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Understanding and fixing plugs and fuses


1st Jan 2015 Home & Garden

Understanding and fixing plugs and fuses
Correctly fitting the appropriate plug, flex and fuse to an electrical appliance is crucial to avoid the risks of fire and electric shocks. Use this guide when checking for faults.

Plugs and fuses

The key factor in deciding what rating of fuse to use is the wattage of the appliance. Modern appliances are supplied with factory-fitted moulded plugs—all that is required is to fit the correct fuse if the original blows.

Which fuse?

3A (red): Use in plugs for appliances up to 690 watts, such as electric blankets, hi-fi systems and table lamps.
13A (brown): Use in plugs for appliances between 690 and 2990 watts. This includes anything with a heating element.


Once every six months check flexes and plugs. This is particularly important with appliances which are portable or which are moved during use, such as a hairdryer, iron, vacuum cleaner or power tools.
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Be sure to:
  • Buy plugs marked 'Made to British Standard BS1363', and fuses made to BS1362. Fit tough rubber plugs to power tools and to garden equipment, to prevent them being damaged if dropped.
  • If discarding a moulded-on plug, cut through the flex close to the plug body. Then deform the pins with hammer blows so the plug, if found, cannot be inserted in a socket outlet and cause the user to receive a shock.

Fitting a new plug

Fitting a plug
Step 1
Disconnect the appliance from the mains and remove the plug from the flex. Use a sharp knife to cut the end off the flex near where it entered the flex grip or at the point where the flex is damaged.
Step 2
Remove 40mm of sheath from the flex. Take care not to cut the insulation on the conductors. Thread the flex through the plug cover, if necessary, and under the loosened flex grip. Trim each conductor with side cutters so it reaches its terminal easily.
Step 3
Use wire strippers to expose a section of metal on each conductor. Twist the wires tightly. Remove the fuse to gain access to the live terminal and connect the conductors to their respective terminals: brown to live, blue to neutral and green-and-yellow to earth.
how to wire a plug
Step 4
Leave a little slack on the earth conductor. For pillar terminals (above), undo the screw, push the bare wire through the hole and tighten the screw. With screw-on stud terminals, remove the stud and wind the bare wires clockwise around the pin.
Step 5
Make sure the conductors lie in their channels within the plug and don't obstruct the retaining screw hole, then tighten the flex grip to hold the sheath firmly.
Step 6
Make sure that no unsheathed cores are visible outside the plug, and check the fuse is the correct rating for the appliance (see table). Remove and replace if necessary. Then fit the plug cover firmly in place and tighten the retaining screw.

Fault diagnosis

No power to appliance
Cracked plug/live parts exposed Replace plug.
Fuse blown
Unplug appliance and check plug and flex for evidence of short circuit causing charring. Replace flex if necessary. Fit replacement fuse of correct rating and test appliance.
MCB tripped or circuit fuse blown
Reset MCB or replace blown fuse. If fault recurs, consult an electrician.
Flex discontinuity
Check each conductor with continuity tester and replace flex if faulty.
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