Inverter tripping shore power

[smileypete]

I have recently installed a Victron for someone on their boat, and it is showing the same symptoms. It was OK for the first 24 hours but now it trips the RCD at frequent intervals.

 

Amazingly it even trips the RCD which I fitted to the output side of the Victron, can anyone make any suggestions as to how this can even be possible? Particularly as there is at the moment nothing plugged in to any of the sockets, and also it is being operated in "Charger only" mode.

 

All is fine if the Victron is removed from the equation (by pulling out the 240v input and output plugs, and plugging them together) which seems to confirm that there is no fault anywhere else.

 

In this case it is a fairly old unit, model 12/800/35, but it has spent most of its life packaged in its box.

 

Is this one of the earlier models before the one with the potentially flaky NE bonding design?

 

If it is, first thing could be to check for loose connections on both upstream AND downstream of the RCD, these can cause strange tripping. Also if the install is a 2.5mm² ring on a 16A supply, try turning it into a radial, it might just help.

 

Failing that, try fitting a 'type A' RCD, these reportedly handle spikes and harmonics better than the more common 'Type AC' which most installs have, linky to one plus some discussion:

 

http://www.ebay.co.uk/itm/40-amp-2-pole-2-module-rcd-/121186430558?pt=UK_BOI_CircuitBreakers_RL

http://www.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=20624

 

As for the more modern Victron with the slow relay problem, I'm surprised they didn't just use a multipole relay to isolate the shoreline side and switch the NE bond in simultaneously. Maybe it's possible to retrofit a relay to do just that.

 

cheers, Pete.

~smpt~

[Keeping Up]

This gives me a few other things to look at, when I get the chance to revisit next week. I don't know the age of the unit I'm working on but I believe its previous owner got rid of it after a very short time because it kept causing problems, and it has hung around in a box for a while since then; plenty of time for a poor connection to have developed, I suppose. The manual shows a slightly different schematic (only one AC output) but it is essentially the same. I don't know of course whether or not the unit matches the manual that I found on-line; that manual suggests cutting the earth wire connection to the relay; but I don't intend to take any step that could leave the installation with no E/N bond when the inverter is on (I might do it on my own boat, but not on somebody else's)

 

The type A RCD may help but that means changing three RCDs, two on the boat and one on shore, which would be a significant expense to incur if it proved not to have the desired effect. It's questionable whether I'd even be allowed to change the one on shore; I'd need to be pretty certain of my ground (pun intended!) before doing that.

 

The slow relay may be part of the problem, but probably isn't all of it because the RCDs have been known to trip themselves when the unit has been operating in a stable state for a few hours; unless of course the supply itself is subject to short breaks.

 

I'm puzzled that even the RCD on the output side is tripping, given that it is so far feeding not a ring main but just 6ft of wire with a socket at the end. I have a suspicion that an extension lead may have been plugged in to the socket, albeit with nothing else plugged into the end of it, so I will need to check that lead. It may be a complete red herring though.

 

I slightly suspect high-frequency signals, or surges, or something like that, and I am wondering if a rearrangement of the way the earth is bonded to the hull might make a difference, and also whether a couple of strategically placed RFI filters might help (with or without them having a connection to earth ???).

[smileypete]

I understand that the old Victron combi had no N/E bonding at all; plugging a basic socket tester into the output when the shoreline is disconnected and the inverter is running should tell if the earth is connected, or use a multimeter between N and E.

 

If it is a later unit with the slow internal N/E bonding relay it probably won't be cured by changing RCDs, also that doesn't explain the random trips when the unit has been on for some time, though there may be two separate problems.

 

To do the N/E bonding externally I'd consider using a multipole changeover relay with the coil powered by the shoreline inlet; 2 poles would connect the shoreline inlet L and N to the unit, and the opposite contact of the other pole would bond between N and E on the output of the unit.

 

But (disclaimer) this is something I'd recommend is only done by a qualified electrician or someone equally competent, who can fully understand the install and what they're doing, and take responsibility for it. (disclaimer over)

 

Looking for loose connections would be a good start, had a neighbour with nightmare random RCD trips which turned out to be a loose connection in the shoreline bollard, tap the bollard and RCD tripped, QED

 

cheers, Pete.

~smpt~

Edited October 13, 2013 by smileypete

[by'eck]

 

As for the more modern Victron with the slow relay problem, I'm surprised they didn't just use a multipole relay to isolate the shoreline side and switch the NE bond in simultaneously. Maybe it's possible to retrofit a relay to do just that.

 

cheers, Pete.

~smpt~

 

Quoting from the Victron manual again

 

With this relay (H), the neutral conductor of the AC output is grounded to the chassis when the back feed safety relay is open.

 

 

I am assuming this backfeed safety relay is the commonly referred to pass through relay. The suggestion is that this then triggers the N/E relay.

 

I'm sure your suggestion of using a multi-pole relay would provide a solution. Three poles to make/break the shore power L, N, & PE and a fourth to break/make the N/E inverter link - all operated simultaneously.

[smileypete]

 

I'm sure your suggestion of using a multi-pole relay would provide a solution. Three poles to make/break the shore power L, N, & PE and a fourth to break/make the N/E inverter link - all operated simultaneously.

 

You shouldn't need to break the shoreline E if you break both the shoreline L and N.

 

If you like you could use two contacts to break the shoreline L and N, one to common the output N and E, and one to enable the output L.

 

That way if the relay fails to operate, the output from the inverter is disabled, instead of getting an output without the N to E bonding.

 

cheers, Pete.

~smpt~

Edited October 13, 2013 by smileypete

[by'eck]

 

You shouldn't need to break the shoreline E if you break both the shoreline L and N.

 

If you like you could use two contacts to break the shoreline L and N, one to common the output N and E, and one to enable the output L.

 

That way if the relay fails to operate, the output from the inverter is disabled, instead of getting an output without the N to E bonding.

 

cheers, Pete.

~smpt~

 

Fair point regarding breaking shoreline cable earth since thinking about it, it will be connected to hull anyway.

 

I think a more relevant issue though is to ensure that the inverter can't possibly fire up if the shoreline power is present whether relay has failed or not.

 

I'm not denying the importance of N/E connection either though.

Edited October 13, 2013 by by'eck

[NBDensie]

 

Fair point regarding breaking shoreline cable earth since thinking about it, it will be connected to hull anyway.

 

I think a more relevant issue though is to ensure that the inverter can't possibly fire up if the shoreline power is present whether relay has failed or not.

 

I'm not denying the importance of N/E connection either though.

I dont know if it's relevant but dont forget these boxes are inverter chargers. If they are plugged into the shoreline the charger side will trickle charge the engine battery and do clever multistage charging things to the domestic batteries.

[smileypete]

 

Fair point regarding breaking shoreline cable earth since thinking about it, it will be connected to hull anyway.

 

I think a more relevant issue though is to ensure that the inverter can't possibly fire up if the shoreline power is present whether relay has failed or not.

 

I'm not denying the importance of N/E connection either though.

 

Not sure what you mean; thought we were talking about a problem with an inverter/combi with passthrough. Part of the problem may be it's passing shore power through before the internal N/E bond relay is opened in time.

 

cheers, Pete.

~smpt~

[by'eck]

 

Not sure what you mean; thought we were talking about a problem with an inverter/combi with passthrough. Part of the problem may be it's passing shore power through before the internal N/E bond relay is opened in time.

 

cheers, Pete.

~smpt~

 

Hi Pete,

 

Sorry, yes misinterpreted which relay you were referring to since there at least two involved.

 

Coming back to the issue, I wonder given the number of cases on this thread alone, why Victron have not tackled it since they seem aware. No similar problems with Sterling or Mastervolt Combi's with auto N/E bonding it seems.

[smileypete]

 

Hi Pete,

 

Sorry, yes misinterpreted which relay you were referring to since there at least two involved.

 

Coming back to the issue, I wonder given the number of cases on this thread alone, why Victron have not tackled it since they seem aware. No similar problems with Sterling or Mastervolt Combi's with auto N/E bonding it seems.

 

No problem, was just trying to come up with a workaround using an external relay, for the early Victrons without auto N/E bonding or the later ones with a slow N/E bonding relay that needed disabling. But thinking about it...

 

 

If you like you could use two contacts to break the shoreline L and N, one to common the output N and E, and one to enable the output L.

 

using a 4th contact on the relay won't work that way, you wouldn't have any output when the shoreline is on, doh!

 

S'pose the way to do it would be use 2 contacts to switch L and N for the loads between the shoreline input and combi output, and one contact to switch the combi output N/E bond in.

 

A fourth contact could be used to switch out L for the loads you only want to run on shoreline, it could also switch in a warning neon to tell you the inverter is on.

 

cheers, Pete.

~smpt~

Edited October 14, 2013 by smileypete

[GUMPY]

All I had on my old victron was a 230v relay NC between N& E . Apply shore power and it opened.

Direct loads didn't go the inverter

[Keeping Up]

I visited the boat again today, here is a quick summary of what I found.

 

The boat had been moved to a different shore supply for 4 days. Here, if it could be made to switch on without any RCDs tripping, then the on-shore and inlet RCDs remained stayed switched on - although the one on the Victron output did once trip overnight. This strongly suggested that the original shore supply may have problems because on that supply it would always trip everything out several times each day (or more particularly, each night)

 

There was no apparent problem with the Victron's connector to the control board - a quick waggle did not cause anything to change. A N/E bonding relay was obviously fitted to the unit.

 

Switching on, all three RCDs would usually (but not always) trip; that is the one on the Victron output, the one on the shoreline inlet, and the one on shore. The one on the Victron output would even trip if its output cable was disconnected. If it had not tripped, pressing its test button caused all three RCDs to trip. Changing out the RCD for a better quality one, seems to have completely cured this issue. The cheap RCD may have been faulty, or perhaps its construction meant that although it was well-balanced at 50 Hz, it was inherently unbalanced at higher frequencies so that any surges or switching transients would trip it; and if this was the case, maybe this would in fact unbalance the whole system enough to trip the other two RCDs.

 

Almost every time, switching the Victron off from its front panel switch, would trip the inlet and on-shore RCDs. I suspect that the N/E bonding relay is slow to release, but I couldn't prove that or even test for it. It is just possible that the front panel switch (which certainly does not have a positive feel to it) makes intermittent contact as it opens, causing a brief chatter from the relay, but again I couldn't test for that. Instead, an alternative regime of always first switching off the incoming mains at the garage unit which precedes the Victron, completely cures this issue.

 

When I left it, the system felt as if it was completely stable. No amount of switching appliances off, or plugging and unplugging the shore line, caused a false trip. It remains to be seen whether it will remain stable with time on this supply, and what will happen in a few weeks time when it is reconnected to is original shore supply.

[smileypete]

Well done, good result!

 

If you have more problems it might be worth checking which way round the RCDs are wired, usually the top terminals go to supply and the bottom two go to loads. It may not always matter but am not 100% sure it makes no difference.

 

The problems with the original shore RCD may well be a loose connection inside the bollard etc.

 

cheers, Pete.

~smpt~

Edited October 17, 2013 by smileypete

[Keeping Up]

Good points Pete.

 

I know the RCDs inside the boat are wired the right way round since I fitted them myself, but I can't tell about the on-shore one. Nor can I test the original shore supply for loose connections, the moorings owner won't allow boaters to have access to the cupboard where they are housed, not even to reset it when it trips (which is a problem if the RCD keeps tripping intermittently, especially as all the boats there share the same RCD which is certainly not an ideal situation!)

[WotEver]

S'pose the way to do it would be use 2 contacts to switch L and N for the loads between the shoreline input and combi output, and one contact to switch the combi output N/E bond in.

 

A fourth contact could be used to switch out L for the loads you only want to run on shoreline, it could also switch in a warning neon to tell you the inverter is on.

 

That appears to be exactly what the diagram in post #10 shows.

 

That diagram is poor in that it doesn't show either how the relay is energised, nor which contacts are NO and which are NC.

 

Tony

[smileypete]

 

That appears to be exactly what the diagram in post #10 shows.

 

That diagram is poor in that it doesn't show either how the relay is energised, nor which contacts are NO and which are NC.

 

No, what the diagram shows and what I said in post #35 are about as different as they can be.

 

cheers, Pete.

~smpt~

Edited October 18, 2013 by smileypete