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Safety Earth Neutral Bonding
#1
Would someone please explain to a noob how Earth Neutral bonding occurs in hybrid inverters that can potentially have many different power sources, each of which should have bonding connected differently.

Is bonding automatically (dis)connected by the inverters as required during off grid, generator, mains and battery supply connections?

My understanding is that marine, RV and residential all have different requirents(??). Are these configurable or does a buyer need to check specs and buy the correct model.

I'm looking to have a substantial (>10kW) inverter charger fitted to a boat and would like to be able to ask meaningful questions of suppliers and see if domestic inverters can be configured to suit.

Many thanks
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#2
This is usually determined by the manufacturer of how they handle the Grounding/Neutral. Some will say to bond them, others say do 'not' bond them. You have to read the manufacturers instructions on how to do this.
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#3
I don't know - but I would guess the voltage would matter as far as the importance of this?.   I'm thinking 12v is not as dangerous (ground / human-shock) as higher voltages such as 48v or higher.   What voltage are you planning to work with?
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#4
The ground/neutral can only be bonded a one point, and that's typically your main service panel. Sub-panels have separate busbars for ground and neutral that are not connected.

It's best to ask the manufacturer of the inverter if they support neutral-ground bonding and if it's done automatically internally. Some do, and some don't. Then contact a licensed electrician to confirm the correct way to wire it and make sure it's complying with your local regulations. Remember, a hybrid is still grid-tie and likely requires a permit anywhere.
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#5
Thanks guys. That's very helpful.

I've contacted MPP to check on their inverters but to date no reply. Does anyone know how they treat bonding? Is it fixed or auto/configurable based upon power source?

Thanks again
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#6
Just and FYI. I've received thos reply from MPP:

"by default, under inverter mode the output N and G will automatically bind. under bypass it'll depend on the AC input. If input N/G already short, then output will be short, too.
Thanks,
Best Regards
-Maximum Solar Taiwan"

I take it to mean that an internal bridge is in place when operating in inverter mode and in bypass, ie with a mains supply, an exiting bridge on the input (if any) will also ne effective in the output.

Let me know if anyone has experienced.otherwise

Cheers
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#7
There is a N-E relay in the MPP units, well at least in my PIP5048MK.

Ive tested it.

If mains is present on the input will use upstream neutral earth bonding of the existing installation.

If the input mains is disconnected you can here the internal relay change state and the relay inside inverter makes a neutral-earth connection.

As far as i can tell the input voltage on the live terminal to neutral is what governs the internal N-E relay.

Ie mains on input, internal N-E relay is switched so no internal N-E connection and input and output neutral connections are effectively joined together to allow upstream installation MEN to allow circuits downstream to function correctly. This is true for bypass and inverter modes.

Switch the input live out with input N and E still connected and the internal relay changes state/ de-energises disconnecting the input to output neutral connection and makes the output neutral to earth bond.
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#8
Many thanks Dovepark. This is exactly what I was seeking.

Looks like I can rely on:

the shore 'mains' power connection providing an unbroken G/N bridge
The MPP providing an internal G/N bridge when operating as a battery inverter only
My generator providing a G/N bridge when it is connected and running for AC and recharging power.

Thanks again.
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#9
Additional info from MPP techs:

"In Solarpower under setting “Shorten N/G relay in battery mode” if it is “Enable.”

If “Enable”, inverter will short N/G in Batter Mode(Off-Grid) and open N/G if out of Battery Mode.
If “Disable”, inverter won’t short N/G under any Mode.

Should you have any other questions please feel free to ask. thank you"
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