Should Xantrex Inverter Have Bonded Ground

[Retiredfields]

I recently stayed at a BLM campground with electric. For whatever reason, they put GFI breakers on the 30 amp circuit. In 12 years on the road, this is only the 2nd place I've found with GFI on the 30 amp. I could not use either, as I tripped the GFI.

My rig immediately tripped the GFI breaker, so I decided to investigate. With all internal breakers off, the GFI still tripped. I then tested the common to ground resistance, at the breaker box, and it was a dead short, so my common was bonded to ground. I then disconnected both common wires, coming from the Xantrex input and output sides, at the breaker boxes. Now my common and ground, at the breaker box, were no longer bonded.

So, the Xantrex appears to be bonding the common and ground. The manual is not clear about this topic. It says the output side is not bonded, but says nothing about the input side.

Does anyone have any input on this? I would appreciate someone measuring the resistance between your common and ground circuits and posting the results.

Thanks

[GMDavidson]

I've had the same problem with my current MH and my previous MH (not an Alpine). I curious too?

[RustyJC]

See page 2-7, Figure 2-2 of the Xantrex installation manual HERE. Note the lower contact on the internal relay shown in Figure 2-2. Also note the AC wiring diagram on the input (AC supply) side of the inverter. Does this help?

Rusty

[dgerstel]

Ken,

http://www.xantrex.com/web/id/918/docserve.aspx

The Xantrex installation manual for the RS2000 on page 8 says "A source of 120 volts AC single-phase, 60 Hz alternating current is needed to provide energy for charging batteries and to pass through to AC loads. AC input can be supplied from an AC source like the utility grid (power company), from a generator, or from the output of a transfer switch. These sources must have their neutral conductors bonded to ground. See “AC Output Neutral Bonding” on page 9."

I haven't looked at mine to see where it is bonded. I have always found that if plugged into a GFI, the coach will trip it.

[Retiredfields]

Thanks Dale, that is what I was looking for.

[RustyJC]

From the manual I referenced:

Quote:

The inverter/charger provides a system that automatically connects the neutral conductor of the inverter’s AC output circuit to safety ground (“bonding” it) while the inverter/charger is inverting, and disconnects it (“unbonding” it) when the inverter/charger is connected to external AC power. This system is designed to conform to installation codes that require AC sources such as inverters and generators to have their neutral conductors tied to ground at the source of power in the same way that the neutral conductor from the utility is tied to ground. These same codes specify that the neutral can only be connected to ground in one place at any one time.

Shore power AC has this neutral-to-ground bond made at the power distribution panel supplying power to the shore power receptacle. Neutral should not be bonded to ground within the RV's shore power AC side per NEC code - that's why the inverter has a relay that unbonds it when shore power is connected. If neutral is bonded to ground in the RV (i.e., downstream of the shore power box's GFCI) with shore power connected, that explains why the GFCI trips.

This is consistent with the Xantrex instructions Dale posted, but what isn't said is WHERE the neutral-to-ground bond takes place on the shore AC power side.

Rusty

[Retiredfields]

Rusty, thanks for the follow-up. If I understand things correctly, the neutral and ground of a GFI circuit are not bonded, so the GFI can determine if there is some current loss to ground.

Since my common and ground are always bonded, unless I disconnect the inverter wires, then either Xantrex is doing the bond or WRV has some hiddden bond somewhere on the inverter circuit. It appears to me that the Xantrex is bonded on the input side. The wires run directly from the inverter to the breaker panel, so I don't know where else the bond could be.

[RustyJC]

Neutral and ground should never be bonded downstream of the shore power load distribution panel or the RV generator panel, per NEC code. That's why the relay I referenced in post #3 unbonds neutral from ground when AC power is applied from either the shore power box or the RV genset. The GFCI trips if current returning on the neutral leg isn't exactly the same as current flowing out the hot leg. Therefore, any ground current (such as would take place if an appliance shorts to ground) will unbalance the neutral current and trip the GFCI.

Yes, the Xantrex bonds neutral to ground when incoming AC power is not present (the inverter is considered to be the "generator" at that point), but it should energize the relay shown in the Inverter/Charger in Figure 2-2 to break the bond when incoming AC power is applied. Again, take a look at the wiring diagram in Figure 2-2 and see if yours is wired that way. It sounds like the neutral leg is connected to both the neutral terminal and the ground screw on the AC input side of the inverter - do you see any jumpers between the neutral terminal and ground screw on the AC input terminals of the inverter?

Rusty

[mythplaced]

I found that when I plugged into the 15A circuit at home the GFI would trip...

I discovered that I had the inverter ON when I was plugging in...

New process that does not trip the GFI

1. turn off all accessories (inverter)
2. turn off coach battery disconnect
3. plug in shore power
4. Set control panel to 15A
5. turn on coach batteries

Life is good

[RustyJC]

Mike,

Sounds good to me. I guess I was assuming that the inverter was turned off when the shore power was being plugged in. Bad assumption on my part!!

Rusty

[Retiredfields]

Sounds to me like the Xantrex common/ground bond relay is normally closed. When external power is applied, the relay opens. I would suspect that the GFI is much faster than the relay, so the GFI always sees a bonded common and blows before the Xantrex relay can open.

[RustyJC]

Ken,

Could be. It sounds like Mike has found a workaround for that.

Rusty

[mythplaced]

Quote:

Originally Posted by mythplaced I found that when I plugged into the 15A circuit at home the GFI would trip... I discovered that I had the inverter ON when I was plugging in... New process that does not trip the GFI turn off all accessories (inverter) turn off coach battery disconnect plug in shore power Set control panel to 15A turn on coach batteries Life is good

Oooops got #4 & #5 reversed...

Should be..

1. turn off all accessories (inverter)
2. turn off coach battery disconnect
3. plug in shore power
4. turn on coach batteries
5. Set control panel to 15A

Actually I don't know if the control panel even functions with the coach battery disconnect off..

[dgerstel]

Xantrex is not shut off by either disconnect switch.