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Old 01-23-2020, 07:21 PM   #51
Kevin.Hutch
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Default Re: 2 inverters?

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Originally Posted by avanti View Post
There is nothing magical about "Mother Earth"--it is simply a handy reference point for measurement purposes. It lets us pretend that voltages are absolute, when in fact they are as a practical matter always relative. But even this doesn't really work. Power engineers who design high voltage power transmission lines need to worry about creating significant (and occasionally dangerous) current flows in the earth. "Ground" has its limits even as a conventional "zero voltage" point.

A vehicle chassis is a perfectly legitimate "ground", and can serve exactly the same logical function as "earth ground". When we go to Mars, there will be a "Mars ground" as well. They all do the same thing.
Absolutely disagree the "Magical part" of mother earth is that when and only when it becomes the reference for a power source there is a hot/active and neutral situation that is potentially fatal to a person standing on "mother earth".

The so-called ground in a vehicle chassis is rarely connected well to mother earth due to the tyres and as such a fault condition can have the chassis hot and dangerous with respect to mother earth. Then if that so-called ground fault is on the load side of the GFCI or RCD they will not trip unless there is a similar "ground" of earth connection on the source side of the GFCI or RCD to create a residual current return to the live wire feeding the GFCI or RCD.

A major failing in the GFCI or RCD implementation, as it not only considers neutral or live to mother earth connection at the source it mandates it and is difficult to achieve in a vehicle or boat without a shore power earth lead.
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Old 01-23-2020, 07:27 PM   #52
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Default Re: 2 inverters?

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Since each inverter controls or facilitates its requisite loads grounding, if the outlets are grounded to the inverter ONLY with the ground wire (not chassis grounded), then multiple inverters can be run simultaneously and to separate outlets.
It is only a recent thing that inverters have neutral/ground switching, many inverters are permanently neutral/ground wired, but most have outlets isolated from ground.

This is fine if there is only one outlet but is potentially hazardous if more than one outlet is provided.
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Old 01-23-2020, 07:35 PM   #53
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Default Re: 2 inverters?

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Originally Posted by Kevin.Hutch View Post
It is only a recent thing that inverters have neutral/ground switching, many inverters are permanently neutral/ground wired, but most have outlets isolated from ground.

This is fine if there is only one outlet but is potentially hazardous if more than one outlet is provided.
My ProWatt SW600 offers protection with its single GFCI outlet on it. I use an extension wire from it to my desktop wall outlets. The outlets and their housing are isolated from the chassis/chassis grounding.

These outlets run simultaneously with other outlets connected to a 3000W inverter. These outlets that are connected to this inverter are protected via the circuit breakers between the load and the inverter, and the neutral bonding grounding controlled internally.



.

Last edited by OrioN; 01-23-2020 at 07:38 PM.
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Old 01-23-2020, 08:14 PM   #54
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Default Re: 2 inverters?

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Originally Posted by OrioN View Post
My ProWatt SW600 offers protection with its single GFCI outlet on it. I use an extension wire from it to my desktop wall outlets. The outlets and their housing are isolated from the chassis/chassis grounding.

These outlets run simultaneously with other outlets connected to a 3000W inverter. These outlets that are connected to this inverter are protected via the circuit breakers between the load and the inverter, and the neutral bonding grounding controlled internally.



.
If there is no ground or earth bonding between one of the live source wires before the GFCI then a live to ground fault on the load side will not trip the GFCI. Easy to test as GFCI breakers usually have a residual current test button on them and pushing it will test if there is a ground connection before it. This lets the potential for an earth fault after the breaker to go undetected, waiting for a second that is unlikely if there is only one outlet. Look up Electric Shock Drowning to see how deadly a poor earth connection can be.

I have tested extensively with Honda EU20i isolated output gensets using an external power board with built-in RCD (GFCI) and it never trips due to the lack of a neutral connection to the earth before it.

For that reason, in my motorhome, I replaced my RCD with an RVD Residual Voltage Detector that detects a 40v difference between either live wires and ground thus detecting the first earth fault, it also has an RCD function just in case.

In earth fault detection, it takes two faults to create a potentially fatal situation and if there is a neutral then the first fault has occurred, just waiting for the second.

The same applies to most inverters, specifically on boats where the neutral/ground connection is a no-no because of galvanic corrosion.

BTW way RCD is the terminology used in Australia as GFCI implies it isolates all ground faults.
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Old 01-23-2020, 08:48 PM   #55
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Default Re: 2 inverters?

All of these complications are moot

if you do not wire mains power circuits and outlets.

I like to keep things simple:

99.9% of consumption is direct DC, no inverters

any AC load devices plug directly into their inverter

if there were an AC outlet, it would be impossible for it to be fed by more than one inverter

the only thing fed directly from shore power or the genset is the charger, and that just physically plugs in

if I had electric aircon, it would also plug in like the charger, but likely to a separate AC circuit or genset from the charger
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Old 01-23-2020, 08:53 PM   #56
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Default Re: 2 inverters?

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Originally Posted by OrioN View Post
Let me be the first one here to respond with/from actual experience....



... I run dual inverters. A 600W for daily desktop or entertainment, and a 3kW for doing the heavy lifting (and charging).

They both power the same physical AC outlets, but never simultaneously.

Their output and connection is controlled by a simple AC Changeover/Rotary Cam Switch.

https://new.abb.com/docs/librariespr...1.pdf?sfvrsn=2


Attachment 124022


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Quote:
Originally Posted by john61ct View Post
All of these complications are moot

if you do not wire mains power circuits and outlets.

I like to keep things simple:

99.9% of consumption is direct DC, no inverters

any AC load devices plug directly into their inverter

if there were an AC outlet, it would be impossible for it to be fed by more than one inverter

the only thing fed directly from shore power or the genset is the charger, and that just physically plugs in

if I had electric aircon, it would also plug in like the charger, but likely to a separate AC circuit or genset from the charger
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Old 01-23-2020, 09:12 PM   #57
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Default Re: 2 inverters?

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Originally Posted by Kevin.Hutch View Post
Absolutely disagree the "Magical part" of mother earth is that when and only when it becomes the reference for a power source there is a hot/active and neutral situation that is potentially fatal to a person standing on "mother earth".

The so-called ground in a vehicle chassis is rarely connected well to mother earth due to the tyres and as such a fault condition can have the chassis hot and dangerous with respect to mother earth. Then if that so-called ground fault is on the load side of the GFCI or RCD they will not trip unless there is a similar "ground" of earth connection on the source side of the GFCI or RCD to create a residual current return to the live wire feeding the GFCI or RCD.
I can't really follow what you are trying to say, but I am pretty sure you are confused.

Perhaps you are trying to describe the well-known "hot skin" condition that can occur as a result of certain mis-wirings of shore power connections. This certainly can occur. But, with a properly wired shore outlet and with a properly wired vehicle, the vehicle chassis is bonded to earth ground in exactly one place. The problem case requires a bonding to earth--just an incorrect one.

If, on the other hand, you are talking about a situation with no shore-power connection (and thus no bonding to earth), then no on-board fault can produce a "potentially fatal" potential between the chassis and earth, since it takes two current paths to do so, one of which would have to be referenced to earth.

I repeat: The logic of the situation is identical whether we are using the chassis or Mother Earth as the ground reference. a GFCI cannot tell the difference and will behave similarly. It would also work on Mars.

I apologize if I am simply not understanding what you are trying to explain. Perhaps a diagram would help.
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Old 01-23-2020, 09:14 PM   #58
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Default Re: 2 inverters?

Quote:
Originally Posted by avanti View Post
I can't really follow what you are trying to say, but I am pretty sure you are confused.

Perhaps you are trying to describe the well-known "hot skin" condition that can occur as a result of certain mis-wirings of shore power connections. This certainly can occur. But, with a properly wired shore outlet and with a properly wired vehicle, the vehicle chassis is bonded to earth ground in exactly one place. The problem case requires a bonding to earth--just an incorrect one.

If, on the other hand, you are talking about a situation with no shore-power connection (and thus no bonding to earth), then no on-board fault can produce a "potentially fatal" potential between the chassis and earth, since it takes two current paths to do so, one of which would have to be referenced to earth.

I repeat: The logic of the situation is identical whether we are using the chassis or Mother Earth as the ground reference. a GFCI cannot tell the difference and will behave similarly. It would also work on Mars.

I apologize if I am simply not understanding what you are trying to explain. Perhaps a diagram would help.
Just like water, electrons circle or flow in the opposite direction in Auz, or south of the equator....
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Old 01-23-2020, 11:21 PM   #59
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Default Re: 2 inverters?

40 years in the electrical industry and I can't figure out what you guys are talking about.

My inverter feeds a small 120 volt breaker box. The neutral is connected to the enclosure at this location only. This is called the bonding of the neutral. All metallic parts of the van are also bonded to this location via bond wires in the cables. That's it. No connection to earth/ground is required as the electricity is separately derived in the van. This way, the breakers will trip when a hot wire makes contact with any of the metalic parts of the van. Yes, the GFCI receptacles will also work with this set up. The ground connection is only to provide a path for lightning or static electricity anyways. Use a piece of rubber dragging on the ground to dissipate that if it's a problem. Shore power connection to the van is what complicates things as the shore power should be bonded back at it's source. I prefer to use the shore power to only feed my battery charger thus avoiding any multiple path issues. In other words, never connect the van 120v panel to shore power, keep it isolated. I always use the batteries/inverter/battery charger when on shore power.

Last edited by AirJoseph; 01-23-2020 at 11:34 PM.
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Old 01-23-2020, 11:36 PM   #60
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