Earth Leakage question ?

[Delfini]

I have a number of 240v ac outlets around the boat - alongside they are powered from the marina shore power through a 32A Marinco connector and via a breaker on the switch panel - at sea the same set up but sourced from the onboard inverter

A few days ago the Earth Leakage breaker started to trip when running from shore power when I turned on the 240v outlets - other 240v powered equipment onboard (like the microwave and the battery charger) worked OK - I assumed it must be some sort of water ingress to one of the sockets after washing the decks

However although the earth leakage trip fires every time when running from shore power and when I turn on the outlets via the breaker - if I disconnect the shore power and run the same outlets from the inverter, everything works fine

The wiring to the sockets is the same for shore power and inverter and the earth (according to the diagrams) is common - the only difference is the source of the power

Im at a bit of a loss to understand what might be happening and would appreciate any thoughts ?

 

[VicS]

When you say "earth leakage breaker" you presumably mean an RCD (residual current device) ?

If so the microwave and battery charger should be powered via it as well as the sockets. If it only trips when the sockets are powered it suggests a fault in the sockets or their circuit. Sea water in some where as a result of your split cockpit drain hose. ????

I suspect the reason it does not trip when the system is powered from the inverter is because of some shortcoming in the way the inverter is wired. Even a fault with their circuits (or you coming in contact with live wiring ) when using the inverter may not trip it.
If that is so you do not have the protection from electrocution when using the inverter that the RCD should provide. What make and model is the inverter?

 

[PaulRainbow]

I have a number of 240v ac outlets around the boat - alongside they are powered from the marina shore power through a 32A Marinco connector and via a breaker on the switch panel - at sea the same set up but sourced from the onboard inverter

A few days ago the Earth Leakage breaker started to trip when running from shore power when I turned on the 240v outlets - other 240v powered equipment onboard (like the microwave and the battery charger) worked OK - I assumed it must be some sort of water ingress to one of the sockets after washing the decks

However although the earth leakage trip fires every time when running from shore power and when I turn on the outlets via the breaker - if I disconnect the shore power and run the same outlets from the inverter, everything works fine

The wiring to the sockets is the same for shore power and inverter and the earth (according to the diagrams) is common - the only difference is the source of the power

Im at a bit of a loss to understand what might be happening and would appreciate any thoughts ?

Almost certainly the inverter is wired incorrectly.

What make/model of inverter and who fitted it ? Is the Earth and Neutral bonded at the inverter and is the Earth connected to "the water" (usually via the anode, but varies with boat construction).

It is vital that you fix the failure of the RCD to operate when you use the inverter before using the inverter. After fixing that you can investigate the reason the RCD trips on shore power. Failure to do so will almost certainly leave you with an unsafe installation, where, if someone touches something live they get electrocuted, as the RCD will not trip.

 

[Boater Sam]

Are you disconnecting the shore power lead from the boat, at the boat?
Check that your inverter is wired correctly with the neutral connected to the ground at the inverter, before the rcd.

 

[Graham376]

Is the Earth and Neutral bonded at the inverter and is the Earth connected to "the water" (usually via the anode, but varies with boat construction).

Some years ago, we used to trip the pontoon rcd on one particular pontoon, not on others. Turned out that a recently installed inverter had neutral and earth bonded, which was causing the problem. Isolated the inverter output and problem went away. Not unusual for pontoon sockets to be wired incorrectly.

 

[starfire]

When it is made safe, I bet the culprit is the water heater element.

 

[PaulRainbow]

Some years ago, we used to trip the pontoon rcd on one particular pontoon, not on others. Turned out that a recently installed inverter had neutral and earth bonded, which was causing the problem. Isolated the inverter output and problem went away. Not unusual for pontoon sockets to be wired incorrectly.

Inverter Neutral and Earth MUST be bonded at source, as MUST all AC sources. If they cannot be bonded, for ANY reason, the inverter should not be fitted.

 

[PaulRainbow]

When it is made safe, I bet the culprit is the water heater element.

I don't know whether it is, or not, but the water heater should be on its own breaker.

 

[Delfini]

When you say "earth leakage breaker" you presumably mean an RCD (residual current device) ?

If so the microwave and battery charger should be powered via it as well as the sockets. If it only trips when the sockets are powered it suggests a fault in the sockets or their circuit. Sea water in some where as a result of your split cockpit drain hose. ????

I suspect the reason it does not trip when the system is powered from the inverter is because of some shortcoming in the way the inverter is wired. Even a fault with their circuits (or you coming in contact with live wiring ) when using the inverter may not trip it.
If that is so you do not have the protection from electrocution when using the inverter that the RCD should provide. What make and model is the inverter?

Yes when I refer to an Earth Leakage breaker Im referring to an RCD - all shore powered 240v services are switched via their own circuit breaker and via the RCD - the diagram supplied with the boat shows shore power feeding the inverter and the output of the inverter supplying the 240v outlets and the microwave - the battery charger and other 240v services ie water heater/electric grill etc take their supply from the shore power circuit before it reaches the inverter so I assume they are unavailable when Shore power is off - Ill need to check that - at least it explains why the sockets don’t trip the RCD when powered by the inverter but I don’t know why the inverter isn’t complaining about an earth fault when the RCD clearly is - according to the diagram the inverter neutral is connected to protective earth when in “inverter mode” - the inverter is a Mastervolt 24v 1500W unit supplied with the boat when new

So it looks like Im looking for an earth leakage fault in one of the sockets or the wiring and also why the Inverter isn’t concerned

Thanks for the guidance

 

[PaulRainbow]

The inverter installation is wrong.

 

[starfire]

I don't know whether it is, or not, but the water heater should be on its own breaker.

On most boats, the neutrals are commoned, with only single pole not double pole breakers.

On any complaints of 'the rcd keeps tripping' its the first thing I go for. The rcd 'sees the fault through the common neutral.

With the proliferation of mains powered electronic devices on boats, chargers, fridges washing machines etc, each with their own interference suppression to earth, there is a summation of leakage to earth, It might be only a few mA on each device, but total it up & It can get near the limit for a 30mA rcd,
it normally Doesn't take much for one thing to tip it over the edge.

 

[PaulRainbow]

£50 says it's not the water heater.

 

[Boater Sam]

Check first the mains fed items connected to shore power only, like the immersion heater, any battery charger, etc.

Immersion elements are queer things, they can have neutral to earth faults yet work normally. I have one that trips the rcd when I first return to the boat after winter yet if I leave it on for a day, afterwards it is then fine .

 

[starfire]

£50 says it's not the water heater.

Might have to be a virtual ??

 

[Delfini]

£50 says it's not the water heater.

Its definitely not the water heater which has its own circuit breaker and turns on no problem - its definitely one of the 240v sockets or wiring

 

[Delfini]

The inverter installation is wrong.

I checked the paper circuit diagram on the boat and its a bit different to the pdf I have on file at home - I couldn’t really understand why the shore power supply was connected to the inverter - my paper diagram shows a multi pole relay which allows selection of shore power or inverter and shore power not connected to the inverter - which makes more sense. I still don’t know why the inverter is happy to supply the sockets but that’s another problem - first need to find the earth leakage which will require isolation of each of the sockets - luckily they are all supplied from a common live and neutral via a Wago rail mount terminal block system

 

[starfire]

Its definitely not the water heater which has its own circuit breaker and turns on no problem - its definitely one of the 240v sockets or wiring

You got one circuit for the sockets or several ?
Any shaver sockets on the same circuit ?

Might be time to isolate the power, separate the wiring feeding the sockets so you can test each cable between sockets & put an insulation test on, could show a faulty or damp cable.
Failing that use a multimeter on ohms, that might show something, low resistance between live or neutral to earth. BUT, unplug the boat first & pull the fuse for the inverter.

 

[PaulRainbow]

I checked the paper circuit diagram on the boat and its a bit different to the pdf I have on file at home - I couldn’t really understand why the shore power supply was connected to the inverter - my paper diagram shows a multi pole relay which allows selection of shore power or inverter and shore power not connected to the inverter - which makes more sense. I still don’t know why the inverter is happy to supply the sockets but that’s another problem - first need to find the earth leakage which will require isolation of each of the sockets - luckily they are all supplied from a common live and neutral via a Wago rail mount terminal block system

Can you post the schematic, or PM me and i'll give you an email address to send it to.

I would suggest you hold off of fixing the fault until you determine why the RCD does not trip when you use the inverter. Send me the schematic and i'll try to narrow it down for you.

 

[Delfini]

Can you post the schematic, or PM me and i'll give you an email address to send it to.

I would suggest you hold off of fixing the fault until you determine why the RCD does not trip when you use the inverter. Send me the schematic and i'll try to narrow it down for you.

Here is the schematic - Id like to understand how the RCD is connected and suggestions as to why it doesn’t trip using the Inverter - as you can see the diagram shows the same RCD in both supply options

Thanks a lot for your guidance

 

[starfire]

I wonder if the earth to the inverter is loose or disconnected ?