Isolating Inverter Neutrals

[Frankly]

Keep in mind that some of the inverter/chargers are intended for UPS operation (switchover time is of the essence). The old Freedom units did have a significant delay in charging changeover after the SP was connected.

I can't imagine putting my entire AC system on the inverter output, absent minded as I am my AC and water heater would quickly drain my batteries. Most simply separate the receptacle circuits and put them on the IC output.


My Renogy IC (would fall in the CC category) is programmable for various operating modes but does include a transfer switch/relay that grounds the neutral in the inverter mode.

Not to ressurect a dead horse but i still find it interesting that Honda (one of the largest equipment mfgs on the planet) decided to leave the neutral floating on a device absolutely designed for portable use.


Frankly

[smac999]

Originally Posted by a64pilot

Oh, and there is no 30 sec “test” interval either, shore power is passed on immediately, and the spec transfer interval for the inverter if shorepower is lost is 16 milliseconds.

Every single xantrax, magnum, and victron inverter/ charger I’ve seen has a 10-30 sec delay when plugging into shore power (or gen) before it will pass through power and start charging. It will continue to Invert during this time if it’s enabled.

There is no delay from shore to invert when unplugging.

[smac999]

Originally Posted by a64pilot

Mine doesn’t, the inverter only closes and bonds the neutral and ground together when the inverter, is inverting, not when it’s laying idle.
1. So every single Magnum inverter / Charger will trip a GFI breaker when wired according to Magnums instructions?
2. No Magnum inverter / Charger can be used to power the whole AC side of the boat, but must have separate devices / plugs specific just for inverter use?

Wire your inverter according to the instructions, if it doesn’t work, call the manufacturers product support.

Magnum’s instructions show a separate inverter neutral bus.


If the inverter was powering the whole boat. The shore netureal would go into the inverter. And the inverter output would go to the ships netreal bus. Here you only have 1 bus. But it’s still separate then the shore netreal.

If you do not have issues with all common neutrals, You either have an iso transformer, or are not using gfi / elci main breakers.

[smac999]

here is 2 circuit drawings I posted a few years ago.

[SVHarmonie]

Originally Posted by a64pilot

You don’t need a separate neutral bus for an inverter that only powers it’s own separate circuits.
You will however need a relay or switch that prevents having both the neutrals connected at the same time.
It’s just too easy a problem to fix without installing a separate bus, and not that my opinion means anything, but why would you want a separate inverter electrical system? You can do that, but it’s illegocial.

Switching the neutral is not just an inverter “thing” the neutral should be switched with an onboard generator too.
We don’t with portables because we use the shorepower plug there, and you can’t be connected to the shorepower neutral because the cord isn’t connected.

Just because you haven’t seen them, doesn’t mean they do not exist.

I have seen boats with just a few AC outlets the designer felt were essential that connected ONLY to full time inverters. They were not connected to shore power at all, and so had a separate neutral “bus” from shore power.

This is not necessarily an optimum solution, or one I would do, but it exists, and it is the reason for the ABYC rule about separate neutrals formalizing what any smart marine electrician would know.

[a64pilot]

Originally Posted by smac999

Magnum’s instructions show a separate inverter neutral bus.


If the inverter was powering the whole boat. The shore netureal would go into the inverter. And the inverter output would go to the ships netreal bus. Here you only have 1 bus. But it’s still separate then the shore netreal.

If you do not have issues with all common neutrals, You either have an iso transformer, or are not using gfi / elci main breakers.

No, that’s only if you have separate inverter loads, which means of course a separate electrical system.
You can do that, but I don’t know why anyone would want to, I want to be able to run anything off of either shore power. Generator or inverter, without having separate electrical systems. Having a separate plug for the toaster is silly in my opinion, and requires sub panels separate wiring and separate receptacles.
But you can of course do it.

I never said that they didn’t exist, it’s one way to accomplish something, just In my opinion it’s a Rube Goldberg solution.

What will trip a gfci is multiple neutral connections or no neutral connection, with the relay and or generator transfer switch, you only have one neutral connection, out of three available. There are never any “common neutrals” your only connected to one of three available neutrals, as well as hot wires, none are ever paralleled.
That was my point to begin with, that you do not have have a separate bus to accomplish what is desired, you do have to separate neutrals, just as you have to do with a generator, or are you supposing a separate third electrical system for the generator too?
Shorepower, inverter, and generator are the same, they are just sources of electrical power and you do not have to have separate busses for each power supply, you can, but it’s foolish in my opinion.

My Magnum passes shorepower thru pretty much instantaneously, if you lose shore or generator power and the inverter is turned on, voltage drops below a user defined set point the inverter kicks in in 16 milliseconds.
Now that your on the inverter, if shore or generator power is restored, it will stay on the inverter for 15 sec to allow the external voltage to stabilize, then connect the external power and disconnect the inverter.

Now not all inverters come with a relay, but you can add a transfer switch to one that doesn’t, just like you do with a generator, personally I like an automatic transfer switch, mechanical ones mounted on a panel is unnecessary.
That would prevent paralleling an inverter with shorepower, because many won’t survive that, I forgot and cooked a cheap one myself.

[CharlieJ]

SVHarmonie #14
Correction: At no time is the safety ground switched (by a switch or a breaker) against good practice and ABYC E-11.

[SVHarmonie]

Originally Posted by CharlieJ

SVHarmonie #14
Correction: At no time is the safety ground switched (by a switch or a breaker) against good practice and ABYC E-11.

Well, wrong, partly. It must never have a switch or breaker that could disconnect it, of course not. But you are misunderstanding the rule.

The safety ground most certainly IS switched inside an inverter/charger because when it disconnects from shore power it HAS TO. There are exceptions, but not many.

Same with running a generator. The transfer switch MUST move the safety ground from shore power to generator neutral. It has to. It can’t without a switch.

[a64pilot]

Frank, I think Honda generators have a floating neutral because they do not have a transfer switch and are not wired in “correctly” in most instances, if they had a neutral to ground bond, then when Jim Bob connected it to his house, now his house has two neutral to ground connections and that’s not within regulations.
https://generatorbible.com/blog/bond...ating-neutral/

[a64pilot]

Last thing and then I will quit, the Inverters that do have a time delay, I’, sure they don’t need 30 sec to check power, that’s done nearly instantly, but some may have a delay to allow a generator to stabilize before connecting a draw to the generator.
The automatic transfer switch that I use has an option for a 60 sec delay on the generator leg, that I enabled, so that once the generator come on line the transfer won’t occur for 60 sec after, to allow the generator to stabilize.

So far as not connecting your whole electrical system to the inverter. You do have to power manage your electrical system, but I have to anyway, just my 185 amps of chargers can suck down pretty much all available power, I can blow though 30 amps if I turn on both AC’s and the toaster or have a large charger load or run the heat gun, etc, etc. so you do have to watch it.
However to assist me in not overloading the electrical system, I installed Blue Sea Digital amp meters, and they have alarm set points, under or over voltage, hz rate and max amps, so I set mine to alarm at 25 amps, cause that is all that I’m comfortable pulling though a shorepower cord.

[CharlieJ]

SVHarmonie:
Your original assertion was that (#14): "The selector switch MUST be a three pole switch that switches hot, neutral and ground." This is what i was referring to when I posted #23.

Well, wrong, partly. It must never have a switch or breaker that could disconnect it, of course not. But you are misunderstanding the rule.

I certainly am not misunderstanding the rule. The rule is that the safety ground will not be broken by a OCPD or a switch and you clearly state in #14 that "The selector switch MUST be a three pole switch that switches hot, neutral and ground." This remains dangerously incorrect.

The safety ground most certainly IS switched inside an inverter/charger because when it disconnects from shore power it HAS TO.

If by "switched" you now mean that there is a relay that creates a N > G bond when the inverter/charger is inverting, this is correct.

Same with running a generator. The transfer switch MUST move the safety ground from shore power to generator neutral. It has to. It can’t without a switch.

Marine generators generally have a N > G bond at the output of the generator not at the source selection switch.

To be clear:
1. In the USA on compliant recreational boats there is to be no switch or OCPD in the safety ground circuit that breaks the continuity of the safety ground wire.

ABYC E-11.5.3.5. There shall be no switch or overcurrent protection device in the AC grounding (green) conductor

2. The safety ground and the neutral conductor are to be bonded at all sources of AC power. On boats these sources are the secondary of a transformer, the output of an inverter/charger when inverting, an inverter when inverting and the output of a generator.

3. The safety ground conductor provides a redundant, low impedance path for fault current to return to the source and trip an OCPD to clear the fault.

[a64pilot]

Originally Posted by SVHarmonie

Well, wrong, partly. It must never have a switch or breaker that could disconnect it, of course not. But you are misunderstanding the rule.

The safety ground most certainly IS switched inside an inverter/charger because when it disconnects from shore power it HAS TO. There are exceptions, but not many.

Same with running a generator. The transfer switch MUST move the safety ground from shore power to generator neutral. It has to. It can’t without a switch.

Not necessarily, you can have many ground connections I believe, so that all that is bonded is the neutrals, the grounds I believe can stay connected, all three of them in the case of a shorepower, inverter, and generator.

Not certain about that, but pretty sure.

But I have been wrong many times.

[Frankly]

Absolutes covers a lot of terittory when disussing electrical systems, but short of isolation transformers (sometimes), only one AC ground point and rarely if ever switched (somebody will surely come up with an exception).

Multiple ground to neutral connections are not the original sin, more of a book keeping issue. You can have four or five and a ground fault will still trip the breaker and disable the circuit and GFI will provide protection even without a ground.


Frankly

[smac999]

Originally Posted by SVHarmonie

Well, wrong, partly. It must never have a switch or breaker that could disconnect it, of course not. But you are misunderstanding the rule.

The safety ground most certainly IS switched inside an inverter/charger because when it disconnects from shore power it HAS TO. There are exceptions, but not many.

Same with running a generator. The transfer switch MUST move the safety ground from shore power to generator neutral. It has to. It can’t without a switch.

A ground is never switched. The gen, inverter, and shore ac grounds are permanently joined. Only The hot(s) and neutral are switched. No ac ground is ever switched on a boat.

I think you are trying to talk about ground to neutral bond switching. Which is different. The location of where the ground to neutral bond happens will change. But all grounds stay attached to themselves