Why would an appliance trip the electrics when although plugged in it is not switched on at the wall?

Answer 1

If the question is asking about an appliance plugged into a normal wall-mounted switched socket outlet, if the switch is in the Off position no live electricity should be fed to any appliance that is plugged-in, but it is always possible that the wall outlet has been wired wrongly so that its switch is in the Neutral wire instead of where it should be, in the Live or Hot wire. Then, if there is a fault as is described in the second answer (see below), it would cause the circuit breaker to trip Off to break the supply of power even if the wall socket outlet's switch is in the Off position. Another possibility, which is by no means unusual but can tricky to diagnose, is if there is a short between a Neutral and a Ground wire anywhere in the building and the main breaker panel contains an RCD protective device (also known as a GFCI) as is required nowadays for all new installations or full building rewires in a 50Hz area such as the UK or Eire. With an RCD in the main breaker panel to protect all power circuits, if there is a short between a Neutral and Ground wire anywhere in the wiring then the protective device will trip even if no power is being taken by any appliance. For instance if the Neutral and Earth wires were carelessly stripped of insulation to connect them to the terminals of a socket outlet and the Earth wire was not properly sleeved with yellow and green sleeving, the Neutral and Earth wires can easily touch and this would cause an RCD to trip.

Such faults typically show up when a main consumer fuse box has been upgraded to a modern consumer panel containing an RCD and miniature circuit breakers but the old wiring and socket outlets were simply left in place without beuing thoroughly checked. When the old consumer fuse box was in place - before the RCD was installed - any Neutral and Ground wires which were touching behind a socket outlet would not have caused the circuit' fuse or circuit breaker to shut off the power! For more information see the answers to the Related Questions shown below. <><><>

It apparently has a short between the hot power lead and the casing of the appliance. Since the casing is grounded, as it should be, this presents a direct short across the incomming power leads and trips the circuit protector. That keeps you from being shocked or electrocuted. This is a good thing. Replace the appliance. <><><>

As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.

Before you do any work yourself,

on electrical circuits, equipment or appliances,

always use a test meter to ensure the circuit is, in fact, de-energized.

IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS.