Bonding a service panel that is off grid

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I'm installing a solar electric system in my off grid cabin. I plan on earth grounding the service panel with its own ground rod. My pv panels will have there own ground rod. My question is should the service panels neutrals and grounds be bonded, or should they be kept separate? Thank you in advance for any assistance in this matter.

 

[Ohms42pA]

I'm installing a solar electric system in my off grid cabin. I plan on earth grounding the service panel with its own ground rod. My pv panels will have there own ground rod. My question is should the service panels neutrals and grounds be bonded, or should they be kept separate? Thank you in advance for any assistance in this matter.

I'm not an expert and just regurgitating what I've learned here and elsewhere over the years.
I would think you want 1 N/G bond in your main service panel.
If you ever hook a generator up you need to pay attention / understand its N/G bonding requirements.
I would also only install 1 ground rod if feasible or bond your ground rods together.

Edit, wait for some experts to chime in with more.

 

[Samsonite801]

I'm installing a solar electric system in my off grid cabin. I plan on earth grounding the service panel with its own ground rod. My pv panels will have there own ground rod. My question is should the service panels neutrals and grounds be bonded, or should they be kept separate? Thank you in advance for any assistance in this matter.

You only want one N-G bond in the system (in the structure) and it should be as close to the power source as possible (keeps the two paths for neutral and ground separated for as long of distance as possible and joins them at closest point to power source).

Many inverters provide an N-G bond inside them only if/when they are turned on (inverting). They are usually switched open or closed by a relay, so if you put the inverter into bypass, and are receiving generator power on the AC input of the inverter, the N-G bond will break and open on the inverter, and then you would use an N-G bond point at the generator, you'd have the generator grounded to the grounding pole there as well, and confirm it is making an N-G bond there (not all generators are N-G bonded from factory), as it will then be the active power source.

You can do a few simple checks with a multimeter to see how your inverter handles the N-G bond while inverting, while in bypass, etc, to know for sure how it behaves.

At least this is how I always understood it to be set up the safest, and adhere to NEC...

There was a PDF somewhere I read before where they went into all the details of switching the N-G bond point when using multiple power source options, trying to find it again, was a good read... I'll edit post and put the link in if I can find it. If you don't have multiple power sources, then only the inverter will handle the N-G bond.

But it is a simple concept overall, just have one bond, and in case of using more than one power source, then have a means of moving that bond to be closest to the power source.

 

[Pgh-skip]

I do plan on supplementing the charging of my batteries when sunlight alone will not fully charge them. So now I'm totally confused. Please tell me what I need to do to make my system safe. Should I ground my generator to the earth ground for my service panel?

 

[NorthTown2022]

There was a PDF somewhere I read before where they went into all the details of switching the N-G bond point when using multiple power source options, trying to find it again, was a good read... I'll edit post and put the link in if I can find it. If you don't have multiple power sources, then only the inverter will handle the N-G bond.

Look forward to reading this!

 

[Samsonite801]

I do plan on supplementing the charging of my batteries when sunlight alone will not fully charge them. So now I'm totally confused. Please tell me what I need to do to make my system safe. Should I ground my generator to the earth ground for my service panel?

Sounds good. So you need to find out how your inverter behaves, in regards to the N-G bond (within the Auto Transfer Switch function behavior of the inverter).

I know on my MPP Solar LV6548 inverters, when the inverter is turned ON, the inverter closes a relay contact which joins the neutral and ground at that point (since it is the power source).

If you shut off the LV6548 inverter (put into bypass mode), then it releases that N-G bond there, and just passes the AC input wires separately, right through the unit (this is its ATS functionality) to the AC outputs...

So now if you feed that AC input with a generator, then it becomes the new power source, and so you need to make sure that the generator is N-G bonded (not all generators come N-G bonded).

So if the inverter is the primary power source only while inverter is turned ON, the generator would then be referred to as the 'separately derived system' (if the ATS or inverter opens the N-G bond)...

But suppose if the inverter type you have never breaks the N-G bond under any condition, then in that case a generator would not need to be grounded with a ground rod and no N-G bond needs to be made there (grounding it only through the cable conductor back to where the N-G bond device is).

Here is some more info:

Ground a Generator? Simply Explained for Non-Electricians | Home Battery Bank

As a general rule, a residential portable generator does not need to be grounded to the earth via a ground electrode or rod in any configuration unless it is supplying power to a house with a transfer switch that switches the neutral in the main panel. This makes the generator a separately...

homebatterybank.com

Mike Holt Enterprises - the Leader in Electrical Training.

Mike Holt worked his way up through the electrical trade from apprentice electrician through electrical contractor, to become one of the most recognized experts in the world as it relates to electrical power installations. He was a Journeyman Electrician, Master Electrician, and Electrical...

www.mikeholt.com

https://www.mtecorp.com/pdfs/AppsNote01.pdf

 

[JRH]

Sounds good. So you need to find out how your inverter behaves, in regards to the N-G bond (within the Auto Transfer Switch function behavior of the inverter). I know on my MPP Solar LV6548 inverters, when the inverter is turned ON, the inverter closes a relay contact which joins the neutral and ground at that point (since it is the power source).

If you shut off the LV6548 inverter (put into bypass mode), then it releases that N-G bond there, and just passes the AC input wires separately, right through the unit (this is its ATS functionality) to the AC outputs...

So now if you feed that AC input with a generator, then it becomes the new power source, and so you need to make sure that the generator is N-G bonded (not all generators come N-G bonded, and is grounded using a ground rod.

So if the inverter is the primary power source, the generator would then be referred to as the 'separately derived power source'...

So suppose if the inverter type you have never breaks the N-G bond under any condition, then in that case a generator would not need to be grounded with a ground rod and no N-G bond needs to be made there (grounding it only through the cable conductor back to where the N-G bond device is).

Here is some more info:

Ground a Generator? Simply Explained for Non-Electricians | Home Battery Bank

As a general rule, a residential portable generator does not need to be grounded to the earth via a ground electrode or rod in any configuration unless it is supplying power to a house with a transfer switch that switches the neutral in the main panel. This makes the generator a separately...

homebatterybank.com

Mike Holt Enterprises - the Leader in Electrical Training.

Mike Holt worked his way up through the electrical trade from apprentice electrician through electrical contractor, to become one of the most recognized experts in the world as it relates to electrical power installations. He was a Journeyman Electrician, Master Electrician, and Electrical...

www.mikeholt.com

https://www.mtecorp.com/pdfs/AppsNote01.pdf

I like ole Mike H. …. and those 150.00 dollars shirts he wears…. Smart guy.

 

[Samsonite801]

I like ole Mike H. …. and those 150.00 dollars shirts he wears…. Smart guy.

Yeah he is for sure! I just wanted to make sure people understand his great points as well.

So to reiterate again for the OP... Whether or not you N-G bond and ground the generator (or alternate power source) with a ground rod, depends on how the inverter handles it's N-G bond in the ON/OFF states (active vs bypass)...

And if the inverter has N-G bond (like most of them do), then you would never want two N-G bonds, so in your breaker panel mounted after the inverter AC output should not be N-G bonded there.

One point to make as well. On my LV6548 system, I do not plan to charge my batteries using the AC input with the inverter's internal battery charger (at least initially), because it only allows charging batteries when the inverter is in bypass/standby, so then your generator must be big enough KW to power the battery charging, and run all the house loads directly (since inverter would be turned off in order to charge batteries from AC input).

So my plan, I purchased two 48v battery chargers that I will connect to each 120v leg on the generator to just charge only the batteries while my inverter is turned on, that way my generator will just be a simple appliance, not connected to anything in my system except to the standalone battery chargers. Then it won't be considered a 'separately derived system'...

This way I will just let the inverter handle the N-G bond, where it will close it when inverter is turned on, and when turned off, it will just be sitting there and no AC power at all (since I'm off-grid)...

If I later decide to also wire the generator into the AC input of the inverter, then I will have to N-G bond my generator and ground it to a ground rod, not a big deal either, but just to illustrate further so it hopefully makes more sense.