Sine Wave Inverter Anomaly

[SoundGuy]

After following this recent discussion about how to best utilize a sine wave inverter for RV use I decided to go ahead and buy the 1000 watt model mentioned in this discussion since it was on sale for just $199 at Canadian Tire, certainly the lowest price for this size in these parts. My primary use for it is to power 120 vac fans in the camper when dry camping, and based on battery reserve possibly to power our coffee machine, toaster, and my wife's hair dryer, my current limitation of course being the single G27 battery that's presently on the trailer. After musing about it for awhile I decided I'd prefer to wire the inverter "whole house" so I could power the trailer's entire 120 vac system by simply plugging the main service cable into the inverter, the limitation of course being the inverter's maximum 1000 watt rating. I decided to install the inverter on a shelf hung from the joists in the front passthrough compartment where it would be protected from the weather, ventilated, easy to reach, yet occupying otherwise unused space. 6 feet of 4 gauge for both the positive and negative input cables got me to the battery where I ran the positive through an 80 amp fuse. The 120 vac output cable was a few feet of 10 gauge main service cable I happened to have on hand, terminated with a 15 amp Leviton WetGuard connector. For anyone interested, a series of 4 pics starts here.

Time to check everything so although I KNEW everything was wired correctly I proceeded cautiously and before plugging anything in at all decided to check the inverter output with a polarity checker. UH OH ... open ground! :h Hmmm, I never expected that but then I can't say I've ever checked any inverter output with a polarity checker before ... but no question about it, both inverter output receptacles are showing an open ground and indeed if I measure between hot and ground my voltmeter is showing 0 volts rather than a nominal 120 volts as it should and as there is between the hot and neutral. After thinking about it for awhile I decided to go ahead and plug in the main service cable, reasoning the trailer itself would provide the necessary ground ... and bingo, it did. So - it all works just as it should, the inverter easily powers all the aforementioned appliances, BUT I have to wonder why this inverter's output receptacles are not grounded. The inverter does have a chassis stud so it can be grounded to the trailer chassis but that makes no difference at all - it appears the inverter's output is simply lacking ground. Unfortunately the owner's manual is really simplistic and has no schematic so I'd like to ask if those owning a sine wave inverter have ever run into this same situation with their inverter's output not being grounded? :@

[SoundGuy]

SoundGuy wrote:
FWIW I think I'm back to "square one" on this whole bonding issue. :S I read through the entire 41 pages of that 2008 / 2009 discussion on bonding and when none of the "experts" could agree I decided to just leave it as is for now as it seems to work just fine even with my Surge Guard in the circuit. The inverter's output I left un-bonded, simply wiring it's output to feed the trailer's main service cable, which also seems to work just fine with the SG in the circuit. The subject of using a GFCI on a genset output also came up in that discussion but again no one seemed to agree so for now I have bothered with that either. Maybe BFL13 was right when he said back on Page 1 of this discussion "Ignore the non-problem!"

So after musing about this some more I find it difficult to believe that despite all the debate over bonding that some very bright people at Mother Honda don't know what they're talking about and based on their own understanding of the subject decided long ago that for the use for which they expect their EU2000i genset to be used that releasing it to the market with a floating neutral was probably the better, and safe, choice. Indeed, my own EU2000i has powered anything I've asked it to without any bonding modification, from my house furnace to the trailer, with the Surge Guard in circuit or not. Since I'm also now successfully powering the trailer with my new, unbonded 1000 watt sine wave inverter, with the Surge Guard also inline, I've decided to remove the bond from my genset sound reduction box as well, if for no other reason than consistency and because it all seems to WORK just fine without bonding, regardless of what that polarity checker, or the "experts", may say. :R

Thanks to all who contributed to this discussion! :B

[MrWizard]

Yep..non problem...Not An Anomaly

[SoundGuy]

FWIW I think I'm back to "square one" on this whole bonding issue. :S I read through the entire 41 pages of that 2008 / 2009 discussion on bonding and when none of the "experts" could agree I decided to just leave it as is for now as it seems to work just fine even with my Surge Guard in the circuit. The inverter's output I left un-bonded, simply wiring it's output to feed the trailer's main service cable, which also seems to work just fine with the SG in the circuit. The subject of using a GFCI on a genset output also came up in that discussion but again no one seemed to agree so for now I have bothered with that either. Maybe BFL13 was right when he said back on Page 1 of this discussion "Ignore the non-problem!" 😛

[brulaz]

BFL13 wrote:
The inverter's chassis ground must NOT be wired back to the inverter's neg input! It has to go to the frame on its own. They usually want about #8 AWG for that wire.

Vector inverter manual says the chassis ground is only for reducing RF interference for televisions etc, so no big deal

My Can Tire (I think I already posted this) 1000 PSW inverter chassis ground made a neg path from the shore cord's ground prong (plugged into the inverter) which by-passed my neg path (mostly frame) based battery disconnect switch, so I just did not use the chassis ground and all was well.

Small inverters like my "Source" (was Radio Shack) 400w, that I use now for "whole house" to make the receptacles live, with the shore cord into it, doesn't even have a chassis ground. It has no remote on/off either so I just leave it out front in the cargo bay, "on" all the time. The stand-by drain is tiny and being on solar you don't sweat the small stuff.

And I bet it was BFL13 who gave me that advice.

[brulaz]

SoundGuy wrote:

brulaz wrote:
By the way, SoundGuy,
how did you wire that wimpy little case ground post on the inverter. Separate wire to trailer chassis or just a jumper to the inverter's battery neg post (which winds up wired to chassis at the battery).

IIRC a separate wire to chassis is what's recommended?

Sorry I missed this earlier. :S

If you're referring to the inverter's owner's manual it's pretty bleak and says absolutely nothing about that "little case ground on the inverter" - no mention at all, doesn't even show it in pics, nada - so I didn't connect it at all. Further, on Page 4 it warns "Do not connect any AC device which has it's neutral connected to ground to the unit". By extension, that to me also means don't bond the inverter's output.
...

The "separate wire to chassis for case ground" advice I got here on the forum when I was installing my solar controller and separate 120VAC battery charger. So guess that's what I'll do. I too have been un-impressed with the inverter's manual. But guess we get what we pay for.

Missed that "Do not connect any AC device which has it's neutral connected to ground to the unit". Agree, another reason not to bond.

[BFL13]

The inverter's chassis ground must NOT be wired back to the inverter's neg input! It has to go to the frame on its own. They usually want about #8 AWG for that wire.

Vector inverter manual says the chassis ground is only for reducing RF interference for televisions etc, so no big deal

My Can Tire (I think I already posted this) 1000 PSW inverter chassis ground made a neg path from the shore cord's ground prong (plugged into the inverter) which by-passed my neg path (mostly frame) based battery disconnect switch, so I just did not use the chassis ground and all was well.

Small inverters like my "Source" (was Radio Shack) 400w, that I use now for "whole house" to make the receptacles live, with the shore cord into it, doesn't even have a chassis ground. It has no remote on/off either so I just leave it out front in the cargo bay, "on" all the time. The stand-by drain is tiny and being on solar you don't sweat the small stuff.

[SoundGuy]

brulaz wrote:
By the way, SoundGuy,
how did you wire that wimpy little case ground post on the inverter. Separate wire to trailer chassis or just a jumper to the inverter's battery neg post (which winds up wired to chassis at the battery).

IIRC a separate wire to chassis is what's recommended?

Sorry I missed this earlier. :S

If you're referring to the inverter's owner's manual it's pretty bleak and says absolutely nothing about that "little case ground on the inverter" - no mention at all, doesn't even show it in pics, nada - so I didn't connect it at all. Further, on Page 4 it warns "Do not connect any AC device which has it's neutral connected to ground to the unit". By extension, that to me also means don't bond the inverter's output. It also "suggests" connecting the inverter to the battery using "25 mm (squared), 90 cm long cables". Checking the American Wire Gauge Chart shown here that tells me I should have used 3 gauge cables no longer than 36" each ... but because I wanted the inverter located inside the front pass through storage compartment each run had to be ~ 6 feet and because the best I could get at the time was 4 gauge that's what I used. However, according to this Blue Sea Chart 4 gauge should be entirely suitable. :h

[brulaz]

road-runner wrote:
EMS as defined by Progressive Industries = Electrical Management System

"Progressive Industries Portable Electrical Management Systems (EMS) provide full RV protection against all adverse power conditions." , what is commonly called a "surge protector". It does not manage energy use.

EMS as defined by the rest of the world = Energy Management System, manages loads to keep circuits from overloading.

I believe the "open ground" discussion in this thread is related to the unfortunately named Progressive Industries EMS, which is really a "surge protector", another bad name for a power quality monitoring and protection device. Nothing to do with the other EMS, Energy Management System.

Your "power quality monitoring and protection device" probably best describes it.

It does not manage loads but is more than a basic surge protector.

Anyway, the transfer switch/relay I'm installing will do what Mr Wizard recommends, bypassing the EMS.

[MrWizard]

My statement still applies, ... remove it or turn it off..It does not belong between inverter and loads
Surge protection is for Shore POWER, an inverter can not give you power line type surges and transients

road-runner wrote:
EMS as defined by Progressive Industries = Electrical Management System

"Progressive Industries Portable Electrical Management Systems (EMS) provide full RV protection against all adverse power conditions." , what is commonly called a "surge protector". It does not manage energy use.

EMS as defined by the rest of the world = Energy Management System, manages loads to keep circuits from overloading.

I believe the "open ground" discussion in this thread is related to the unfortunately named Progressive Industries EMS, which is really a "surge protector", another bad name for a power quality monitoring and protection device. Nothing to do with the other EMS, Energy Management System.

[MEXICOWANDERER]

EMS = Automatic Load Shedding.

The nutso buzz-word world of today is an open invitation to lie, cheat, exaggerate, misrepresent, and manipulate the consumer market. Pie In The Sky ratings of watts, BTU, db, potential, speed, capacity and other ratings parameters, makes an unwary consumer have as much chance as a three legged antelope on the Serengeti. Its disgusting, and its getting worse.

[road-runner]

EMS as defined by Progressive Industries = Electrical Management System

"Progressive Industries Portable Electrical Management Systems (EMS) provide full RV protection against all adverse power conditions." , what is commonly called a "surge protector". It does not manage energy use.

EMS as defined by the rest of the world = Energy Management System, manages loads to keep circuits from overloading.

I believe the "open ground" discussion in this thread is related to the unfortunately named Progressive Industries EMS, which is really a "surge protector", another bad name for a power quality monitoring and protection device. Nothing to do with the other EMS, Energy Management System.

[MEXICOWANDERER]

Trace Engineering produced one heck of a detailed White Paper on this with regard to their marine version of their inverters. I have no idea if the contents are available online but it is worthy of a detailed search. What I gathered is the subject is chock-full of pros and cons, and it is up to the user to learn then decide which connection is best for them.

[MrWizard]

An EMS aka power management system goes between the breakers and the loads, it shuts down one or more appliances as to not over load the source of shore power
In a factory install the EMS is not inline after inverter output, or with inverter powered on loads
All this discussion of EMS and inverter, comes from diy inverter install, wanting to plug shore cord into inverter for easy whole house outlet use
When using OEM install with dedicated inverter outlets on pass thru, or sub panel, the EMS is before the inverter NOT after, the EMS does not operate when dry camping using inverter power
For diy whole house , when dry camping and plugging shore power cord into the inverter, turn OFF the EMS

[road-runner]

Knew I'd seen reference to this issue somewhere. It was in the Prog Ind EMS manual.

They say in an RV you should "never bond the neutral and ground together for any reason". Bonding in an RV "will create a ground fault condition and may result in electrical shock and or fire hazard"

Pretty explicit; the neutral and ground should remain isolated in an RV, unlike a house.

So separate from whether the Inverter can deal with it, Prog Ind EMS explicitly says no.

IMO you are mis-interpreting the statement in the manual. Considering how many years this "open ground" issue has been around I think it's pretty lame that Progressive Ind does not directly address it. Back to opinion, if you place the bond at the inverter or generator, you are not touching the RV's electrical system, which is what the warning is about. You are bonding at the power source. The RV's electrical system ends at the shore power plug. Say you have 2 inverters or generators, one that's permanently bonded and the other where you added the bond yourself? What's the difference from the EMS's point-of-view?

Not meant to be a statement for or against bonding, just to say it's ok if you decide that's what you want to do.