I agree - this is why I’m not necessarily trusting my measurements and am awaiting a clamp for my Fluke multimeter to verify. It was late and it was dark (I disconnected all DC loads). I don’t know where the residual current was coming from and should have checked the voltage but its possible that my connections were poor (that would result in less current, not more) so I’m doubly curious. I would also think 150ma would trip the GFCI instantaneously and not after a minute or more. I was able to get the charger to remain on for a few hours yesterday to get the battery fully charged so I’m not sure what changed (this was without any AC loads so whatever I did was not a solution - I need to at least be able to run the refrigerator).
Again, I was reading the current downstream of the MP2 and tonight I intend to remeasure this current and also the current upstream of the MP2 which is a little harder to access. I have a spliced ground cable in the MCB box I installed upstream of the MP2 and will shunt the current there.
One aspect I am remembering… I of course switched all the load and supply breakers off prior to connecting my multimeter leads and I distinctly remember seeing a fluctuating but fairly high current reading of between 100-180ma prior to switching any breakers back on. I don’t know what could be causing that or if it is even legitimate/accurate. I was perplexed at the time but assumed it was some sort of capacitance I was detecting. The current definitely settled out once I switched the AC supply and load back on and this is where I saw the 150ma reading.
My only guess is that the chassis ground of the MP2 is connected to the DC negative bus bar and if the MP2’s ground relay connects the AC ground to the chassis ground (or if it is always connected, I don’t know) then that would point to a DC wiring fault of some sort since the batteries were the only thing connected I think. This is even more suspect since the current on the ground dropped to literally 0ma when I switched off all DC loads and MPPTs.
I can tell you how it is done in Australia. The outlet at a marina or caravan park are maximum 30mA trip level and minimum of 15mA. If it were 4-6mA we would be tripping breakers continuously.
My previous posts dripped of frustration, which is palpable and valid. Though after taking measurements last night it is very clear to me that I need to investigate elsewhere in the camper and work my way back to the MP2. I’ll be the first to come back here and admit I have a wiring issue, if it turns out that I indeed have one. There are too many open threads on this topic with no salient answers - if this is the issue, then maybe it will encourage others to go back and do the same.
Just to clarify, this is an RV/Caravan parked in the driveway of my home. This is a fairly typical setup in the US and a google search indicates that the GFCI tripping is a very common problem here. I think most people are bypassing or lifting the ground connection to remedy the symptom and there are probably a myriad of causes - this isn’t what I want to do. The real solution would be for me to install a 50a 120/240 split-phase pedestal near the camper and to just plug into that since that’s what campgrounds do (with no GFCI involved). My situation is perplexing since the entire system worked just fine before adding the MP2. I did upgrade to lithium batteries and relocate them inside so there is some unused/leftover wiring in the old battery box. Again, I’m not immune to mistakes so I think the first action I need to take is to go through the new wiring with a fine tooth comb and then remove all the old wiring to eliminate the possibility of something still connected to a positive bus bar somewhere and shorting to something else.
Ok, I accept that an outlet…a single outlet…may be ok with a trip setting of 4-6mA. That means one single appliance is powered from one single outlet and it is individually protected by that outlet. A single vacuum cleaner is quite different to a large boat or a large RV.
You are now talking about a complete electrical system, not just a single outlet. The accumulation of leakage currents from many different loads requires a higher trip level because it is an accumulation of leakage and not the leakage of one single device. See the post earlier in this thread and check out the paper showing the accumulation of the leakage from devices in a vessel. These are measured numbers and show what the typical leakage currents are.
Victron Multipluses and Quattros do not come standard with a power plug attached. They are meant to be installed in well designed, permanent installations and hardwired into service. That is why they come with screw terminals and protective covers and dont just plug into an outlet like a toaster or a jug.
It is not a mystery that tripping occurs if the outlet feeding any complex electrical system has a trip limit of 4-6mA. The paper referred to earlier on this post shows that the leakage from just a single EMI filter of one single IEC inlet is 0.35mA. That is just the inlet, no equipment connected yet. It is not a fault, it is not a problem, it doesn’t need to be fixed but it is an unfortunately electrical engineering fact .
The accumulation of these small leakage currents soon builds up. The best way to tackle this is to measure the leakage and see what it is. That way you can make an informed choice as to what to do.
I appreciate your efforts and don’t necessarily disagree with you. But it’s also a simple fact that in the US, the law dictates that the GFCI must operate under those parameters, whether you or I accept that or not.
The vast majority of people with RVs will need to, at some point, plug the unit into a 15a residential outlet and that outlet will almost assuredly be outdoors. If that outlet is outside, by law it has to be a GFCI. I’m not saying that the Victron Multiplus is causing my problem, but if it contributes to the leakage, even a little bit, then it is causing the problem and therefore unsuitable for US installations.
These units are regularly sold and installed in US RVs. Airstream even offers it as standard kit on some of their models. Again, it’s most likely a wiring fault of mine but I’m just telling you how it is in the US and the tolerances here are extremely low.
At this point, I’m forced to assume that there is either a problem with my specific Multiplus or maybe, in fact, all MP2s since this seems to be a very common problem.
What I’ve done since my last update:
Rewired the AC in/out of the MP2 using ferrules this time to prevent any possible strays
Rewired the and properly fused the DC house system
Disconnected all solar panels and chargers
Dropped charging amps to 15a - should be very doable for the GFCI
With no AC or DC loads connected, the MP2 still trips the breaker after a minute or so. The exact same symptom as before.
I tested the current leakage on both sides of the MP2 with my Fluke 115 by shunting the ground and measured zero milliamps
Not trusting this, I ordered a clamp attachment for the Fluke - it also measured zero milliamps
So not I’m not trusting the current measuring capabilities of the Fluke so I bought a cheap clamp meter off Amazon - it also measured zero milliamps but oddly measured a small DC current (this is probably due to it being cheap as it measured the current even without a wire passing through it).
I am now suspicious of the GFCI so I routed an extension cable into the kitchen and plugged into an outlet there which has a GFCI installed at the main breaker panel - surprise, this GFCI also tripped (20a circuit BTW).
I’m now sitting here with a ground lift plug installed on the outlet which I suppose I don’t entirely trust but the MP2 is no longer causing the GFCI to trip and I’m able to charge the battery. The MP2 is clearly doing something which is causing the GFCI to trip but for the life of me I can’t figure it out.
The use of the ground wire and the meter in shunt mode to test for leakage is interesting but not really definitive. The ground leakage could be taking place outside of the actual ground wire and in fact it sounds like it is. The idea of “ground” potential is that it is everywhere and not confined to that single wire. The real test is to use a sensitive clamp meter to test for imbalance between active and neutral. Any imbalance of active and neutral does signify that some leakage somewhere is taking place.
The path is from Active to a ground somewhere and that ground is not necessarily the ground wire. In fact it is the imbalance of the active and neutral that causes the GFCI or RCB or whtaever you want to call it to open. That is why they are called a “Core Balanced Relay” because the imbalace of the currents in a core with active and neutral passing through it causes the device to open circuit. The GFCI does NOT measure ground wire current.
I am not sure of the sensitivity of the meters or clamp accessory you are using but it does need to be quite sensitive. For instance a normal electricians clamp meter does not have the sensitivity for this measurement. Fluke do produce a 368 model meter which is very good for this work but quite expensive. Other cheaper brands can be found that I think would do a good job. Your meter in shunt mode is sensitive enough but you need to clamp two wires and not just check the ground wire. That is why you need a meter sensitive enough to measure down to a milliamp in clamp mode. That is not a normal requirement for a clamp type multimeter.
Ground leakage is evidenced by an active and neutral imbalance. If you clamp around active and neutral, in the absence of ground leakage they should be equal (and opposite) and cancel to no reading at all when you use the clamp meter with both conductors passing through the clamp.
When you measure the leakage as an active, neutral imbalance, you will see that some leakage must be there to cause the core balance device to trip. Please understand that some leakage is measurable in practically everything because of the capacitive current which flows between two conductors. Even a long extension lead has a measureable leakage current because of the capacitance between the active and ground conductor.
If you clamp the active and neutral with a suitable meter you will see the leakage occur and you will see the reason for the GFCI opening. It is great you are following up on this and soon all the mystery will be removed when you can see exactly what is going on.
FYI, earlier I did clamp L1, L2, and N and also saw no current. The cheap meter I bought only shows 2 decimal places so if there was current, it was less than 10ma. I’m going to try one more time…
Also I’m not sure about L1, L2 and N. That is not a terminology I am used to so maybe I am describing a situation that is different to the system used in your region.
I’ve just read about the Multiplus 120x2 so get your meaning now around L1 and L2. I can’t speak from experience with this setup as I have never installed one of those.
In the US, homes are wired in a configuration known as “split phase”. The power flows through 2 primary “legs”/conductors: L1 and L2 (black wire and red wire, respectively). These are taken from either end of a transformer being fed 240v. The neutral “N” is fed from the center tap of that transformer making either leg only 120v but 240v between the legs because they are 180* out of phase. This is how we power large appliances alongside all our 120v devices - the large appliances use L2 as the neutral/return, so to speak.
The camper is also fed the split phase current over 2 hot legs (L1 and L2) and it also gets the white neutral/return. There is a 4th conductor in the ground wire that is also fed to the system. In my case, L1, L2, and N are on a 3-pole 50a breaker inside the camper and the ground is just hard wired thru.
The measurement I took earlier was likely faulty as I tried to clamp all 3 conductors at once. Just now I clamped L1 and neutral (the MP2 only uses L1 to charge and there are no AC loads) and I read 120ma which is inline with my prior measurement.
It’s odd because the RV is obviously on tires and the jack is resting on a plastic stand - it is completely isolated from ground, as far as I can tell.
I tried clamping all three again just now and, while I’m not 100% sure its accurate, I did read over 100ma. It read zero at first - I think there is an issue with getting the clamp to close in the tight space I’m working in. I held it shut and ultimately picked up a high reading of over 100ma.
If it is accurate, then I don’t know where that large of an imbalance is coming from.
None of this makes sense to me really - and I’m starting wonder how much misinformation is out there.
For instance, at 100ma (or even half that) I would expect the GFCI to trip immediately and not stay closed for up to a minute or more.
What’s curious is I’m not measuring any ground current at all by shunting or clamping the ground wire but I’m measuring a fairly high imbalance between the hot and neutral. And even more curious is going on a few hours now, the ground is completely lifted so the GFCI is only seeing hot and neutral and is happy as a clam. I’m currently charging the battery with about 12amps and running the refrigerator as well. No GFCI trips.
I have done quite a bit of work on marine systems that are tripping in Australia and I can guarantee that it is relatively simple to understand once you can measure the leakage. Marine systems are prone to this because sometimes, large boats with quite complex and extensive electrical systems are fed from one single outlet on the dock.
In Australia that outlet is protected by a 30mA RCD. A 30mA RCD can trip at 15mA and still be within spec. In practice, we have found they trip at about 20-22mA. That does not occur in a house because the distribution board has several RCDs that protect a small section of the house. The entire house is not protected by one RCD like is the case for some large boats plugged into one outlet on the dock.
if we had a situation where the outlet at the dock had a trip level of 4-6mA we would not be able to keep power on any of the larger vessels. They all have larger leakage than that. That is not a critisism, it is not a fault, it is not a problem needing fixing. It is just very simple mathematics.
I understand how they do it in Australia but that is irrelevant to my situation. FYI, RVs also need to have GFCIs on most of their branch circuits. It just so happens that we also have to feed power from a GFCI when parked at our home. I know this causes problems when two GFCIs are on the same circuit which is why I have those branches turned off in the RV.
I’m beginning to suspect that the RV’s AC distribution panel being tied to PE in one place and the MP2 being tied to PE in another is causing the issue. They are literally only a few feet apart but if the resistance is high enough, some capacitance could be forming between them. It’s worth running a wire to find out so I’ll try.
It’s not unlikely that you might not have any issues with your rv ac panel at all. This is a common issue for the mp2 120v devices. A simple Google search comes up with many results of the same. If they were all user/installation error related, Victron would have been proactive in squashing any rumors to the contrary, but they have not. I believe they are actually the one that suggested it may be because of the low trip threshold for the North American GFCI. I may be wrong about that, my memory sometimes is not kind.
I have installed a lot of these units in the US and many of them exhibit the same behavior. I have went so far as to connect several mp2 devices (over a period of a few years worth of installations) directly to a GFCI outlet in my main power pedestal, with nothing connected on the output side of the multi, and still it trips within a minute or so. This tells me that the leakage is within the multi. There is a fellow and I can’t remember who, that claims they are all installer error and he will guarantee that he can connect any mp2 to a GFCI on his bench and it will work just fine. My opinion is either his GFCI has a much higher threshold than the 4 - 6 ma, or I call bs.
I’m not an electrical engineer, quite the contrary, but I’m beginning to understand what might be a working theory for my scenario.
The majority of the MP units installed in RVs aren’t installed near the original AC panel but close to the batteries, as recommended. This means the AC panel is grounded in one place and the MP is likely grounded somewhere else. My theory is the MP creates leakage downstream through its ground switching or through its normal course of operation. The GFCI measures the delta between hot and neutral, not ground. When the MP is operated and the circuit is connected to the GFCI ground, the leakage builds and slowly exceeds the threshold. When you lift the ground through a 3-to-2 prong adapter, the RV behaves like a capacitor because of the resistance between the 2 PE bonds and slowly charges but eventually the potential becomes too great and forces the leakage current back to draining through neutral. This obviously makes me a little a uncomfortable but I’ve taken direct measurements from the ground line and detected no dangerous currents. Furthermore, the circuits within the camper are mostly protected from branch lines on their own GFCIs. This tracks because plugged into a proper RV pedestal at a campground, there is no GFCI on the 30a and 50a connections - the MP2 is perfectly happy to pass all of its capacitive leakage to neutral or ground without the GFCI gatekeeping the current.
I’m obviously very bad at explaining things so I apologise for that. I will have another shot.
If you connect one device to the 5mA trip GFCI, it will work ok as the single device will have a low level (but measurable) of leakage current.
If you connect 20 of those same devices to the 5mA GFCI, it will trip because they all have a little leakage current and they add up to be above the 5mA trip level.
The reason the Campgrounds do not have GFCI set at 5mA on their outlets is they know for a fact they will trip.
