connecting inverter with bonded neutral to panel with same ?

[ashenash]

Hi all, I'm a long-term reader and a first-time poster to this excellent board. I knew I could get good answers here.

I have a Wagan Proline (5000 watt 120 volt 42 amp) inverter on my offgrid solar w/batteries system. I would like to connect via an interlock or manual transfer switch to my house breaker panel (GE Gold Load Center 20 circuit)
The inverter has hardwire connections for house distributed wiring and the manual states "neutral bonded to ground internally per code"
The house main panel has neutral bonded to ground per code.

Knowing that there should only be one place where the neutral and ground are bonded, I was stumped.

So I called Wagan and the lead tech told me "no problem just connect like this"
1. Wire the inverter neutral straight thru/no breaker to the panel neutral
2. Wire the inverter ground straight thru/no breaker to the panel ground
3. Wire the inverter hot to a 50 amp breaker in the panel
4 Ground to earth the inverter chassis (house panel has water pipe ground)
5 For the 20' run use 10/2 with ground romex or marine grade

When I asked about the multiple neutral/ ground bonds he said "No problem, there really is no neutral on 120v single phase inverters we just call it that"

So, does all this add up to good advice ? Just wire into the panel , breaking only the hot wire ? And grounding the inverter chassis to earth ?

I want to believe this guy, he seems very knowledgeable . Just want to make sure I asked the right questions.

I am ready to lose the extension cords and get this wired up. I can handle these connections safely but will use a pro if it gets more complicated
Thanks in advance for your input

 

[Dennis Alwon]

The forum rules will not allow us to help you with diy projects even though you are an electrical engineer. We have moderators here who are EE's and they cannot get answers to diy questions.

However I will allow this to stay open if this one statement is dealt with without giving a how to

When I asked about the multiple neutral/ ground bonds he said "No problem, there really is no neutral on 120v single phase inverters we just call it that"

 

[GoldDigger]

The forum rules will not allow us to help you with diy projects even though you are an electrical engineer. We have moderators here who are EE's and they cannot get answers to diy questions.

However I will allow this to stay open if this one statement is dealt with without giving a how to

On most 240 volt inverters for US use, the inverter only sends current through the L1 and L2 lines, regardless of any voltage imbalance. The neutral connection, if there is one, is there only to allow monitoring of the L1 and L2 to neutral voltages to detect circuit problems. Current manufacture inverters for US use are required by UL to sense for that imbalance and shut down if it exceeds preset limits.
When the same inverter (with isolated output and/or fed from an isolated (ungrounded) PV array) is connected line to line, as in a 208Y/120 system or a 240 delta, the neutral monitoring is disabled.

 

[electrofelon]

On most 240 volt inverters for US use, the inverter only sends current through the L1 and L2 lines, regardless of any voltage imbalance. The neutral connection, if there is one, is there only to allow monitoring of the L1 and L2 to neutral voltages to detect circuit problems. Current manufacture inverters for US use are required by UL to sense for that imbalance and shut down if it exceeds preset limits.
When the same inverter (with isolated output and/or fed from an isolated (ungrounded) PV array) is connected line to line, as in a 208Y/120 system or a 240 delta, the neutral monitoring is disabled.

Not following you here. Can you clarify/expand on this? Are you talking about inverters with or without split phase output? How could this be the case for the former? I am not aware of any inverters that have 240 volt output with no neutral for split phase use - at least not in the context of off grid inverters.

When I asked about the multiple neutral/ ground bonds he said "No problem, there really is no neutral on 120v single phase inverters we just call it that"

A few things: To be concise, we should clarify that with a 120v system there may be a grounded conductor, but there is no neutral. Also maybe you or he left out that you were supposed to remove the main bonding jumper from the panel, then there would not be multiple N-G connections? Also not sure where that #10 wire size came from for a 42 amp load.....

 

[__dan]

So I called Wagan and the lead tech told me "no problem just connect like this"
1. Wire the inverter neutral straight thru/no breaker to the panel neutral
2. Wire the inverter ground straight thru/no breaker to the panel ground




When I asked about the multiple neutral/ ground bonds he said "No problem, there really is no neutral on 120v single phase inverters we just call it that"

It's a question for the manufacturer, but there is the possibility the inverter "is not" internally solidly connecting the neutral to the earth/equipment ground. If not, the neutral would be connected to ground by an impedance, and if so, not offer a true parallel path for neutral current over the equipment ground.

Normally, the solid N to G connection would be necessary to pass fault current at low impedance, to trip the breaker in a fault. But the inverter will not operate natively this way. The inverter output will be natively current limiting in a fault, possibly to 200% of rating for a few seconds, and maybe not enough to trip the output breaker. The inverter will fault detect and be natively current limiting by its nature. That's in a ground fault with the inverter as the only source. With two sources, the utilty source can provide damaging fault currents to the inverter IGBT's, possibly before the inverter breaker trip point.

It's something to clarify with the manufacturer, they may be able to state clearly, the neutral "is not" solidly connected to ground, but connected by impedance that also fault detects.