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leander avatar image
leander asked

RCD Keeps Tripping

Hi,

We have a Multiplus 24/3000/70. Our "mains" supply comes from a community hydro-electric turbine (that supplies 9 households) which generally supplies between 500w and 2kw to each household. We also have a battery bank for Power Assist and also when the hydro trips/stops working.

The mains/hydro (240v, 50Hz) supply comes through a white box that contains a 30mA RCD and then through to the inverter and than out to a consumer unit and onwards to the house.

This system has been running very well since it was first installed in the summer of 2018. However, in recent weeks the RCD in the white box has been tripping several times a day. We have replaced the RCD with a new one but are still having problems with the tripping. Our electrician has said that he thinks our inverter, while operating quite normally, is leaking current to earth which is causing the sensitive RCD to trip. He would like to know what value of RCD is recommended by Victron (he suspects it will be 100mA)? Can anyone help?

Just one other thing, our hydro-electric turbine has just collapsed this week (new bearings needed...or some other mechanical issue). I was wondering if, in the weeks preceding the collapse of the turbine, it wasn't running well and causing fluctuations in frequency/voltage/current and it was these fluctuations causing the RCD to trip....although, having said this, none of the other households fed linked to the hydro seemed to be having issues.

Thank you.

Best wishes,

Leander





MultiPlus Quattro Inverter Charger
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Alexandra avatar image Alexandra ♦ commented ·

@Leander

RDC tripping happens when there is current where it is not supposed to be. It can be caused by a poor earth neutral bond, if that is how your house is wired. Corrosion can set in anywhere. It is possible your house has the least path of resistance to earth which is why you experienced an issue and no one else did.

That being said motors not in great condition leak current to earth also causing RCD tripping. We had a generator do this on a site also was developing a faulty when the RCD started tripping it also ran a bearing about a week later. Hydro is basically a motor so that may be the cause. A pump not in great condition on the output of the inverter can also cause RCD tripping

Its an easy check to see if there is an earth neutral leak anyway, a multi meter between the two points will tell you.

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seb71 avatar image seb71 Alexandra ♦ commented ·

Earth faults happening somewhere before (upstream) the RCD won't trip it.

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leander avatar image leander seb71 commented ·

Hi @Alexandra and @seb71, thank you so much for your responses. I'm a little unsure of how these threads work so I've already replied to one comment below which no doubt you can see. So, as you can see, the hydro-turbine is now back up and running and, whilst we had a trip almost immediately after it came back on, it now seems to be running smoothly. The plot thickens and we wait to see what happens next....hopefully nothing! Thank you once again.

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5 Answers
wkirby avatar image
wkirby answered ·

I presume that the RCD is upstream of the MultiPlus?
Did your electrician test the MultiPlus? They would perform an earth leakage test at the AC-IN and AC-OUT with the MultiPlus completely disconnected. What were the test results?

When the MultiPlus is connected to the main supply (incoming hydro supply to your house) it will be in pass through mode. This means that anything downstream of the RCD which is leaking current to earth will cause your RCD to trip. This includes anything connected to the output of the MultiPlus. Any of your house wiring or appliances could be causing the fault.
Do you have an RCD on the output of the MultiPlus? You should have an RCD at the output of the MultiPlus so that when the MultiPlus is running from battery, you still have earth leakage protection to your house wiring and appliances. In battery mode the incoming supply is disconnected that the upstream RCD is not functional.

RCD ratings should be chosen to provide discrimination, dependent upon the electrical wiring rules for your region. As a stand alone appliance, a 30mA RCD would be fine for the MultiPlus, it should not leak any earth current. Tests should be conducted to prove this.
However, you should have 30mA RCD's downstream of the MultiPlus, so the upstream RCD should be chosen to provide discrimination. Your electrician should know the rules for RCD discrimination.

Sorry for the 20 questions, but earth faults are difficult to diagnose.

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leander avatar image
leander answered ·

Hi wkirby,

Thank you so much for your response. I shall endeavour to answer your questions. However, before I go any further, you should know that the hydro-turbine was fixed and came back on-line last night at about 19.30. Following this the RCD did trip within about 20 minutes of the hydro coming back on. However, since I re-set the RCD it's been just fine. So, everything has been running smoothly for about 17 hours now (prior to the hydro turbine collapse we were having to re-set the RCD about once every hour or so). So, I'm beginning to wonder if the RCD tripping has had something to do with the how the turbine has been running.

So, onto the questions.

Yes, the RCD is upstream of the Multiplus

No, the electrician has not tested the Multiplus (as far as I'm aware)

Yes we do have an RCD on the output of the Multiplus. Well, in fact, we have a consumer unit with an array of 9 30mA RCDs, each for a different circuit in the house.

I shall forward your response to our electrician. However, in the mean time, everything seems to be running smoothly and we wait with bated breath to see what happens in the next 24 hours or so.

Thank you once again,

Leander

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klim8skeptic avatar image klim8skeptic ♦ commented ·

I am not so sure that serially stacking RC's is a good idea. (RCD on both input and output of the multi)


easysolar.jpg

Surely an RCD on the input of a multi is going to trip when GROUND RELAY in the multi connects N to PE.

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easysolar.jpg (57.1 KiB)
wkirby avatar image wkirby ♦♦ klim8skeptic ♦ commented ·

RCD's in series can be done as long as there is discrimination so the the downstream one will operate first. I asked the OP to ask their electrician about this. The rules vary per region.

The ground relay closes after the backfeed relay opens. So, the ground relay will not affect the upstream RCD.

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leander avatar image leander wkirby ♦♦ commented ·

Hi, Thank you once again for all the info. I'll forward it all to our electrician.

Since yesterday our RCD has tripped about four times. This is less frequently than it was tripping before but it still needs to be sorted out.

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klim8skeptic avatar image klim8skeptic ♦ wkirby ♦♦ commented ·

"RCD's in series can be done as long as there is discrimination so the the downstream one will operate first. I asked the OP to ask their electrician about this. The rules vary per region "

RCD's are a bit funny.

9 rcd's on the output could each contribute 4ma leakage... before tripping the input rcd.

Earth to Neutral leakage will also trip rcd/rcbo.

KISS is important. Maximum protection on the output, nominal protection on the input.

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seb71 avatar image
seb71 answered ·

You said you have a consumer unit with nine 30mA RCD for house circuits.

Downstream of the Multiplus, besides those nine circuits, are there additional circuits, without RCDs (only with MCBs)?

-------

The RCD which trips (the one upstream the Multiplus) is an RCCB or an RCBO?


30mA might be too sensitive, but on the other hand you said you had no issues for years, until recently.

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leander avatar image
leander answered ·

There are no additional circuits without an RCD. The 9 RCDs in the consumer unit are RCBOs.

The upstream RCD that keeps tripping is an RCCB.

We used to live in temporary accommodation before we built the house we live in now. We had no consumer unit in the temporary accommodation...just a line in from the white box (with the RCD) and two sockets on the end of the line.

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seb71 avatar image seb71 commented ·

Ah, this changes things.

So the RCD tripping coincided with your move from the temporary home to the permanent home, if I understood correctly.


One possible cause is that on each circuit (or on several circuits) you might have small earth leaks which do not trip those 30mA RCBO, but combined they do trip the upstream RCCB, which is also 30mA.


If that is the cause, the solution would be to replace the upstream 30mA RCCB with an 300mA RCCB (for selectivity). Maybe even a type S one (time delayed).

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leander avatar image leander seb71 commented ·

The timing of the tripping doesn't tie in as neatly as one would like with the move from the temporary home to the permanent home. We moved in to the permanent home about two and a half years ago. At that point we had the Multiplus and consumer unit (but at that time we only had about 4 circuits with RCBOs....further circuits have been added since so that we had the full nine by about a year or so ago).

The tripping has only really started in the last few weeks but the idea of earth leakage from all or some of the circuits seems to fit, although I'm not sure what would have prompted the tripping to start recently (I was wondering if humidity/dampness might be a factor...it's been very wet here of late) . Our electrician suspects the Multiplus is leaking to earth. He was thinking a 100mA RCCB would be recommended by Victron but it sounds as though a 300mA RCCB would be fine. Do Victron specify a particular size or does it depend on the regulations of the region you are in? We are in the UK.

Thank you once again,

Leander

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seb71 avatar image seb71 leander commented ·

Can you completely bypass the Multiplus and test if the upstream RCD still trips or not?

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spazpeker avatar image
spazpeker answered ·

My Multiplus II (x2 in parallel) also tripped when first installed, it worked fine without Grid but tripped as soon as the grid was connected, i too had multiple RCBO's on the output.

after reading everything on this community site i changed the input RCD to a screwfix

Wylex Lifeline 100A 100mA DP Type S Time Delay RCD (563HV)

now works perfectly.

i guess i must have some minor earth faults on multiple RCBO's that add up.

Thought i would post this for anyone else in a similar position

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