As part of your visual inspections you may well find that the appliance’s fuse is over rated for the appliance.
It is essential that plugs have the correct fuse within them to ensure that, should a fault develop within the appliance, the fuse will blow and disconnect the power supply to the appliance.
As an example, a 3 amp fuse only allows a current of up to 3amps to flow through it. If any more comes through the fuse then it will rupture, cutting off the supply to the appliance.
Choosing the Correct Fuse
The correct fuse should be fitted to the appliance. The way the code of practice indicates this should be done is by looking at the appliance power rating. This is generally written in Watts. If the appliance is under 700watts then a 3amp fuse should be fitted. However if the appliance is over 700 watts then a 13 amp fuse should be fitted.
This, however, is not a perfect system to use. Most motor powered equipment can have high startup currents even though the rating on the appliance is under 700 watts. This would cause a 3 amp fuse to break. Therefore the only exception to the rule would be motor powered equipment. In these cases you should be fine with a 13 amp fuse.
Working Out a Fuse Rating With No Other Information
So what do you do if an appliance doesn’t tell you the fuse rating, and there’s no fuse already inside the plug? In order to determine the fuse rating, all you need to do is work out the following calculation:
Power ÷ Voltage = Current
Divide the power of the appliance (in watts) by 230V (standard UK mains voltage).
Imagine if an appliance rating was 1900W. Dividing this by 230V gives us a rating of 8.3 Amps. Fit the next highest fuse to the appliance which would be a 13 amp fuse.
IT equipment should have a 3 or a 5 amp fuse fitted to the appliance as a general guide.
Written by Barry Atkins
