Proper Grounding of Solar panels

[Bigbear]

I am about a week away from hooking all the componets up for my new (not quite finished) offgrid home.  I have read several different methods of grounding, please help me with the proper method.  My system will have 4-130 watt panels, 1-400 watt AirX, gas generator, 8 battery bank, 1200 watt sign wave inverter, AC panel, switches, fuses etc.  Should everything be grounded to just one ground rod (or several tied together) with one continous bare ground.  Should the solar panel mount be grounded seperate, or should it also tie in with the whole system, this also goes for the AirX.  Or should the AirX and solar panels have a system ground rod at each location.  The AirX will be 40 feet high, 1 1/2" pipe with guy wires going to 3' ground augers.  The solar panel mount is an old satellite dish modified to hold the 4 panels, sit on a 4" pipe buried about 4 feet deep.  Should the gas generator also have a ground rod?  I have wired the house to run off of the battery bank, and also run a seperate system for the washer, dryer (220) and 2 outlets in the kitchen for large 120 loads.  I want to run a 220 wire from gas generator to a seperate box just for these loads, but I also want to have the gas generator power a 40 amp battery charger when we run the large loads, or when there is no sun or wind.  Will this cause a problem with the grounding?  I also want to install a manual transfer switch, bringing 120 from generator to the main AC panel, when generator is off it will go back to the inverter and batteries.  Is it OK to use one of the 120 outlets from the generator for this and also have the 220 outlet run the seperate AC loads that are in a seperate AC panel.  How would I go about the grounding of this?

Sorry for all the questions, but I want to get it right the first time, local electritions seem abit un-schooled when it comes to offgrid hookups.  Thanks in advance.  BEAR  

[WXYZCIENCE]

-local electritions seem abit un-schooled when it comes to offgrid hookups.-

Bear, you ask hard questions. Would have to actually look at your setup to give you qualified advice. My first advice is to get rid of the dryer if you can, old fashion clothes-line in the back yard. Second, transfer switches need to be wired correctly or you may fry the inverter. Maybe others on this board will jump in.Joe

[wphfla]

Try looking at this schematic at Homepower Magazine.  The green lines are the grounds.  Perhaps it will answer some of your questions.

http://www.homepower.com/education/syspartscabin.cfm?search=cabin%20schematic

Kevin

[Phil Timmons]

I noticed your title said "Grounding of Solar Panels" (DC) but . . . .

Your questions seemed to move focus to the AC side of the operation?

Not trying to be a logic/grammer weenie, but rather to reinforce that you are working in two different domains on the same site.

In general -- as far the panels (and all components of the tracker/frame) go . . . we  hard bolt connect lugs onto each and every part of the array and tie them together with a bare #6 copper wire and onto a hard grounding rod at the base of the array.  That is what we tend to do for the DC outdoor components.  These act to protect the arrays (aluminum frame) and moving steel or aluminum parts of the tracker from lightning.  Where I have read specs on Federal Contracts for these type installs, the ground rod (for the panels described above) is generally supposed to be at least 50 feet away from any other AC system ground, and not tied into any cold water or building steel.

However, when crossing the inverter, we are in the domain of AC grounding systems.  And that is very detailed and specific within the NEC, Article 250.  In general, in that domain, we tie the grounded (neutral) wire and grounding wire (NOTICE THE "ed" vs. "ing" ending -- THEY ARE NOT THE SAME THING) together ONLY in the Main Disconnect, and the cold water pipe (if metal), gas pipe (if one exists) and any building steel frame is "bonded" back to the grounding system.  And then the neutral = grounded (white or grey) goes out on circuits as the return path on 120 volt circuits, or as a return path on the mixed 220 loads, such as a cooking range.  The grounding (bare or green aka equipment ground) also goes out to all equipment, but only conducts power back to the grounding electrode rod in the case of a fault.

A caution about using multiple grounding points for AC systems -- like from a generator in your example -- is that one ground does not always equal (voltage wise) another ground on the same site.  

You are correct about the observations of everyone being unclear about grounding regarding RE connections.  Last time I looked at the Code regarding whether one side of the DC should be grounded or not, that was unclear, as well.

I know that is a lot of confusing details, so if I did not make sense, or if anyone noticed anything in error, please ask for more detail, or feel free to correct me.

[TomW]

Phil;

Great info! Personally, I ground all the outside stuff,Towers, poles, masts, panel frames, etc to a 6 ft ground rod with heavy gage bare copper at the base of that unit. My philosophy is that if you give lightning an easy path to the earth it will gladly follow it. The A.C. side is done as you noted but that was all done by the original installers. My inverter is grounded as per Outbacks instructions but I forget exactly how it was done other than it has its own 6 ft ground rod. The RE stuff is all separate from the grid power so there are no possibilities of ground loops. We get a lot of sky sparks here and the ground at the meter pole is connected to 6] 25 foot copper #6 radials 2 ft deep in the yard that I installed after the first bolt that took out nearly everything that was plugged in when I first moved in. That one went thru UPSes and surge suppressors like they were copper bars. Insurance didn't begin to cover replacement costs, so we decided to beef up the protection.

Cheers.

TomW

[jmk]

 www.windsun.com/Lightning_Protection.htm This site has the new NEC code on a schematic. They show up to three ground rods, but being your off grid you would only need two. They show that all three will have to be connected, even the dc. The thing that they warn you about not having a complete bond is that if you have two items in the cabin that are grounded to two different bonds the ground current can be of different voltages like stated above. The problem that occurs is if you are hit by lightning the metal frames of the grounded chassis can shoot the lightning bolt from one to the other right inside your cabin. They also say that this not the safest way to do it, but if an inspector is looking at it he will look at the code like a bible.  I quit hooking my stuff up because it is so confusing. If I do it the way they draw it up my tower that's 150' away will have to be connected to the bond at the grid meter. Seems stupid to me! I think the way they said to do it above would be the best, but just don't get any apliances or controls to close together.

 Above it was stated that the dc bond shouldn't be any closer than 50'. I put my batteries in the garage twenty feet from the ac bonding point. The ground rod I drove for the batteries is just outside from the batteries,(25' away from the grid ac ground rod.) The NEC says to conect them booth together. I wonder if I should just move it to fifty feet away?    

[Phil Timmons]

The 50 foot part was just part of one set of specifications I was reading for a solar project for one particular Federal project.  I do not know that this means it should be extrapolated to mean that is a standard for all installations.  (or even any installations including the project so spec'ed)

I find engineering errors all the time.  Including my own.

Like you say and the observation made at the start of this topic . . . this can all be confusing, even for the engineers spec'ing the jobs.  On a brighter note, I am looking at taking a Test Engineer job with UL (Underwriter's Laboratories) for site power testing (includes all sort of grounding issues) so I might wind up being the expert I never sought to be.  

A funny story on two different grounds connecting with each other -- a computer control/networking engineer told me this . . . so it must be true . . .  Seems that Dow Chemical (the same Dow that helps you do great things -- and made Agent Orange) built two buildings on their big site near Midland, Michigan.  One was on solid ground, the other on top of their own chemical dump (including Magnesium compounds).

When the engineers tried to tie a data line between the buildings, they kept blowing up the computer equipment.  Turned out the dump created a large underground battery, and the voltage different between the "grounds" of the two buildings was around 300 volts DC -- and that was destroying the electronics equipment, which was grounded on both ends.

[Bigbear]

This forum is the best, thanks for all the fast replys.  Your right, my question does lead from solar panel to AC, but it all seems to tie together.  I have made a very crude drawing  http://photos.imageevent.com/paintballpictures/backhoeproject/websize/House%20wiring.JPG

The solar panels will go to a charge controller, and then to the copper buss bars that each battery is tied to.  The AirX will go direct to the buss bars.  From all the reading, wow, losts of reading, I have found on this subject, it appears I should have a ground rod for the Solar Panel mount, one for the AirX, one for the battery area (generator included), one for the AC panel (120 only from inverter) and the seperate 220 panel from generator (supplies 2 120 receps and 220 for dryer) and then tie all the ground rods together with large copper wire.  This would go along with the normal bonding and grounding of the system.   Does this sound OK?  BEAR

[Phil Timmons]

It s o u n d s just insanely excessive, but yeah, I think you are correct -- that meets just about anybody's everybody's claims and expectations.  I see you even have gas lines to deal with.  Sounds pretty wild, but I do not see a down side to it.

On the other hand, an area that I know I do not know about is the hook up of the "Air X," which I guess is a commercial windmill?  Some risks I can see in the direct battery hookup could be a short in winding gives a short in the batteries?  Or a lightning strike on the windmill hits the batteries also with the direct connection?  Like I say, I know that I do not know about windmills, like this, but do most guys use charge controllers to keep their batteries and windmills separated?

[Bigbear]

Thanks Phil, the AirX is commercial made, per the instructions, it says not to hook it through the charge controller (Morningstar Pro30).  It has it's own controller and when batteries are full will use the excess to slow the machine down.  Power from the windmill will have a fuse and then a switch that will either throw power to the buss bars or short out the power head, causing the machine to stop.  If the tower is hit, I am hopeing the ground rod at the tower, ground anchors or the ground rod at the batteries will take care of it without much damage.  I had planned to hook most things up this weekend, but a 10" rain changed the plan.  My new septic tank was full of water, but not covered with dirt yet.  The rain floated the tank up about a foot on one end and damaged the pipes and now it is not level.  I guess the weekend will be spent on the backhoe and shovel to fix this sitback.  But a little slap in the face now and then lets me know I'm just one man with too many jobs going at one time.  BEAR

[jmk]

 That's the kind of stuff that happens to me. I have so many things going on that it seems like there is no more time. When I was younger It sempt like there was all kinds of time. Where did it go?