3 phase and single phase in the pontoon box - a dangerous combination sometimes.

[fuss]

Many pontoons have both 3 phase and single phase sockets in the same box around Europe.
This can create a very dangerous situation for the 240v people.

If the power box maintenance or installation is not up to scratch, it is possible to get 400v up your shore power cable, which will then have a negative effect on all your 240v devices that happen to be plugged in at the time.

It will often damage them beyond repair and also has the potential to cause a fire.

The solution for ultimate safety is to make a 3 phase to single phase adapter plug so that whenever you come across a 3 and single phase pontoon box, you use the 3 phase socket with your adapter.

You might have to do a deal over the power cost, or maybe not, but at least there is no chance of a severe over voltage senario.

 

[Graham_Wright]

Many pontoons have both 3 phase and single phase sockets in the same box around Europe.
This can create a very dangerous situation for the 240v people.

If the power box maintenance or installation is not up to scratch, it is possible to get 400v up your shore power cable, which will then have a negative effect on all your 240v devices that happen to be plugged in at the time.

It will often damage them beyond repair and also has the potential to cause a fire.

The solution for ultimate safety is to make a 3 phase to single phase adapter plug so that whenever you come across a 3 and single phase pontoon box, you use the 3 phase socket with your adapter.

You might have to do a deal over the power cost, or maybe not, but at least there is no chance of a severe over voltage senario.

I understand your concerns, but not all three phase supplies come with a neutral. Reasonably familiar with the woeful standards of electrical installations in France, maybe the only safe solution is to measure before connecting.

 

[KellysEye]

>Many pontoons have both 3 phase and single phase sockets in the same box around Europe.

Out of interest which marinas in which countries please?

 

[William_H]

OP feers seem to me to be OTT. There should be a different kind of socket outlet for 240vAC single phase. The outlet socket for 3 phase should be vastly different. I can't imagine a single phase outlet socket being incorrectly wired and remain so. The marina would be so liable if there was damage or a fire. (I am of course assume Oz standards but surely????) good luck olewill

 

[fuss]

OP feers seem to me to be OTT. There should be a different kind of socket outlet for 240vAC single phase. The outlet socket for 3 phase should be vastly different. I can't imagine a single phase outlet socket being incorrectly wired and remain so. The marina would be so liable if there was damage or a fire. (I am of course assume Oz standards but surely????) good luck olewill

Its not that its incorrectly wired, of course there is a different socket for 3 and single phase, normally this situation occurs when the wires in the box are loose and the 3 phase is used to create the single phase in the same box. Someone rattles the box, or maybe uses the water tap (often in the same box) and then the wires go where they should not.

Wait a bit, you will see that others have experienced 400v up their shore lead.
This also addresses the other posters comment about the neutral wire.

 

[findus]

Its not that its incorrectly wired, of course there is a different socket for 3 and single phase, normally this situation occurs when the wires in the box are loose and the 3 phase is used to create the single phase in the same box. Someone rattles the box, or maybe uses the water tap (often in the same box) and then the wires go where they should not.

Wait a bit, you will see that others have experienced 400v up their shore lead.
This also addresses the other posters comment about the neutral wire.

Fuss,
If there is a loose wire, the marina has a problem anyway. The installation will be safe and the RCD/MCB will switch of at faults. William_H is absolutely correct. I would not worry.

Findus

 

[fuss]

Fuss,
If there is a loose wire, the marina has a problem anyway. The installation will be safe and the RCD/MCB will switch of at faults. William_H is absolutely correct. I would not worry.

Findus

Well, I don't want to argue on the forum.

you either believe me that there is a possiblilty or you don't.

RCD will not trip when it gets 400v up it.

 

[NUTMEG]

Thread drift. I removed the shore power plug on my 'new to me' boat yesterday. I found it has TWO male plugs, and the socket on the boat is female. So that's live pins at the plug!

Now that IS dangerous!

 

[JumbleDuck]

If the power box maintenance or installation is not up to scratch, it is possible to get 400v up your shore power cable, which will then have a negative effect on all your 240v devices that happen to be plugged in at the time.

To get 400V you would need to get a different phase connected to your neutral, without blowing any fuses or breakers anywhere. Does that happen often?

 

[William_H]

As far as I understand 3 phase is effectively 3 different active wires and a neutral (usually). Like 3 different supplies. You tap off 240v AC single phase from any one of the 3 phase wires and neutral. The supplier would try to spread the load as equal as possible across all 3 phases. So your neighbour might be on a different phase.
The 400 volts is the voltage that appears between the different active wires. If incredible as it may seem your neutral wire got disconnected from marina neutral and connected to anothyer phase yes you would have 400 volts AC instead of 240VAC. The RCD would probably not rip but the current circuit breaker should trip at the excess current for large current items. Smaller (current) appliances would smoke badly.
In my house we have 3 phase supply. Originally fitted for an electric instantaneous hot water service. Now changed to gas. The electrical outlets of the house are divided into 3 parts each on a different pahse. Likewise the lights are divided into 3 parts each on a different phase. So 3 RCD/ overcurrent circuit breakers for power 3 for lights.
each breaker is 15 amps so we can if we use the rights power outlets use 45 amps total in multiple appliances. Actually we use very little current but it is good to know.
Never any fear of 400 volts to an appliance.
olewill

 

[GEB]

There is no need for any wires to get crossed to produce over voltage. All it takes is for the distribution system neutral to become disconnected (even for an instant).

A star connected three phase distribution system that supplies single and three phase loads must have a neutral otherwise the phase voltages will drift with changes in the load on each phase.

You can blame Mr Gustav Kirchhoff for this. When the neutral is lost one of his laws demands that a rebalancing takes place, and if there can be no neutral current the voltages must change to compensate.

This situation is not restricted to marinas it can (and does) happen on any three phase system as described above.

In the extreme the phase voltage (230V) can approach the line voltage (400V).

GEB

 

[fuss]

The 400 volts is the voltage that appears between the different active wires. If incredible as it may seem your neutral wire got disconnected from marina neutral and connected to anothyer phase yes you would have 400 volts AC instead of 240VAC. The RCD would probably not rip but the current circuit breaker should trip at the excess current for large current items. Smaller (current) appliances would smoke badly.
olewill

The current circuit breaker will not trip. We are talking voltage here... its got nothing to do with circuit breakers.

I did not originaly post that this happens as a theory. It is a fact that it does happen.

I thought my original post might have been of help, but the thread seems to demand that we discuss basic level electricity with explanations on why breakers do not trip when they get overvoltage.

 

[JumbleDuck]

There is no need for any wires to get crossed to produce over voltage. All it takes is for the distribution system neutral to become disconnected (even for an instant).

A star connected three phase distribution system that supplies single and three phase loads must have a neutral otherwise the phase voltages will drift with changes in the load on each phase.

Surely the phase voltages are set by the supply system? Or do you mean that the centre of the star will move away from neutral (nominally zero) if not tied to it?

You can blame Mr Gustav Kirchhoff for this. When the neutral is lost one of his laws demands that a rebalancing takes place, and if there can be no neutral current the voltages must change to compensate.

In a properly balanced three-phase system there is no neutral current.

This situation is not restricted to marinas it can (and does) happen on any three phase system as described above.

Quite.

 

[GEB]

Yes - if the neutral connection is broken near the source there will be a voltage difference (magnitude and angle) between the supply neutral and the 'star point' of the load. In the case of a three phase system being used to supply single phase outlets (phase & neutral) the 'load' is the single phase outlets now connected to a floating star point.

Three phase systems supplying single phase loads are rarely balanced so a neutral current is the norm.

GEB

 

[Colvic Watson]

Thread drift. I removed the shore power plug on my 'new to me' boat yesterday. I found it has TWO male plugs, and the socket on the boat is female. So that's live pins at the plug!

Now that IS dangerous!

Ouch!

 

[lw395]

The best protection might be what we call an 'overvoltage crowbar circuit', which trips the breaker if the suply volts are too high, or possibly if the neutral is too far from gnd.
You might be able to get a surge protector to do this?

Mains is not my field though, I've worked a lot on lower voltages, and a bit on higher...