FilterGuy
Solar Engineering Consultant - EG4 and Consumers
Funny.... I was raised in MO and went to CA to earn my money....
LV6048 output neutral-ground bonding?
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Ozark Tinkering
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Oh I wandered back and forth for many years and followed big work. Mostly powerhouse work.
Ozark Tinkering
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That piece of 1750kcmil in my hand is a souvenir from cayuga indiana powerhouse. 1lb. per inch. They paid good money to terminate that stuff. That's a 2 man job. ?
RE: I hate reading NEC Code.
NEC isn't the only code the reads like a riddle. I have been in construction going on 40 years. The last 30 of those in the multifamily industry where the codes I have to follow most are ADA/ANSI ..Federal Fair Housing Chapter 7...California CBC Chapter 11 ... Massachusetts 521 CMR. All of them read like a cryptic puzzle.
Reminds me of this image I have seen posted on the wall of many site trailers:
NEC isn't the only code the reads like a riddle. I have been in construction going on 40 years. The last 30 of those in the multifamily industry where the codes I have to follow most are ADA/ANSI ..Federal Fair Housing Chapter 7...California CBC Chapter 11 ... Massachusetts 521 CMR. All of them read like a cryptic puzzle.
Reminds me of this image I have seen posted on the wall of many site trailers:
@FilterGuy in Post #18 you stated: Also, Do NOT disable the dynamic bonding by removing the screw mentioned in post 11.
Can you provide the reason why?
I don't doubt you, however it doesn't provide enough information to make a decision.
In my mind, removing the screws would allow me to use the currently installed non neutral switching transfer switch as the inverter would not provide it's own NG bond when on battery/inverting. The NG bond would then be provided by the main service panel.
Thanks in advance.
Can you provide the reason why?
I don't doubt you, however it doesn't provide enough information to make a decision.
In my mind, removing the screws would allow me to use the currently installed non neutral switching transfer switch as the inverter would not provide it's own NG bond when on battery/inverting. The NG bond would then be provided by the main service panel.
Thanks in advance.
BuffaloTrace
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Less wire switching is more simple in my book, but perhaps being able to accommodate both bonded and non bonded N-G would be pertinent in the ever evolving home generator systems.
There doesnt seem to be any standard for this at the moment, yet it seems growatt and mppsolar are heading in the direction of being seperately derived systems with an internal N-G bond. I believe in using the manufactured equipment for it's intended use is better than having to modify it for some other use. This make sense for when operating in offgrid mode in conjunction with utility power as main supply.
I'm interested in 2 systems, interchangeable with little to no change being made to existing home wiring, aside from using an existing generator plug as was intended for use with a ICE backup generator combined with a lockout switch. This enables the use of a generator (solar or ICE) for loads other the main panel most of the time, but has the ability to switch to main panel electrification without moving or changing circuits on the existing residence for the rare occasion that the grid is down. Being able to safely switch between the two, without having them connected by way of using the utility AC pass thru features at all.
There are many reasons to use AC pass thru features for charging capabilities, but if a solar inverter system is designed correctly for this use case, that function is rarely used.
Seems that I may need to add a basic 2 pole switch after the residential generator inlet, and prior to the main panel lockout breaker to comply with code IF the inverter does not contain N-G bond, and basically run as floating neutral generator. If Inverter utilizes NG bond than one would need a neutral switching switch... perhaps an appropriate angle to this would be to incorporate both, or add another generator inlet plug that can accommodate one or the other. Hmmm....
There doesnt seem to be any standard for this at the moment, yet it seems growatt and mppsolar are heading in the direction of being seperately derived systems with an internal N-G bond. I believe in using the manufactured equipment for it's intended use is better than having to modify it for some other use. This make sense for when operating in offgrid mode in conjunction with utility power as main supply.
I'm interested in 2 systems, interchangeable with little to no change being made to existing home wiring, aside from using an existing generator plug as was intended for use with a ICE backup generator combined with a lockout switch. This enables the use of a generator (solar or ICE) for loads other the main panel most of the time, but has the ability to switch to main panel electrification without moving or changing circuits on the existing residence for the rare occasion that the grid is down. Being able to safely switch between the two, without having them connected by way of using the utility AC pass thru features at all.
There are many reasons to use AC pass thru features for charging capabilities, but if a solar inverter system is designed correctly for this use case, that function is rarely used.
Seems that I may need to add a basic 2 pole switch after the residential generator inlet, and prior to the main panel lockout breaker to comply with code IF the inverter does not contain N-G bond, and basically run as floating neutral generator. If Inverter utilizes NG bond than one would need a neutral switching switch... perhaps an appropriate angle to this would be to incorporate both, or add another generator inlet plug that can accommodate one or the other. Hmmm....
Ozark Tinkering
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A SDS will require a 3pole transfer switch between it and the grid. That's the standard in the U.S.A.
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I'm thinking the design team in Usa, China may be a tad light in the area of NEC knowledge and will catch up later...like after the Chinese new year.
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FilterGuy
Solar Engineering Consultant - EG4 and Consumers
My statement has to be taken in context. It is clear from the response from MPP that the intended design for the inverter is to NOT have the input neutral tied to the output neutral. The intended design is that the output neutral would be isolated from the input neutral and the inverter will add an N-G ground when the system is being driven off the battery.
I have not seen a diagram of your use of the non-neutral-switching xfer switch, but from the description, I am assuming there would be a solid connection between the inverter input Neutral and the inverter output neutral. It is not clear to me if the inverter design can handle this or not. I sent an email to MPP asking this very question but I never heard back.
Zwy
Solar Wizard
For those wondering, SDS- Separately Derived System
Which brings in neutral switching, correct?
Ozark Tinkering
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Yup.
FilterGuy
Solar Engineering Consultant - EG4 and Consumers
The simple way to think of this is:
1) If the AC power source has a Neutral-Ground bond, it is a separately derived source and a transfer switch between it and a utility must switch neutral
2) If the AC power source does not have a Neutral-Ground bond, it is NOT a separately derived source and a transfer switch between it an a utility must NOT switch neutral.
Notes:
* The definitions around an SDS is more nuanced than that, but for our purposes, this is fine.
* Where things get complicated is when the utility is on the input of the inverter, there is no N-G bond created in the inverter, and there is a transfer switch that selects between the inverter output and the utility. Since there is no N-G bond the rule would say that you should not switch neutral, but that ends up with the inverter input-neutral tied to the inverter output neutral.....and the documentation for a lot of the lower end inverters does not say whether this is acceptable or not. Some inverters like Schnider and SolArk are designed for the neutrals to be tied together (and they never create an NG bond). Inverters that generate an N-G bond when in invert mode are intended to have separate neutrals, but some of them can operate with a common neutral.
BuffaloTrace
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If the screw is removed as earlier post indicated, and used in such a way as Philatio describes, through a generator plug generally used for a residential generator without N-G bond. The inverter operating in battery mode would share a common neutral (with the utility) effectively when plugged in to a main panel using a standard generator plug and main breaker lockout switch (prevents backfeed through L1 and L2).
Again, I'm into the simplicity of using a standard generator inlet combined with the UL approved and original lockout breaker setup, but I dont like the idea of messing with screws in the inverter, of course unless this was the design intent of said screw...
Again, I'm into the simplicity of using a standard generator inlet combined with the UL approved and original lockout breaker setup, but I dont like the idea of messing with screws in the inverter, of course unless this was the design intent of said screw...
Zwy
Solar Wizard
It also can make the case hot and any ground fault won't be cleared when in inverter mode.
Go back to this post and the response by MPP.
https://diysolarforum.com/threads/lv6048-output-neutral-ground-bonding.33719/post-417481
Note, the N-G bond is open in line mode and shorted in inverter mode.
Neutral is switched in the inverter at the transfer switch.
Zwy
Solar Wizard
This diagram https://diysolarforum.com/threads/lv6048-output-neutral-ground-bonding.33719/page-2 has a loop no matter what. There should not be a ground wire between inverter subpanel and main entrance panel.
Ground should be wired from main panel to inverter and from inverter to inverter subpanel.
This is where I get lost. Maybe I'm just dense and don't get it. I'm usually pretty good at following logic.
If the screws, one on each board, are removed, doesn't that make it a floating neutral inside the inverter even when in battery mode?
How could the case of the inverter be hot if the inverter output is connected to the main panel via an L14-30 inlet box, which carries G-L1-L2-N from the inverter to the main panel. The grounds in the inverter are also tied to an EGC screw connected to the case.
The 30a inlet box is connected to a break it before make it 10 circuit transfer switch which is wired directly to 10 circuits in the main panel.
As far as AC input, I was just going to wire the male end of the L14-30 generator cord into the inverter, and plug it into a dedicated L14-30 outlet from the main panel.
The way I understand this, now the AC input & output will behave the same and use the main panel NG bond. No NG bond in the inverter when in battery mode.
Please help me understand why if it won't work this way.
Thanks in advance.
If the screws, one on each board, are removed, doesn't that make it a floating neutral inside the inverter even when in battery mode?
How could the case of the inverter be hot if the inverter output is connected to the main panel via an L14-30 inlet box, which carries G-L1-L2-N from the inverter to the main panel. The grounds in the inverter are also tied to an EGC screw connected to the case.
The 30a inlet box is connected to a break it before make it 10 circuit transfer switch which is wired directly to 10 circuits in the main panel.
As far as AC input, I was just going to wire the male end of the L14-30 generator cord into the inverter, and plug it into a dedicated L14-30 outlet from the main panel.
The way I understand this, now the AC input & output will behave the same and use the main panel NG bond. No NG bond in the inverter when in battery mode.
Please help me understand why if it won't work this way.
Thanks in advance.
BuffaloTrace
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This is what I assumed, and can be confirmed using continuity test. This is extremely similar to what my use case would be as well. If given the "blessing" of the manufacturer with positive personal test confirming, than I will assume floating neutral and grounded inverter case. Is not this out residential ICE generators are designed to operate?
Would this affect how the AC pass thru function of the inverter operates?
I'll be looking into inverters designed to operate in this way. I dont think we are the only ones that could benefit, as I think generator inlet plugs and interlock kits are extremely common for residential. My neighbor had his whole panel replaced (100a) with a new Square D (200a) and they added a 30 amp circuit with a generator interlock device for this function. Not sure if he even knows what it's for, but he had a good electrician, extremely nice work.
Zwy
Solar Wizard
It would depend on the ground screw, some ground screws are for grounding the inverter case. It will operate, however it may not clear a ground fault of the case. The reason why is current always returns to the source, whether it is grid or the inverter.
Now, as far as removing a screw and having a floating neutral, it would depend again on the screw and where the relay bonds N-G when in inverter mode. The question becomes why you would want a floating neutral? Having a floating neutral from source will not allow a ground fault to to clear and trip the breaker.
I would not remove any screws.
One needs to know the path back to source. And which source you are coming from and if N-G are bonded.
Are you running this in some type of big loop?
Correct. When in bypass mode the inverter relies on the main panel N-G bond.
When in battery mode, the source is the inverter and N-G bond occurs in the inverter. Unless you modify the unit so it doesn't. But again, why would you?
I'm trying to understand why you want to bypass the N-G bond controlled by the inverter when in battery mode and the inverter is powering the loads.
When under AC power, the unit will not be N-G bonded internally and relies on the N-G bond at the main panel before the unit. When in inverter mode and inverter is powering the loads, the unit bonds N-G which is at the source.
You need 2 panels, one before the inverter and one after. The first panel from grid is N-G bonded, this panel is referred to as main service panel. The second panel after the inverter is not N-G bonded, it is considered a subpanel.
Last edited:
Ok, everything is hooked up in now. Well batteries and inverter anyway. I can now run tests. I'm hoping those that have been contributing to this discussion can help me out and point me in the direction I need to be pointed as I step through this.
Current Test:
AC charging the batteries. To do this I have a dedicated 20a circuit with a standard 20a outlet.
I have a 2x20a to L14-30 Y adapter plug plugged into the male half of an L14-30 generator cord that is wired to the inverter AC input. While the inverter is in standby mode (power button in off position) the batteries are being charged. The second I turn the inverter power button to the on position the breaker pops.
Guidance?
Current Test:
AC charging the batteries. To do this I have a dedicated 20a circuit with a standard 20a outlet.
I have a 2x20a to L14-30 Y adapter plug plugged into the male half of an L14-30 generator cord that is wired to the inverter AC input. While the inverter is in standby mode (power button in off position) the batteries are being charged. The second I turn the inverter power button to the on position the breaker pops.
Guidance?
Zwy
Solar Wizard
Sounds like a ground fault or you have a load larger than the breaker. You posted this:
LV6048 output neutral-ground bonding?
I am not using the LVX6048. I was going to but purchased the LV6048 instead. The transfer switch can do 240 according the the manufacturer: MODEL 310CRK MODEL DESCRIPTION Pro/Tran 2 MAX. GENERATOR RUNNING WATTS 7500 PHASE Single MAX. SINGLE-POLE CIRCUITS 10 MAX. DOUBLE-POLE...
diysolarforum.com
The Reliance 310C does not switch neutral and as such there will be a ground fault as the N-G are bonded at the main service panel.
If you intend to treat the Reliance 310C as a subpanel and run loads off it continously, then you simply run neutral from main panel to inverter AC input, then from inverter AC output to the Reliance 310C. Do not have a neutral between the main panel and Reliance 310C. All circuits powered by the Reliance 310C will need their neutral returned to a neutral busbar in the Reliance 310C. This neutral is not to be bonded to ground.
Zwy
Solar Wizard
It may not be a NEC requirement, however you missed one important point. If the N-G bond occurs in the main panel and the inverter is powering the loads, the N-G bond will be a ground fault and trip the breaker on the inverter as it is the source, not the main panel.
This is why the neutrals should be in the subpanel after the inverter and not in the main panel.
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