Open ground on electrical.

**LMagelitz** · 03-16-2024, 08:34 AM

Originally Posted by Scott'n'Wendy

Upstream? Or downstream?
I would think upstream...I don't have a Southwire device...but the op describes it as a surge protector, and they are fairly basic so I'll bet as Jkwilson has suggested it is upstream. IE CG or house cct issue.

I’m throwing in with @jkwilson and @Scott’n’Wendy ….it’s upstream, or a defective device. 50a RV systems don’t have a neutral to ground bond, so the entire equipment grounding system is isolated looking downstream of the device. It’s supposed to be “open”, unless or until there is a fault. Looking at the upstream side though is different, there should be a neutral to ground bond, and this is what the device isn’t seeing, either because it’s not there (not likely), a bad connection, or the device is defective.

**Scuba Steve** · 03-16-2024, 08:52 AM

Ok guys.. more details.. the surge protector is a 50 amp Southwire model 34950. I am plugged into my warehouse where I store it. I wired the RV panel box directly from my breaker box. I am a retired general contractor and have done electrical work for years. I do not get an open ground when I test at the box. My RV power cord has the outer protective jacket pull out of the plug and I am having this replaced under warranty from Grand Design next week.
I had this same problem when at campgrounds. It would be ok for days and then the power would go off and the surge protector showed open ground. This new unit has been on for about 7 weeks now and just started showing the open ground and shutting down. The RV had not been moved or unplugged since the new protector was installed at my RV panel which is under an awning and not exposed to the weather.

**xrated** · 03-16-2024, 12:27 PM

Originally Posted by LMagelitz

I’m throwing in with @jkwilson and @Scott’n’Wendy ….it’s upstream, or a defective device. 50a RV systems don’t have a neutral to ground bond, so the entire equipment grounding system is isolated looking downstream of the device. It’s supposed to be “open”, unless or until there is a fault. Looking at the upstream side though is different, there should be a neutral to ground bond, and this is what the device isn’t seeing, either because it’s not there (not likely), a bad connection, or the device is defective.

You are correct in that the neutral and ground busses are separate in the RV, but that is because the shore power pedestal is, or should be bonded. It's no different that at your house and you run power to a sub-panel, let's say out in your detached garage. The neutral/ground bond is in the main breaker panel and it is in fact a violation of the NEC to have two neutral/ground bonds. There is a ground though, that runs from the RV grounding buss, through the plug in on the side of the trailer, through your 4 conductor shore power cable and then into the shore power pedestal.

**Scuba Steve** · 03-16-2024, 12:58 PM

I made another post with some clarification on my equipment and connection. If you read this and have any insight please respond. I have quite a bit of electrical experience.

**Scuba Steve** · 03-16-2024, 01:03 PM

I’m just puzzled that it worked for 7 weeks and then this showed up. If it was an open ground at the main breaker box then it should have detected this when it was first plugged in.

**jkwilson** · 03-16-2024, 08:11 PM

Originally Posted by Scuba Steve

I’m just puzzled that it worked for 7 weeks and then this showed up. If it was an open ground at the main breaker box then it should have detected this when it was first plugged in.

To detect an open ground, the unit is going to check voltage from ground to hot, which should be 120. If both hots to ground are about 120V, the unit is going to conclude that there is a conductor connected to the ground pin of the receptacle that is connected to the neutral somewhere in the system. Depending on the sophistication of the EMS, this may be enough to satisfy it that there is a ground in the circuit. A more advanced system might monitor current in the ground and neutral wires using Hall Effect sensors or coils to identify a downstream neutral bond, but the best I can tell from reading their site, this unit doesn’t do that.

So how could this system be fooled into thinking the ground wasn’t present? If something glitchy happened with a hot or neutral that affected the ground measurement , you’d think the EMS would notify you of that so we can suppose it’s not that.

So what are we left with?

A bad EMS. Switching to a second EMS seems to rule that out.

An intermittent ground from receptacle to panel. The fact you had the same problem at a campground seems to rule that out.

Easy stuff is gone. What if there is neutral bond somewhere in the trailer? The effect on the power cord and within the EMS would be 1/2 the current flowing to the RV flowing in the ground wire. A questionable connection in the grounding conductor might result in an increase in voltage on the ground wire with consequent decrease in hot to ground voltage. Maybe that would be enough to trigger the open ground fault detection. A bit of a long shot, but I’d measure to see if there is continuity between ground and neutral in the trailer with the cord unplugged from the EMS.

I’d still put my money on a second defective EMS if I had to bet.

**bjlakatos** · 03-20-2024, 03:30 PM

My progressive ems reported an open ground a few years back. It was in the middle of the summer when AC were running constantly. The error occurred at a different park. Inspection of the pin/blades that plugged into the pedestal revealed some corrosion. It took some Emory cloth to get the blades/pin back to bright and shiny and problem was resolved. Now I put a light coat of dielectric grease (with routine cleaning) on the pins/blade.