Proper grounding/ bonding for off-grid pv solar setup with back-up generator

[cbskies]

Grettings everyone!
First I want to say that I have been coming to this forum for quite some time and have always found it to be a great source of information and clarification, a big thanks to everyone here! This is my first post so please bear with me.

I have a friend who had purchased a back-country cabin and his original electrician abandoned the solar project so I have stepped in to help get it finished. I am a licensed residential wireman but have little experience with solar. We have gotten the system up and running but I have found myself confused over the proper grounding for this system, any help would be greatly appreciated.

First a description of the system. Approximately 100-150' from the cabin he has a pole-mounted DC pv array with 6 panels wired three panels in series for two parallel DC circuits with a maximum output of approximately 1500W. This pole is a large metal pole (8" diameter maybe) concrete-encased approximately 8' in the earth, continuous metal mounting from pv array rack to the continuously welded structure of pole. About 15' from the pole there is a small shed which contains the PV array combiner box which has two 125V / 20A DC disconnects and sends one DC circuit to the cabin.

Also in the shed is a propane powered 8kw generator. About 25' from the shed is an approximately 300' water well with a 230v 9A AC well pump with pump controls in the shed. From the shed there is a single 2" PVC conduit run to the cabin crawl space.

Inside the cabin mech room he has an Outback charge controller (FLEXmax80), a 48v 500Ah battery bank, and an Outback FX series inverter setup (pretty sure it is the FLEXpower TWO system) which feeds an AC subpanel. Both AC and DC sides of the inverter have separate 6awg copper runs going to a single ground rod, and there is a system bonding jumper on the AC side bonding the AC neutral to ground.

So for clarification, in the 2" PVC there are four wires, 6-2 romex going from combiner box to charge controller, 10-3 romex going from backup generator to ac inputs on inverter, 10-2 romex going from pressure switch in cabin to well pump controls, and a 14-2-2 romex which is being used (2 conductors) as signal wire for turning on/off generator from the aux outputs of the master inverter through a 12v relay.

From my description you may already be aware of code violations here, namely high and low voltage wiring sharing the same raceway (pvc from shed to house). As stated I am picking up an abandoned project and just want to get the system running for now and safely/ properly grounded and bonded as per NEC. The area is about 7-8' buried in snow so separate underground conduits will have to be addressed later.

So here are my questions:
Currently there is an equipment grounding conductor in the 6-2 romex run from the DC side ground bus on the inverter which goes out to the pv combiner box in the shed. Do I need to run an equipment grounding conductor from the array/ pole to the combiner box ground bus? From my (limited) understanding the pole on which the array is mounted should serve as an adequate grounding electrode for the array correct? If I run an equipment grounding conductor to the array won't this create a large ground loop between the cabin grounding electrode and the pv array pole? Having watched Mike Holt's youtube video on Grounding Myths I am under the impression that this is undesirable especially in the case of a nearby lighting strike which is likely as this cabin is high in the mountains.

Along the same note, should I have an equipment grounding conductor running from the cabin to the well casing? Wouldn't this well casing serve as a far better grounding electrode than the ground rod outside the cabin and again wouldn't this create another large ground loop in the system? It would in fact be three grounding electrodes tied together, the cabin ground rod, the pv pole, and the well casing. Is this ok? Currently I understand this to be undesirable, in the case of a large voltage gradient due to nearby lightning strike as there could potentially be very high voltage currents running through the grounding system potentially damaging equipment, or is this incorrect?

Third, currently the neutral and ground of the backup generator seem to be bonded as I get 120v AC from both hot legs of the generator to the generator chassis. Currently the generator does not have it's own grounding electrode. I am under the impression that the ground to neutral bond should remain in the AC side of the inverter as the inverter is the main source of power for the cabin, and the generator is typically only for charging the batter bank should it get low, so do I need to remove the ground to neutral bond in the generator and then ground the generator chassis using the equipment grounding conductor in the 10-3 romex running from the cabin? Also this generator has it's own separate stand alone 12v battery and small pv array for startup. the negative of this battery is also run to the generator chassis as would be typical I believe. Currently I have disconnected the equipment grounding conductor between the inverter ac ground bus and the generator thinking it would be best to give the generator it's own grounding electrode.

So i've been scratching my head over these questions and not having been able to come up with answers in other posts or in videos, or the code book itself, I've finally created an account and posted here, thanks a million to anyone who can give me some grounding guidance!

 

[jaggedben]

First off, before going into detail...

I think you are confusing grounding and bonding and not appreciating what the latter does. Having everything connected to grounding electrodes will not provide fault return paths where breakers and other devices need them to trip. Yes, there are potential dangers from having grounding electrodes 'all over the yard' with only meager equipment grounding connecting them, if lightning strikes. There are also potential dangers of the electrical system setting things on fire if you don't have proper bonding, i.e. equipment grounding conductors.

From my description you may already be aware of code violations here, namely high and low voltage wiring sharing the same raceway (pvc from shed to house).

Actually there is no violation based on voltage, if all those wires are rated for the highest voltage. However it is a violation having the PV output circuit in the same conduit as anything else.

As stated I am picking up an abandoned project and just want to get the system running for now and safely/ properly grounded and bonded as per NEC.

Will this actually be inspected? There might be differences between what is safest and what the code requires, especially with respect to lightning. It's my opinion that the NEC is not about preventing lightning damage from close-by strikes. There's actually another code for that NFPA 780. The NEC will generally guide you towards bonding everything together so as not to have voltage potentials from the electrical system that could shock people. This may actually increase the danger of lightning damage, especially if done inadequately.

Currently there is an equipment grounding conductor in the 6-2 romex run from the DC side ground bus on the inverter which goes out to the pv combiner box in the shed. Do I need to run an equipment grounding conductor from the array/ pole to the combiner box ground bus?

Per code you need to have a functioning GFDI, which means yes, you need that equipment grounding conductor. You are really close to meeting the first exception to 690.5, in which case you wouldn't be required to have GFDI. The problem is your PV circuit comes back to the dwelling. If you can some how change that so the inverter isn't in the dwelling then you wouldn't need the GFDI and I suppose you could not really need an equipment grounding conductor. The code still requires equipment bonding though.

From my (limited) understanding the pole on which the array is mounted should serve as an adequate grounding electrode for the array correct? If I run an equipment grounding conductor to the array won't this create a large ground loop between the cabin grounding electrode and the pv array pole? Having watched Mike Holt's youtube video on Grounding Myths I am under the impression that this is undesirable especially in the case of a nearby lighting strike which is likely as this cabin is high in the mountains.

The pole sounds like an adequate electrode, although I think code requires 10' in the earth. I'm no expert on lightning, but my understanding is that you might be better off running a larger ground here than no ground at all. Keep in mind that lightning will try to find a way from one place to the other and might follow the circuit conductors if there's no grounding wire. See comments above.

Along the same note, should I have an equipment grounding conductor running from the cabin to the well casing? Wouldn't this well casing serve as a far better grounding electrode than the ground rod outside the cabin

Again, the purpose of an EGC isn't merely to create a connection to earth, it's also to create a fault path so a breaker will trip. If the hot conductor touches the well casing the breaker won't trip through the earth, but could shock somebody who touches it. What danger are you more scared of, lightning damage or electrical shock? Sorry if I'm repeating myself.

and again wouldn't this create another large ground loop in the system? It would in fact be three grounding electrodes tied together, the cabin ground rod, the pv pole, and the well casing. Is this ok?

My take is that it's more likely to be okay if you size your conductors according to the rules for the grounding electrode system, i.e. #8 minimum. If you have #14 EGCs connecting them that is probably not okay in a lightning strike. I think Mike Holt would agree?

Third, currently the neutral and ground of the backup generator seem to be bonded as I get 120v AC from both hot legs of the generator to the generator chassis. Currently the generator does not have it's own grounding electrode. I am under the impression that the ground to neutral bond should remain in the AC side of the inverter as the inverter is the main source of power for the cabin, and the generator is typically only for charging the batter bank should it get low, so do I need to remove the ground to neutral bond in the generator and then ground the generator chassis using the equipment grounding conductor in the 10-3 romex running from the cabin?

I'm pretty sure that's what I'd do, yes. You should not have two neutral-ground bonds in the system. Hopefully removing the bond from the generator is a feature it allows, rather than tampering.

 

[cbskies]

First off, before going into detail...

I think you are confusing grounding and bonding and not appreciating what the latter does. ....

Thanks, yes I think you are right, I had some grounding functions confused here, it seems the question comes down to equipment vs personnel protection and NEC would give the personnel protection the higher priority, understandably so.

So essentially I should run a min #8 ground to the shed in order to bond both the well casing and pv array despite the fact that they both serve as grounding electrodes themselves, and this in order to open the appropriate breakers in the case of a ground-fault.

No inspection pending, the original electrician nor the home owner ever pulled a permit, I would like to see it as close to NEC as possible, at least for now as he is living there and it is mid winter. I feel like the NEC takes priority over NFPA lightning code so I'm inclined to give it precedence especially where regards personnel protection.

For clarification on the generator, If I can remove the bonding jumper on the generator, I should then run an equipment ground to it and bond also with the well and array, correct?

 

[jaggedben]

So essentially I should run a min #8 ground to the shed in order to bond both the well casing and pv array despite the fact that they both serve as grounding electrodes themselves, and this in order to open the appropriate breakers in the case of a ground-fault.

To be clear, my expertise is in PV, not lightning, so I'm best at telling you what you're sacrificing if you don't bonding stuff together. In addition to maybe having a fault and a shock hazard on an AC line from a breaker not tripping, you might also have a PV ground fault which could cause a fire. Most likely if you didn't bond things together, that would happen on the PV array itself. The Outback should have a GFDI device, that if everything is bonded will alert you to any fault to metal in the PV wiring (by shutting off). If you don't have things bonded, then a first fault on the array (say, the positive to the pole) will not be detected and a second fault (in the negative) gives you a solar powered short that will not be shut off by any breaker.

I'm going to beg off giving you specific advice on what's best from the lightning angle. I think it's fair to say that, theoretically, if lightning strikes nearby, the size wire you need to safely carry the current from a voltage gradient depends on how far away the lightning is, which you can't predict. I gather some people would tell you to install a surge protection device or two around this setup, like where the wiring enters the cabin, to prevent bad stuff from happening to anybody or thing inside. But I'm not the guy to give you advice on the particulars of something like that.

For clarification on the generator, If I can remove the bonding jumper on the generator, I should then run an equipment ground to it and bond also with the well and array, correct?

Yes. I would also check the Outback manual, in case they have some information alternative setups.