Vetus SPP230 Manuel D'utilisation page 14

5 Full explanation of operation
The maximum permitted current varies strongly from one yacht harbour to another and
is generally given in Amperes, the unit of electric current, abbreviated to the letter A. The
power is also sometimes given in Watts which can be converted to A fairly easily (see
below).
How many A you may use is generally shown and the harbour master can tell you this
when reserving.
If in doubt do not hesitate to ask - this is a perfectly normal question.
The maximum permitted quantity is almost always shown as one of the following amper-
ages:
2 A (about 450 Watt, very little, fortunately this is not very common in West Europe)
4 A (about 900 Watt), not very much but this does occur)
6 A (about 1400 Watt, quite common)
10 A (about 2300 Watt, quite common)
16 A (about 3600 Watt, not so common, usually with an own kWh meter).
The relation between Watt and A can be calculated as shown below for most electrical
appliances used on board:
P = U x I or Watt = Volt x A. The voltage is then about 230 V.
Watt ≈ 230 x A thus an appliance that uses 2.6 A has a power of 230 x 2.6 ≈ 600 Watt
or in reverse,
A ≈ Watt : 230 i.e. an appliance of 800 Watt uses 800 : 230 ≈ 3.5 A
You could add up how many Watts all the appliances use and then keep a check yourself
that you did not use more than permitted.
However, in many cases it is not easy to determine how much current you are actually
using at a given moment. It is easy to add this up for the lights but a fridge switches on
and off automatically when it needs to provide cooling and an electric water boiler also
does this when it is necessary to bring the water back to the required temperature. It then
switches off again and you do not notice this at all. Such a boiler can take between 500
Watt (about 2A) and 100 Watt (about 4A) just by itself.
If you then use a kettle or a coffeemaker (400 to 1400 Watt), an electric heater (400 to 2000
Watt) or an air conditioner (400 to 1000 Watt) that regularly switches on and off as well you
can easily exceed the permitted power.
Automatic circuit breakers are almost always used in new harbour installations but just as
in houses the old-fashioned type of fuses that burn out can often still be found.
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090901.01 Shore power protector