Electricity and boats

Just heard an interesting bit on R4, about the history of electricity in boats.

In the 1890s, there was a thriving electric boat buisness in the Thames, hiring out boats to people for the day.

The rise of the internal combustion engine killed them off.

Look at the history of the land speed record too. There's an interesting gap between steam and petrol taking over, filled in by electricity.

BTW - electric motors of this period are _very_ collectable.

I took an electric launch out on the Broads a couple of years back .. very quiet and I believe would run for a couple of (full) days between charges ..

Re the electric on a boat ... a mate lived on a converted Thames barge for about 15 years and I doubt for one moment *any* consideration was given to the safety of the hookup? (I visualise basic T&E running through the water ... )

All the best ..

T i m

Ian Stirling wrote in news:6eghc.32383$h44.4764938 @stones.force9.net:

Musta been the fumes

mike r

Could have been . ;-)

Joking aside, an electric (narrow) boat is about the best use of electric (battery) power.

Most need some form of ballast so why not make it batteries.

They can (easily) carry higher quantity of basic cells (higher capacity for less money)

They give the plates a smooth ride (just like floating on water) ;-)

A boat uses a 'fluid coupling' (propeller) so no shock loads on the trasmission.

Low speed / low current drain / good battery life.

Nearly silent

No (local) emmisions

Large flat surface on the roof for solar panels.

Overnight stops for charging (offpeak mains hookup or genny & wind turbine).

Simple compact mechanics.

An outboard motor could be used for extended trips / backup.

I just wish I'd had the money to put it all into practice .. ;-(

All the best ..

T i m

I don't see why not, especially if the connecter is rated at 16A. If it is, it would be best not to use the 6A MCB as well.

Firstly if the generator is 240v-_ish_ it might be best not to use it to supply the sockets. It may go to a much higher voltage off load which could fry any delicate electronics connected to the sockets.

Best to measure the voltage to see if this is the case, and if so it would be much safer to supply any electronics via an inverter connected to the battery. Even if not it could be worth doing it as one day you might swap the generator or it may develop a fault.

Apart from that I don't see why not if the generator earth is connected to the boat's mains earth, if that's what is recommended. I'd expect that the earth in the generator is connected to neutral anyway.

Yup!

No, as the RCD cannot detect an imbalance without there being an alternative return path.

Eg your stainless steel microwave develops a neutral to earth fault. Then inside the metal toaster a live wire touches the casing. While holding on to the toaster you grab the metal handle on the microwave....

OK it's a pretty unusual set of circumstances but you have just completed a circuit between live and neutral. Without an earth the RCD does not detect any difference between live and neutral current, so stays on.

If there is an earth the RCD will trip as soon as the microwave develops the neutral to earth fault as some current will flow back through earth instead of neutral. Or if a live wire in the toaster touches earth there will be a fault current back through earth and the RCD will trip.

Only if both the earth in the microwave and toaster both get disconnected do you lose the protection of the RCD, but that's very unlikely.

Also some electronics require an earth to fiter the supply, without that they are more at risk of being damaged, and the casing could 'float' at a fairly high voltage.

How you connect mains earth to the hull is another matter. Earthing the hull can cause problems with electrolysis so the recommended way is to earth is via a 'galvanic isolator' which is a set of chunky diodes which block any low voltage DC but conduct any AC fault currents safely.

If the earth is left floating and a live wire before the RCD touches the hull, the whole hull becomes live which could cause a fatal shock as you step aboard. Having a galvanic isolator would prevent this as it would conduct a fault current back through mains earth and the fuse/MCB in the marinas supply should blow/trip.

One way of providing a galvanic isolator is to use a suitable bridge rectifier which is a handy set of diodes connected back to back. This would have to be on a heatsink to stop it overheating in case of a fault. If there were a couple of terminals provided to a meter could be connected across it to check for any stray DC voltages.

Sorry this all sounds a bit complicated but getting electrocuted or having the hull corrode away is not the nicest thing to happen.

Hmmm, he'll go far as a manager ;) If he installs the RCD with a socket next to it and the earth connected to the hull he should be OK for now. He can plug an extension lead into the socket and sort the rest of the wiring and galvanic isolator out before long.

cheers, Pete.

Ooops, can anyone spot the deliberate mistake?

Mustn't post technical stuff after a couple of beers....

cheers, Pete.

On Tue, 20 Apr 2004 23:59:57 +0100, in uk.d-i-y Pete C strung together this:

Which particular one are you meaning? I could be being pedantic over a couple though.

I tried that once, to much the same effect!

Depends. You need to be careful about cascade connecting RCDs or you might find the upstream one trips before the downstream one. With just a few appliances on a boat I don't see this as a serious problem. IMHO all the mains needs to go through a standard 30mA RCD for shock protection. If this means two 30mA devices connected in series then so be it, a proper dock side supply should already have an RCD but an extension lead run forma toilet block or pub might not...

Yes, you are already aware of the earthing issues. The generator does need it's chassis bonding to local, real, earth via a spike and suitably rated wire. It would be prudent to check that what ever is designated "neutral" from the generator is also securely bonded to the generator chassis and thus the local real earth.

The RCD in the boat will shock protect the circuits down stream of it, it does trip on imblance between L and N.

BTW IP44 is not a connector type but a water/dust/finger protection rating. I suspect you mean the round blue plastic plugs/sockets otherwise know as BS4343 or CEE17. Though I see Screwfix refer to them as IP44... Note that Screwfix do not sell BS4343 chassis plugs or inlets (ie have pins showing, males) only outlets (sockets, females), indeed BS4343 chassis inlets are tricky to find.

I lived in Paris for a year, much of it spent sharing a houseboat with an alcoholic pyromaniac whose hobby was torching the electrics as fast as I could rewire it. I moved ashore before we needed to light the gas-fired heater, as CO poisoning seemed an inevitability.

We once went for a weekend cruiize up the Seine, blowing out the main battery feed in some rustic anchorage about 60 miles away. I went for a walk in the nearby woods to avoid throttling the idiot and calm down. Found an abandoned Renault 5 dumped there, stripped out the alternator wiring harness and used that for enough of a rewire to get us home.

Quite a few generators have their earth connected between line and neutral to give

line - 110VAC - earth - 110VAC - neutral.

Between line and neutral is 220V and both line and neutral are at

Go ahead, I'm sure there's a few un-deliberate ones!

The one I meant was:

In this case the two faults would complete a circuit between live and neutral via the floating earth and trip the MCB. You'd only get a shock if one of the earths on the appliances was disconnected.

Although using a generator gives you isolation, there is still the possibility of problems between different equipment, which an RCD and connected earth will protect against.

cheers, Pete.

You can get IP67 versions of the sockets, which I would prefer to use on a boat.

Colin Bignell

Lots of useful info. guys. Many thanks.

I'll forward it to the boatman himself. Sorry that I didn't think to look for a waterways newsgroup.

Regards Richard

On Wed, 21 Apr 2004 12:54:33 +0100, in uk.d-i-y Pete C strung together this:

Why don't you want him to use the 6A mcb? Why not use a ups with power conditioning or similar with the generator rather than a battery and inverter, far cheaper. All the faffing with the galvanic isolator could be avoided if he used a floating earth arrangement, with isolating transformer(s). (I think, not fully clued up with boats)!

Yep, I noticed that one was the biggie!

Sorry, I didn't mean cascade the 16A and 6 A MCBs - just that the Screwfix CU is so equipped.

Richard

Richard Savage wrote in news:4086ACAA.2010405 @nildram.co.uk:

Sorry that I didn't think to

Can't think why; you've got the gen, I hope, and I've had an interesting read

mike r

For the microwave?

So the chap was going to spend £250 at Machine Mart for a genny that he may use away from the moorings an £50 of bits from Screw Fix He is now going to spend a grand on a good genny and maybe as much on a soft start isolating transformer. I bet that made his day.

On Wed, 21 Apr 2004 20:02:01 +0100, in uk.d-i-y "brian" strung together this:

Eh?

No-one said doing things properly is cheap.