Grounding Monitor Interrupters - Do Olivers Have This Already?

[DunnYet]

From a newsletter I received ...

"The 2026 Edition of the National Electric Code (NEC) is now published, which finalizes the grounding monitor interrupters requirement. All RVs with 30A or 50A electrical service will be required to install a Grounding Monitor Interrupter (GMI), which is a loss-of-ground device. Before electrical current can pass into the RV, a GMI will check the receptacle for a proper ground connection. During use, the GMI will also monitor the ground connection to the RV and, if lost, will disconnect the power to the RV."

Full article at https://www.rvia.org/news-insights/grounding-monitor-interrupters-rvs-and-their-impact-rv-parks-and-campgrounds?utm_source=Iterable&utm_medium=email&utm_campaign=campaign_15242097&campaignSource=RVLIFE

I have never heard of this before - is this something that I already have and just don't know it? Does my Watchdog handle this? Does the built in EPO?

Inquiring minds want to know 🙂 so I was going to check here and see if anyone else is familiar with this or if I'm just late to the party.

[CRM]

2 hours ago, DunnYet said:

I have never heard of this before - is this something that I already have and just don't know it? Does my Watchdog handle this? Does the built in EPO?

Inquiring minds want to know 🙂 so I was going to check here and see if anyone else is familiar with this or if I'm just late to the party.

A Watchdog with EPO will shut off the power if the ground is missing, Not sure about the Progressive units that come in Oliver's, though..

Edit- according to AI the Progressive EMS does cut off power when the ground is missing. Would still check the owners manual to be sure. 

Edited October 10 by CRM

[srthomsen]

I wonder, does this apply to only newly manufactured RVs etc OR does the code apply retroactively to those in service (I can't see that happening}?

[Tom and Doreen]

The Progressive industries EMS that Oliver supplies does check for an open ground, Error #2 as does the Watchdog; We use both devices. 

[DunnYet]

Sounds like Oliver was ahead of the curve again!

[CRM]

18 hours ago, srthomsen said:

I wonder, does this apply to only newly manufactured RVs etc OR does the code apply retroactively to those in service (I can't see that happening}?

No, they can retroactively enforce this. Though anyone who doesn't have this sort of protection is crazy not to have it added to their RV. And have it hard wired inside the RV... If you rely on pedestal protection you're not protected from an open ground if the power cord or it's connections are damaged beyond it.  

[jd1923]

6 hours ago, CRM said:

Though anyone who doesn't have this sort of protection is crazy not to have it added to their RV.

Yep, agreed! OTT did not install one on our older hull, so after asking Forum members, as to "Why?" I installed the same PI EMS shortly after purchasing our Oliver. We had the same EMS model in a Class C, and the 50A version in a Class A we had in the past. They are standard and code compliant.

As far as electrical installations, it's relatively simple and I also agree with CRM, that pedestal protection has the issue he cited and others.

 

[CRM]

5 minutes ago, jd1923 said:

Yep, agreed! OTT did not install one on our older hull, so after asking Forum members, as to "Why?" I installed the same PI EMS shortly after purchasing our Oliver.

 

Our Hull 45 was without any electrical protection also so I installed a hard wired Hughes Power Watchdog as well as their Autoformer voltage booster. Looking to upgrade to their new "Watchdog Powercenter" once it's back in stock. It combines the Autoformer voltage booster and Watchdog protection into one unit to protect from low voltage, surges, and wiring issues. Pricey, but worth it, IMHO... 

Watchdog Powercenter

[CRM]

Spoke with a friend today who is very knowledgeable on the subject and he said that none of the EMS products on the market right now satisfy the requirements of the upcoming code for Grounding Monitor Interrupter's in RV's. He said while they might cut power when a ground is missing they will not protect in other rare scenario's where power is on the ground wire. 

[jd1923]

3 hours ago, CRM said:

where power is on the ground wire. 

I’m trying to think of a scenario where this is possible. The possibility of power to ground is the reason why circuits are protected by fuses or breakers!

 

[mossemi]

On 10/10/2025 at 3:26 PM, CRM said:

Edit- according to AI the Progressive EMS does cut off power when the ground is missing. Would still check the owners manual to be sure. 

I think this scenario occurs when connecting to a generator without a bonding plug.

Mossey

[Steph and Dud B]

The problem they cite for the regulation is a "hot skin" condition where voltage leaks into the trailer frame (and skin on metal skinned trailers) via a short or bad appliance and can't reach ground because of an open ground connection to the pedestal. In this situation a person can complete the circuit to ground by touching a metal part of the trailer and potentially get electrocuted. I suppose, in that scenario, there would be voltage on the trailer ground wire as well as the other grounded metal parts. Still, any device that detects an open ground and cuts power should prevent that scenario. 

(BTW, I did get a little jolt from one of our trailers once because of a poor ground connection.)

[CRM]

51 minutes ago, jd1923 said:

I’m trying to think of a scenario where this is possible. The possibility of power to ground is the reason why circuits are protected by fuses or breakers!

 

A bootleg ground at the pedestal with an internal fault in the RV could do it. Not sure if the EMS would even see this as a fault. 

[Snackchaser]

5 hours ago, CRM said:

Spoke with a friend today who is very knowledgeable on the subject and he said that none of the EMS products on the market right now satisfy the requirements of the upcoming code for Grounding Monitor Interrupter's in RV's. He said while they might cut power when a ground is missing they will not protect in other rare scenario's where power is on the ground wire. 

Your friend is correct!  The Oliver’s Progressive Industries Power Management System will shut-off power for an “open ground,” but it does not comply with the 2026 NEC changes that also requires monitoring for an “energized ground.”   Either of these conditions can result in a “hot skin” shock hazard!

Cheers!  Geoff

[Steph and Dud B]

If the ground in the pedestal was energized wouldn't the metal pedestal body itself also be energized? That would be super dangerous.

[Steph and Dud B]

Speaking of damaged pedestal wiring, we saw this smashed meter on a pedestal in a COE campground in Arkansas.

[CRM]

49 minutes ago, Steph and Dud B said:

If the ground in the pedestal was energized wouldn't the metal pedestal body itself also be energized? That would be super dangerous.

Depends on the wiring fault, but it could become energized under the right conditions.  

[jd1923]

14 hours ago, Snackchaser said:

requires monitoring for an “energized ground.”

Not being a theory guy, can somebody give a real example of this? (an Energized Ground) Maybe Geoff?

Also, I’ve never heard of retroactive code enforcement. My home was to code in 1980, not today! And unless I file permitting to remodel something it can exist as built grand-fathered.

[CRM]

49 minutes ago, jd1923 said:

Not being a theory guy, can somebody give a real example of this? (an Energized Ground) Maybe Geoff?

 

If the ground is bonded to neutral at the pedestal, instead of a separate direct run back to main panel ground as it should be, the ground conductor will become the neutral if the neutral connection is lost inside the trailer. 

[CRM]

Here's a more detailed explanation courtesy of AI- 

Bonding the ground and neutral together at an RV pedestal creates a secondary neutral-ground bonding point, which violates the National Electrical Code (NEC) and RVIA building codes that require only one bonding point in a distributed electrical system.
 This single, primary bonding point must be located at the main service panel, such as the campground's incoming service panel.
 When the ground and neutral are bonded at the pedestal, it establishes an additional connection between the neutral and ground conductors, which can lead to several hazardous conditions.

If the neutral conductor fails (e.g., due to a loose connection, corrosion, or damage), the current from the load will seek an alternative return path. With a secondary bonding point at the pedestal, this current can flow through the grounding conductors, including the equipment grounding conductor (EGC) and the RV chassis.
 This causes the safety ground, which should normally carry no current under normal conditions, to become energized and carry the full load current.
 This condition is dangerous because it can result in a "hot skin" on the RV, meaning the metal frame and any connected appliances become energized at 120 volts.

If the ground conductor also fails in this scenario, the risk of electric shock increases significantly. A person touching the RV while standing on the ground could receive a severe or fatal shock due to the energized chassis.
 Furthermore, this secondary bonding can cause ground loop currents, which may induce hum or buzz in audio systems and can trip GFCI outlets even with minimal load current.

In summary, bonding the ground and neutral at an RV pedestal creates a dangerous condition by allowing fault current to flow through the safety ground, potentially energizing the RV chassis and creating a serious shock hazard. This is why the bonding must be performed only at the main service panel and not at the pedestal or within the RV itself.

[ScubaRx]

5 hours ago, Steph and Dud B said:

Speaking of damaged pedestal wiring, we saw this smashed meter on a pedestal in a COE campground in Arkansas.

You really need to especially careful around a situation like this. Just putting your hand near could result in a very nasty cut.

[Steph and Dud B]

3 hours ago, jd1923 said:

Also, I’ve never heard of retroactive code enforcement.

The new rule isn't retroactive, it only applies to new RVs.

[ScubaRx]

https://rvelectricity.substack.com/p/gmi-grounding-monitor-interrupter

[Rivernerd]

On 10/16/2025 at 8:59 PM, Snackchaser said:

Either of these conditions can result in a “hot skin” shock hazard!

It seems to me this is another advantage for fiberglass trailers, like our Olivers vs. aluminum, like Airstream.  Although the aluminum chassis in an Oliver is a good conductor, the fiberglass "skin" is not.

Does anyone know if 30A receptacle testers presently on the market will detect bonded neutral and ground connectors at an RV pedestal?  If not, I expect the code change will prompt market introduction soon.

[Snackchaser]

26 minutes ago, Rivernerd said:

It seems to me this is another advantage for fiberglass trailers, like our Olivers vs. aluminum, like Airstream.  Although the aluminum chassis in an Oliver is a good conductor, the fiberglass "skin" is not.

Does anyone know if 30A receptacle testers presently on the market will detect bonded neutral and ground connectors at an RV pedestal?  If not, I expect the code change will prompt market introduction soon.

Although fiberglass is not conductive, the frame, bumpers and hitch are!  

It's possible for a trained person with the right equipment to check if the neutral is bonded at the pedestal.  But there is no quick test plug-in device.  

It has long been the case that the neutral must be bonded to ground only at the main service.  However, there are probably tens of millions of sub panels that are incorrectly grounded.  But there are also many other improper wiring issues that are even more significant hazards.  There is an old electrician's saying about apprentices, handyman's, and  DIY'ers;  "They know enough to be dangerous."   Just be wary of armchair advice, it's what they don't know that will get you!

Cheers!  Geoff