Inverter-Charger Floating Neutral

[jtown]

Hi everyone,
For reference, I have the following inverter/charger and distribution panel:
- Inverter/Charger: https://ca.renogy.com/3000w-12v-pure-sine-wave-inverter.../
- Distribution panel: https://www.boatandrvaccessories.com/.../wfco-wf-8930...

On the output of my inverter/charger, I get the following voltage readings:
- Live-Neutral: 120V
- Live-Ground: ~25V
- Ground-Neutral: ~25V

I have figured that the neutral and ground are not being bonded by my inverter/charger. When I’m connected to shore power and my AC loads are being powered by shore power, I don’t have any issues with the output as the shore power has already bonded neutral-ground.
I’ve been troubleshooting with Renogy for months trying to figure out this issue, but they have been absolutely useless. The resolution was finally to send me a new inverter/charger, but I am having the same issues as before.

From my understanding, the inverter/charger should be bonding the output when not connected to shore power. When it is connected to shore power, the inverter/charger is meant to disconnect neutral-ground, thereby ensuring the neutral-ground aren’t bonded twice.

My guess is that the inverter/charger thinks that I have bonded the neutral-ground somewhere else in the system. Although would love to know if anyone else has had this issue? Or if anyone knows this product well enough to diagnose the issue?

My short term solution is to bond the neutral-ground in my distribution panel when I’m not connected to shore power. Then when I am connected to shore power, I’d disconnect them. It’s not an ideal setup as I’d have to connect/disconnect this every time - although I don’t plan on using shore power all that much anyway. Is there a better solution if I can’t figure out the code of the issue? I had the thought of adding a switch so I could easily bond and unbond. Someone in another forum told that if I do this, then I could risk issues due to unknown internal build quality and if it does have a reactive coupled centre tapped design will be compromised

Thanks!!

 

[Solar_freak]

Hello, I have the same problem with my mxmoonfree 6000w inverter. When the line for the loads is connected to grid power all my outlets have grounds. But as soon as I hook it up to my inverter, no grounds.Also the outlets on the inverter itself have no grounds? this is my second inverter with the same problem? When I check voltage at the converter I have 48v on neutral and 72v on live, add them up and you have 115v? Something is fishy?

 

[jtown]

From my understanding, some inverters are designed to have a floating neutral - which seems to be the case for both of us here.

My main question is whether or not it is safe to connect the neutral-ground in the distribution panel. I have heard in another forum that it may not be safe to do so depending on the inverter design.

 

[Solar_freak]

I do not know about that my friend? Sorry

 

[TacomaJoe]

I was thinking that I read something like this before, then realized that it was my own comments in your

Inverter Charger weird output when not connected to utility power (i.e., using the bypass)​

thread.

 

[mikefitz]

had the thought of adding a switch

You could use a relay powered by shore AC power to control the bonding.

However according to the manual for the 3000 watt inverter charger, this should not be necessary,

 

[jtown]

You could use a relay powered by shore AC power to control the bonding.

However according to the manual for the 3000 watt inverter charger, this should not be necessary,
View attachment 179783

Unfortunately this is not the case. Apparently some Renogy inverters have this and mine does not.

Is there a relay that is also an RCD for this purpose? Thanks

 

[Solar_freak]

From my understanding, some inverters are designed to have a floating neutral - which seems to be the case for both of us here.

My main question is whether or not it is safe to connect the neutral-ground in the distribution panel. I have heard in another forum that it may not be safe to do so depending on the inverter design.

Hey jtown, I talked to John @ the inverter service center. I think they are in TenNessie , any way he said if you combine the neutral and the ground you will burn up you inverter!

 

[Solar_freak]

Also, I found out why I have 65v on one leg and 55v on the other leg at the inverter…120v… that is normal for chineses inverters, that’s just the way they make power. It is NOT up to code and will give you an open ground reading at your loads.

 

[Road Runner]

On the output of my inverter/charger, I get the following voltage readings:
- Live-Neutral: 120V
- Live-Ground: ~25V
- Ground-Neutral: ~25V

Sounds like a "Floating", not bonded, neutral. An Ungrounded System.

If you used a regular multimeter to do the AC voltage measurements the 25Vac Live-ground and 25Vac neutral-ground may be nothing more than a ghost, phantom, voltage reading. Not actually real. Example of what I am talking about... Take your multimeter, set it on AC voltage, insert one test lead probe into the HOT contact of a wall outlet in your home (Hot contact is the smaller of the two slots), and then just hold the other test lead probe of the meter in the air. The AC voltage reading on the meter display may be bouncing around, or it may be somewhat steady. It is not real though. It is what is called a ghost, phantom, voltage.

Why? The internal resistance of a regular digital multimeter is usually around 10 meg ohms. Very little current is needed when measuring for voltage. So unless both probes are connected solidly across an actually known source the meter is prone to a ghost, phantom, voltage reading.
Example:

To get an accurate AC voltage reading you would need a meter with a LoZ, (Low Impedance) circuit setting on the meter.
OR you could put a load like may be a 120V 25 watt incandescent light bulb, using a pigtail socket, across the L-G and N-G and then measure for AC voltage with your meter across the 25W load. If the output of the inverter is floating you will measure 0 Vac L-G and across N-G.

.