Mains Electricity onboard boats
Most of us take it for granted until its not there.
For those of us that liveaboard our boats, having an ample supply of power is just as essential.
Many marinas, boatyards and residential moorings will have a mains power supply available. Simply plug in your power lead and you have 240 volts mains power connected to your boat.
Boats use a similar system to caravans and motorhomes using a power lead with two waterproof connectors, one each end. One plugs into the mains supply and one plugs into the boats mains electricity system if it is fitted with one.
What is the boats mains electricity system then?
Many boats are now fitted with a mains circuit. Typically, this will consist of a waterproof socket fitted to the outside of the boat that will receive the plug from the mains connection lead. Wiring from this socket then connects to a distribution unit that is fused. Most modern distribution units use trip switches rather than the old fuse wire.
From the distribution unit wiring can be run throughout the boat to incorporate your power sockets and lighting.
This is a very basic installation. Depending on your needs mains systems can be much more complex and is really to detailed to go into here.
So now you have a mains electrical system on your boat and you are plugged into the marinas power supply you can use any of the normal mains operated appliances but what if you want to take the boat cruising? You can't take the marinas power with you.
All is not lost as their are ways to provide mains electricity while cruising or living on a mooring without mains power.
Here are some of the options open to the liveaboard that does not have convenient access to a mains supply.
Inverter
Inverters are electronic devices that convert 12 volt DC current to 240 volt AC mains power. They come in various sizes from 150 watts to 3,000 watts +.
Smaller inverters are suitable for running small equipment like a computer, TV or phone charger and larger ones can run equipment like washing machines and driers.
Inverters will discharge your batteries quickly with high loads and extended use if you do not run your engine to keep the batteries charged. Inverters are very good at providing mains power for short periods.
240 volt AC Alternator
These devices attach to the boats main engine. They are similar to a car alternator except they produce 240 volts AC current instead of 12 volt DC current as a car does.
Again, these come in different outputs to suit your needs but remember power is only generated when the boats main engine is running. If your mooring dries out at low tide this could be a problem.
Generator
Both petrol and diesel generators in a range of outputs are available and can be a flexible solution. Small petrol generators are now reasonably priced and very quiet when running. These are suitable for smaller appliances run for a short period. Larger diesel generators have more power and can run larger appliances but are rather noisy and will not please people nearby if run late into the night!
There is no hard and fast rules on which is better, you should choose what is best for your own situation.
You may wish to combine different options which many people do.
Some liveaboards like to continuously cruise so having a good and practical electrical system on their boat is essential. To achieve this any boat will need a good bank of domestic batteries. Without a dedicated mains supply the domestic batteries will provide all your electrical needs so they must be in good condition and maintained well. The larger the battery banks the better and the longer they will last between charges.
If your only means of mains power is from an inverter make sure the inverter is only connected to your domestic batteries and not your engine starting battery. All boats should maintain a battery that is only used for engine starting. If your domestic batteries are discharged you will still be able to start the engine and charge the domestic batteries again.
You can work out how big your domestic batteries should be by working out your typical power usage for the equipment you have onboard.
Here is an example of how to calculate your power usage.
Deep Cycle batteries are generally used to supply the boat's "household" power and are measured in Amp-Hours (AH or Ah).
Typical power usage:
Low power lights = 1 Amp
Navigation lights = 3 Amps
Laptop computer = 5 Amps
Refrigerator = 5 Amps
Small pumps = 3 Amps
Heavy duty pumps = 5 Amps
To calculate your "daily energy use: for each appliance, multiply the Amps by the number of hours each day that it is used. Add all these daily "Amp Hours" used together, then multiply the total by your system voltage (ie: 12,24,240 etc) this figure is your daily "Watt Hour" energy usage.
To calculate the size of battery you will need, use the following:
Daily “Watt Hours” divided by your system voltage.
Example: 1000 / 12 = 83.3 AH.
So to supply 1000 Watt Hours for 1 day you will need a minimum of an 83.3 AH battery. Typically, due to power loss and discharge depth a larger capacity battery should be used. In this example a 110 AH battery would be needed.
As you can see from the example there is more involved to power management when you do not have access to a mains power supply.
Finally, here are some general tips on mains power aboard a boat.
1. When connecting your power lead from the supply to your boat, make sure the cable does not go into the water.
2. Make sure your boats mains system is fused, if not you could end up renewing all your expensive appliances instead of a fuse!
3. The mains power on your boat is the same as that supplied to a house so treat it the same and follow all the normal safety precautions.
4. Mains electricity and water do not mix well so make sure you do not mix them.
5. If using a generator or your boats engine to supply mains power remember to shut them down at night to avoid disturbing others close to your boat.
If you want to find out more on this subject there are some good books available on boat electrics. Try a search on Amazon or other good bookshops
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© 2005. Living On Boats.
www.livingonboats.co.uk
Martin Chinery has lived on boats for over 7 years. He writes articles for and runs the Living On Boats website.
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'Bargain Basement'
I often look around for boats that are for sale at a reasonable price and could make a suitable liveaboard boat. It is surprising what you can find so I thought I would feature one vessel in each edition of the newsletter to show what can be found. I'll call this 'Bargain Basement' and see what little jems we can come up with.
This months 'Bargain Basement'
FOR SALE: 38'x9'6'' Omar park home on floating pontoon. West London £35,000
38'x9'6'' Omar park home on floating pontoon on secure moorings in West London marina, garden, shed, 2 bedrooms, kitchen, shower room, bath, front and back decks, gch, double glazed, solid fuel stove, launderette on site, 2garages available to rent from local authority, mooring fee £227.49pm, council tax £12pm. Southall station 10mins, Heathrow 15 minutes drive. All local amenities
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Exclusive to newsletter subscribers
Well, we did say that you would get information that is not available on the website by subscribing to the newsletter so for all those looking for a suitable liveaboard boat to rent then the following might be of interest.
Please note that I have agreed with the owner to only display the contact details for the next 4 days so if you are interested do not hang around.
For Rent: Twickenham Barge For Rent
Charming double bedroom barge with roof garden, walk in closet, comfortable living room, both electric & coal heating, shower, broadband connection, access to laundry. 5 min strawberry hill, 15 min Twickenham. 45-60 min to Central London. £800 pcm exc.
Contact: XXXXXX Twickenham UK
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