here, but I have been reading the forums for a while now planning my project.

I'm in the process of installing a new 32 panel ground mount at my home using Iron Ridge racking and Enphase mircoinverters. I'm mounting (16) panels each on 2 separate ground mounts a few feet apart (they are only split into 2 arrays due to the sloped nature of my property). The ground mount is approx. 230' from my home, my plan is to mount the Enphase AC combiner box inside my basement, and run (2) #4's out to each array. So far I have the racking up and I'm now waiting for a sunny day to get the trenching going.

However, I do have a question about grounding, and having read all the related posts and now I'm feeling more confused than ever.

Based on the Enphase documentation the microinverters don't require a GEC or EGC, however the Ironridge racking documentation suggests a single ground connection per array.

My plan was to run a ground wire from the combiner box in my basement out to the array with the conductors, however, the more I read the more I think this probably isn't the right plan, as it sounds like if there were a lightning strike nearby it could travel back to my house.

Should I be installing a ground rod for each array and bonding the mounting frame to ground that way? And if so I assume I need to tie the ground rod for each array together? And would it make sense to install a single ring around both arrays with a ground rod at each corner? Also, if I install ground rods at the arrays do I need to bond those ground rods back to my main service ground rod? This will involve an additional 100' of trenching as my utility ground is located on the other side of my house to where the conduits from the arrays will be entering my basement.

Obviously my main concerns are not setting my house on fire in the event of a nearby lightning strike, and also ensuring the whole mounting frame doesn't become live in the event of a fault condition or damage to the wiring.

Thanks in advance for any advice you may have for me.

David

[bcroe]

Hi All.


I'm a newby here, but I have been reading the forums for a while now planning my project.

I'm in the process of installing a new 32 panel ground mount at my home using Iron Ridge racking and Enphase mircoinverters. I'm mounting (16) panels each on 2 separate ground mounts a few feet apart (they are only split into 2 arrays due to the sloped nature of my property). The ground mount is approx. 230' from my home, my plan is to mount the Enphase AC combiner box inside my basement, and run (2) #4's out to each array. So far I have the racking up and I'm now waiting for a sunny day to get the trenching going.

However, I do have a question about grounding, and having read all the related posts and now I'm feeling more confused than ever.

Based on the Enphase documentation the microinverters don't require a GEC or EGC, however the Ironridge racking documentation suggests a single ground connection per array.

My plan was to run a ground wire from the combiner box in my basement out to the array with the conductors, however, the more I read the more I think this probably isn't the right plan, as it sounds like if there were a lightning strike nearby it could travel back to my house.

Should I be installing a ground rod for each array and bonding the mounting frame to ground that way? And if so I assume I need to tie the ground rod for each array together? And would it make sense to install a single ring around both arrays with a ground rod at each corner? Also, if I install ground rods at the arrays do I need to bond those ground rods back to my main service ground rod? This will involve an additional 100' of trenching as my utility ground is located on the other side of my house to where the conduits from the arrays will be entering my basement.

Obviously my main concerns are not setting my house on fire in the event of a nearby lightning strike, and also ensuring the whole mounting frame doesn't become live in the event of a fault condition or damage to the wiring.

Thanks in advance for any advice you may have for me. David

Your situation has some things in common with mine. If shading is not an issue, you could
save a lot of copper and reduce resistive losses with a string array feeding DC over the distance
to an inverter near your meter. Do calculate the losses over a 460 plus foot loop.

Solar panels do not mind being tilted, your construction might be simpler following your
terrain. Look at the yellow level against this 66 foot array on a 10% grade, a digital angle
laser level makes it easy to keep it straight.

If you are expecting snow, you can mitigate its effects with your array design.

Concrete and rebar properly combined can provide a really good lightning
ground, at every ground contact. You still need a personal safety ground of the
frame, for any array faults.

Bruce Roe

TiltPV3.JPG

[SunEagle]

Hey Bruce. You need a little Round Up under those panels or the weeds will start to add shade.

[bcroe]

Hey Bruce. You need a little Round Up under those panels or the weeds will start to add shade.

I check every time I mow. Takes a while to get up to that height. The mower actually
reaches under the array in summer tilt, I think those plants are behind it. In winter it
is straight up but there are no plants.

Maybe a small walker mower in a tiny waterproof shed out there would be good. Bruce Roe

[emartin00]

Hey Bruce. You need a little Round Up under those panels or the weeds will start to add shade.

nah, he just needs some sheep!

[Ampster]

nah, he just needs some sheep!

That is what they use in Denmark. I think Roundup is banned there.

[bcroe]

nah, he just needs some sheep!

A (summer) advantage of an array with so much ground clearance, is the grass grows
pretty well under it. That matters here, where grass is needed for erosion control. Bruce Roe

[BoloMKXXVIII]

That is what they use in Denmark. I think Roundup is banned there.

I just use white vinegar. It is very cheap and safe for animals. Kills weeds quite well.

[kenyoncad]

Hi Bruce. That array is wild, I've never seen one like that before. My set up is pretty much set as i have the frame up, and already bought the panels and microinverters.

I'm trying to figure out my grounding so i can dig any trenches needed for a ground ring at the same time as my electric trenches while I'm renting a trencher.

How are you grounding your array?

i’m thinking of doing 3 ground rods, one each side of the 2 arrays and one in the middle, and bonding the middle one to both arrays, that way everything is connected together.

[bcroe]

About the best lightning ground is a big wire (6 gauge etc) bonded to rebar in your concrete
foundation. I have about 54 of these distributed over 250 feet. A gnd rod is better than
nothing, results vary depending on your soil (resistance). I have a dozen of these. None
of these handle a wiring fault, so the 6 gauge goes on to the inverters and building ground
for safety.

I cannot comment on ground ring benefits.

The array looks like that because I got tired of clearing snow. It may easily be set to a good
summer production angle, then for winter set vertical to best reject snow (not a bad winter
production angle). The gap keeps snow from the upper panel, from sliding onto the lower
panel, and the ground clearance is above snow accumulation. Bruce Roe