Appliances are (for our purposes) either Class 1 or Class 2.

The difference is as follows:

Class 1 Appliances use a Circuit Protective Conductor or Earth wire. This means that this earth wire is connected to any exposed metal parts of the appliance. Hence if the basic insulation fails the user is protected by the fact that the exposed parts of the appliance cannot become electrically charged above earth potential. Modern installations would detect this failure and immediately operate an RCD to interrupt the supply, whereas on older installations a fuse should blow in this situation. (RCD's protect people whereas Fuses protect circuits). It is essential therefore that the condition of the earth wire is sound, and the earth bonding test is designed to check this.

It is also recommended that when fitting or removing plugs and sockets the earth lead should be wired first and removed last.

Class 2 Appliances however, do not use this Earthing technique, so the mains plug will be connected to only two conductors, neutral and phase (Live).

Appliances designed to operate without an earth connection will be constructed with supplementary insulation in addition to the basic insulation provided in Class 1 appliances. Appliances designed to operate in this manner will (or should) be marked by the manufacturer with the "double insulated" sign. (Two squares, one inside the other).

As far as the visual inspection is concerned, the procedure for Class 1 and Class 2 items is similar, except that inspection of a Class 1 appliance should visually assess the integrity of the earth or "CPC" connection.

The Formal Visual Inspection Although referred to as a visual inspection, there are many instances when other human senses will alert the QTO (Qualified Testing Officer) to a potential or actual fault condition. Overheating can felt, arcing may be seen or heard or even smelt. So be aware that all senses are in fact useful and none should be ignored.

Also the person inspecting the appliances has a duty under the Health & safety at Work Regulations to clearly label machinery with guards missing, even if that machinery is electrically safe.

1/ The initial inspection should be to inspect the casing of the appliance for deterioration or damage. All covers should be intact and in place. There must be no holes into which it is possible to insert a finger and possibly touch live areas or components.

2/ Next look at the cable. Taped joins are not acceptable. No cuts or other damage is allowed except perhaps for very light scuffing of the outer casing in some situations, but even then the outer casing must not be worn through to show the insulation of the conducting wires within. In the case of bedside or table lamps special attention should be paid to any in-line switches which may be employed. Older examples of these often have ineffective or non-existent cable clamps. Also twisted joints in the cable can often be pulled out of the switch casing, particularly if the switch acts on one conductor only. In these cases the unswitched conductor is often cut to facilitate excess length removal and the end result is seldom truly satisfactory.

3/ Connecting plugs and sockets should be considered next. It is necessary to remove the covers to these if a meaningful assessment is to be made. Look for the following:

a: That the insulation of the individual conductors is not damaged.

b: The individual conductors themselves are not damaged. (Strands are sometimes damaged when removing insulation leaving only a few strands to carry the current drawn by the appliance)

c: The individual conductors MUST be connected to the correct terminals. Green / Yellow to the Earth Terminal Blue to the Neutral Terminal Brown to the Live Terminal

d: The individual conductors must be cut to the correct length with insulation right up to the terminal. Also the CPC or Earth lead should have more slack than the other two so that if the lead is pulled it breaks away last.

e: The cord grip must be effective and operating on the outer sheath of the cable.

f: The fuse must be of a suitable type and the correct rating. (See Appendix C)

g: The cover of the plug / socket must be properly fitting and secure. h: The plug pins must not be bent or distorted and should be of the modern plastic half sheathed insulated type. Since February 1995 it has been a requirement that virtually all electrical equipment manufactured in or imported into the United Kingdom will be supplied complete with a suitably fused 13Amp plug.