question

boater avatar image
boater asked

"Ground Relay" Setting

Multiplus 12/3000, installed on a boat. When I connect the boat to shore power, I trip the GFCI when attempting to turn on the multiplus. Everything else on the boat works fine without tripping the GFCI. The multiplus behaves fine when operated by the onboard AC generator or an external shorepower AC source without a GFCI breaker.

I want understand why this is happening. That has got me curious about the 'Ground relay' option, which I have left in the default 'on' state.

As I understand it, this relay should open when the multiplus is connected to an external AC source. Do I have this right? Does it open before drawing power or might it be closed for a split second when first connected to AC and thus causing the neutral of the AC to be tied into the boats grounding system and tripping the GFCI?

I also have the option 'PowerAssist' set to the 'on' state. Does this option affect the way the 'Ground relay' functions? Perhaps it never opens, even when connected to AC when the 'PowerAssist' option is set to 'on' as the unit is 'always' read to invert?

Thanks

Multiplus-II
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

8 Answers
Alexandra avatar image
Alexandra answered ·

@Boater

The ground relay is closed when inverting to make its own neutral earth link for the safety circuits to work.

It opens once the inverter has established whether the incoming power meets parameters for connection.

Power assist does not affect the relay open and close. Power assist means power is added from your baterry for a load if needed to prevent overloading or tripping the incoming breaker.

More on each function can be found here.

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

boater avatar image
boater answered ·

Thanks much for your reply. I still need a bit more clarification because it seems that something still doesn't quite make sense.

If ground relay operation is dependent on whether the inverter is inverting, and Power assist affects when the inverter is inverts, wouldn't Power assist necessarily affect ground relay operation?

I guess I could ask the question a different way. With both Power assist and Ground relay options ON, does the inverter tie neutral to ground when connected to AC and the inverter is assisting (inverting)?

7 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Alexandra avatar image Alexandra ♦ commented ·

@Boater

Power assist only works when you have a grid connection.

Ground relay only works when you are disconnected from grid.

Usually with power assist it will be because I have set my inverter to a 4amp input, the load I am switching on is a 10amp load. The inverter then uses the battery to assist the power restricted inout to keep the load running. At this point the ground relay is not connected.

If the inverter is power assisting on connect then maybe it is worth switching it off? To test your theory there, since obviously disabling the ground relay is not an option. But i do doubt that that is an issue

0 Likes 0 ·
boater avatar image boater Alexandra ♦ commented ·

Thank you again for taking the time to help.

So it appears that your original statement that the ground relay ties neutral to ground when inverting was incomplete--it seems that it ties neutral to ground when inverting and not in the Power assist state--i.e. when inverting and not tied to external AC. Correct?

0 Likes 0 ·
Alexandra avatar image Alexandra ♦ boater commented ·

There is a short video here that explains power assist more.

Inverting and power assist are two different states.

Power assist can only happen with you are connected to and using a limited grid/shore connection. yes power assist uses power from the battery but it is not in inverter mode.

Inverting (or inverter only use) is battery only use (no grid involved - possibly with solar if you have any) and the time the ground relay is closed.


This document also explains about the Power Assist functionality;

https://www.victronenergy.com/upload/documents/White-paper-Achieving-the-impossible-EN.pdf


0 Likes 0 ·
boater avatar image boater Alexandra ♦ commented ·

Thanks again for your reply. I'm learning more about the system which is great.

However, you appear to be confusing 'inverter mode' with 'inverting'. When the device is in PowerAssist mode, the way it "uses power from the battery" when needed is by inverting the DC battery power into AC power. This is detailed in Example 2.4 in the document you referenced "...The bidirectional converter starts operating as inverter... "

I was happy to read more detail about the PowerAssist mode and how it works but even that document doesn't describe how the Ground relay functionality works when in PowerAssist mode and inverting. It would seem that PowerAssist mode likely deactivates Ground relay functionality, even when inverting, but it's still not clear to me.

Sorry for being so particular, it's my nature. I do appreciate the help.

0 Likes 0 ·
Alexandra avatar image Alexandra ♦ boater commented ·

I hear what you are saying, however if there is power coming into the AC (and you have not selected inverter only on the GX or DMC) that ground relay is open. It does not make the connection again until you have disconnected either physically or through the GX.

And even though it is using power from battery to aid your incoming current limit it is not fully inverting (it is synchronised and connected to the grid/shore -ground relay open) it is power assisting.

If the GFCI is tripping during use like this then an appliance (maybe triac based or another funny speed or temperature control) is leaking power to ground and causing it to trip. Or it could just be very sensitive.

0 Likes 0 ·
boater avatar image boater Alexandra ♦ commented ·
Good to know the Ground relay is not connecting neutral to ground while in PowerAssist mode.

I (and the literature you reference) disagree with your statement that it isn't "fully inverting" during power assist. Yes it synchronizes its inverter output with the incoming AC waveform, but this does not mean it is not inverting.

As stated previously, when the MultiPlus is removed from the circuit the GFCI does not trip. It is something that the MultiPlus is 'doing' or the way interacts with something else in the system that is causing the trip.

0 Likes 0 ·
Alexandra avatar image Alexandra ♦ boater commented ·
When a Victron inverter is invertering, it is making its own sine wave and setting its own operating output voltage.


When it is connected to an input source it is synchronizing with the source, two different operations. It may also be using the battery as a source for power assisting, but it is not 'fully inverting'. (there is probably a better term for it - but i don't know it)

When synchronised if the voltage is lower or if the frequeancy is unstable you experience the instability in the house loads.

0 Likes 0 ·
Alexandra avatar image
Alexandra answered ·

@Boater

There are quite a few threads on here which pretty much say the same thing.

There must be an issue you have not oicked up yet with wiring or an appliance.

I will start you off on one here.

4 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

boater avatar image boater commented ·
Thanks. I have read that and other threads--all helpful but none quite like my particular case. In my case I have isolated the cause to the Multiplus itself. If I bypass the Multiplus I can operate everything without tripping the GFCI. When the Multiplus is powered on, even in charge-only mode, as soon as you hear the relays in the Multiplus click, the GFCI trips.

My approach to solving the problem is to learn as much as practically feasible about the unit. The Ground relay operation is not described in the manual with enough detail to fully understand it, hence my questions.

Just because I ask about details regarding the Ground relay operation does not mean that I think it is the cause but rather that because I do not understand its operation, I cannot rule it out as the cause, hence my desire to learn about those details.

0 Likes 0 ·
kevgermany avatar image kevgermany ♦♦ boater commented ·
Touch of extra knowledge for you. May be a red herring. The multi has big capacitors which need to charge on startup. This causes quite a high inrush current. Could this be part of the problem?
0 Likes 0 ·
boater avatar image boater kevgermany ♦♦ commented ·
Thanks for chiming in, that is an interesting thought. However, it is not tripping the over current breaker, just the GFCI. I have tried it with 50A, 30A, and 15A service w/and w/out GFCI protection and the fault always follows the GFCI.

I suppose I could 'charge' the caps by plugging into a non-GFCI outlet w/the Multiplus powered up and then quickly switch over to GFCI power and see if it still trips.

HOWEVER, your post did give me reason to think a bit more--I always utilize the input current limit on the Multi Control panel. Typically, I have it set low, to something around 5A by default. I do now wonder if I am regularly going into PowerAssist mode when powering the MultiPlus on (for reasons you stated) and the MultiPlus is using current from the batteries to charge the caps (meaning it is inverting), which may activate the Ground relay function. You've definitely given me something to try.

I also intend to play around with the PowerAssist and Ground relay options to see if they have any impact--I will start by deactivating both of them and then one at a time to see if this teaches me anything.

0 Likes 0 ·
kevgermany avatar image kevgermany ♦♦ boater commented ·
Another thought. Devices with high start up currents, like microwaves can also cause the problem. Maybe the GFCI is over sensitive, are other types available?
0 Likes 0 ·
Alexandra avatar image
Alexandra answered ·

@Boater

If the relay in orange is closed the one in yellow is open. The yellow one is the ground relay.

screenshot-20221122-062257.jpg


screenshot-20221122-062257.jpg (177.7 KiB)
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

sharpener avatar image
sharpener answered ·

And to comply with type approval requirements the ground relay does not make contact until just after the backfeed relay opens (since I hear you ask @Boater) so there is no point in time when both are closed.

2 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

boater avatar image boater commented ·
Thanks for the response...this is the essence of my question. Is this information detailed anywhere in the documentation? It makes sense that this is how it would behave.
0 Likes 0 ·
sharpener avatar image sharpener boater commented ·

Not to my certain knowledge, maybe somewhere like "Wiring Unlimited"? I have looked through the Type Approval certificate VICEN_02691_201124090551.pdf and there is no mention of it I can see.

But it has to be true or it would trip my RCD, which does not happen.

0 Likes 0 ·
lorenzoit avatar image
lorenzoit answered ·

Good morning, I think your system configuration is perfect and you don't need to make any changes. When you connect your system to shore power, there would be no problems with the position of N and L if only normal charged loads were present inside your boat (or camper) such as a battery charger, a hair dryer, microwaves, etc. Even if there was an inverter connected to the battery there would be no problems. But inside your system there is also an inverter combined with the charger. When using your multiplus appliance, your installer has RIGHTLY installed a 0.03 A differential which is needed for your safety. It should always be installed on all inverters ( even if they are not combi ) This output differential to be installed correctly must be CONNECTED WITH THE NEUTRAL AND THE CHASSIS TOGETHER ) . Only in this way and safe, I have seen many installations where the L-N outputs are connected to the L-N inputs, but this way is useless. Your multiplus appliance therefore needs, being combined with an inverter, that the inputs (L - N) be respected. When you connect to Shore power, I imagine you are using a non-reversible industrial plug. You can't know the position of L-N if it's wired the right way or the same as yours. So if you only use the battery charger function you won't have any problems, in this case the position of the terminals doesn't matter, but as soon as the inverter turns on, output N is put in communication with the chassis and with the ground of the plug where you are connected. (shore power). If the plug is against your L it becomes N and N becomes L . The consequence is that L is connected to ground and the RCD trips. To solve this problem I think you need to have a reversible plug, where you can easily change your connection. Or equip yourself with two power cables and before connecting, check where the L is with a phase finder (like a pen that plays). You must not exclude the security that vicron has within its multiplus.

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

lorenzoit avatar image
lorenzoit answered ·

Good morning, I think your system configuration is perfect and you don't need to make any changes. When you connect your system to shore power, there would be no problems with the position of N and L if only normal charged loads were present inside your boat (or camper) such as a battery charger, a hair dryer, microwaves, etc. Even if there was an inverter connected to the battery there would be no problems. But inside your system there is also an inverter combined with the charger. When using your multiplus appliance, your installer has RIGHTLY installed a 0.03 A differential which is needed for your safety. It should always be installed on all inverters ( even if they are not combi ) This differential to be installed correctly must be CONNECTED WITH THE NEUTRAL AND THE CHASSIS TOGETHER ) . Only in this way and safe, I have seen many installations where the L-N outputs are connected to the L-N inputs, but this way is useless. Your multiplus appliance therefore needs, being combined with an inverter, that the inputs (L - N) be respected. When you connect to Shore power, I imagine you are using a non-reversible industrial plug. You can't know the position of L-N if it's wired the right way or the same as yours. So if you only use the battery charger function you won't have any problems, in this case the position of the terminals doesn't matter, but as soon as the inverter turns on, output N is put in communication with the chassis and with the ground of the plug where you are connected. (shore power). If the plug is against your L it becomes N and N becomes L . The consequence is that L is connected to ground and the RCD trips. To solve this problem I think you need to have a reversible plug, where you can easily change your connection. Or equip yourself with two power cables and before connecting, check where the L is with a phase finder (like a pen that plays). You must not exclude the security that vicron has within its multiplus.

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

calbak avatar image
calbak answered ·

Hi Boater, did you find the problem? I have exactly the same thing happening on a new Multiplus install and it has me and my electrician stumped!

1 comment
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

boater avatar image boater commented ·
It is the offseason where I am, so I have not. It is on my list of things to address before the boat is launched. Fortunately, I have access to both GFCI and non-GFCI outlets next to the boat that will help me troubleshoot.


This item is on my list, just hasn't made it to the top yet. I will be sure to follow-up on this thread. If you find the culprit before me, please update the thread.


Good luck.

0 Likes 0 ·