"Occasional" 240v

[rogerthebodger]

I made a quick and dirty video to demonstrate a test...

That is quite interesting.

I note you used a centre tap inverter where the earth wire is connected to the centre tap.

This is very similar to the way that on out door work site safety transformer works where the highest voltage between either the line or neutral is 110/120 volts and I dont think those site transformers have a RCD

Would you do the same tests with a non centre tap inverter. I would like to know how you wire a non centre tap inverter which is more like a incoming shore power line.

 

[<152587>]

Victron Quattro has some interesting info, see page 12 of the manual for the warning.

 

[PaulRainbow]

I don't understand why the RCD did not trip when you connected your tester between RCD live out and inverter (centre tap) earth

<snip>

You seemed surprised yourself in the video.

That is quite interesting.

I note you used a centre tap inverter where the earth wire is connected to the centre tap.

It's very unlikely that the inverter is a centre tap model. If it was, it's got a serious issue, as the RCD should have tripped.

It's worth testing the inverter by applying a load across the terminals, rather than the tester, a simple light bulb would suffice.

 

[rogerthebodger]

The requirement, as I read ISO13297, is not to connect AC protective earth to DC negative per se, but to "the main grounding/earthing point of the craft".
In many cases the negative terminal on the engine block is used for this purpose, in which case both DC negative and AC protective earth are joined at this point in order to connect to "ground" (the water). But the DC system might also be of the fully insulated two-wire type, that is, no connection to ground/earth.

This is exactly my view.

As most boats have a fully insulated two-wire type DC system there is no requirement for a AC earth to DC negative connection.

On a metal boat there could be a single wire DC system when the hull is used as the negative connection. This can cause strange current flows so I went for a fully insulated systen where I even insulated the engine electrically from the hull to ensure this. This insulation from the hull is more important on aluminium hull boats.

 

[rogerthebodger]

Victron Quattro has some interesting info, see page 12 of the manual for the warning.

Can you post a link.

 

[VicS]

Victron Quattro has some interesting info, see page 12 of the manual for the warning.

There are several versions on line. Page 12 is different in them all. Which one should we be reading?

 

[PaulRainbow]

This is exactly my view.

As most boats have a fully insulated two-wire type DC system there is no requirement for a AC earth to DC negative connection.

Most boats do not have fully insulated DC systems, most have the dc negative connected to the engine block, at least. In which case (from the ISO) :

"Direct from the ISO, refering to the AC PE :

4.2 The protective conductor shall be connected to the craft's d.c. negative ground (earth) as close as practicable to the battery (d.c.) negative terminal."

Which is exactly what i keep saying.

On a metal boat there could be a single wire DC system when the hull is used as the negative connection. This can cause strange current flows so I went for a fully insulated systen where I even insulated the engine electrically from the hull to ensure this. This insulation from the hull is more important on aluminium hull boats.

There are additional requirements on metal boats, which i'm sure you are aware of. The ISO states :

"4.3 For craft with fully insulated d.c. systems (see ISO 10133), the a.c. protective conductor shall be connected to the hull of a metallic hull craft, the craft external ground (earth) or the craft lightning-protection ground plate, if fitted."

This is why i also keep pointing out that your steel hulled installation differs to the OPs non-insulated installation in a plastic boat.

 

[VicS]

It's very unlikely that the inverter is a centre tap model. If it was, it's got a serious issue, as the RCD should have tripped.

I agree. The voltage readings that were supposed to confirm it did not "add up"

It's worth testing the inverter by applying a load across the terminals, rather than the tester, a simple light bulb would suffice.

but with an RCD tester on the bench that's the obvious thing to use

 

[<152587>]

There are several versions on line. Page 12 is different in them all. Which one should we be reading?

Yeah just noted that. I searched Victron site, downloads, Quattro, firmware XXXX etc. appears on page 10, section 4.3, connection to ac

 

[PaulRainbow]

but with an RCD tester on the bench that's the obvious thing to use

For testing the RCD, yes. For determining whether or not the inverter is a centre tap model, no.

The multimeter Matt used to measure the voltages will show a high voltage, even if there are only ma present, giving a deceptive result. Same as when testing for circuit volts with a multimeter, it may show 12.4v, but stick a light bulb in the circuit and it won't illuminate.

 

[rogerthebodger]

Most boats do not have fully insulated DC systems, most have the dc negative connected to the engine block, at least. In which case (from the ISO) :

"Direct from the ISO, refering to the AC PE :

4.2 The protective conductor shall be connected to the craft's d.c. negative ground (earth) as close as practicable to the battery (d.c.) negative terminal."

Which is exactly what i keep saying.

I don't understand why it is a requirement to connect the protective connector to the engine block unless its the assumption that the engine block is also connected directly to a metallic part of the hull.
With flexible mounts and flexible couplings is not the case in all moden installations.

There are additional requirements on metal boats, which i'm sure you are aware of. The ISO states :

"4.3 For craft with fully insulated d.c. systems (see ISO 10133), the a.c. protective conductor shall be connected to the hull of a metallic hull craft, the craft external ground (earth) or the craft lightning-protection ground plate, if fitted."

Yes but what is meant but "fully insulated d.c. systems"

In the old days when engines were rigid mounted with rigid couplings and all underwater metal fittings connected together you would not have a fully insulated d.c. systems, but today where is is considered not required to connect all under water fittings together (Bonding) and insulated engines with rubber mounting and rubber couplings even with the DC system connected just to the engine it is a fully insulated system. If some one bonds every thing as in the old days yes you don't have a fully insulated system by the very nature of the installation.

Metl boats are different because if there is a short to the hull any where, the stainless steel hand rails and safety lines, rigging and mast will be live and a person could get a potentially leathal shock if a hand rail was grabbed on a wet deck.

On a GRP boat these metal fittings tend to be insulated from each other so no distribution if one part becomes live.

 

[BabaYaga]

Most boats do not have fully insulated DC systems, most have the dc negative connected to the engine block, at least. In which case (from the ISO) :

"Direct from the ISO, refering to the AC PE :

4.2 The protective conductor shall be connected to the craft's d.c. negative ground (earth) as close as practicable to the battery (d.c.) negative terminal."

Which is exactly what i keep saying.



There are additional requirements on metal boats, which i'm sure you are aware of. The ISO states :

"4.3 For craft with fully insulated d.c. systems (see ISO 10133), the a.c. protective conductor shall be connected to the hull of a metallic hull craft, the craft external ground (earth) or the craft lightning-protection ground plate, if fitted."

This is why i also keep pointing out that your steel hulled installation differs to the OPs non-insulated installation in a plastic boat.

I believe you are quoting from the year 2000 version of ISO13297.
In the 2012 version the wording is different, no mention of "as close as practicable to the battery (d.c) negative terminal".
I think there is also a later version of this ISO (which I don't have access to).

These texts are not easy to interpret and I certainly don't claim to understand it all. But my over all view from reading the 2012 version is that the often repeated "AC PE should be connected to DC negative" is misleading, as the purpose really is to establish a connection between PE and ground (the sea). That is, in my interpretation, an alternative path to ground in case the PE connection through the shore cable should not function.

The definition of a "fully insulated two-wire d.c system" according to ISO10133 (2012 version) is that both positive and negative "remain isolated from the ground (earth)".
In my interpretation this means that even if the DC negative is connected to the engine block, the DC system could still be seen as fully insulated, provided that there is no electrical connection between the engine block and the sea. As could be the case for instance with a flexible coupling between gearbox and shaft, which is not bridged.

 

[VicS]

Yeah just noted that. I searched Victron site, downloads, Quattro, firmware XXXX etc. appears on page 10, section 4.3, connection to ac

I still cannot see what you are referring to.

If you post a link to, or just the URL of, the document you refer to we will all be able to read the same one.

 

[<152587>]

http://www.victronenergy.com select downloads, manuals etc.

 

[VicS]

http://www.victronenergy.com select downloads, manuals etc.

A direct link to, or the URL of, the document you want us to read would have made it easier to find.

Is this the page you want us to read, if so what part in particular

 

[PaulRainbow]

I don't understand why it is a requirement to connect the protective connector to the engine block unless its the assumption that the engine block is also connected directly to a metallic part of the hull.
With flexible mounts and flexible couplings is not the case in all moden installations.

It isn't a requirement to connect it to the engine block, it has to be connected to the DC negative. One possible reason is to protect anyone in the water, close to the boat, from electric shock where AC positive has "leaked" into the water, the RCD would be sure to trip if the AC ground was connected to the DC negative. It would assume that there was a connection from the DC negative to the water though (as you say). It may also be that when they say "fully insulated" it means insulated from the water, that would make more sense.

It would also allow the RCD in Matts test to have tripped, if he had connected the AC ground to DC negative.

There are a lot of variables involved if you try to think of a solution for all types of inverter, in all types of installation, on all types of boat. Which is why i've consistently said i'm talking about the OPs situation.

 

[PaulRainbow]

"AC PE should be connected to DC negative" is misleading, as the purpose really is to establish a connection between PE and ground (the sea). That is, in my interpretation, an alternative path to ground in case the PE connection through the shore cable should not function.

I'd pretty much agree with that, but it's not just shore power PE failures, it's to provide protection from generators and inverters.

The definition of a "fully insulated two-wire d.c system" according to ISO10133 (2012 version) is that both positive and negative "remain isolated from the ground (earth)".
In my interpretation this means that even if the DC negative is connected to the engine block, the DC system could still be seen as fully insulated, provided that there is no electrical connection between the engine block and the sea. As could be the case for instance with a flexible coupling between gearbox and shaft, which is not bridged.

Indeed, it's those things that need consideration when installing AC equipment. It's no good just bonding AC neg and PE, no good just bonding AC PE to DC neg, one has to consider what paths to "earth" exist.

 

[PaulRainbow]

I still cannot see what you are referring to.

If you post a link to, or just the URL of, the document you refer to we will all be able to read the same one.

There are various Victron manuals (of course) a common Victron theme is that the AC negative is connected to the inverter case, which in turn has to be connected to ground. This would have to be the DC negative, steel hull, ground plate etc previously discussed. It cannot rely on shore power ground, as it can be used at sea.

 

[rogerthebodger]

It isn't a requirement to connect it to the engine block, it has to be connected to the DC negative. One possible reason is to protect anyone in the water, close to the boat, from electric shock where AC positive has "leaked" into the water, the RCD would be sure to trip if the AC ground was connected to the DC negative. It would assume that there was a connection from the DC negative to the water though (as you say). It may also be that when they say "fully insulated" it means insulated from the water, that would make more sense.

It would also allow the RCD in Matts test to have tripped, if he had connected the AC ground to DC negative.

There are a lot of variables involved if you try to think of a solution for all types of inverter, in all types of installation, on all types of boat. Which is why i've consistently said i'm talking about the OPs situation.

It would make more sense if the AC ground wire was connected to a metal object in the water giving direct conductivity to the sea, then if there was any leakage in the AC line into the water the RCD would trip.

If the DC was not isolated or insulated it would not matter if it was also connected to the DC negative

The DC negative as such is not relevant its what the DC negative is also connected to like the sea through the engine/stern gear, so why not just connect the AC earth direct to the sea and ignore the DC negative so it not directly relevant

This would then apply to all hull types it the AC earth connection to the sea that important in all cases.

 

[PaulRainbow]

RS components 600w inverter.

A. Which RS inverter please ?
B. No instructions ?
C. Is there a manufacturers name on it ?