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Grounding Inverters NEC


InPhase
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First, I'll say that I am NOT one of those "gotta follow the rules because that's the rules!" kinda person. But I do respect something that is right and true. The National Electrical Code is a profit driven machine. It is only written and published to make money for the National Fire Protection Association, a private company. There are many sections of the modern NEC that are expressly written to funnel money to manufacturers. But not the grounding section, Article 250. The grounding requirements of 600 volt or less systems in the NEC make sense once you come to grips with a key problem that is so common, electricians and engineers themselves are confused sometimes:

There's more than one kind of "ground"! 

In electronics, ground refers to the point of reference considered as "0 volts". Often the negative of the DC supply, or the center point of dual power supplies. Ground can be a current-carrying conductor.

In a car, the negative battery terminal is connected to the frame and considered "ground", which is consistent with how an electronics tech might use the term. But for power wiring in buildings, IT'S DIFFERENT! It's even more confusing because colloquially, we have muddied the waters by using the term "ground" to mean two related but different functions.

That bare wire connected to a rod or water pipe

That wire is what the NEC calls a "Grounding Electrode Conductor". It's purpose is to connect the neutral of your electrical system to the actual planet Earth. This serves to direct high voltage events, such as lightning or power line faults on the primary, away from your internal wiring. Other than that, that Earth-connected wire does NOT have a use inside your building. The electrical system will function just fine without it. But that wire also happens to be connected, at your main service, to

That bare or green wire on all the branch circuits from your breaker panel

The NEC calls that wire the "Equipment Grounding Conductor" and that is where the problem starts. Yes, it is connected to the ground, but its use is not to direct any current to the Earth. Its use is to connect all the non-current-carry metal parts of electric appliances together to equalize the potential across them, and to provide a path BACK TO THE SERVICE NEUTRAL to complete a circuit in case of a line-to-case fault somewhere inside the building. 

SHORT CIRCUIT CURRENT DOES NOT RETURN TO THE EARTH

Electricity flows in complete circuits. The Earth itself has too much resistance to allow a current large enough to trip a breaker most of the time. The bare "ground" wire is there to do that. So, at your service, the neutral is connected to one wire that goes to the dirt, and a second wire that goes to the round holes on all your outlets. I wish we would call the green or bare wire the "Equipment Bonding Conductor" instead of a ground wire. I think a lot of confusion would clear up.

So, one conductor of your system is connected to the Grounding Electrode Conductor and the Equipment Grounding Conductor. In a 120/240 volt 3-wire system, it is the neutral. 3 wires come in from the utility, and 4 wires come out. That new wire is not meant to carry a current under normal circumstances. So while it is true that the ground wire and the neutral are connected, never use the ground as a current-carrying conductor. If it ever becomes open, all the grounded metal cases and  frames attached to the same ground will be energized.

The NEC generally doesn't care about how circuits under 50 volts are grounded, and grounding solar panels is another subject altogether, so let's assume everything up to the batteries is all A-OK code wise. Let's also assume this is an off grid setup. You have a beautiful Genetry Solar inverter ready to wire up to your breaker panel. The NEC would treat this as what it calls a "Separately Derived System", and it is basically the same as a utility supplied system. You have three wires coming from your inverter. How do you ground this to code?

Two Ways to Ground your Inverter

You have to connect that inverter neutral to ground, both the Earth kind and the equipment bonding kind. The code allows this connection at either the inverter, OR the first means of disconnect. But not both. It is called a "System Bonding Jumper" in the code. Without this connection, a short circuit from line to ground will NOT trip a breaker or blow a fuse like it should. There is no complete fault current path without that connection. Here is a pic of both acceptable ways. Pretend the transformer in the pic is the inverter output:

 

 

 

 

 

 

 

 

 

 

SeparatelyDerivedSystemBondingJumper250.30(A)Z(1).jpg

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I'm good with everything you stated.  Good info!

My question is about the earth-ground connection on a powerjack control board.  They connect it to the receptacle ground and to the inverter case.  Fine.  If that's all you are going to do.

But, I connect my powerjack to my house breaker panel.  Since neutral is the center tap of the inverter transformer, I've always been leary of connecting the inverter's earth connection to, well, anything. So I never have.  That transformer center tap ends up being connected to the breaker panel neutral, which, as you so clearly pointed out, is connected to earth at one point or another.  I don't know what reaction I would get also connecting the earth-ground connection on the pj control board to what ends up being that same neutral/center tap.  On 110v control boards, the N connection would be effectively shorted to the earth connection.  Seemed like a bad idea.

So I leave the earth connection connected to the inverter receptacle and case, but never carry it out of the inverter case.  Maybe I'm worrying about nothing.  Maybe I'm doing somehting 'bad'.  If so, I'm ready for enlightenment.

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I don't have a PJ, so I can't look myself, but is there continuity from that board ground to anything else like the high voltage output or battery input? On the inverter I own, the ground of the receptacle is connected to the metal case, but that is it. There is a lug to connect to an earth ground. So, in the case where my main panel is where neutral and ground bond together, the way to ground my inverter would be to bring a wire from the neutral/ground bar to the metal case of the inverter.

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2 hours ago, InPhase said:

I don't have a PJ, so I can't look myself, but is there continuity from that board ground to anything else like the high voltage output or battery input? On the inverter I own, the ground of the receptacle is connected to the metal case, but that is it. There is a lug to connect to an earth ground. So, in the case where my main panel is where neutral and ground bond together, the way to ground my inverter would be to bring a wire from the neutral/ground bar to the metal case of the inverter.

Inside a PJ inverter, there are 4 10nF (0.01uF) high voltage decoupling capacitors.  One each from battery positive, and battery negative to chassis.  Then another set from L1 and N to chassis.  That's it. 

I understand that UL1741 requires some form of ground-neutral bonding in inverters; on the GS inverters, we have a 50A relay that shorts ground-neutral together if needed (i.e. inverter mode, but not charger mode, etc.)  This is pretty common in off-grid inverters; some squeak past the switching requirement with some big warnings and a spade terminal that the user can connect/disconnect for the necessary function.

@InPhaseThoughts, ideas?  We plan to pass UL1741, so we might as well get it all right before paying for a test!

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All pj control boards have an 'earth-ground' connection point on the control board that is apparently only connected to output potentials through 4 mov's.  No direct connection.  Thru 2 mov's to L1 and thru 2 more mov's to L2 (or to neutral if its a 110v control board).  Seems to me it probably wouldn't be an issue, but it probably also provides no benefit or protections in connecting it to house ground, so why take chances?

IMG_2901.JPG

IMG_2902.JPG

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Might want to look a smidge closer.  Most of those "blue devices" are really high voltage capacitors...look for a capacitor size code such as "103", a PCB reference of "Cxx", and a schematic drawing of a capacitor on the silkscreen.  The ones I have are marked "CD103M".  Kinda funny that the manufacturer (matching logo) doesn't acknowledge they make this size...https://www.songtian-ste.com/?post_type=products&page_id=16395/

I believe these caps were originally intended to sorta comply with UL1741, which requires that a grounded chassis basically has to be centered in the AC waveform.  Works OK if the board is running 240v...but if it's running 120v, now the chassis is centered between L1 & N.

PJ DOES use MOVs, however...but the board reference ID is not "Cxx", it's "MOVxx".  With the appropriate schematic symbol on the silkscreen, and it's directly across the AC input terminals.  The one I have is marked "14D561K".  Web search turns up it clamps at 925v...some protection, huh??  https://www.mouser.com/ProductDetail/Bourns/MOV-14D561K/?qs=CQ3B1E%2bbPs3fNJrywqtkng%3D%3D

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21 minutes ago, Sid Genetry Solar said:

Inside a PJ inverter, there are 4 10nF (0.01uF) high voltage decoupling capacitors.  One each from battery positive, and battery negative to chassis.  Then another set from L1 and N to chassis.  That's it. 

I understand that UL1741 requires some form of ground-neutral bonding in inverters; on the GS inverters, we have a 50A relay that shorts ground-neutral together if needed (i.e. inverter mode, but not charger mode, etc.)  This is pretty common in off-grid inverters; some squeak past the switching requirement with some big warnings and a spade terminal that the user can connect/disconnect for the necessary function.

@InPhaseThoughts, ideas?  We plan to pass UL1741, so we might as well get it all right before paying for a test!

I haven't read all of UL1741 because I can't afford it🤣 But from what I know of it, I agree with the principle. Let the inverter handle all the grounding and bonding internally and keep the grounds and neutrals separate externally. So 4 wires come from the inverter. That would be best for a new system built from the ground up.  But on existing systems with a neutral ground bond in place, it would be nice to be able to remove the bonding jumper from the inverter.

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15 minutes ago, InPhase said:

But on existing systems with a neutral ground bond in place, it would be nice to be able to remove the bonding jumper from the inverter.

So on the new GS Rev. B control boards, you would simply set the "Ground Bond" setting to "Off" to disable the internal ground-neutral bonding.  Yeah, I like settings 😁.  (Older Rev. A.1 boards don't have a ground bond relay.)

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  • 2 weeks later...
On 2/27/2021 at 10:30 AM, InPhase said:

You have to connect that inverter neutral to ground, both the Earth kind and the equipment bonding kind. The code allows this connection at either the inverter, OR the first means of disconnect. But not both. It is called a "System Bonding Jumper" in the code.

 

On 2/28/2021 at 9:37 AM, Sid Genetry Solar said:

So on the new GS Rev. B control boards, you would simply set the "Ground Bond" setting to "Off" to disable the internal ground-neutral bonding.

So if I'm understanding you two correctly if my panel has the neutral to ground bond I would connect the 4 wires (L1, L2, Neutral and Ground) from the inverter to my electric panel and set the inverter's "Ground Bond" setting to off?

If my panel wasn't bonded then I'd still connect the 4 wires and then have the setting on?

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1 hour ago, Cali Carlos said:

So if I'm understanding you two correctly if my panel has the neutral to ground bond I would connect the 4 wires (L1, L2, Neutral and Ground) from the inverter to my electric panel and set the inverter's "Ground Bond" setting to off?

If my panel wasn't bonded then I'd still connect the 4 wires and then have the setting on?

Ha, I guess that's the general gist.  In other cases, like if the ground-neutral bonding was in a connected generator, you'd also have to set the function to "off."

Something about grounding loops...

 

Please note, the OUTPUT of the inverter must not be connected to a live breaker panel.  At best, it'll error and refuse to start...and worst case, it'll blow up the inverter.

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In my humble opinion, (OK, maybe not so humble), most of these regulations are designed to make money for government agencies/inspectors and/or contractors.  That said, I don't want anyone to do anything unsafe.  But, as long as your electrical panel is correctly installed and connected to ground properly, it doesn't really matter whether you connect the ground connection on your inverter control board to house ground. 

Your powerjack split phase inverter neutral output wire will be grounded as soon as you connect it to your electrical panel. If one chooses to connect the inverter's ground connection to that same ground connection on your electrical panel, you are effectively connecting the inverter's ground connection directly to the inverter's neutral lead/connection.  To me that seems like a poor choice.  Maybe it's fine, but I'll leave mine unshorted.

4 minutes ago, Sid Genetry Solar said:

Please note, the OUTPUT of the inverter must not be connected to a live breaker panel.  At best, it'll error and refuse to start...and worst case, it'll blow up the inverter.

I'll second that!  I have to admit I have blown up an inverter by accidentally connecting it to a live grid panel.  Expensive mistake and boy did I feel stupid!

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15 minutes ago, dochubert said:

In my humble opinion, (OK, maybe not so humble), most of these regulations are designed to make money for government agencies/inspectors and/or contractors.  That said, I don't want anyone to do anything unsafe.  But, as long as your electrical panel is correctly installed and connected to ground properly, it doesn't really matter whether you connect the ground connection on your inverter control board to house ground. 

Quote

The grounding we are concerned with here is NOT about the planet Earth. What we want to accomplish with grounding is really a bonding of all non-current-carrying metal together to establish an equipotential plane AND to intentionally connect that plane to the system neutral. It causes all the non electrical metal to be at the same potential so that no current can flow between enclosures. Connecting it to the neutral ensures there's a complete path for fault current to flow through. If you don't connect the ground to the neutral, breakers won't trip during short circuits to ground.

Your powerjack split phase inverter neutral output wire will be grounded as soon as you connect it to your electrical panel. If one chooses to connect the inverter's ground connection to that same ground connection on your electrical panel, you are effectively connecting the inverter's ground connection directly to the inverter's neutral lead/connection.  To me that seems like a poor choice.  Maybe it's fine, but I'll leave mine unshorted.

Quote

You WANT the ground and neutral connected. That is how the whole grounding system works. Electricity doesn't flow to the Earth during a fault. Electricity flows in complete circuits from one terminal of the transformer to the other. If a live wire from a bad cord touches the metal inverter case, that case will be energized unless you have grounded it to the neutral.

 

 

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On 2/28/2021 at 12:08 PM, Sid Genetry Solar said:

Might want to look a smidge closer.  Most of those "blue devices" are really high voltage capacitors...look for a capacitor size code such as "103", a PCB reference of "Cxx", and a schematic drawing of a capacitor on the silkscreen.  The ones I have are marked "CD103M".  Kinda funny that the manufacturer (matching logo) doesn't acknowledge they make this size...https://www.songtian-ste.com/?post_type=products&page_id=16395/

I believe these caps were originally intended to sorta comply with UL1741, which requires that a grounded chassis basically has to be centered in the AC waveform.  Works OK if the board is running 240v...but if it's running 120v, now the chassis is centered between L1 & N.

PJ DOES use MOVs, however...but the board reference ID is not "Cxx", it's "MOVxx".  With the appropriate schematic symbol on the silkscreen, and it's directly across the AC input terminals.  The one I have is marked "14D561K".  Web search turns up it clamps at 925v...some protection, huh??  https://www.mouser.com/ProductDetail/Bourns/MOV-14D561K/?qs=CQ3B1E%2bbPs3fNJrywqtkng%3D%3D

You found that missing too huh? I looked it up when I blew up the Upower and they didn't make them according to their website. As far as the 10.3 boards go, the ones I have have places for 2 between Ground to Neutral and 1 from Line 1 to Ground.  They only used 1 in each one though so one of the N to G slots is empty. And if you check with an Ohmmeter, you will not see any connection between the Case Ground and Neutral. But if you put the meter on a capacitance setting instead, it does show up as 34pf if done on the board and 35pf at the case and the output's Neutral terminal.

I did not bond my Ground to the Neutral in my breaker panel in the shed. I did ground the Ground Rod to the inverter case and the Grounds in the outlets. There is a GFCI outlet on the 120 Volt outlets and it is lit up when the power is on and it does trip when tested. Something I could not do when I was using the 120 Volt outputs of the Jupiter MSW 2000 Watt inverter or any of the 120 Volt Reliable PSW Inverters as as soon as you powered one on, the GFCI would trip. As I had read about most of the 120V HF inverters blowing up if wired to a house with a bonded panel, I built the automatic transfer switch for the refrigerator as a completely isolating unit. If in inverter mode, it uses the inverter Neutral/Ground. If in commercial power mode, it uses the Main Panel Neutral/Ground.  I should check and see if the GFCI would function on the other leg of the 240 but do not think it would. Which would be another example of PJ not fully understanding split phase. The other being no filtering of Line 2.

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Grounding a receptacle to the Earth is useless at best and dangerous at worst. This is what I talked about in the OP. There's different kinds of grounding, and everyone is confused because of it. GFCIs don't need a ground to function. They work perfectly fine on an ungrounded system. The test button doesn't look for a ground. It sends a little current around the sensor instead of through it, which looks like a fault to the circuitry. Dirty power can trip a GFCI, and the high frequency noise on the output of a HF inverter certainly could do it.

 

Here's the bottom line: If you have a transformer sending power into your building, the neutral of that transformer should be bonded to the grounding system of the building. Where that bond happens at is variable, depending on where the transformer connects and how the utility service, if any, is connected.

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  • 3 weeks later...

Late comment, but still worth it.

Don't assume you can take the designated neutral or arbitrarily decide to call one side of a floating supply neutral and tie it to the ground pin/lug/wire with high frequency inverters.  There are designs out there where the supposed earth wire is actually at half AC supply voltage WRT to the two current carrying wires (single phase supply).  If you join one of those wires to the earth pin you run the risk of damaging / writing off the inverter as you'll effectively be shorting one 'side' out.  Some inverters will detect the problem and not destroy themselves though.

If you are wrestling with proper grounding of a high frequency inverter and the manual doesn't explicitly state what to do you can test reasonably safely.  Place a low wattage light bulb (rated for your mains supply voltage) across a current carrying wire and earth.  If it lights, even dimly, you can not join those two wires.  Repeat the test for the other current carrying wire.  If in either case the light does not glow at all, measure the voltage across the light.  It should be well under 5% of your supply voltage if it is just leakage via noise suppression capacitors (or any other number of leakage points, high frequency inverters leak like a sieve).

You can not measure for voltage between the current carrying wires and earth with a digital meter, or a FET based analogue meter either, as the meter will not load any leakage current sufficiently and indicate voltage even though there is only microamps of current available.

If you are attempting to wire a RCD/GFCI to an inverter where the earth is not safe to bond you may find your RCD/GFCI will still function normally if you stake the nominated earth point on the inverter to ground as sufficient current can still flow between the two current carrying wires and that 'live earth'.  Of course a proper test of the installation needs to be done to confirm that current shunted from the two current carrying wires to earth will actually cause the RCD to trip.

This issue affects both cheapie Chinese inverters, assuming they even have earth pin connected which is no guarantee, and name brands alike including some respected brands in the USA in case you were thinking you were safe.  The big difference there is the respected brands spell it out clearly in the manual that 'thou shalt not connect these together'.

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In my humble opinion, and of course there are exceptions, high frequency inverters should be left in the automotive field plugged into a cigarette lighter. In that case, grounding isn't really important. When you start connecting them to buildings, the game changes and the risk goes up. A low frequency inverter with a transformer output is the "right" way to power a non-mobile structure.

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Each to his own but all the big boys of the industry have high frequency inverters, even Victron, intended to be wall mounted for premises wiring.  Portable HF inverters in vehicles still need to be wired to the vehicle's chassis for safety.  The AC output in most is isolated so you can't get a shock by coming between one of the current carrying conductors and the vehicle chassis if all is well.  There is still a risk of an AC line cord becoming pinched, say in a door, and one of the current carrying conductors being shorted to the vehicle chassis and then you have a dangerous situation..  There is also the risk of a HVDC fault in the inverter placing HVDC on the inverter's chassis WRT the vehicle's chassis and if you get across that you are just as dead.

A portable HF inverter can be used in a premises perfectly safely provided it is used as intended.  Take a look at a typical portable HF inverter (having holes for screwing it down doesn't make it not portable), it has sockets.  That's a big clue as to how it should be used.  In order to one-up the competition cheap inverter manufacturers have often just bodged on a terminal strip suggesting the unit can be hard wired to a normal premises installation and that just isn't the case for some of them as the neutral/earth bond in the premises will cause problems for the inverter.

Portable inverters often fall into the IT class of wiring,  I = All live parts isolated from earth or one point connected to earth through an impedance, T = Direct electrical connection of the exposed-conductive-parts to earthing independently of the earthing of any point of the power system.  If the output remains isolated there is no more risk of AC shock than in any premises wiring system where an RCD (GFCI) is in use.  The trick is maintaining that isolation.  If you start running extension leads around the place for convenience it becomes much harder to guarantee those leads won't be nicked and cause the AC output of the inverter to be referenced to the earth so people want extra protection of an RCD.

There used to be a design of portable inverter where there was no isolation between the DC and AC side.  Instead of transformer(s) being used in the HVDC stage they used buck converters.  Insane I know, but they did exist.  If the AC output ever became tied to ground there would be lethal voltage between the battery terminals and the earth.  Likewise any fault that caused the AC supply to appear on an appliance chassis would put lethal voltage between the appliance and battery terminals.  From what I've seen it's not possible to buy them any more, most countries have banned them but I'm sure someone in China still makes them and the responsibility for safety with direct import falls on the purchaser.

Grid tied solar inverters often use buck/boost transformerless designs which is why earthing and fusing properly with grid tied inverters is essential.

My own portable HF inverter is a fully isolated design, sockets only no terminal strip, with the inverter chassis earth being used for RFI suppression (safety caps tie active/neutral to chassis) and HVDC protection.  It's permissible to join neutral and the inverter's chassis ground and stake that to the ground to allow an RCD to function.  Like your intent though, I'd not be using this unit to power a premises fixed wiring system.  That's where a proper wall mounted fixed wiring only (no sockets) HF inverters should be used.

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HF is better

LF is better

My mopar can trash your chevy

The point to remember here is that those of us using powerjack or powerjack style LF inverters to power our houses need to understand that when we connect the inverter output to the breaker box, we are connecting the center tap of the transformer output directly to ground.  (assuming USA wiring)  We have accepted responsibility.  We can no longer blame problems on the power company.

Running your residence with an inverter is not something to be undertaken lightly.  Potentially lethal forces are being manipulated.  Obviously from the discussions above there are differences of opinion on how best to connect things.  Each of us needs to be very aware of exactly what we are connecting, and how to remain safe while doing so.  The rest is preference and detail.  (and the devil is in the details)

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I come away with all this back & forth not sure if there's any benefit grounding the inverter chassis. I haven't grounded my existing system & unless I'm told otherwise by Genetry staff, I won't ground my new inverter they're sending shortly. I will say this tho, I have my inverters 120 neutral tied directly to my grid neutral. When I switch between grid & utility power, I'm just swapping the hot sides & haven't had any trouble with that set up so far after a year in use.

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4 hours ago, Bossrox said:

I come away with all this back & forth not sure if there's any benefit grounding the inverter chassis. I haven't grounded my existing system & unless I'm told otherwise by Genetry staff, I won't ground my new inverter they're sending shortly. I will say this tho, I have my inverters 120 neutral tied directly to my grid neutral. When I switch between grid & utility power, I'm just swapping the hot sides & haven't had any trouble with that set up so far after a year in use.

There is no back and forth really. Personally, I have only been speaking about what the electrical code says. As an installer and troubleshooter, I've seen enough diverse installations to know that what the code says makes sense, at least in the area of system grounding. The benefit to grounding your inverter case is that it will save you from being electrocuted should a wiring fault occur that energizes the case. It may never happen. Or it might happen to someone else in the house. Ultimately, it's your inverter and wiring to do with as you please, but know that over 100 years of electrification has proven the benefits of grounding and bonding.

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5 hours ago, Bossrox said:

I come away with all this back & forth not sure if there's any benefit grounding the inverter chassis. I haven't grounded my existing system & unless I'm told otherwise by Genetry staff, I won't ground my new inverter they're sending shortly.

I personally am not a fan of grounding, due to a large amount of equipment damage as a result of "properly grounded" systems.  (Thanks a lot, local lightning strike.)  Up to you; the chassis really doesn't connect to anything internally anyways.  (A few decoupling caps to both the battery input and AC output, that's it.)

 

5 hours ago, Bossrox said:

I will say this tho, I have my inverters 120 neutral tied directly to my grid neutral. When I switch between grid & utility power, I'm just swapping the hot sides & haven't had any trouble with that set up so far after a year in use.

You know, there's a function in the GS inverters for that: ATS 😉.  I probably will need to add some features to the inverter to fully take advantage of this function, but that's what customer feedback is for...

While I don't particularly like the idea of connecting an off-grid inverter to the grid (potential damage due to lightning strikes), that's up to you.

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It's another case of misunderstanding between earth ground and equipment ground. The ground that would bring a bolt of lightning into your internal wiring is a different ground than the ground that clears a fault in the supply. They are tied together but are not the same thing. The code for a "proper" grounding system is a minimum. It allows for a single electrode connection to the Earth. But the reality is, a bolt of lightning can induce thousands of volts of potential difference over a very small distance. There isn't much that you can do with that on a utility-supplied system because it's impossible to isolate it completely and the service neutral is tied to earth on both ends, so there's a parallel resistance with another uneven voltage drop. And your neutral is tied to your neighbor's neutral. And your copper water pipe is tied to your service neutral, which is tied to every other neutral on the block.... And on it goes. But an off grid system is different. 

For example, I worked on a project where a remote geophysical monitoring station was blowing through electronics almost monthly. The powers that be decided they needed a bigger supply, so they put 1 kW of PV on it. It got worse. It was always arcing damage in the electronics but no visible sign of lightning striking the outside. The problem got worse due to the minimal grounding. The system was grounded with a 4 foot rod in the dirt to the negative battery terminal. The new PV array was also grounded on the negative to its steel pole so distance from the shack. Even nearby strikes can cause enough current to flow in that loop to do damage.

After getting the funding, the solution that worked was to run "spokes" radially from the equipment shack of 2/0 bare copper. They were Cad Welded to a ring of copper around the shack. Another ring encircled the other end of the spokes. It would look like a bicycle wheel if viewed from above. The radius was something like 15 yards. Ground rods were driven at the middle and each end of each spoke. The rods were the worst part. We had to haul everything in on 4 wheelers, but that still wasn't as bad as driving the rods. Anyway, it's been at least two years since any unexplained blow ups have occured. With earth grounding it's all about creating an equipotential zone where the local impedance is so low that no significant potential can exist between distant points.

And I stress that grounding metal cases of appliances is a different animal. Completely different. Just named the same🤬

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RFI is something to be considered too.  Completely floating systems can radiate crap like crazy unless a heap of time and effort has been put into containing it.  Ask any amateur (ham) radio operator and I'm sure they'll talk your ears off about that switching power supply / inverter / thing that caused them no end of grief.

When it comes to inverters it's a case of horse for course.  Sometimes a LF (big transformer) type is appropriate, sometimes a HF (wee transformer) type is.  I use which ever suits the application.

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