timselectric
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Is the wiring the same for an off grid 230VAC inverter?
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timselectric
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The autotransformers sole purpose in this 240v only loads panel is to provide a N/G bond connection point.
The grounding system for any new power source is created by and begins at its N/G bond.
Connecting to the other sources grounding system doesn't provide a path for fault current on the new system, back to its source. This fault current path is how a fault gets cleared by the protection device. (Breaker or fuse)
zanydroid
Solar Wizard
Not a great one source. I mostly read this forum and figured out who the good sources are, also I have DM threads going on with a few members.
For some assembly and power tools stuff I used the volunteer training videos (on YouTube) from Sunworks.org, since they are a proper nonprofit with liability insurance covering volunteers working on the roof they are highly encouraged to have more accurate videos unlike typical YouTube channels.
zanydroid
Solar Wizard
In a 230v system the N-G bond is at 0v and the L-N is at 230VAC
In a 120/240 system L-G is always 120VAC, it is L-L that is 240VAC. Some equipment (including circuit breakers) are rated for only around 120VAC to ground. So this is the case that the autotransformer serves. It constructs a neutral point in the middle of the 230V, that can then be used as the ground and neutral point, to remain within spec for components and consistent with standard wiring (EG with a single phase system in US you would rarely have neutral&ground be so far voltage wise from L, probably never). In a 120/240 world there are annoyingly little things that need neutral even though primary loads are 240. Power meters, smart breakers, SPDs ...
In some 208 systems the L-G is always 120, in others it varies by phase, with EG corner grounded having two phases at 208VAC L-G and one phase at 0V L-G.
EDIT: "including circuit breakers" obviously there are 240V listed breakers too that can plug into panels. But the default you get at Home Depot will be 120/240
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cs1234
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- N-G bond in main breaker panel on exterior of house, has most of the 240vac loads.
- Earth ground is a ground rod / whatever else builders put into foundation, connected to main service panel.
- Separate subpanel exists in garage with most of the 120vac loads for the house, only one 240vac load, AC source comes from main service panel where the N-G bond is
- Separate 120vac inverter, capable of floating or not floating the neutral
The buildings ground is N-G bonded at the main service panel, but the neutral isn't shared by your inverter with the main building. Do you have to install it's own separate earth/building ground to use for the separately derived AC system (the inverter) because of the N-G bonding in the main service panel?
Or, is it ok to share the earth ground (say by running a ground from the inverter straight to the ground rod) between the two separate systems because they both have similar 120vac potential on the wiring, even though they wouldn't be in sync (phase?) if they somehow met at the same time when a fault occurs?
zanydroid
Solar Wizard
I think in another thread it was mentioned that there is one grounding system allowed per building so you would tie the separately derived system into that. You don't have to run it to the ground rod. Most isolated would be to main panel, or a subpanel.
If a fault occurs it will generally clear right away. The separately derived system will likely not care about neutral jumping to a different VAC. I don't think the insulation would be overvolted in most parts of the system either since everything moved up together.
There is likely an official or semiofficial informative NEC diagram showing this configuration so you could also just YOLO it and delegate responsibility to reasoning through and understanding it to NEC
If a fault occurs it will generally clear right away. The separately derived system will likely not care about neutral jumping to a different VAC. I don't think the insulation would be overvolted in most parts of the system either since everything moved up together.
There is likely an official or semiofficial informative NEC diagram showing this configuration so you could also just YOLO it and delegate responsibility to reasoning through and understanding it to NEC
zanydroid
Solar Wizard
Can't remember if I weighed in on this yet. US panel would be my choice becaus it's much easier to get proper UL listed parts for it and to get help from an electrician or US DIY forum. Which outweighs the minor advantages of a EU style consumer unit (EG guaranteed to work without autotransformer, can import accessories like RCD and energy meters that work on 230V). IMO those advantages are only for thought experiments or wiring something up for fun, not for anything in production.
cs1234
Solar Wizard
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Would you N-G bond the inverter that's running separately, or leave it floating? Keeping in mind there is an existing N-G bond in the main panel, even though the inverter isn't touching any of the rest of that wiring except through however you've coupled it up by grounding to the building ground.
timselectric
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The existing grounding system.
One grounding system for everything.
Just know that you are grounding it only to protect yourself from faults on the existing system. Not the separately derived system. Because it's not a grounded system. But because it has exposed metal parts, it must be protected from faults on the other system that is already powering loads in the building.
The two systems don't interact with each other during normal operation. But faults will always try to find a path home.
Personally I have no love for a separately derived system, or an ungrounded system. Unless it's a portable self contained system.
If it's permanently installed, I prefer it to be as safe as possible. (Grounded and Common neutral, always)
timselectric
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Absolutely
cs1234
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If it's permanently installed, but a separate source, you can share neutrals between them without potential problems? The separate inverter and the utility AC? How do you go about doing that, running a neutral and ground from the inverter back over to either the main or subpanel?
timselectric
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If it's a completely separate system. You don't have a common neutral option. That was referring to a separately derived system.
For a completely separate system. I will always have a N/G bond. The only non grounded permanently installed systems I will be a part of, are industrial systems (where people are trained and qualified to be around the equipment being powered). I only install grounded systems in commercial and residential environments (where people don't have to know anything, and just assume that they are always safe) .
zanydroid
Solar Wizard
In normal operation there would not be any current flowing on the EGC so I don't think the separate N-G bonds would have a deleterious effect on each other.
What is the advantage of common neutral over just common ground?
Doesn't any kind of transformer either rule out common neutral or require some allowance for extra neutral current flow and VAs in the transformer? Hmm actually I think it is fine as long as you don't have common line from second system and common neutral at the same time.
timselectric
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Common neutral applies to two sources serving the same loads, alternatively. Usually through a transfer switch of some kind.
You don't want a common neutral between primary and secondary of an isolation transformer. That would create a parallel path with the ground. Technically, they're already common, if both sides are grounded systems.
zanydroid
Solar Wizard
Ok got it , the first situation makes a lot of sense. I thought the common neutral was for the latter and I was surprised.
timselectric
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That's my fault. I kinda lumped them together in one post.
MartyByrde
Off-Grid Innovator
There’s been a lot of discussion about the Neutral.
8048WP-T (8KW 48V) – Maximum Solar Online
maximumsolar.online
When looking through the manual for the MPP PIP8048WP-T it shows Neutrals listed for AC output. I am planning to run three units in 3-phase output. I do not plan to run dual-output from this unit. My understanding was that 240v would have L1, L2, and Ground. Would all three inverters N and G be bonded at the main panel?
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timselectric
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Because that's a European unit L1 to Neutral is 230v.
And 3 units combined for 3-phase will be 400v/230v.
Line to Line is 400v
Line to neutral is 230v.
You can't use this 3-phase configuration for North American 240v equipment.
Quattrohead
Solar Wizard
Don't do anything until you've research this better, there's a load of really bad information in this thread that I don't like.
In the 240 volt world the neutral is grounded at the source and the so-called hot is your 240 volt connection. I don't know where people are getting auto transformers to use for neutral ground bonding, that is not correct.
You will have a dedicated ground, the so-called neutral that is also bonded to ground and your live. That is all you need.
In the 240 volt world the neutral is grounded at the source and the so-called hot is your 240 volt connection. I don't know where people are getting auto transformers to use for neutral ground bonding, that is not correct.
You will have a dedicated ground, the so-called neutral that is also bonded to ground and your live. That is all you need.
timselectric
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They are trying to make a European 240v (L,N) inverter power North American 240v (L,L) equipment.