Storage: Power issue

[John From Detroit]

Heck GFCIs don't play well when another GFCI is downstream from them...

Done that many times. NEVER a problem. Not once.

 

[Domo]

Done that many times. NEVER a problem. Not once.

I'm glad to hear you've not had any issues.

Please google when a GFCI is connected as the LOAD of another GFCI (i.e., in series).

I've seen and corrected false triggers by moving downstream GFCIs from the upstream LOAD terminal to the upstream LINE terminal.

I've been surprised that others report they have never had/seen any issue when GFCIs are wired "in series" as opposed to "in parallel."

 

[workinonit]

I agree. Depends on how they are wired. They can cause issues when one is connected to the load side of another. It also depends on what is running on the GFI. Inductive loads sometimes cause issues. I had to replace my RV GFI receptacle that my fridge was running on with a breaker. I couldn't stop it from tripping. The GFI breakers don't seem as sensitive to inductive loads. But stacking GFIs can definitely be problematic.

 

[Gary RV_Wizard]

In my experience the only "nuisance" with series GFCI is that when one GFCI trips, they all trip. That's by design.

There is no reason for a GFCI to ever pass current to the ground instead of neutral, even during a self-test or reset. In fact, a GFCI is supposed to function properly without a ground wire present at all. And as long as the downstream GFCI passes a test current only to the neutral side, it cannot "confuse" the upstream GFCI. Whatever it does, it's just another load.

I see no reason an inductive load is any different from the GFCI perspective. Whatever the load is, it's just some amount of amps in the wire. If the difference between hot & neutral exceeds 6 ma, the GFCI trips.

However, some loads are more prone to producing ground faults than others, leaking a few milli-amps to ground. Motors (classic inductive load) are an example. Removing the GFCI gets rid of the nuisance, but doesn't get rid of the current leakage problem. You just have to hope the amp leakage never gets high enough to be really dangerous.

 

[Kirk]

While searching on the internet I found the following information.
"Pumps, fractional horsepower induction motors, and the motors found in appliances like refrigerators and washing machines are common inductive loads that can cause GFCI trips. The transformers inside some LED bulbs and other electronic devices contain inductive coils that can contribute to nuisance trips. While older GFCIs were more susceptible, newer ones can also be affected, especially by electrically noisy loads with variable frequency drives or chopper power supplies. "
And also: "Yes, inductive loads can affect a GFCI, with the primary issue being "inductive kickback," which is a temporary voltage spike created when an inductive device (like a motor or transformer) is switched off. This spike, along with electromagnetic interference (EMI) from the inductive load, can cause a GFCI to "nuisance trip" or false trip. While older GFCIs were more susceptible, newer ones can also be affected, especially by electrically noisy loads with variable frequency drives or chopper power supplies. "

But there is another thing that could also contribute in an RV that is probably more common than either of those answerers, if you are considering a GFCI that supplies power to the RV power cord. A GFCI is designed to trip with a difference between hot and neutral of only 4-6 milliamps, or .004 to .006A. Since the power cord of the RV is treated as one single appliance, everything inside that is connected to the 120V supply with any leakage at all will be combined in the result. That means that if you have your refrigerator on 120V and it has .002a leakage to ground and at the same time the converter has another .002a leakage and connected to an outlet is a lamp with .003a of leakage, the GFCI that supplies the RV will now see a leakage of .007a and it will open. The result is that quite often an RV my trip a GFCI supply but not the one that supplies each of those loads because the are eash supplied by a different GFCI outlet. For that reason, the NEC does not require that the 30A or 50A outlets for an RV be GFCI protected.

 

[Gary RV_Wizard]

For that reason, the NEC does not require that the 30A or 50A outlets for an RV be GFCI protected.

It's my understanding that the more recent levels of the NEC do require GFCI for newly installed 30A/120v outlets. I've read reports that COE parks are getting their 30A outlets upgraded.

There is typically a several-years-long lag between the approval of a new NEC and its adoption by the various states and cities, so there isn't just one NEC for the entire country at any given moment in time. And it's common for states and cities to tack on their own modifications or additions as well.

 

[Kirk]

It's my understanding that the more recent levels of the NEC do require GFCI for newly installed 30A/120v outlets.

What I found is that beginning in 2026 the NEC will require Ground Monitoring Interrupters on RV pedestal 30A and 50A outlets. But those are quite different from the present GFCI. Here is what I find by way of the difference:
A Ground Monitor Interrupter (GMI) works by continuously checking the integrity of the earth (ground) connection in an electrical system, often in applications like RVs or EV chargers. Unlike a GFCI which monitors current flow for imbalances, a GMI specifically tests if there is a valid, low-impedance ground path. If the GMI detects a high-resistance or missing ground connection, it will prevent power from being supplied to the device or disconnect it from the power source, ensuring safety by preventing a dangerous "hot skin" condition.

 

[workinonit]

In my experience the only "nuisance" with series GFCI is that when one GFCI trips, they all trip. That's by design.

There is no reason for a GFCI to ever pass current to the ground instead of neutral, even during a self-test or reset. In fact, a GFCI is supposed to function properly without a ground wire present at all. And as long as the downstream GFCI passes a test current only to the neutral side, it cannot "confuse" the upstream GFCI. Whatever it does, it's just another load.

I see no reason an inductive load is any different from the GFCI perspective. Whatever the load is, it's just some amount of amps in the wire. If the difference between hot & neutral exceeds 6 ma, the GFCI trips.

However, some loads are more prone to producing ground faults than others, leaking a few milli-amps to ground. Motors (classic inductive load) are an example. Removing the GFCI gets rid of the nuisance, but doesn't get rid of the current leakage problem. You just have to hope the amp leakage never gets high enough to be really dangerous.

Here's what I can tell you as an absolute. I have seen it in my years of wiring residentially and industrially. GFIs don't stack well line to load. Most times it works fine and sometimes it doesn't. Some particular inductive loads will trip a GFI. Every now and again one will do it but most do not. I suppose some inductive loads at some point in the startup process don't exhibit balanced line and neutral for some short time period. GFI receptacles are more prone to nuisance trips that a quality GFI breaker. Not all but some. My fridge on my RV does it. One of my freezers in my garage does it. I don't use GFI receptacles anywhere after losing a freezer full of meats and vegetables to one. But, breakers are much more expensive.

 

[Gary RV_Wizard]

What I found is that beginning in 2026 the NEC will require Ground Monitoring Interrupters on RV pedestal 30A and 50A outlets. But those are quite different from the present GFCI. Here is what I find by way of the difference:
A Ground Monitor Interrupter (GMI) works by continuously checking the integrity of the earth (ground) connection in an electrical system, often in applications like RVs or EV chargers. Unlike a GFCI which monitors current flow for imbalances, a GMI specifically tests if there is a valid, low-impedance ground path. If the GMI detects a high-resistance or missing ground connection, it will prevent power from being supplied to the device or disconnect it from the power source, ensuring safety by preventing a dangerous "hot skin" condition.

Right, GMI is an entirely different function than GFCI. The only thing they have in common is the word "ground".

 

[Gary RV_Wizard]

The possible requirement for GFCI for an RV power source is a very complex situation. There are several different sections of the NEC that can apply, depending on the location, usage, and wiring method, including some explicit exceptions. Most notably NEC section 551 grants a broad exception for 30A/120v and 50A/240v outlets, but only when installed in RV parks. The same outlet on the side of your home or garage would normally require GFCI. Crazy? Maybe, but the NEC is full of exceptions intended to allow practical wiring methods for specific situations.

 

[CharlesinGA]

I know this thread has digressed from the original question, how to monitor power in the coach, but with regard to the GFI in series with another GFI, I have never seen a situation where neither one tripped simply because another one was in the series.

When I first wired my shop, (a metal building, aircraft hangar actually) I did not install any outside power receptacles. Later I added a weather resistant Bell box and a commercial grade 20 amp Hubbell GFCI receptacle. This was after tripping over cords a couple of times when they were strung from inside.

I decided to install a receptacle in the trailer for a space heater. The ideal location is the end of the front dinette and so I installed it in an existing circuit. It is the first thing in the circuit about 12 inches from the power center. the remainder of the circuit is supplied off the LINE side of the receptacle. I had the trailer just outside the door and powered with a 14 gauge extension cord and adapter to the twist lock inlet. This was supplied by the GFCI I installed on the outside of the building.

Now, I used a commercial grade Leviton GFCI for the one in the trailer (it is within 6 ft of the sink) and when I went to test it, it didn't trip, the one on the building did. I even tried it with the plug in tester, and same thing, the one on the building was faster and tripped first. I ended up plugging the trailer into a non-GFCI receptacle inside the building and then testing it, it tripped just fine. It was simply slower than the Hubbell GFCI supplying it.

Charles