"Occasional" 240v

[lw395]

There is also the issue that if you connect earth to neutral and don't bond to the shore earth, then you can find there is signifcant voltage between metal parts of your boat and shore ground. This can particularly happen when the boat is ashore, it's an unpleasant surprise to feel 50V AC or so between the aluminium ladder and the guard rails.
More likely to be an issue in a metal boat.
The tingle won't kill you, but it might be enough to make you fall off the ladder.

 

[lw395]

A full short circuit will blow the fuse in the supply cable ! Remember, plug in RCD>>13a fuse>>>cable to tools.

I'm not talking about wiring a house or a factory up, i'm talking about the OPs small inverter, connected to a battery, supplying a drill or grinder (or anything else he wants to plug into it).

Exactly.
Keep it simple, stick to double insulated tools. And check them for damaged cases and cables from time to time.
There is so much stuff out there which only has a two core flex, it's not much effort to avoid earth issues entirely.

 

[matthewriches]

 

[solent clown]

funny, it never bothered me in a vehicle. I suppose on a dry boat there is no more hazard than on land. Maybe I should just let common sense be the arbiter of safe use, and not plug in if the boat is half full of water and karen is firing off flares.
KISS may be the way to go instead of me overthinking again

 

[rogerthebodger]

Indeed the RCD doesn't require an earth as it is a balance scale device :- Current in = Current out with a normal limit of 30 ma. If the current does not balance it defect means it has found another route of return and trips.

This requires the neutral must be connected to earth to provide the return path. Without it might as well leave the RCD in its box.


Bonding the neutral to the earth circuit provides a return path for either conductor foreign a fault circuit, allowing the RCD to operate as desired.

I do consider what training in electrical engineering design some people on hear have.

Paul do you know Kirchoff's current law . I did this a second year university doint my Mechanical engineering degree.

https://www.electronics-tutorials.ws/dccircuits/kirchhoffs-current-law.html

As superheat6k confirms above if there is no neutral earth wire connection at the supply the RCD cannot trip as there will be NO imbalance of current through the RCD.

In Fact its the connection of one of the supply cables to the earth wire/pin that makes that conductor neutral and the one that is not connected live.

There are different systems i.e a balances supply that has no earth system and both conductors are floating above ground potential.

The UK and South Africa are tied to ground sa shown below

The RCD must be fitted between the distribution panel and the plug outlets on this diagram

Like this

In our single ended system we only need to have a single pole switch to make a device safe where in the balances system you must switch both conductors to make the appliance safe. This also goes for fusing.

This is also why on a single ended system it is important that any shore power connection phase is the same as on the boat.
This is also why

 

[lw395]

Neutral is generally NOT GROUND in UK domestic power distribution.
There is current flowing in the neutral wire from the transformer to the house. This wire has both resistance and inductance. Therefore the two ends are at different potentials.

 

[solent clown]

Roger, with the neutral, that is more or less what I learned during my mech eng too, many many moons ago. That was the source of my paranoia with this install as I imagined it may have complications on a boat. It was only the idea of fitting RCDs, and making them function correctly that was my initial concern.

 

[rogerthebodger]

Roger, with the neutral, that is more or less what I learned during my mech eng too, many many moons ago. That was the source of my paranoia with this install as I imagined it may have complications on a boat. It was only the idea of fitting RCDs, and making them function correctly that was my initial concern.

In my view RCD and earthing is less important and a GRP boat as the hull and deck is insulated anyway.

Its a different matter on my steel boat as if the hull becomes live it would kill some one.

I cannot understand why the mains earth would be connected to the battery negative but alot of people think it must be.

On my steel boat my earth is connected to the hull through a GI and my batteries are isolated from the hull to reduce any galvanic currents that could flow.

You GRP boat owners dont have to consider that much as everything is isolated from each other.

 

[lw395]

But the neutral is grounded at the source on UK domestic supplies - normally at the star point of the local Delta Star step down transformer at the substation. The star point provides the neutral between the three distribution phases. It is earthed to the transformer case and normally by some form of substantial ground plate or embedded spike. Effectively the local transformer at the substation is the supply source in a domestic situation. The neutral cable itself is just a wire - it will not have any inductance within and of itself, although by definition the power flowing will having an element of inductance from the induction coils that form the transformer. In regard to grounding this is irrelevant because the grounding is after the inductive part of the circuit. Inductive loads on domestic supplies are fairly negligible.

So although current will run through the neutral, and could be slightly out of phase with the voltage (power factor likely to be better than 0.98), the supply is as far as is feasible balanced between the three distribution phases to the various premises being supplied from any particular transformer, with the ideal being that no current at all runs through the neutral star point at the transformer, although in practice some imbalance will almost aways exist. Even on a long run from the transformer, due to the size of the distribution cables the neutral potential (voltage) will be fairly close to earth potential. The Americans refer to the Neutral as the Grounded conductor, with the Protective Earth as the Grounding conductor.

It is simple to measure the voltage between neutral and earth with any decent multimeter, and invariably you will see 0 volts.

That is largely nonsense.

If you can sell me some zero inductance wire, there is a ready market for it.

https://www.allaboutcircuits.com/tools/wire-self-inductance-calculator/

If you can do it with zero resistance too, that would come in handy.

It's very common for N and E to be different enough that shorting them will trip RCCBs.
There may not be much power available between N and E, but it does not take much to cause e.g. electrolysis problems over time.

 

[superheat6k]

That is largely nonsense.

.

All comments made in good faith in reply to this thread have been deleted, with a request to the mods that embedded comments also be deleted.

I shall respond here no further. Good luck to the OP with whatever you decide to do, but please base nothing on any advice I may have given here, it is obviously nonsense.

 

[Lon nan Gruagach]

Get battery appliances, yes that includes angle grinders! Then the only socket you need is for a double insulated battery charger.

Now, about mains, floating supplies and grounding battery 0V.

IF your inverter offers a truly floating supply, embrace it, cherish it and above all check all parts of the system frequently. You must have 2 simultaneous faults for a floating supply to be dangerous.

IF you insist on RCCD for your protection then you get into domestic wiring territory whereby all exposed metalwork of any services or building structure must be bonded to your protective earth. Since battery 0v is an exposed bit of metalwork of a service it ought to be earthed.

 

[PaulRainbow]

In my view RCD and earthing is less important and a GRP boat as the hull and deck is insulated anyway.

Its a different matter on my steel boat as if the hull becomes live it would kill some one.

I cannot understand why the mains earth would be connected to the battery negative but alot of people think it must be.

On my steel boat my earth is connected to the hull through a GI and my batteries are isolated from the hull to reduce any galvanic currents that could flow.

You GRP boat owners dont have to consider that much as everything is isolated from each other.

In Europe, your installation would be illegal on any new build.

 

[PaulRainbow]

I do consider what training in electrical engineering design some people on hear have.

Me too.

Paul do you know Kirchoff's current law . I did this a second year university doint my Mechanical engineering degree.

https://www.electronics-tutorials.ws/dccircuits/kirchhoffs-current-law.html

Do you know how an RCD works ?

As superheat6k confirms above if there is no neutral earth wire connection at the supply the RCD cannot trip as there will be NO imbalance of current through the RCD.

That;s nonsense.

The RCD must be fitted between the distribution panel and the plug outlets on this diagram


Like this

The OP isn't wiring a house, he's wanting to use a drill or grinder on a boat, from an inverter. The boat will have no connection the his 240v positive, or negative. The only way he can get a shock is if he touches the positive and the negative at the same time, if he does that the RCD will trip. If there is an overload or short circuit, the 13a fuse will blow. Simples !

If a piece of equipment developed a fault and the positive came into contact with the case he still won't get a shock, unless he sticks his finger in the negative at the same time. Oh, wait, he still won't get a shock because the RCD will trip.

I'll say it one more time for the hard of understanding, i'm not talking about wiring a house, a factory, a steel boat, a barge or a 75ft fly bridge motor cruiser, i'm talking to the OP, regarding his simple inverter to run his drill !!!

 

[Lon nan Gruagach]

Me too.

Do you know how an RCD works ?



That;s nonsense.



The RCD must be fitted between the distribution panel and the plug outlets on this diagram


Like this

The OP isn't wiring a house, he's wanting to use a drill or grinder on a boat, from an inverter. The boat will have no connection the his 240v positive, or negative. The only way he can get a shock is if he touches the positive and the negative at the same time, if he does that the RCD will trip. If there is an overload or short circuit, the 13a fuse will blow. Simples !

If a piece of equipment developed a fault and the positive came into contact with the case he still won't get a shock, unless he sticks his finger in the negative at the same time. Oh, wait, he still won't get a shock because the RCD will trip.

I'll say it one more time for the hard of understanding, i'm not talking about wiring a house, a factory, a steel boat, a barge or a 75ft fly bridge motor cruiser, i'm talking to the OP, regarding his simple inverter to run his drill !!![/QUOTE]

Err, in your scenario, touching live and neutral at the same time with no ground connection,the RCCD will not trip. All current still flows from live to neutral, just that some of it will go through the casualty.

 

[PaulRainbow]

Err, in your scenario, touching live and neutral at the same time with no ground connection,the RCCD will not trip. All current still flows from live to neutral, just that some of it will go through the casualty.

Nonsense

 

[Lon nan Gruagach]

Nonsense

I am sure that it is not nonsense.
If touching the live won't trip the RCCD we can assume that the subject is insulated from the protective earth of the supply or that the supply is floating (extremely bad practice with a RCCD)
If the subject also touches the neutral there is still no path for the current to bypass the RCCD, so no reason for it to trip.
Unless you are referring to the neutral before the RCCD without actually stating that.


Edit add:
It is also incorrect to state that conductor to earth faults via a person won't cause a shock due to a RCCD tripping. Those are some of the most unpleasant shocks I have had. Any inductor in the connected appliances will fire huge voltages back across the subject. Whilst not lethal it is very painful.

 

[ShinyShoe]

funny, it never bothered me in a vehicle. I suppose on a dry boat there is no more hazard than on land. Maybe I should just let common sense be the arbiter of safe use, and not plug in if the boat is half full of water and karen is firing off flares.
KISS may be the way to go instead of me overthinking again

Yes quite right. You said she is clumsy. She will burn herself on the flares. You do the fares. Surely she can manage to plug a socket in ;-)

 

[rogerthebodger]

Me too.

Do you know how an RCD works ?

Yes I know very well how a RCD works.

RCD's were a legal requirement before they were in the UK.

The RCD works on the imbalance in the current flowing in the live and neutral current sensors in the RCD and if there is a difference more than 20mA in RSA 30mA in the UK the circuit breaker ( not overload breaker) will open cutting off the supply.

Now tell me where does the difference in current flow to ?

This shows the alternate path for the leakage current through ground or via the appliance green/yellow (UK) (earth) wire.

in the case of a non double insulated appliance the earth wire is connected to the metal case then back through the earth (green/yellow? wire back to the supply transformer where its connected to the neutral supply wire.

This supply connection is also connected to ground spike or any other earthing connection (a submerged metal item on a boat to provide a duplicate fault return path.

You did not answer my question about Kirchhoff's current laws (conversation of current) so you just don't know. The difference between a Technician and an Engineer. (C Eng)


Have a look at this also

 

[Heckler]

Mate, I have lost count of how many I have thrown away at work! Now we have yachts instead of dinghys I will be more recycling minded with such things.

On my cheap tools from Aldi, when the batteries cratered, I took the old cells out and soldered a twin core cable to the terminals and put a ciggy lighter plug on the other end. The battery was 14.6? so the 12.7 ish from my house batteries is good enough. The battery pack is then interchangeable with all the Aldi tools and a bonus was that it fits my Draper drill as well. I have fitted ciggy lighter sockets around the boat for usb charger connections so I can use anywhere on the boat.

 

[sarabande]

Any probs with the (normal) 15A cigarette socket limit ? Several of my battery drills etc range between 200 and 400W.