Open Ground at outlets after installing Renogy 3000W Inverter/Charger

[Beeb2]

Hey everyone,

I just installed my Renogy 3000W Inverter Charger. I have multiple 120V outlets throughout my bus, each of which is a GFCI outlet and I have ground wires run to every outlet (using 10/3 wire). All the outlets run back to a distribution panel.

When I plug an outlet tester into any (and all) of my outlets, they all return an Open Ground reading. But they're all grounded...

Any suggestions?

 

[DeMac]

Earth Ground

Your Neutrals & and Grounds are likely Bonded, but
possibly, there is no bond to the Earth. When we write the word Ground, the Planet Earth is the ground.

I read the description and interpreted:
"a copper wire bonded to each receptical's green screw and traveling to a distribution panel."
Where have you bonded the grounding loop to the Earth?
(●) just a few questions...

● To where in the distribution panel, are other ends of the bare or green #10 bonded? That is, to what/which bar inside the distribution panel?

●Is the Green Bonding screw installed in the Distribution Panel? (therefore bonding the Neuts & Gnds)

Please discribe how the distribution panel is bonded to the Earth...
Maybe one of these ways?:

● via an SO cord, plugged into a grounded power pedestal

● Panel plugged into an outdoor receptical (gfci)

●Solid #6 Cu Bonded to an 8ft Earth driven Ground Rod

Please upload a photo of your distribution panel. This should be an easy fix.

*Hopefully, Meathead will jump in to help put this into layman's terms.

 

[Meathead]

I had the same problem with renogy 3000 inverter. There is no physical ground (rod in the ground). Your ground is in the renogy 3000. All of your green/bare wires tie in to the green/ground wire from the 3000.
I believe this is called floating ground.

Don’t ground to bus.

Don’t tie white and green together.

I did as you did and made every outlet a gfci. You only need one per circuit. Somehow the 3000 doesn’t like all those gfci’s. Maybe some can offer the technical explanation for this but I couldn’t make it work.
—————————
Likewise your shore power grounds at the pedestal. There are tools to check if the campground pedestal is grounded properly. (and you should always check).
—————————-
Also your generator is grounded at the generator, or should be. I have an Onan 7K RV generator and the manual says ground at the generator.

I hope I didn’t over step based on my abilities. I just thought layman’s terms would be helpful.

[emoji3522]Dave

 

[Jono14]

I suspect Neutral Ground Bond is missing

I installed a Giandel inverter with no G-N bond in a skoolie and it initially gave this same result - "open ground" - using a Klein plug tester. In addition, the GFCI plugs would not pop when pushing the GFI test button on the tester.

Adding a G-N bond to the inverter solved it. (I had a simple system with no direct shore power so no worries about 2 bond points.)

I would check for the presence of a G-N bond when inverting.

 

[Rucker]

Hey everyone,

I just installed my Renogy 3000W Inverter Charger. I have multiple 120V outlets throughout my bus, each of which is a GFCI outlet and I have ground wires run to every outlet (using 10/3 wire). All the outlets run back to a distribution panel.

When I plug an outlet tester into any (and all) of my outlets, they all return an Open Ground reading. But they're all grounded...

Any suggestions?

Wow, 10/3 is fantastic overkill! What do you use the third wire for? :')

The rule is that the neutral wire and the ground must be bonded, and only in one place, and that must be at the source. If your source is an inverter, the bonding must be there.

My Renogy 2K bonds neutral and ground at the inverter (as it should), so I'm assuming your 3K will be configured the same-not an open ground, but you should check that first. You should have a built-in receptacle on the face of the inverter, so check that with your tool; otherwise, you can also check the 120VAC output by turning off the inverter and putting an ohmmeter across neutral and ground-there should be continuity.

[If there's no continuity (open ground) you can easily fix the condition by creating a jumper plug, assuming there's an open receptacle integrated into the inverter. There's a very well written article that describes this here: https://www.rvtravel.com/rv-electri... correct this by plugging,in your house or RV. You shouldn't need to do this for your Renogy, and the above trick is only good for devices that don't do autotransfer from shore power-those inverters need to be tested for their behavior and proper ground conditions in all states since you can't necessarily trust the documentation.]

If you do have continuity (bonding) at your inverter and an open ground condition at the receptacles, you'll need to look at the wiring-maybe a ground wire connection came loose. If you used wire nuts, that's the first place I'd check.

I saw in another comment that you shouldn't ground to the chassis-there's a difference of opinion on whether that's the right thing, but it's sort of off topic here.

 

[DeMac]

Chassis Ground

The chassis ought to be bonded to the ground bar in the bus's distribution panel. Particularly, with 120v/AC systems.

Not being grounded could allow the steel parts of the bus to become energized without shorting the OCPD.

The occupants, also ungrounded, would be unable detect the current until one touches the Earth & bus at the same time. At which point the circuit would become complete and the flesh acts as a resistor.

Mammals over 100lbs will receive an unpleasant adrenaline rush. Shoeless kids and pets, may not survive.

DIY Electric.What's the worst that could happen?
FAAFO.

 

[Booyah45828]

I believe outlet testers look for continuity between neutral and ground at the outlet in order to test for the presence of a ground. The grounding wire could be grounded correctly with rods in the earth and cables between chassis and ground lug and all that, and the tester could still throw a flag if there is no ground-neutral bond.

Most renogy inverter/chargers have an automatic relay built into the inverter that creates the ground-neutral bond when the unit is in inverter mode, and disables that bond when connected to shore power/generator.

In order to diagnose this correctly, we need to know what power source you're currently using, as that will determine where the ground-neutral bond should occur. If it's in inverter mode and running off batteries, and no bond is present, I'd say the automatic relay in the unit has failed. If it's on shore power/generator, I'd say your shore power/genset doesn't have the correct ground/neutral bond and you need to move further upstream to find the issue.

If that all looks good, you could possibly have the line and neutral terminals reversed, but I believe most outlet testers would alert you to that though.

 

[TheHubbardBus]

Like Rucker said, I don't understand the 10/3 wire. Did you just use it because you had it for free? What did you do with the extra wire?

Also, when you speak of all outlets being GFCI, are you talking about multiple GFCIs on the same circuit? If so - while it is 'doable' - it's not exactly necessary, nor best practice. And could cause some frustration if you're daisy-chaining each GFCI off the load lines of the one preceding it.

 

[DeMac]

10 Wire.Awesomeness

I assumed 10/2 was used. Lots of folks confuse the trade name as there are a total of three wires in 10/2, four in 10/3 and five in 10/4.

Not all receptacles are rated for 10 wire. Usually, only the 20A rated accept #10 (30A) Copper wire. Most receptacles & switches are 15A.

(ditto on the redundant gfcis)

 

[TheHubbardBus]

Not all receptacles are rated for 10 wire. Usually, only the 20A rated accept #10 (30A) Copper wire. Most receptacles & switches are 15A.

Thanks very much for clarifying that, DeMac. I was actually going to ask this very question, but didn't want to muddy the waters too much. :bow:

 

[Rucker]

I believe outlet testers look for continuity between neutral and ground at the outlet in order to test for the presence of a ground. The grounding wire could be grounded correctly with rods in the earth and cables between chassis and ground lug and all that, and the tester could still throw a flag if there is no ground-neutral bond.

The tester will indicate the lack of a ground-neutral bond because that's the only way the 'grounded' light can fire. To complete that circuit and light up the light, the hot goes back to the source via the ground wire-which is bonded to the neutral thus completing the circuit. Diagram and other informative details at this link:
https://www.morganinspectionservices.com/understanding-three-light-receptacle-tester/

Most renogy inverter/chargers have an automatic relay built into the inverter that creates the ground-neutral bond when the unit is in inverter mode, and disables that bond when connected to shore power/generator.

I was skeptical of this point and did a little googling. Apparently the feature you describe is documented but according to Renogy 'is not yet deployed' (!).

The rest of my comments below apply to the charger/inverter model. The 'battery only' inverter doesn't see or know about shore power since none passes through the device.

In order to diagnose this correctly, we need to know what power source you're currently using, as that will determine where the ground-neutral bond should occur. If it's in inverter mode and running off batteries, and no bond is present, I'd say the automatic relay in the unit has failed. If it's on shore power/generator, I'd say your shore power/genset doesn't have the correct ground/neutral bond and you need to move further upstream to find the issue.

[Note: find a buddy electrician to do this next step if you are inexperienced with wiring. Don't fool around with residential power if you're new to this. Not to be fooled with, stay safe and unelectrocuted!] For the charger/inverter type, the only way I can think to test if the bonding toggles as described would be to disconnect all 120VAC loads off the inverter, apply shore power and check for resistance (ohms) between the inverter's 120VAC output neutral and ground. With shore power applied it should measure the resistance of the wires all the way back to the bonding on the shore power main panel, so more than a few ohms. With no shore power it should read zero ohms, indicating no resistance and perfect continuity--thus bonded at the inverter. If your results are different, that would be a thing...

The fact that the manufacturer doesn't cover any of this in their documentation is an indication they don't understand or don't care about real-world use of their devices.

 

[Beeb2]

Thanks all! Sorry for the delay in responding. I was traveling all weekend.

Let me try to answer some of the questions:

1. I used 10 gauge wire (apparently it's 10/2, not 10/3) because some online wire gauge calculator told me that's what I needed. Now that I go back to the calculator to double-check, it's giving me a different answer so I don't know what I did wrong the first time. But it's in now, so it is what it is.

2. There are 3 wires from each outlet (only 1 outlet per circuit). They are black, white, and green, and connect to the distribution panel at the breaker, neutral bar, and ground bars respectively. I have double-checked that they are connected correctly at the outlets, and my outlet tester also does not indicate reverse polarity. I have 3 wires coming from the inverter to the distribution panel - black, white, green. They connect to the main breaker, neutral bar, and ground bar respectively.

3. I checked my distribution panel's wiring diagram again, and see that it says the ground bar is supposed to be grounded to the chassis. I do not currently have that, and I wonder if that is part of the problem (though some here are saying not to do that...???)

4. I have NOT yet tested it while plugged into shore power. My current situation is entirely while running off of inverter power from the battery.

5. A few sources online say that the ground and neutral are bonded at the inverter, but I haven't found an official source, and Renogy is not responding to me.


I think I answered all the questions...?

 

[Rucker]

Good stuff. From your response my guess is your 120VAC distribution panel does NOT have bonding between the ground and neutral wires (because you are showing open ground).

It still sounds like the inverter does NOT toggle ground when switching from battery to shore power and back.

Are you pretty comfortable with using a multimeter? If so, I would do the continuity check at the inverter as mentioned above to verify this, copied here:

[Note: find a buddy electrician to do this next step if you are inexperienced with wiring. Don't fool around with residential power if you're new to this. Not to be fooled with, stay safe and unelectrocuted!]

For the charger/inverter type, the only way I can think to test if the bonding toggles as described would be to disconnect all 120VAC loads off the inverter, apply shore power and check for resistance (ohms) between the inverter's 120VAC output neutral and ground. With shore power applied it should measure the resistance of the wires all the way back to the bonding on the shore power main panel, so more than a few ohms. With no shore power it should read zero ohms, indicating no resistance and perfect continuity--thus bonded at the inverter.

If you have no continuity (not zero ohms, not 1-5 or so ohms, but 'open circuit') under that condition you do not have bonding at the inverter as you should. We can talk fixes once you've confirmed your readings.

 

[Beeb2]

Sounds good. I've used a multimeter once before. I'll brush up on how to safely do this before attempting. If I don't feel comfortable, I'll get help. Might be a few days.

 

[Beeb2]

Ok, well I hit a snag, but here's what I got so far:

1. The manual DOES say it has an automatic Neutral-to-Ground Bond switch. When connected to shore power, the neutral of shore power should connect to the neutral out of the inverter charger. At the same time, the neutral-to-ground bond switching relay will un-bond the neutral out connector of the inverter charger from the chassis of the inverter charger.

Note: The chassis of my inverter charger is grounded to the chassis of the bus.​

It continues on to say that it will automatically take care of the neutral to ground bonding when there is AC power going from the inverter to AC loads when shore power is not available, or when shore power is sent to charge the battery when shore power is available.


2. With NO SHORE POWER, the ground and neutral output of my inverter do NOT have continuity.

3. With NO SHORE POWER, the ground in my distribution panel DOES have continuity with my bus chassis, even though the ground bar in my distribution panel is NOT grounded to the bus chassis.


I was going to test with shore power, but I just discovered that my Furrion 30A inlet and my Camco 30A cable don't have matching heads. So I'm going to have to resolve that before I can test with shore power.

 

[Rucker]

Ok, well I hit a snag, but here's what I got so far:

1. The manual DOES say it has an automatic Neutral-to-Ground Bond switch. When connected to shore power, the neutral of shore power should connect to the neutral out of the inverter charger. At the same time, the neutral-to-ground bond switching relay will un-bond the neutral out connector of the inverter charger from the chassis of the inverter charger.

...as it should.

Note: The chassis of my inverter charger is grounded to the chassis of the bus.​

This is good. Grounding all ground wires in the 120VAC system in the bus to the bus chassis is preferred (despite what some say). The overall reduction of risk of shock is lower, though debate rages. Let me know if you care to see pros and cons and come to your own conclusion and I'll dredge up the discussion link.

It continues on to say that it will automatically take care of the neutral to ground bonding when there is AC power going from the inverter to AC loads when shore power is not available, or when shore power is sent to charge the battery when shore power is available.


2. With NO SHORE POWER, the ground and neutral output of my inverter do NOT have continuity.

Contrary to documentation, sadly. From what we've heard anecdotally Renogy admits the damned thing doesn't toggle (yet, apparently).

This is tricky, and according to electrical code, unsafe. The quick fix I alluded to is problematic because it would need to be removed each time you plug in to shore power. I would not recommend it at this point.

3. With NO SHORE POWER, the ground in my distribution panel DOES have continuity with my bus chassis, even though the ground bar in my distribution panel is NOT grounded to the bus chassis.

This is good and as expected. And btw you can and should ground the ground bar in the panel to chassis for extra protection. Just no bonding between neutral and ground at that 120VAC panel in your bus.

I was going to test with shore power, but I just discovered that my Furrion 30A inlet and my Camco 30A cable don't have matching heads. So I'm going to have to resolve that before I can test with shore power.

It will be interesting to see what you get. I'm guessing an ohm reading from 1-10 ohms, indicating it's bonded back at the residential panel. If it reads near zero ohms that would be laughable because it would indicate the automatic toggling Renogy does is opposite what it should be.

Can't wait to hear what you find out.

 

[Rwnielsen]

Make yourself a plug, 110 volt, tie the neutral to the ground and ignore the hot. Plug that into any of your outlets and then test the others with your checker. It's called a bonding plug and I use them in all of my generators or they'll show an open neutral. If that solves your issue, just bond the neutral to ground at the inverter. It is, after all, the source.

 

[Rucker]

Make yourself a plug, 110 volt, tie the neutral to the ground and ignore the hot. Plug that into any of your outlets and then test the others with your checker. It's called a bonding plug and I use them in all of my generators or they'll show an open neutral. If that solves your issue, just bond the neutral to ground at the inverter. It is, after all, the source.

That was my original thought but this is a charger/inverter, so that creates problems when on shore power.

I agree it's the simple solution for something like a generator or an off-market inverter only. But in this case it's supposed to toggle ground and it isn't behaving as expected.

Let's see what the test results are with shore power.

 

[incubus]

GFI's measure current in and out. If there is a difference they open circut. Inverters dont nessarly put out a clean wave of current. Tends to waver hence trips gfi. You are correct about not tying ground and common together. Never ground to bus. Wet night you grab door handle an you become the path of least resistance.

 

[Jono14]

Not grounding to chassis?

...Let me know if you care to see pros and cons and come to your own conclusion and I'll dredge up the discussion link.

Rucker, as an "older" shade-tree mechanic, now working in solar systems, I've assumed tying ground bar to chassis is best - so I would be interested in the discussion if you or others can find the link