DC current leakage problem

[Dr Bob]

Anyone help with a DC current leakage problem. We have recently started to use our marina berth a bit more and connected to shore power via a galvanic isolator - a cheap one, see photo below. Now the pram cover is up, I can see there is a faint glow in one of the LED's indicating dc current leakage (never saw it in the summer on the few occasions we used it). The battery to earth connections seem fine and the earth connector on the Victron Multi (charger/inverter) 12V 2000W - probably 10 years old - I havent checked as not sure how to get to it.

One observation though, when I plug into shore power with the victron off,  there is no LED on. When the victron turns on, there is no LED until the battery charger lights come on (bulk, float etc) but there is power to the 240V boat electrics in the 30 secs or so before the battery charger fires up. Does this point to the battery charger being at fault? I think I need a qualified electrician to come and look it over. In the meantime is a faint glow in the LED a signal to keep the shore power disconected most of the time - dont want the boat dissolving away? How reliable are these LED diodes and how do I measure a current or voltage in the earth line of the shore power?

On the photo, it is the  top right LED that is lighting.Could it indicate current flow from the shore power up the earth wire or is it always a fault on the boat?

Any recommendations for a good electrical engineer in the Braunston/Napton area?

[dmr]

Its possible that a faint glow might be normal acceptable operation and indeed confirmation that the GI is doing its stuff.

It looks like you GI does not give direct access to its incoming and outgoing earths which is sad. Whenever I use a shoreline (which is probably only once or twice each year) I measure the voltage, both AC and DC, across the GI.

Essential the GI is back to back series diodes so will block or disconnect the earth wire till a voltage of about 1.2 is present at which point it connects the earth wire (the diodes start to conduct). As long as this voltage is significantly below 1.2 volts then you are protected, but are also warned that "stuff is going on" and you might be in trouble if you didn't have the GI fitted.  I have seen up to 800mV at one marina.

I don't understand exactly why the LED glows only when you have stuff turned on. It might just be that your charger is leaky and causing an earth current to flow, its also possible that its drawing a fair bit of current and somehow causing an earth potential issue with the marina supply. Can you turn on a hair-drier or other high current device and see what that does?

These things can be quite difficult to track down so as long as you are well below the 1.2v threshold its probably not worth spending a lot of money on an "engineer". If you do need help then a good qualified electrician who understands outdoor installations might be better than a boat "engineer", who at worse might be a semi skilled mechanic/filter changer who know a bit about wiring.

..............Dave

[Flyboy]

27 minutes ago, Dr Bob said:

Anyone help with a DC current leakage problem. We have recently started to use our marina berth a bit more and connected to shore power via a galvanic isolator - a cheap one, see photo below. Now the pram cover is up, I can see there is a faint glow in one of the LED's indicating dc current leakage (never saw it in the summer on the few occasions we used it). The battery to earth connections seem fine and the earth connector on the Victron Multi (charger/inverter) 12V 2000W - probably 10 years old - I havent checked as not sure how to get to it.

One observation though, when I plug into shore power with the victron off,  there is no LED on. When the victron turns on, there is no LED until the battery charger lights come on (bulk, float etc) but there is power to the 240V boat electrics in the 30 secs or so before the battery charger fires up. Does this point to the battery charger being at fault? I think I need a qualified electrician to come and look it over. In the meantime is a faint glow in the LED a signal to keep the shore power disconected most of the time - dont want the boat dissolving away? How reliable are these LED diodes and how do I measure a current or voltage in the earth line of the shore power?

On the photo, it is the  top right LED that is lighting.Could it indicate current flow from the shore power up the earth wire or is it always a fault on the boat?

Any recommendations for a good electrical engineer in the Braunston/Napton area?

 

Do you have a "Correct Polarity" light on your power panel?   Sometimes these consist of a neon connected between Live & Earth which will light when the polarity is correct. Obviously this would cause a small live/earth leakage and may be enough to cause your GI LED to light up. I've had this with a metered galvanic isolator showing a small earth leakage so I simply disconnected the neon indicator and no more leakage.

[Dr Bob]

Thanks Dave, that is useful. OK, no direct access to incoming and outgoing earths is bad. I guess I could try 2 things. Firstly take out the GI and in its place have a 3 core cable with the earth exposed so I measure the voltage down it. I assume here I would need to cut the earth wire and just connect a voltmeter to the two cut ends so the voltmeter is completing the earth circuit. I could then measure AC and DC volts on the multimeter. Second option is to leave the GI in place but expose the earth wires so they I can get a multimeter on the earth before and after the GI. What then would I be measuring. I would like to see in this case if the GI is working and is disconnecting the earth wire. Could i just expose the earth wire on the shore power side and use the boat earth as the other point to connect to?

I will try the high current draw (hair drier) next to see what it does.

[Dr Bob]

9 minutes ago, Flyboy said:

Do you have a "Correct Polarity" light on your power panel?   Sometimes these consist of a neon connected between Live & Earth which will light when the polarity is correct. Obviously this would cause a small live/earth leakage and may be enough to cause your GI LED to light up. I've had this with a metered galvanic isolator showing a small earth leakage so I simply disconnected the neon indicator and no more leakage.

Flyboy, the boat is 2002 built with a lot of the orginal systems still present but I have not been able to work out how they work. The AC distribution panel below has 4 lights but none ever come on. The breakers work! and the switch to the right delivers power (battery charging and 240V to the Victron Pheonix multi and then to the boat circuit) when in position 2 but in position 1 it only seems to activate the battery charger function of the victron as in this position there is no 240V on the boat circuit. 

There is also a Pheonix multi remote panel above it but this has no function at all and doesnt seem to be connected. I dont know if this is because a newer Victron combi was fitted and didnt work with the original remote panel - or if it is the original victron combi that was fitted to the boat as new and the panel has just given up.

 

[Dr Bob]

57 minutes ago, dmr said:

I don't understand exactly why the LED glows only when you have stuff turned on. It might just be that your charger is leaky and causing an earth current to flow, its also possible that its drawing a fair bit of current and somehow causing an earth potential issue with the marina supply. Can you turn on a hair-drier or other high current device and see what that does?

..............Dave

Dave, I tried turning a hair drier on but it had no effect on the glowing LED. To be clear, when the shore power is connected and feeding power to the boat for the 30 secs before the battery charger cuts in, the LED is not glowing. It is only when the battery charger lights come on that the glow starts, and the batteries are fully charged - been on shore power for 3 days - so the battery charger will not be taking too much current.

Not sure if you turn off the battery charger on the Victron pheonix multi off and just have the 240v going to the boat system.

[dmr]

49 minutes ago, Dr Bob said:

Thanks Dave, that is useful. OK, no direct access to incoming and outgoing earths is bad. I guess I could try 2 things. Firstly take out the GI and in its place have a 3 core cable with the earth exposed so I measure the voltage down it. I assume here I would need to cut the earth wire and just connect a voltmeter to the two cut ends so the voltmeter is completing the earth circuit. I could then measure AC and DC volts on the multimeter. Second option is to leave the GI in place but expose the earth wires so they I can get a multimeter on the earth before and after the GI. What then would I be measuring. I would like to see in this case if the GI is working and is disconnecting the earth wire. Could i just expose the earth wire on the shore power side and use the boat earth as the other point to connect to?

I will try the high current draw (hair drier) next to see what it does.

The earth coming out of the GI should go to boat earth so yes, you could measure here. You will need to somehow gain access to the earth wire going into the GI and obviously this carries all the usual warnings about messing about with the mains so take great care and get help as required. Once you've done the test then cover up the earth wire because even though its unlikely it could become live one day under certain fault conditions.

It sounds like the "problem" relates to the battery charger rather than a true "earth potential under heavy load". Modern electronics often have various filter components right across the mains input, and also chop up the incoming mains at a high frequency, and its possible that this or something similar is causing enough current to make the LED glow. LEDs can give a little glow with very low currents. GIs often include capacitors to try to handle this "modern electronics" issue. My guess is that nothing is wrong but I am just a jack of all trades electronic (ish) engineer rather than a specialist here. Looking at the voltage across the GI with a 'scope might be interesting but I have heard that some boats don't actually carry a 'scope.

..............Dave

[forsberg]

1 hour ago, Flyboy said:

Do you have a "Correct Polarity" light on your power panel?   Sometimes these consist of a neon connected between Live & Earth which will light when the polarity is correct. Obviously this would cause a small live/earth leakage and may be enough to cause your GI LED to light up. I've had this with a metered galvanic isolator showing a small earth leakage so I simply disconnected the neon indicator and no more leakage.

The above is one plausible reason.

As your polarity light perhaps do not work there is the possibility that you have neutral and live mixed up somewhere in your installation.

Check that Neutral and live are correct at the Victron.

Due to the EMC-directive some electronics may have supressor circuitry between Neutral and Ground which could have unwanted results if Live and Neutral are switched.

I would be surprised if the fault is in the Victron but a common electrician would probably make that assumtion as the Led goes on when the charger starts.

The Led on the GI is reliable, but it could also indicate that the GI itself is half broken.

 

 

[BruceinSanity]

2 hours ago, Flyboy said:

Do you have a "Correct Polarity" light on your power panel?   Sometimes these consist of a neon connected between Live & Earth which will light when the polarity is correct. Obviously this would cause a small live/earth leakage and may be enough to cause your GI LED to light up. I've had this with a metered galvanic isolator showing a small earth leakage so I simply disconnected the neon indicator and no more leakage.

My experience is that a polarity warning light is more common, a neon across neutral and earth which lights if there is voltage across them. I think the Victron provides connections for that.

If I were you, Dr B, I'd leave well alone and get a competent sparky to take a look. AC is not to be trifled with.

[dmr]

Yes, if your going to spend sometime on shorepower then it would be good to test the GI, especially as its a recently acquired boat. Again this needs access to the going in and coming out earth wires, and a multimeter. And for this test Disconnect from the mains before doing it. The multimeter will most likely have a "diode test" switch selection, failing this one of the resistance ranges might work. Measure the "diode" between in and out, then reverse the multimeter leads and measure again. Essential you are looking for a reading of 1.2 or 1200 or similar in both directions.  

It is just possible that your warning diodes might mess up this test, so see if you can find the GI instruction book.

A diode needs about 0.6v or 600mV to switch on, so 1.2 or 1200 for two in series. The multimeter will inject a little current then measure this voltage. The GI contains "back to back diodes"  so will give this reading in both directions.

[Flyboy]

12 minutes ago, BruceinSanity said:

My experience is that a polarity warning light is more common, a neon across neutral and earth which lights if there is voltage across them. I think the Victron provides connections for that.

If I were you, Dr B, I'd leave well alone and get a competent sparky to take a look. AC is not to be trifled with.

Using this configuration ,the neon will only light with reversed polarity present. There are many panels that show an illuminated neon when polarity is correct.  Dr. Bobs panel appears to be of this type but seems not to be connected so not the cause of the problem. I think the earth leakage is more likely to be in the charger.

[Dr Bob]

20 minutes ago, Flyboy said:

Using this configuration ,the neon will only light with reversed polarity present. There are many panels that show an illuminated neon when polarity is correct.  Dr. Bobs panel appears to be of this type but seems not to be connected so not the cause of the problem. I think the earth leakage is more likely to be in the charger.

Flyboy, I had a closer look at the 'correct polarity' light and it is lit - just very dimly when connected to shore power, so maybe this is the reason. I will take a look inside the AC distribution box to see if I can see where the wiring to that bulb is going. None of the other 3 bulbs light up though.

[Dr Bob]

Thanks to all who responded. Bruce, I will take your advice and get someone qualified in to look at it but one thing I can do is just check if the GI is isolating the earth. I have a Y splitter cable which I can attach  to the shore power box. One side of the splitter can feed the GI and then the boat. The other side of the splitter can then be connected to my spare shore power cable and brought onto the boat and near to a boat earth. With shore power on, the GI on, the battery charger on, I should then be able to just look to see if there is a closed circuit or open circuit between the spare shore power cable earth and the boat earth. If it is just a bit of DC leakage <1V then the GI should do its job and give an open circuit. If the leakage is too high then it will be a closed circuit. I can repeat with the GI out of circuit and it will be a closed circuit. All I need to do is ensure I stick the multimeter probe into the earth hole and not the live or neutral and measure resistance. I feel confident I can do that safely. Do you all agree that will tell me if the GI is working? Is what I am proposing safe? I am assuming if there is any sort of current on the earth system then the RCD would trip.

If it is working I will then ignore it. I am thinking Flyboy is right with the neon warning light causing the issue.

[cuthound]

You don't have The GI connected to anything to test it. 

This video shows the principles of using the diode testing function of a multimeter to test a GI.

 

[Flyboy]

1 hour ago, Dr Bob said:

Flyboy, I had a closer look at the 'correct polarity' light and it is lit - just very dimly when connected to shore power, so maybe this is the reason. I will take a look inside the AC distribution box to see if I can see where the wiring to that bulb is going. None of the other 3 bulbs light up though.

I would just disconnect the "correct polarity" light and see if this cures the problem. 

[Iain_S]

15 minutes ago, cuthound said:

You don't have The GI connected to anything to test it. 

(snip)

I agree, but a serviceable G.I. might be forced into conduction by something else. 

IIRC, Gibbo had some thoughts on this, although I don't believe his theoretical condition was ever found "in the wild".

e.t.a. http://www.smartgauge.co.uk/galv_tran_02.html

Edited November 16, 2017 by Iain_S
Link added

[cuthound]

1 minute ago, Iain_S said:

I agree, but a serviceable G.I. might be forced into conduction by something else. 

IIRC, Gibbo had some thoughts on this, although I don't believe his theoretical condition was ever found "in the wild".

That is what the dIode test function of a multimeter does, it uses the 9 volt battery to switch the diodes of the GI on.

Gibbo used a 9 volt battery and test lamp to do the same IIRC. 

[nicknorman]

If it’s only glowing when the charger part of the Combi is on, it’s likely to be the suppression circuitry in the Combi putting some small AC ripple on the earth which is causing the LED to conduct slightly. Not much you can do about it except minimise the time the charger is on.

The current is probably very tiny - it’s important to bear in mind the difference between an LED and a light bulb - the latter requires a fair bit of current to heat the filament to the point its hot enough to be visibly glowing. However an LED isn’t like that, the light emission is roughly proportional to the current and even a tiny current will cause a faint glow.

[Dr Bob]

52 minutes ago, nicknorman said:

If it’s only glowing when the charger part of the Combi is on, it’s likely to be the suppression circuitry in the Combi putting some small AC ripple on the earth which is causing the LED to conduct slightly. Not much you can do about it except minimise the time the charger is on.

The current is probably very tiny - it’s important to bear in mind the difference between an LED and a light bulb - the latter requires a fair bit of current to heat the filament to the point its hot enough to be visibly glowing. However an LED isn’t like that, the light emission is roughly proportional to the current and even a tiny current will cause a faint glow.

Thanks Nick...but if the current is only very low,  then the GI will be isolating the earth, so no problem with the boat dissolving away. That would mean I didnt need to minimise the charging - which I would like to leave on when in the marina (2-3 days at a time)?

1 hour ago, cuthound said:

You don't have The GI connected to anything to test it. 

This video shows the principles of using the diode testing function of a multimeter to test a GI.

 

Thanks Cuthound, just off out for a few hours so will look at video later. Never done a diode test on a multimeter. I assume my meter has one!

[Sea Dog]

I might be off the mark here as I don't know where the led sits in the circuit, but I'd have thought it would be between the shore earth and the boat earth and be reacting to a difference in potential between the two. The pair of diodes won't conduct until 1.4V is exceeded, hence doing the job of isolating the boat earth from the shore earth until that threshold is exceeded (which would more likely be by an electrical fault on the boat than a corrosion current). Any lesser value,  whilst not switching on the diodes, might cause the led to glow yet the boat will still be being protected. I drop this into the conversation only to spark (sorry!) a response from someone who is familiar with this type of galvanic isolator.

[Dr Bob]

55 minutes ago, Sea Dog said:

I might be off the mark here as I don't know where the led sits in the circuit, but I'd have thought it would be between the shore earth and the boat earth and be reacting to a difference in potential between the two. The pair of diodes won't conduct until 1.4V is exceeded, hence doing the job of isolating the boat earth from the shore earth until that threshold is exceeded (which would more likely be by an electrical fault on the boat than a corrosion current). Any lesser value,  whilst not switching on the diodes, might cause the led to glow yet the boat will still be being protected. I drop this into the conversation only to spark (sorry!) a response from someone who is familiar with this type of galvanic isolator.

I hope that is happening. This thread has given me confidence that the weakly glowing LED means much less than 1.4V is passing.

[Ray T]

If you get stuck this chap knows his stuff. Moors at the entrance to Calcutt Marina. He's moved from Stockton but not updated his web page.

http://narrowboatelectrics.co.uk/

Edited November 16, 2017 by Ray T

[RLWP]

Clive Mant: http://www.mantmarine.co.uk/

Good bloke, does electrical stuff

Richard

[Sea Dog]

38 minutes ago, Dr Bob said:

I hope that is happening. This thread has given me confidence that the weakly glowing LED means much less than 1.4V is passing.

Actually Bob, I think (hope) it means that, because there is less than 1.4v potential difference across the device, it isn't passing!

[nicknorman]

42 minutes ago, Sea Dog said:

Actually Bob, I think (hope) it means that, because there is less than 1.4v potential difference across the device, it isn't passing!

If the LED is glowing, it’s passing current! Current between the boat earth and shore earth. But not much.