RF earth leakage from Mastervolt combi

[BruceinSanity]

We've had a problem on our pontoon over Christmas with nuisance trips on the power pole ELCB. We've got four liveaboards using the pole and it looks as if the combined earth leakage from the four has been popping the pole's master trip. None of the four have any problem with individual trips either on the boats or the pole.

 

We've now transferred our shoreline to another pole which only had two boats on it and, touch wood, the problem seems to have gone away. It's been 48 hours now without trouble on either pole where we were getting at least one trip a day at random times of day or night before.

 

It therefore looks as if we were one of the boats contributing to the earth leakage. All our connections seem good and the boat is just under three years old, built to comply with RCD and BSS. We have a Mastervolt combi inverter/charger, which I just learnt the other day uses switched mode power supply to do its business, unlike the Victron which uses transformers.

 

Two questions:

 

1) Could the combi be putting RF down the earth line and so contributing to the earth leakage?

 

2) We've presently got a galvanic isolator, and a docking last summer raised no worries about our anodes, but would fitting an isolation transformer a) protect the boat from galvanic corrosion better (I think I know the answer to that) and b ) stop the RF leakage down the earth conductor of the shoreline?

 

I quite fancy the Airlink BT3231.

 

Many thanks in advance for any advice; I'm going out for the morning, but will be back on line this afternoon.

[by'eck]

ELCB's or residual current devices (RCD) as they are now known are very sensitive. A tiny imbalance in the current flowing in the live and neutral legs will cause them to trip. They are not tripped by current flowing in the earth cable per se but by current leakage from live or maybe neutral to earth.

 

I think you are correct in assuming this a cumulative situation though. Could it be narrowed down to an individual appliance on any of the boats, or indeed an individual boats wiring?

[nicknorman]

I would have thought a more likely scenario is damp in the shore power leads / connectors.

[Keeping Up]

I'd say it was unlikely to be excessive RF leakage; although of course it is possible, it is more likely just the simple mains-frequency earth leakage from the filters which the device will have connected to its input. Add this to the earth leakage of any other mains devices on your boat and the other boats, and the total imbalance could easily be enough to trip the RCD.

[billh]

We've had a problem on our pontoon over Christmas with nuisance trips on the power pole ELCB. We've got four liveaboards using the pole and it looks as if the combined earth leakage from the four has been popping the pole's master trip. None of the four have any problem with individual trips either on the boats or the pole.

 

We've now transferred our shoreline to another pole which only had two boats on it and, touch wood, the problem seems to have gone away. It's been 48 hours now without trouble on either pole where we were getting at least one trip a day at random times of day or night before.

 

It therefore looks as if we were one of the boats contributing to the earth leakage. All our connections seem good and the boat is just under three years old, built to comply with RCD and BSS. We have a Mastervolt combi inverter/charger, which I just learnt the other day uses switched mode power supply to do its business, unlike the Victron which uses transformers.

 

Two questions:

 

1) Could the combi be putting RF down the earth line and so contributing to the earth leakage?

 

2) We've presently got a galvanic isolator, and a docking last summer raised no worries about our anodes, but would fitting an isolation transformer a) protect the boat from galvanic corrosion better (I think I know the answer to that) and b ) stop the RF leakage down the earth conductor of the shoreline?

 

I quite fancy the Airlink BT3231.

 

 

In my long experience of ELCBs/RCDs in moorings, tripping is almost always due to a fault or faults in the supply or boat system. The faults need to be found and fixed, for safety's sake. A few examples, some trivial, some serious:

1 Spiders and cobwebs in the rcd enclosure , tripped constantly until cleaned out

2 Blue appliance inlet filling with rainwater, even though it was inside the boat, it was fitted upside down under a leaky hatch.

3 Rats chewing mains cable in the roof lining of a boat- I expect the rcd saved the critters from extinction!

4 Brand new mains operated infra red cooker thing, got damp in an unattended boat and tripped rcd as soon as it was plugged in.

5 Live Extension lead dropped in the canal.

6 Loss of neutral in a 3phase system , causes all sorts of damage as well as rcd trips ( this was a dangerous fault on the supply side in the street, the supply company were onto it very quickly, after they were made aware.)

I am not aware of any problems caused by SMPSs or mains filters causing tripping unless they are actually faulty. Please get your installations checked , an insulation test will find most problems.

Bill

[Justme]

Using the cheap variable RCD tester I posted about a month or so back would be worth while. You could test the rcd on its own to see at what mA it tripped at & then plug each boat in one at a time & re test to see how many mA are now needed to be dialled in to make it trip. Subtract one from the other & you will see the mA leakage of each boat. Find the one with the excess leakage & then either sort it out or put that one on its own pole.

 

I think 4 boats is to many for one RCD as you could have it tripping when each boat only has 5mA of leakage as most RCD's will trip well under the maximum 30mA.

 

You could get them to change the RCD for a standard trip & all the MCB's for combined RCD's & MCB's (RCBO's?)

[BruceinSanity]

Using the cheap variable RCD tester I posted about a month or so back would be worth while. You could test the rcd on its own to see at what mA it tripped at & then plug each boat in one at a time & re test to see how many mA are now needed to be dialled in to make it trip. Subtract one from the other & you will see the mA leakage of each boat. Find the one with the excess leakage & then either sort it out or put that one on its own pole.

 

I think 4 boats is to many for one RCD as you could have it tripping when each boat only has 5mA of leakage as most RCD's will trip well under the maximum 30mA.

 

You could get them to change the RCD for a standard trip & all the MCB's for combined RCD's & MCB's (RCBO's?)

 

Thanks one and all, helpful as ever, this list.

 

Justme, I have now got one of your RCD testers, and have just used it to test this boat with the shoreline unplugged from the pole, so that I'm only testing the one boat. The internal RCBO tripped at 25mA, suggesting to me that any problem within the boat is pretty trivial. I've already checked my shoreline connectors for internal moisture, spiders, etc, and all was well. I guess I should trace the line from the shoreline inlet on the boat to the Mastervolt and make sure that there are no other probs there, but as I say, we've not tripped the breaker on the new pole.

 

I follow the logic for testing the problem pole itself, I just need a) to make up a blue 16A round plug to a 13A extension socket (to save rewiring the tester itself) and b ) engage in quite some diplomacy with my fellow moorers. There's a distinct tendency on the part of some to say "No, no, there's nothing possibly wrong with my boat, it must be the pole". Which it may be, of course, but the pole RCBO has been swapped for a brand new one once already.

 

I doubt if it would be very easy to swap the existing individual MCBs for RCBOs, would it? The form factor of the RCBO is wider than than the simple MCB.

[nb Innisfree]

We once had a trip problem, after isolating all 230v appliances we tried each one by one and the TV tripped as soon as the plug was switched on, bingo. Except it wasn't because occasionally it wouldn't trip with TV but would with with other various appliances. Turned out to be an inline shoreline polarity checker, never did find out why it was faulty. Point is we only found it by isolating or bypassing stuff one at a time which can take days if fault is intermittent.

[Roger Crown]

PM sent

[smileypete]

Two questions:

 

1) Could the combi be putting RF down the earth line and so contributing to the earth leakage?

IF the combi contains surge arrestors (the actual components are called MOVs or varistors), these can cause nuisance trips if they're a bit faulty, as they start to clamp at a lower voltage.

 

cheers, Pete.

~smpt~

Edited January 30, 2013 by smileypete

[Keith M]

We've had a problem on our pontoon over Christmas with nuisance trips on the power pole ELCB. We've got four liveaboards using the pole and it looks as if the combined earth leakage from the four has been popping the pole's master trip. None of the four have any problem with individual trips either on the boats or the pole.

 

We've now transferred our shoreline to another pole which only had two boats on it and, touch wood, the problem seems to have gone away. It's been 48 hours now without trouble on either pole where we were getting at least one trip a day at random times of day or night before.

 

It therefore looks as if we were one of the boats contributing to the earth leakage. All our connections seem good and the boat is just under three years old, built to comply with RCD and BSS. We have a Mastervolt combi inverter/charger, which I just learnt the other day uses switched mode power supply to do its business, unlike the Victron which uses transformers.

 

Two questions:

 

1) Could the combi be putting RF down the earth line and so contributing to the earth leakage?

 

2) We've presently got a galvanic isolator, and a docking last summer raised no worries about our anodes, but would fitting an isolation transformer a) protect the boat from galvanic corrosion better (I think I know the answer to that) and b ) stop the RF leakage down the earth conductor of the shoreline?

 

I quite fancy the Airlink BT3231.

 

Many thanks in advance for any advice; I'm going out for the morning, but will be back on line this afternoon.

 

Hello

 

All switch mode power supply's do leak a few mille amps to earth

It is quite possible that with four boats connected to the same shore bollard that between you there was over over 30 mille amps being supplied to earth which would have caused enough of an in-balance to trip the bollard RCD.

 

To your question regarding the isolation transformer this would stop any leakage to earth generated on-board your boat

 

Keith

[smileypete]

I doubt if it would be very easy to swap the existing individual MCBs for RCBOs, would it? The form factor of the RCBO is wider than than the simple MCB.

No, RCBOs are single width as they're designed to replace MCBs, they're more expensive (check Ebay for prices) but worth it. The existing RCD would then be replaced by a correctly rated double pole isolator.

 

Having 4 boats on a single RCD is a recipe for future problems so it'd be worth going the RCBO route if possible. Even if you do have an IT fitted there would still be the possibility of nuisance trips from the other 3 boats.

 

Also in the meantime check if there are ANY surge protected extension leads being used on your boat or the other boats, and whether the problem goes away when they're left out. What can happen is one appliance generates a little RFI but it's shorted to ground by a faulty surge arrestor somewhere downstream of the RCD, can be on another boat.

 

cheers, Pete.

~smpt~

Edited January 31, 2013 by smileypete

[BruceinSanity]

Thanks to both KeithM and smileypete for interesting further stuff. I'm going to lean on the marina at least to test the existing RCBO properly and then will see if they can be persuaded to go down the individual RCBO route, but I'm not hopeful. With 580 berths, all the rest would want them, no doubt!

[Keith M]

Thanks to both KeithM and smileypete for interesting further stuff. I'm going to lean on the marina at least to test the existing RCBO properly and then will see if they can be persuaded to go down the individual RCBO route, but I'm not hopeful. With 580 berths, all the rest would want them, no doubt!

 

Hello

 

Since mid 2008 all electrical installation within marinas now come under the jurisdiction of the IET

And without looking up the time scale periodic checks are required on an annual basics and records should be kept

This should include testing the RCD section of the RCBO

It is common practice that each socket outlet on the Shore Bollard has an individual RCD & MCB or RCBO

you could try finding out when the last inspection was carried out

 

Keith

 

No, RCBOs are single width as they're designed to replace MCBs, they're more expensive (check Ebay for prices) but worth it. The existing RCD would then be replaced by a correctly rated double pole isolator.

 

Having 4 boats on a single RCD is a recipe for future problems so it'd be worth going the RCBO route if possible. Even if you do have an IT fitted there would still be the possibility of nuisance trips from the other 3 boats.

 

Also in the meantime check if there are ANY surge protected extension leads being used on your boat or the other boats, and whether the problem goes away when they're left out. What can happen is one appliance generates a little RFI but it's shorted to ground by a faulty surge arrestor somewhere downstream of the RCD, can be on another boat.

 

cheers, Pete.

~smpt~

 

It is quite common now to have a single width RCBO

But the down side is. It may not fit into the space within the Shore Bollard

 

Keith