How safe is your wiring?


Electric current can kill a healthy adult in less than a second. And it cannot be seen, smelt or heard, therefore it is always dangerous. A fundamental principle of BS7671 wiring regulations, is to ensure  circuits are designed, installed & tested, so that they “fail-safe” in the event of a faulty, by disconnecting the power fast enough to avoid endangering people, property or livestock. Also electrical installations do deteriorate with age and usage, so routine checks and tests should carried out at periodic intervals. 


Electricity always generates some heat in a circuit. Larger currents, (higher power items), create more heat. Cables must be correctly selected for the amount of current they supply. Incorrect cables could overheat, initially melting the insulation, then possibly starting a fire, especially if adjacent to combustible items. Loose termination joints in accessories are another cause of overheating in a cable.

Two shower switches where excess heat due to poor termination has caused melting of insulation.

IMG_20160327_200514                               IMG_20141206_092451


In the event of a fault exposed conductive, (metal), parts could become live giving risk of electric shock. For this reason all exposed conductive parts must be connected back to electrical earth.  Some appliances or accessories are ‘Double insulated’ or ‘ClassII’ which do not require an earth connection.  These typically have the Double Insulation symbol printed on them;  However the earth wires in the cables must still be appropriately terminated and never just cut off, so as to ensure earth continuity to any accessories further along the circuit.  Whenever doing any alterations or additions to a circuit, earth continuity is an essential test that should be verified before reconnecting the power back onto the circuit. Before the mid 1960’s earth conductors were not required on lighting circuits. If your property has old wiring without an earth conductor then decorative metal accessories requiring an earth must not be fitted to the circuit.

Metal decorative switch with intact old rubber cables but no earth.                  Plastic ClassII  switch with PVC twin cable without earth.IMG_20151008_110252                                                     IMG_20151008_115602

Old wiring and cable ageing:

Modern PVC cables which became common use from the 1960’s onward can have a lifespan in excess of 70+ years. Some older properties may still  have earlier cables types in use such as Tough Rubber-Sheathed, (or even Lead Sheathed cables in properties older than 1948). As a general rule most non PVC cable is beyond its normally expected safe working life. But its precise condition will depend upon the amount of loading, heat, exposure to UV light or physical movement the cable has been subject to.  It is not uncommon for the insulation on these older cables to become brittle, inflexible and prone to crumble if attempting to replace accessories.  If you think your wiring may be outdated non-PVC wiring it is best to get it tested ASAP to verify its condition and leave undisturbed until it is either replaced or verified as still functionally safe.  (some rubber cables can still be electrically intact).

Examples of old perished rubber wiring,   2x Sockets,    2x Light wiring.

 VIR2                        VIR1

IMG_20151008_105944                    IMG_20160108_144115

Faulty Components:

Even when all of the wiring is safe, correctly designed and installed, there can still be problems where components fail due to natural wear, or due to cheap quality materials used in their construction. If the worst does happen and an accessory fails due to overheating, you do want to be assured that the rest of the supply circuit has correct fusing and protection to disconnect the power before a situation becomes out of control. 

Example of an overheated dimmer switch, showing melting and burning.

External Influences:

Outdoor wiring and accessories can deteriorate due to the effects of weather, especially damp, cold or UV sunlight. But it is also not uncommon for internal fittings to deteriorate due to damp ingress or insects. Corrosion can cause faults on electrical connections, fixing screws, cases and covers etc. Sometimes electrical burning smells, or crackling or buzzing sounds may indicate a faulty accessory, but without routine inspection of the circuits and accessories deterioration can go unnoticed leaving increased dangers in the event of a fault. The types of hazards highlighted here are some of the reasons why wiring regulations recommend domestic installations are inspected and tested every 10 years or change of occupancy.  

Example of an old socket outlet fitted to an external wall with damp problems and a few visits by spiders.

Common Myths about the old traditional Wylex fuse box with wire fuses:

Historically a lot of properties had a Wylex fuse-box with fuses that you had to physically replace the wire in the carrier if a fuse blew. Stories are often told of people saying these are illegal or dangerous or non compliant with wiring regulations. Which are all factually incorrect.

Three typical old Wylex boxes,   3-way,  4-way,   6-way.

      IMG_20151028_091225                    IMG_20160317_090445                    IMG_20151028_090939

As BS7671 wiring regulations is non-statutory it is not possible for a fuse box to be illegal in relation to the wiring regulations.

Any fuse box is dangerous if the protective devices, cable sizes and loads supplied are not correctly matched. Providing they are correctly matched an old Wylex box will not be dangerous assuming it is physically and structurally sound.

The type of fuses used in these boxes are called BS3036, These are still an acceptable means of overload protection as listed in the current wiring regulations table 41.2 page 61. So they can hardly be a non-compliant option of protective device.

Additional external RCD shock protection would probably be needed to make such an installation safer and fully compliant in the event of any addition or alteration work being carried out.

In the event of a fuse blowing they are less convenient and have the danger of someone putting the wrong gauge of fuse wire into the holder, in which case the installation would become unsafe and a potential hazard. (With a modern box the fuses are simple trip switch operation to reset the power once the fault has been cleared.)

An analogy could be a comparison with modern cars -vs- old classic car.  Both can be legally and safely driven on the public highway.

But in the event of poor driving conditions or an accident, a car fitted with Airbags, ABS breaking, Seatbelts, Fog lights, Crumple zones etc.. would be a safer option than an old car without any of these modern safety features.

An old Wylex wired fuse box is not unsafe, BUT it is not AS safe or convenient as a modern  consumer unit.

HOWEVER;  just as older cars need a bit more TLC and servicing to keep them running smoothly an older electrical installation needs to be monitored adequately to maintain a safe and functioning supply to all of your appliances.

If your property has an old Wylex fuse box, it is probable that wiring is also quite old. If you have had no formal inspection within the past 10 years it would be wise to get it checked and tested to make sure there are no hidden dangers with deteriorating circuit wiring.


Some applications of using electricity can introduce increased risk of shock or overload:

Outdoor power (Sheds, garages and workshop):  The risks and dangers of outdoor electricity and external wiring are numerous. Great care should be taken when obtaining power for use in outbuildings. Long trailing leads across gardens should be avoided for any semi permanent arrangement.

Extension leads: Due to the increased risk of overload and damage to flexible cables, extension leads should kept as temporary use only and not used as a permanent source of power. They should never be used still coiled up on a drum reel. Higher power appliances, consuming more than 10 amps each, Cooking, Heating, Washing etc. should be plugged directly into a proper wall socket, not a multi block extension reel.

Hand tools: Portable hand tools must be kept in good working order, never use equipment with broken or damaged cases, covers, flexes, plug tops etc.

DIY work: DIY work has dangers from poor workmanship, lack of correct testing, accidental damage to electrical fittings, or drilling walls where live cables may be run etc.

Electricity and Water: Environments where splashes or washing down occur should have appropriately rated electrical accessories to prevent water ingress and damage.

Lighting: Always use the correct power rating of lamp in a light fitting. Keep lights mounted a suitable distance from walls, curtains or any other surfaces susceptible to damage by the heat from the lamp.

General wear and tear:  Concealed wiring can be deteriorating or damaged unseen over a long period of time. without routine inspection and testing it is impossible to be sure that your installation has not deteriorated to an unsafe condition. BS7671 wiring regulations recommends formal inspection and testing once every 10 years or change of occupancy for domestic dwelling. (every 5 years for rented accommodation).

If you have any doubts about your appliances or wiring, or if you have experienced any strange electrical smells, crackling or sparking noises, or RCD’s randomly tripping then arrange a formal inspection as soon as possible.

-{page end 21Mar19}-

 Posted by at 12:13 am