2 inverters?

hippy

hardware modifier
If they were completely isolated with different battery's feeding them and each with their own sockets I think you would be ok.
Now if you had a device linking them then you could get a problem with a thing called "potential difference" with the earth.
For instance if you plugged a computer in one and the screen in the other there could be voltage on the earth of the VGA cable.
The circuit in one for earth could be a longer path or a difference resistance than the other causing this.

My record is 80volts of AC! With one ringmain of a house being a pme earth system bonded at a local substation and an building extension being earth with a copper rod outside when the owner connected both ringmain together though an AV system the stray voltage on the cases did really strange things this the audio processing and the touchscreens were all locked up solid.
 

john61ct

New member
If they were completely isolated with different battery's feeding them and each with their own sockets I think you would be ok
No, you're definitely OK with running multiple inverters off the same DC buss as their **inputs**.

It is only the AC output side that should not be joined.

The simplest & safest principle is, no feeding external outlets, just plugging your AC load devices directly into outlet(s) on the appropriate inverter.

Next simplest / safe would be a surge suppressor / power strip plugged into that outlet, which of course physically cannot be plugged into more than one inverter at a time.

It is multiple inverters connected to a circuit of "built in wall" outlets (mimicking what's in our shore powered buildings) that is **absolutely** to be avoided.

All the DC negative return references should be a common "ground", being the vehicle chassis common, engine block, frame etc, while

on the AC side it can get more complicated depending on generator/transfer switching / connection to shore power circuits, and **very** important to get it right for safety, so best to use a pro except for super-simple setups.

But if your inverter install documentation specs that its chassis should be "grounded", that can / should be common to the DC / vehicle chassis reference as well.

Of course, none of those common / references actually being true "Earth Ground", that only happens at the single shore power connection point.
 
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Graphite Dave

Dave Orton
I also use two inverters. A 1000 watt pure sine powered by the vehicle 12 volt system and a 1000 watt Magnum inverter/charger/transfer switch. Using a selector switch I can select either real shore power or 120 volt AC power from the vehicle powered inverter. When on shore power from either source the Magnum is off and transfers the power to the single string of duplex outlets. Without shore power the Magnum powers the same string of duplex outlets.

The vehicle powered inverter is only used with the engine running. With a second selector switch I can choose to power the Magnum shore power charger and the duplex string or 750 watt shower water heater or a 750 watt electric baseboard heater.

The Magnum is turned off when 120 volt AC power is not needed to conserve battery capacity.

The primary method of charging the house battery is a 300 watt solar panel. The vehicle powered inverter is my backup method of charging if weather conditions force its use. Seldom need to use the backup method of charging. Either method of charging provides a proper 3 stager charge profile.

https://www.ortontransit.info/electrical
 

Kevin.Hutch

2011 Mercedes 313 906
No, you're definitely OK with running multiple inverters off the same DC buss as their **inputs**.

It is only the AC output side that should not be joined.

The simplest & safest principle is, no feeding external outlets, just plugging your AC load devices directly into outlet(s) on the appropriate inverter.

Next simplest / safe would be a surge suppressor / power strip plugged into that outlet, which of course physically cannot be plugged into more than one inverter at a time.

It is multiple inverters connected to a circuit of "built in wall" outlets (mimicking what's in our shore powered buildings) that is **absolutely** to be avoided.

All the DC negative return references should be a common "ground", being the vehicle chassis common, engine block, frame etc, while

on the AC side it can get more complicated depending on generator/transfer switching / connection to shore power circuits, and **very** important to get it right for safety, so best to use a pro except for super-simple setups.

But if your inverter install documentation specs that its chassis should be "grounded", that can / should be common to the DC / vehicle chassis reference as well.

Of course, none of those common / references actually being true "Earth Ground", that only happens at the single shore power connection point.
This discussion is fringing on the GFCI or RCD of AC circuits discussion which is another very confusing issue with the definitions of Hot/Active and Neutral/Live.

Hot/Active means live with respect to mother earth, Neutral means directly connected to mother earth at the AC source. Most marine and RV AC power systems (Non-shore powered) are isolated systems because it is almost impossible to get a good quality connection to mother earth that can be guaranteed.

By definition, if one side of an AC source is not connected to mother earth then both sides are simply 'Live' with respect to one another.

Multi sourced power combining be it, isolated or active/neutal ones that do no take into account Phase equalizing, as can be done with the Honda Eu20/22 gensets (and others), SHOULD NEVER BE COMBINED without a break before make changeover switch and preferably not even then.
 

john61ct

New member
Or just taking the load's plug out of one source (inverter, shore power, genset) and plugging it into the other.
 

avanti

2014 GWV Legend 3500 I4
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.
 

GeorgeRa

2013 Sprinter DIY 144WB
Or just taking the load's plug out of one source (inverter, shore power, genset) and plugging it into the other.
....which is what I do. Watching TV with shore power available projector is plugged into shore outlet and without shore to the other one. This post is my proof that I am still alive.
 

Kevin.Hutch

2011 Mercedes 313 906
Or just taking the load's plug out of one source (inverter, shore power, genset) and plugging it into the other.
Absolutely 100% agree on and permanent AC wiring on the second inverter.

BTW great fittout with many innovative points.
 
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OrioN

2008 2500 170" EXT
Absolutely 100% agree on and permanent AC wiring on the second inverter.
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.
 

Kevin.Hutch

2011 Mercedes 313 906
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.
 

Kevin.Hutch

2011 Mercedes 313 906
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.
 

OrioN

2008 2500 170" EXT
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.



.
 
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Kevin.Hutch

2011 Mercedes 313 906
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.
 

john61ct

New member
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
 

OrioN

2008 2500 170" EXT
Let me be the first one here to respond with/from actual experience.... :rolleyes:



... 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/librariesp...ockenschalter_en_1scc302003c0201.pdf?sfvrsn=2


View attachment 124022


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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
:popcorn:
 

avanti

2014 GWV Legend 3500 I4
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.
 

OrioN

2008 2500 170" EXT
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....
 

AirJoseph

Member
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.
 
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