Question about inverter

[amauri]

Hello,
While doing some repairs to a bad a/c outlet wire, I used my basic three prong tester to check all outlets in the trailer and found an open ground on the inverter outlet.

We have ProWatt SW 2000 to power the fridge, it was originally installed by the rv mfg.

I would like to know if it is normal to have an open ground fault when testing the inverter a/c output with a 3-prong a/c outlet tester?

The inverter seems to be working normally and has a ground wire connected to it's ground point and the trailer's chassis.

Thx

[Old-Biscuit]

Any outlet fed by inverter should have a hot, a neutral and a Ground

That Outlet has a bad ground connection

[twinboat]

Yes, it's normal.
Many small inverters have a floating neutral and the plug-in tester will not work on them.

It's basically 60 volts per side to ground.

[Persistent]

The Xantrex ProWatt SW 2000 does not have a floating neutral.

https://forestriverinc.com/files/Com...;s%20Guide.pdf

The ProWatt housing is grounded. The 120 volt dupex outlet has ground pins. The output ground pins should have continuity to the RV frame ground. Any ground cabling from inverter to remote outlets should have continuity to ground.

The ProWatt does not have a transfer switch, so the ground connection is not switched.

Test the duplex outlet on the ProWatt using the outlet tester. If there is proper ground there, then the open ground is in the extension cord from the inverter to the refrig outlet.

Outlet testers come with many different capabilities. Sometimes the simple logic circuits become confused and present strange results.

I expect there is an open ground in the circuit. But to be sure I would get out my cheap digital multi meter and measure voltage to frame from outlet ground. It should be zero volts. Then switch to ohms. Ohm reading should be near zero to verify outlet tester.

[dssl]

Did you test the outlet while plugged in, and while on inverter mode?

On my Victron MultiplusII it has a relay that connects the neutral to the ground when in inverter mode. I believe all of the grounds are always tied together. Not sure exactly what the open ground is detecting , If it is looking for a path to neutral then unless your inverter has a neutral to ground relay it won't find a path while in inverter mode, but it will find a path when plugged in.

[amauri]

Thx for all the informative replies.

I am testing directly at the inverter outlet GFCI, before the xfer switch.

With inverter off and using an ohm meter between outlet ground and chassis ground i get infinite reading.
With inverter on, I measure 120 vac between neutral and hot.

Haven't figured out how to safely measure ground continuity while inverter in on and supplying a/c to an appliance yet, but will do that next.

[Persistent]

Haven't figured out how to safely measure ground continuity while inverter in on and supplying a/c to an appliance yet, but will do that next.

You may have already done this when the inverter is "off".

Start by measuring the ohms from ground lug on inverter to metal part of frame. If no continuity then it is possible it is a loose or corroded ground wire connection.

Next measure ohms from lug on inverter to duplex ground pin on inverter. If no continuity then internal break or it is a floating ground system.

I would open and look for cause. It is probably better to call or email Xantrex for instructions. There may be some issue I did not see.

You have already measured from duplex neutral pin to duplex ground pin and found it to be open.

To measure while hot:
Inverter "on" and with extension to refer disconnected, measure voltage from duplex neutral to duplex ground pin. When there is no load on the inverter, voltage should be below one volt. Possibly it should be zero volts.

If zero volts, switch to ohms. I expect there will be no change from when not operating.

I expect duplex neutral pin and ground pin should be connected to one another at the inverter. This is necessary to cause the circuit breaker to trip if there is a short circuit to ground in the appliance connected.

These two pins in turn should be connected to the RV frame through the inverter grounding lug. This is less important for a small off grid system (floating system ground). Some failures could cause the connected appliance to be hot relative to the frame.