V2L Earthing - how?

[Les burrows]

hi Nicko I’m sure I did and but can’t remember I will go again in the morning and edit this post the V2L cable is a MG approved accessory purchase from my dealer
Les

 

[Coulomb]

I found a mains socket tester in my garage

Brilliant!

The tester is saying that the earth is open circuit, current can't pass from live to the earth wire.

The tester likely has roughly this schematic (found with a quick search):

So I can't see how the RCD will work to protect appliances! It's possible that still connect neutral to chassis when in V2L mode, and they bring the earth from the car's chassis to the box, but don't connect it to the sockets' earth pins. They could use that earth wire for the test function, and indeed in this configuration the RCD would protect protect occupants that touch live and the car chassis at once.

But why leave off the connection to the sockets' earth pins? It beggars belief. Maybe they leave the earth lead out altogether to save some pennies, and test against neutral. But that's hardly a real test. In effect they would be saying "there is no way that you can cause a real current imbalance with this, but if somehow you found a way, this is how the RCD would react" (by tripping, if it's working).

[ Edit: Added verbage to clarify some points. ]

 

[Les burrows]

Hi guys sorry it’s a bit late but I got tied up yesterday with rugby football and F1.
So this morning tested the V2L cable RCB and yeh it works no problem.
Les

 

[Nicko]

Hi Les, it tripped with the test button?

 

[Les burrows]

Hi Les, it tripped with the test button?

Yeh sorry Nicko yes press the test button and it trips then I put a load on it around 300w and pressed the test button again and it tripped so yeh it works just like any RCB that’s connected to the mains.
Les

Brilliant!

The tester is saying that the earth is open circuit, current can't pass from live to the earth wire.

The tester likely has roughly this schematic (found with a quick search):

View attachment 16074
So I can't see how the RCD will work to protect appliances! It's possible that still connect neutral to chassis when in V2L mode, and they bring the earth from the car's chassis to the box, but don't connect it to the sockets' earth pins. They could use that earth wire for the test function, and indeed in this configuration the RCD would protect protect occupants that touch live and the car chassis at once.

But why leave off the connection to the sockets' earth pins? It beggars belief. Maybe they leave the earth lead out altogether to save some pennies, and test against neutral. But that's hardly a real test. In effect they would be saying "there is no way that you can cause a real current imbalance with this, but if somehow you found a way, this is how the RCD would react" (by tripping, if it's working).

[ Edit: Added verbage to clarify some points. ]

Coulomb had a quick look and the earth lead is connected inside the double socket as any mains outlet would be
Les

 

[Nicko]

So the question is how does it trip without an earth at the car?

 

[N2STY]

So the question is how does it trip without an earth at the car?

Before you ask that question will the test trip work when not plugged into car?

 

[Jomarkh]

To test it you would need to plug in a faulty device as pressing the Test button just tests the breaker by putting an imbalance between L and N

 

[Nicko]

It should be testing an imbalance between L and N on an earth fault? unless the the test switch is only checking the tripping mechanism?

 

[Coulomb]

Coulomb had a quick look and the earth lead is connected inside the double socket as any mains outlet would be

So you are saying that the two earth pins connect to each other, but also to a yellow and green (possibly just green with no stripe) wire in the cable from the car? And presumably that connects through to the earth pin on the type 2 plug?

will the test trip work when not plugged into car?

Well, no, there would be no power to activate the trip coil.

It should be testing an imbalance between L and N on an earth fault?

Yes, but there are two ways it could do that. It could cause a current to flow via neutral, or it could cause a current to flow via earth. I assumed the latter, as it would test the earth as well. But here is a typical RCD schematic:

I note that a typical RCD in a switchboard (distribution board, DB) doesn't have access to earth wires, unlike the RCD in the V2L. [ Edit: At least as I imagine it. ]

So it looks like they've copied the schematic from a typical household RCD. That explains why the trip button works: the trip button introduces an artificial imbalance in flux in the iron and hence induces a voltage into the sense coil.

It remains my assertion that the RCD in the V2L is essentially useless; I can't think of a scenario where it would save anyone from being shocked.

Since the earth pins are essentially floating, there is no need for an RCD to be added to any aftermarket V2Ls, as I first thought. That was when I assumed that they must have connected the neutral output of the inverter to chassis.

 

[Les burrows]

So you are saying that the two earth pins connect to each other, but also to a yellow and green (possibly just green with no stripe) wire in the cable from the car? And presumably that connects through to the earth pin on the type 2 plug?

No coulomb I didn’t say that what I said was inside the 3 pin socket there is a cable and it is connected to the earth pin in the socket it is a green and yellow, what it connects to on the plug that goes in the car I have no idea as I don’t think that can be opened so I haven’t look in there, but today I will find out which pins give continuity with my meter and post here I have no idea.
Les

 

[Eclectic]

Does this help at all?

 

[Coulomb]

Does this help at all?

Thanks. That appears to show that the earths are connected to each other and to the earth pin on the type 2 plug. Presumably that earth pin connects to the vehicle chassis.