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lawrosa's avatar
lawrosa
Explorer
May 10, 2017

Inverter for RV hookup. Manufacturers reply.

Hi all. So I read contless online info about the whole bonding issue with Rv,s.

I understand the RV is basically a sub panel. The bond is made when you hook up to the pedestal. OK.

with a generator I guess who you talk to you can run both ways. Bonded gen or no bonded gen.. I have a kohler 2800 bonded gen with GFI.

OK now to my inverter that I will hook up in the camper. I will be plugging the RV umbilical cord into the inverter. ( I will turn off charging circuit at converter)

The inverter will be a krieger 1100 model. I already bought it as it has a 3 yr warranty. Upon a test of the invertor with my test plug inverter show open neutral/ground. ( Meaning its not bonded)

I did a test and got continuity from the ground plug to the grounding terminal on the case of inverter.


So I was not sure to make a plug or not to bond the G/N at the inverter. Or leave it as a floating neutral for when I plug in.

Here is my question and response from krieger.

Do you guys know what this means?

Does it mean I should disconnect the ground wire in the dog bone connector I make and just use the hot/neutral wires when connecting to the inverter?

If so can any electricians out there tell me why to do this?

I dont think customer support guy understood what I was doing and he may be wrong...

Question and reply to krieger..


HI,

Possibly you can help me with a technical question.

I have a Krieger 1100 watt inverter. I will be installing this in my rv travel trailer.

The travel trailer is basically a sub panel. So when I plug into the camp grounds pedestal I get the bond at the service entrance.

This would also stand true I assume for my 2800 watt gas generator. When I plug the RV to that I get the bond from the generator. This generator is bonded neutral/ground.

I notice your invertor has an open neutral from my test light. I will
be running a ground wire from the back of the unit to the trailers frame.

What I am going to do is essentially plug the RV into this invertor to power it. This will power all my outlets in the trailer. I will be turning off the charging circuit so there is no endless loop going on.

I am not sure if I should bond the N/G in the krieger invertor. I would plug a n/g plug into the extra outlet to accomplish this.

1. Should I leave this as an open neutral unit or make N/G plug to
bond the neutral and ground? ( Attached is an image of said plug) 2.
What gauge wire should run from grounding terminal in back of unit to
frame of trailer? ( I was going to use 6 gauge)

I hope you understand this and can help me.


Thanks

Mike NJ



HI Mike,

Thank you for the provided information about your application. We recommend using only the hot and neutral on the plug only and do not use the AC ground when connecting the inverter to a breaker panel box. You should use #10 gauge cable when connecting the ground chassis located on the back of the inverter to the frame of the trailer.


Customer Support
Krieger Manufacturing
2933 W. Cypress Creek Road, STE 202
Fort Lauderdale, FL 33309
Tel: 1.954.603.4950



Ok just to be clear in laymans terms,

So you recommend just plugging the RV into the krieger inverters outlet, with no modification to the neutral/ground, even though it will show as open?

Yes I will use 10 gauge or better for the chassis ground.

Also would you be able to supply a schematic for this 1100 watt inverter?

Thank you for your time. Its much appreciated......

Regards

Mike NJ


The modified wave inverter shows an open or floating ground compared to power received from your AC wall outlets. This results in a incompatibility when connecting to a breaker panel box. The best way is to just use the hot and neutral legs on the inverter's AC outlet and do not use the ground connection when connecting to a breaker panel. We still recommend grounding the inverter by connecting the 10 AWG cable to the ground chassis terminal located on the back of the inverter. You can consult with a qualified electrician for proper installation if needed. We do not provide diagrams, schematics, or a parts list to any of our products due to proprietary reasons.


Customer Support
Krieger Manufacturing
2933 W. Cypress Creek Road, STE 202
Fort Lauderdale, FL 33309
Tel: 1.954.603.4950




  • road-runner wrote:
    With respect to the AC output, there are two types of MSW inverters. One type has a true floating output and can be bonded if you wish. Higher end MSW inverters tend to be of this type. The other type of output, common in lower-end MSW inverters, was described in DrewE's earlier post. Both output conductors are hot with respect to chassis ground. What happens when you bond either output depends on whether the inverter has output short circuit protection or not. If it has short circuit protection it simply will stop working. If it doesn't have the protection, it will instantly go up in smoke. Verified (accidentally) by personal experience.


    This is what it says... But I will test voltages tomorrow... I read that I will need a true RMS meter to read propervoltages...
    How This Modified Sine Wave Power Inverter Works
    There are two stages in which this power inverter changes the 12 volt
    DC (or battery) power into 110v AC (household current).
    STAGE 1: This inverter uses a DC to DC converter to increase the DC
    input voltage from the battery to 145 volts DC.
    STAGE 2: The inverter then converts the high voltage DC into 110v AC
    (household current), using advanced MOSFET transistor in a full bridge
    configuration. This design provides this Kriëger® inverter with the
    capability to start and run difficult reactive loads, while providing
    excellent overload capability. The waveform that is generated by this
    conversion is a "modified sine wave" as shown in the diagram below.
  • With respect to the AC output, there are two types of MSW inverters. One type has a true floating output and can be bonded if you wish. Higher end MSW inverters tend to be of this type. The other type of output, common in lower-end MSW inverters, was described in DrewE's earlier post. Both output conductors are hot with respect to chassis ground. What happens when you bond either output depends on whether the inverter has output short circuit protection or not. If it has short circuit protection it simply will stop working. If it doesn't have the protection, it will instantly go up in smoke. Verified (accidentally) by personal experience.
  • MrWizard wrote:
    My take on this
    assumming you are talking about an inverter that has power pass thru to be used with shore or generator power
    Ground the inverter case to frame ground
    Do Not mess with the internal wiring

    A bonding plug is only needed when you have some device that gives you an alert, and won't function


    No pass through or nothing like that... I guess I plan on just plugging it in as designed.. I would feel funny removing the ground wire on the cord im going to make up..

    I wonder what the implications will be though since customer support states otherwise...
  • My take on this
    assumming you are talking about an inverter that has power pass thru to be used with shore or generator power
    Ground the inverter case to frame ground
    Do Not mess with the internal wiring

    A bonding plug is only needed when you have some device that gives you an alert, and won't function
  • I would not mess with adding a bond. Let the inverter operate as designed. If the inverter is mounted on the RV it should have a chassis ground as stated.

    The manual is a bit brief. Follow the instructions and you should be fine. No more, no less.

    KR1100 manual
  • If the inverter frame is bonded to the RV frame and your shore cord ground wire is also bonded to the RV frame I see no need for a ground connection between the Rv's plug and the inverter.
    A inverter made for use both with shore power and stand alone, like the Outback VFX2812M will have a built in transfer switch that bonds the neutral when off grid and does not bond it when on shore power.
  • The inverter chassis should probably be bonded to the trailer chassis, as they say.

    I don't think it makes any practical difference if the power cord has a ground wire connected or not. I would leave it connected. You're just connecting chassis ground to chassis ground with it.

    I would not bond the neutral to the ground at the inverter, especially as the maker recommended against that. Some (not all) MSW inverters will not work with neutral bonded to ground because the output is not isolated from the 12V input (and typically is a bridged output composed of two 60V RMS waves that are 180 degrees out of phase of each other). Attempting to bond neutral to ground on such inverters would short out half of the output circuit. Better inverters do have the high voltage side fully isolated from the low voltage side and those would not have trouble with being bonded, but I would assume any inverter I come across is not isolated until or unless specifically specified or proved to be otherwise.

    RV generators that are permanently installed have neutral and ground bonded together, and I think that is required per the NEC. I don't know offhand if the NEC would require that for an inverter permanently installed and hardwired into the system; it may very well be a requirement. I think yours would not fall under that as it's not hardwired in on the 120V side of things.
  • My Vector inverter manual says the chassis ground is for reducing TV and radio interference, so that is probably why they want you to still use that.

    Another inverter I was using had GFCI receptacles and chassis ground. When the shore power cord was plugged into the inverter it somehow found a neg path to the DC fuse panel. The shore cord is grounded to the frame at the Power Centre and so is the 12v side of things, so 120 and 12 share the frame as negative/ground. The inverter's chassis ground joined in with that

    They are saying you can beat that by not having the ground prong in the plug going into the inverter's receptacle. I suppose you could also just leave it three-prong and not connect the chassis ground.

    It really makes no difference when Rving as far as I can tell, that the inverter is floating neutral. So is my Honda generator. Those who have rigs with an ??EMS?? whatever it's called, do need to bond the receptacle.

    BTW besides the turning off the converter, do put the fridge and WH on gas (not "Auto") too

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