Earth Leakage question ?

[PaulRainbow]

Could be part of the inverter ?

If it was, it would be "behind" the PEN link, it it couldn't work.

 

[starfire]

If it was, it would be "behind" the PEN link, it it couldn't work.

Pro Power Pure Sine Wave Inverters With RCD

 

[PaulRainbow]

Pro Power Pure Sine Wave Inverters With RCD

Does the OP have a Sterling inverter ?

No he doesn't, he has a Mastervolt Mass Combi.

The Sterling unit comes with a fitted RCD AFTER the PEN link, if it was before it, it wouldn't work.

The Mastervolt unit requires a RCD to be fitted, close to the inverter. The boat schematic shows such an RCD, the Mastervolt installation manual shows such an RCD.

 

[PaulRainbow]

I'm getting pretty fed up with inverter threads, every single on has someone or two that just wants to argue about a subject they don't understand.

 

[pvb]

I'm getting pretty fed up with inverter threads, every single on has someone or two that just wants to argue about a subject they don't understand.

But you're very patient....

 

[starfire]

But you're very patient....

I do this stuff for a living & yes I'm qualified to do so.

Not getting into an argument on this, so I'm out of here

 

[Graham376]

I'm getting pretty fed up with inverter threads, every single on has someone or two that just wants to argue about a subject they don't understand.

Paul, It doesn't help when someone buys an inverter from a reputable company, with instructions which make no mention of whether internal rcd fitted or needs fitting in supply or, whether earth and neutral are bonded. Only warning is not to connect to mains supply at the same time. Are you surprised there's confusion, when any typical boat owning purchaser reading the instructions, thinks he/she just has to connect it to the batteries and use it, just like any other appliance?

QSW inverters instructions 2006a.cdr (shopify.com)

Graham.

 

[Delfini]

Felströmsbrytare (Fenno-Swedish) = Jordfelsbrytare (Swedish) = RCD (English)

 

[Delfini]

Paul, It doesn't help when someone buys an inverter from a reputable company, with instructions which make no mention of whether internal rcd fitted or needs fitting in supply or, whether earth and neutral are bonded. Only warning is not to connect to mains supply at the same time. Are you surprised there's confusion, when any typical boat owning purchaser reading the instructions, thinks he/she just has to connect it to the batteries and use it, just like any other appliance?

QSW inverters instructions 2006a.cdr (shopify.com)

Graham.

Just to clarify and if anyone reads this in the future looking for clues for a similar problem - the Mastervolt manual makes it very clear an external RCD should be part of the installation - it seems to me that Nautor (who fitted the inverter in the boat from new) did include an RCD for the inverter but its a question of me finding it - assuming its not part of the RCD on the main switch panel

 

[Delfini]

Follow the wiring from the inverter to the transfer switch, the RCD should be between the two.

When you change the transfer switch to "inverter" there should be an RCD in that supply, close to the inverter.

haha - easier said than done - the inverter is under one of the forward bunks and the transfer switch is behind the main switch panel on the opposite side of the boat - its at least 5m away and via all sorts of contortions - anyway that’s what I will need to do - surely its should be very visible and accessible - Im sure it will be obvious once Ive found it - thanks again

 

[PaulRainbow]

I do this stuff for a living & yes I'm qualified to do so.

Not getting into an argument on this, so I'm out of here

That being the case, you should know the Mass Combi needs an RCD

 

[PaulRainbow]

haha - easier said than done - the inverter is under one of the forward bunks and the transfer switch is behind the main switch panel on the opposite side of the boat - its at least 5m away and via all sorts of contortions - anyway that’s what I will need to do - surely its should be very visible and accessible - Im sure it will be obvious once Ive found it - thanks again

Nothing much is easy on a boat, good look with finding it.

 

[PaulRainbow]

Paul, It doesn't help when someone buys an inverter from a reputable company, with instructions which make no mention of whether internal rcd fitted or needs fitting in supply or, whether earth and neutral are bonded. Only warning is not to connect to mains supply at the same time. Are you surprised there's confusion, when any typical boat owning purchaser reading the instructions, thinks he/she just has to connect it to the batteries and use it, just like any other appliance?

QSW inverters instructions 2006a.cdr (shopify.com)

Graham.

You're right, some inverters come with appalling documentation. Some of the smaller "portable" inverters can just be plugged in and used, but they should not be part of a fixed installation. A fixed installation (such as the OPs) is where the inverter is wired into the boats onboard systems the same as you'd wire shore power in. This has to include neutral/earth bonding, onboard earthing and and RCD, RCBO etc Such installations are questionable as DIY installs.

That said, the frustrating thing about inverter threads on PBO is that they always end up in an argument, where people who don't understand how the installation must be done just confuse things or post dangerous misinformation. This thread is a perfect case in point, i've been saying all along that it has to have an RCD and it's been argued otherwise, when the boat schematic shows an RCD and Mastervolt specify it must have one.

 

[VicS]

This is factory fitted with a Mastervolt inverter.

Even if it's factory fitted because we are looking for the reason the RCD does not trip it would surely be sensible to check it.

That's not sufficient, he needs to check for a proper earth connection, to water. The could be continuity to the busbar and from there to the shore power connection, which would allow for the shore power RCD to trip, but there could be a break between the busbar and the water, which will disable the inverter RCD and the protection it should provide.

The connection to the water provides an alternative ( back up) path for a fault current back to the source ( local dist. transformer) in the event of the shorepower PE connection becoming discontinuous to ensure that the shorepower RCD remains operative.
However , this does not apply to the inverter RCD because the neutral is earthed at the inverter not remotely on-shore like the shorepower neutral. The fault that appears to exist in the sockets circuit should trip the inverter RCD regardless of any connection to the water.

(BTW the inverter in question is not a Mass-Combi as you seem to think. Just a Mass 24/1500, at least not as far as the schematic and the OPs description are concerned. )

 

[PaulRainbow]

The connection to the water provides an alternative ( back up) path for a fault current back to the source ( local dist. transformer) in the event of the shorepower PE connection becoming discontinuous to ensure that the shorepower RCD remains operative.

So, without an earth connection the shore power RCD will not trip ?

However , this does not apply to the inverter RCD because the neutral is earthed at the inverter not remotely on-shore like the shorepower neutral.

Oh, the inverter RCD (same device as the shore power RCD) will trip without an earth ?

The shore power neutral and earth are bonded at source, the same as the inverter and the RCDs are both the same type of device. Both will behave in exactly the same way.

(BTW the inverter in question is not a Mass-Combi as you seem to think. Just a Mass 24/1500, at least not as far as the schematic and the OPs description are concerned. )

Who cares, both must have neutral and earth bonded at source, both must be earthed and both must have an RCD fitted to the inverter out.

 

[PaulRainbow]

That's right.
If there is no path back to the neutral no current will flow therefore the RCD will not trip.
This path is normally the PE conductor . If this becomes broken, for example by a bad connection in a shore power cable connector,. a connection to the water will provide an alternative path

So, no earth connection and it won't trip, but if there is a path to earth (the water) on the boat it will trip.

That's right.
An external earth connection or a connection to the water does not provide a path back to the inverter neutral. That path is entirely provided by the boats internal PE wiring, which is why it is suspect in this case

Meanwhile, the RCD on the boat will trip without an earth. ?

What a load of old rubbish.

The inverter RCD is the same device as the shore power RCD and both are connected in exactly the same way, neutral bonded to earth at source and the earth connected to ground. Under any given fault scenario they will perform in exactly the same way.

You claim "An external earth connection or a connection to the water does not provide a path back to the inverter neutral" but it does, because the neutral and earth are bonded at the inverter, same as shore power is.

The OP has narrowed the fault down to the sockets, if they are isolated the RCD does not trip and he thinks he got water in one of them when he was washing the decks, there is a very small amount of current leaking which is going to earth, causing an imbalance between the live and neutral, tripping the RCD.

When he switches the transfer switch to "inverter" the socket power goes through the inverter RCD, not the shore power RCD and the system now relies entirely on the boat having its own earth (connection to water). That same small current leak will go to earth and the RCD will trip, same as on shore power. If there is no onboard earth connection the current leak will do nothing, it has no path to flow to, the RCD will not trip.

What will happen if the earth connection does not go to ground is that a positive leak to earth will make the earth circuit, including any earth connections on metal faceplates and any metal appliance with an earth connection, live. It will not trip the RCD because there is no imbalance. If someone touches one of those live points and carries the current to earth they will get an electric shock. By carrying the current to earth the person will cause the RCD to trip, hopefully before the shock causes death or injury, an RCD is not a guarantee of survival.

If the earth circuit was connected to earth the RCD will trip as soon as the fault occurs, it will not wait for someone to touch a live object and get a shock. This is why it is vital that an inverter installation is correctly installed and correctly earthed.

Once again, in an inverter thread, you have given incorrect and dangerous advice. Something you seem to do in every single inverter thread, because you think you understand the subject matter because you have read a few installation manuals and some Googled articles online, when in reality you have absolutely zero experience with inverter installations.

That's not a brilliant attitude for an electrician. More like the attitude of cowboy builder.
.

As is also the norm for your posts on electrical matters, you make misleading, incorrect and often dangerous posts, then resort to personally abusing me.

There is nothing wrong with my attitude as an electrician, all correctly fitted fixed inverter installations must conform to certain rules, irrespective of make/model. The must have neutral and earth bonded at source, have a proper earth circuit (earthed correctly) and be fitted with an RCD, RCBO etc.

 

[VicS]

>
>
When he switches the transfer switch to "inverter" the socket power goes through the inverter RCD, not the shore power RCD and the system now relies entirely on the boat having its own earth (connection to water). That same small current leak will go to earth and the RCD will trip, same as on shore power. If there is no onboard earth connection the current leak will do nothing, it has no path to flow to, the RCD will not trip.

Perhaps a simple diagram will help



This shows the path of the fault current , from the inverter L through the RCD , via the fault to the earth conductor, back to the inverter E terminal and finally via the link to the inverter N.

This has created the imbalance which trips the RCD

This will happen even with no connection to the water,

 

[VicS]

What will happen if the earth connection does not go to ground is that a positive leak to earth will make the earth circuit, including any earth connections on metal faceplates and any metal appliance with an earth connection, live. It will not trip the RCD because there is no imbalance. If someone touches one of those live points and carries the current to earth they will get an electric shock. By carrying the current to earth the person will cause the RCD to trip, hopefully before the shock causes death or injury, an RCD is not a guarantee of survival.
If the earth circuit was connected to earth the RCD will trip as soon as the fault occurs, it will not wait for someone to touch a live object and get a shock. This is why it is vital that an inverter installation is correctly installed and correctly earthed.

This is exactly the same situation that my diagram in the previous post illustrates,

A leak from the line conductor (not positive ) to the earth conductor will immediately trip the RCD because the earth and neural are bonded at the inverter output terminals

The RCD trips because there is an imbalance, ........... due to current flowing through the RCD in the line conductor but no current flowing back through the RCD in the neutral.

.