240v inverter earth

[kashurst]

If fault occurs to earth the rcd will trip as there will be an imbalance of current.

yes, and in such a case all we would need is an RCD, so why do we have earthing systems?

 

[Seastoke]

yes, and in such a case all we would need is an RCD, so why do we have earthing systems?

Well no earth no imbalance.

 

[billskip]

Yes the earth to pontoons have to be a completely separate earth , say the earth was connected to the neutral at the pontoon earth and the cable feeding the pontoon the neutral breaks , now the live voltage comes down the live and should return down the neutral , which is not there so it uses the earth which then makes everything metal live , you could die . Hence the separate earth.

I understand what you are saying, but the ground and the neutral are in parallel across the RCD therefore some current will pass down both neutral and earth cables causing a differential between line and neutral through the RCD. So the RCD should trip..

 

[billskip]

Well no earth no imbalance.

When you get the 'shock' it will cause the imbalance...
No imbalance no shock.
No shock no worries.

 

[Seastoke]

I understand what you are saying, but the ground and the neutral are in parallel across the RCD therefore some current will pass down both neutral and earth cables causing a differential between line and neutral through the RCD. So the RCD should trip..

There is no earth connection to an rcd.

 

[Seastoke]

Th earth principal is to protect all things metal becoming live. except things that are double insulated.

 

[kashurst]

Well no earth no imbalance.

 

[billskip]

There is no earth connection to an rcd.

I didn't say there was....I said the earth cable and the neutral cable are in parallel ...the neutral cable going through the RCD and the earth bypassing it.

 

[billskip]

No they are not bonded , I am a little puzzled by how after an inverter an RCD can trip as it measures the load balance between L&N ie leakage to earth , but if they are bonded how can this work.

I think it's this that is causing confusion....you need to draw the circuit and you will see ....the 'bonding' comes before the RCD, the 'load' is taken from the RCD 'output' the ground/earth circuit of the 'load' bypasses the RCD, and connects to the bonding of the incoming and/or ground electrode, any 'leak' from the load circuit to ground will cause imbalance and the RCD will trip.

 

[Seastoke]

More or less, the difference between no physical earth and an actual bonded ground point somewhere relativley close to where the electricity is being consumed is debatable. Some one posted earlier about getting a shock from an electric fence whilst standing in a bucket of water. Yes you would get a bit of a shock as you charged up to the same potential as the fence and no more, because once the electromotive potentials are the same no more current flows - just like a static electricity shock. . See birds sitting on HV power lines, they don't get fried.

In an electric system if there is a fault an RCD or some sort of fuse ultimately stops the current if there is a fault. But in the case of mains electricity or higher electromotive forces there needs to be a way to dissipate that energy in the case of a serious fault - the only way we have to dump that energy is into a mass sufficiently big enough to take that amount of electrical energy without raising its own potential. - is quite literally the Earth. See lightening strikes.

Quite what is the best way to minimise the risk is why we have standards - and over time, knowledge and experience changes the considered opinion. We still don't really understand why lightening conductors mostly work! But they do. Earthing is a little bit similar, it is essentially the last resort of electrical safety.
But whatever, if there is a serious fault the only way to manage it is to dump that energy into a big mass and hope the circuit breaker/fuses et al trips/blows.. Which is why I understand, we have a considered, reliable, quality electrical path to earth. In houses, at generators and on boats via an anode or similar into water - which at relatively low potentials conducts electricity very well.

The one on a boat from a pontoon supply is via the earth wire not the water, water is a very poor conductor of electricity

 

[Seastoke]

I think it's this that is causing confusion....you need to draw the circuit and you will see ....the 'bonding' comes before the RCD, the 'load' is taken from the RCD 'output' the ground/earth circuit of the 'load' bypasses the RCD, and connects to the bonding of the incoming and/or ground electrode, any 'leak' from the load circuit to ground will cause imbalance and the RCD will trip.

Yes I fully understand how electric works up to the socket on the pontoon . I am saying the neutral and earth are not joined anywhere on a pontoon supply

 

[PaulRainbow]

Yes the earth to pontoons have to be a completely separate earth , say the earth was connected to the neutral at the pontoon earth and the cable feeding the pontoon the neutral breaks , now the live voltage comes down the live and should return down the neutral , which is not there so it uses the earth which then makes everything metal live , you could die . Hence the separate earth.

Of course it won't. Electricity has to flow in a circuit, take away the neutral shoreside and the RCD on any boat that has any load on would trip because the current return would indeed go back up the Earth as far as the pedestal, bypassing the RCD, causing an imbalance and tripping the onboard RCD. This is why the neutral/Earth bond is made at the pedestal.

 

[PaulRainbow]

The one on a boat from a pontoon supply is via the earth wire not the water, water is a very poor conductor of electricity

But it is a requirement under current standards (has been for some time now) to have an onboard connection to the water, as a secondary Earth in case of a faulty marina installation etc, and to provide a protective Earth for generators and inverters when away from the dock.

 

[rogerthebodger]

To answer the OP question here is a diagram of a standalone inverter.

This shows the the ground connected to the battery negative which as billskip says he would not do as I would not

It also shows an inverter/charger. As in the in the vectron website then includer a contact that will connect the negative to the earth in inverter mode but disconnect in charger mode



There is a ground buss but no connection to the water

An RCD also must be connected in between the inverter and the AC panel feed followed by circuit breakers or fuses

In my view a ground connection to the water is a must in the case of shore power as well as the green ground wire to the mains devices when shore power is being used

A connection could be added as Paul and BS says would be no harm but I still would life to know if a fault of various types occur how would the leakage current get back to the inverter neutral as is required by kirchoff's law on of the basic laws of electric flow just like newton's law a basic scientific law

Victron inverter/charger wiring diagram. This shows a ground/earth connector which is a must for a land based installation but again how does that work in a totaled insulated environment like a GRP boat

7. Ground, earth and electrical safety

7.2 is true but does not address an insulated environment
7.3 hows how important a RCD is together with grounding in a terrestrial environment
7.4 has a section A boat is disconnected from shore power
The installation is now the main power supply and together with the load forms its own autonomous electric circuit. No current will flow into the hull and into the water.

This i the point I wished to make as victron states in there above link


This only applies to GRP boats and metal boat like mine must have a different setup as the hull and any metal fittings bolted to the hull / deck are conductive so must have a different setup but I will not go into that here

An interesting comment about a dirty or condensation creating an leakage path on a GRP boat . If there was such a cse and there could be would the RCD not trip due to the leakage via the dirt / condensation thus making the system safe

 

[PaulRainbow]

No they are not bonded

The marina offices etc are no different to any other domestic/industrial installation. But you are mistaken, marina shore power is bonded at the pedestal.

I am a little puzzled by how after an inverter an RCD can trip as it measures the load balance between L&N ie leakage to earth , but if they are bonded how can this work.

It works because the bonding is made at the source. The live and neutral go through the RCD, the Earth does not. If there is a fault some current will pass along the Earth wire, bypassing the RCD and causing an imbalance, hence the RCD will trip.

 

[billskip]

. I am saying the neutral and earth are not joined anywhere on a pontoon supply

Maybe they are not, but whether or not, it has no reflection on how an RCD works.....also if a cable is going to break who says which one...could be the earth, which could potentially be dangerous by preventing the RCD from working...that said it could also prevent a leakage/shock ...RCD's imo are the best thing since sliced bread, but they can also be a pita with nuisance tripping.

 

[PaulRainbow]

To answer the OP question here is a diagram of a standalone inverter.

This shows the the ground connected to the battery negative which as billskip says he would not do as I would not

It also shows an inverter/charger. As in the in the vectron website then includer a contact that will connect the negative to the earth in inverter mode but disconnect in charger mode

View attachment 171714

There is a ground buss but no connection to the water

An RCD also must be connected in between the inverter and the AC panel feed followed by circuit breakers or fuses

In my view a ground connection to the water is a must in the case of shore power as well as the green ground wire to the mains devices when shore power is being used

A connection could be added as Paul and BS says would be no harm but I still would life to know if a fault of various types occur how would the leakage current get back to the inverter neutral as is required by kirchoff's law on of the basic laws of electric flow just like newton's law a basic scientific law

Victron inverter/charger wiring diagram. This shows a ground/earth connector which is a must for a land based installation but again how does that work in a totaled insulated environment like a GRP boat

7. Ground, earth and electrical safety

7.2 is true but does not address an insulated environment
7.3 hows how important a RCD is together with grounding in a terrestrial environment
7.4 has a section A boat is disconnected from shore power
The installation is now the main power supply and together with the load forms its own autonomous electric circuit. No current will flow into the hull and into the water.

This i the point I wished to make as victron states in there above link


This only applies to GRP boats and metal boat like mine must have a different setup as the hull and any metal fittings bolted to the hull / deck are conductive so must have a different setup but I will not go into that here

An interesting comment about a dirty or condensation creating an leakage path on a GRP boat . If there was such a cse and there could be would the RCD not trip due to the leakage via the dirt / condensation thus making the system safe

This is the normal nonsense that Roger posts.

He's posted several Victron references above, but oddly, stopped before the section that actually deals with boats.

Once again, the short answer is that the inverter has to be connected to the boats Earth circuit, the Earth circuit should also be connected to the water.

 

[billskip]

, water is a very poor conductor of electricity

In comparison with what?
Water is all you have when at sea...are you suggesting one should bond to the anchor chain?

 

[PaulRainbow]

Maybe they are not, but whether or not, it has no reflection on how an RCD works.....also if a cable is going to break who says which one...could be the earth, which could potentially be dangerous by preventing the RCD from working...that said it could also prevent a leakage/shock ...RCD's imo are the best thing since sliced bread, but they can also be a pita with nuisance tripping.

They are 100% connected at the pedestal, i've just been and double checked that with the pedestal that we are plugged into. 240v between the Earth and live pins and continuity between neutral and Earth.

 

[billskip]

They are 100% connected at the pedestal, i've just been and double checked that with the pedestal that we are plugged into. 240v between the Earth and live pins and continuity between neutral and Earth.

I dont disagree...that's why I said 'maybe' because I cant be sure they all are. It makes sense that they are and no doubt regulations insist, but ...
Sorry about all this @adhdan but it's all part of the fun.