Watt's The Story With Mains Hook-Up?

Our Diamond Dave repairs motorhomes for a living, which makes him the technical guru to consult when things go wrong.

So how do you know how many amps you’re using? Some equipment will quote the Amps used but most will quote Watts. Now who remembers from their school days what all these terms actually mean? Amps, or Amperes to use the proper name, is a measurement of current. Volts is a measurement of electrical pressure and Watts is a measure of power. To calculate Watts you multiply Volts by Amps, so 2A at 230V equals 460W. ­ e full 16A supply would support 3680W – a little over three-and-a-half kilowatts.

But why does anyone need to know this? Over New Year we stayed on a site using mains hook-up to provide power for heating, battery charging and running the fridge. On the second day, our neighbour called on us to say that their electricity supply had gone off, so I duly reset the trip on the hook-up bollard for them. Within seconds of the power being restored, though, it tripped off again. But it wasn’t the RCD blowing – it was the 16A circuit breaker.

Looking into our neighbour’s motorhome I immediately spotted the reason. ­ ey were running their Truma Ultraheat system on the electric setting at 2000W and had then plugged in an electric kettle. ­ is wasn’t a lowwattage travel kettle, but an ordinary domestic one. ­ e total combined power draw would be 5kW, which needs 21A at 230V, hence why the circuit breaker tripped.