New vs Old Wiring ColoursIn 2006, Amendment 2 of BS7671 Wiring Regulations saw a change to “harmonise” the UK colours with the European cable colours for consistency and to avoid confusion. It’s important that properties get their wiring checked, to see if the wiring colours are out of date, have deteriorated over time, and to check if they comply with BS 7671 Wiring Regulations.Some properties across the UK still rely on the old cables, which can be dangerous if not tested. Old cable colours could be due to the age of the property or the wiring system, which simply hasn’t been monitored or tested as regularly.Credit: Wikipedia How have wiring colours changed in the UK?. The neutral black has been replaced by blue.
The line red and has been replaced by brown. The earth is still identified by green and yellow.
Condition of Wiring CablesIf you’re moving into a new home, or you are renovating your current one, make sure you carry out visual checks on the electrics, specifically looking at the colour and condition of the wires.If you have the previous colours, red, black and green earth (or bare earth – very dangerous!), we would recommend you have an electrician test to check the integrity of the cable as it could be more than 50 years old and unreliable.You should also be looking at the condition of cables, as well as the sheathing of the cables. The average lifespan of electrical wiring is 30-40 years and will deteriorate over time, especially if your home uses one of the aged styles of cable sheathing, which are highlighted below. Tough Rubber Sheathed cablesBefore pvc-insulated cables became common in the 1960s, most cables in the home were tough rubber sheathed (TRS). This type of sheathing is recognised by its black exterior.Vulcanised rubber insulated cables (VRI) also grew in popularity during this time. With this cable type being over 55 years old, it has become obsolete in domestic dwellings.
Cable types and installation methods The standard circuit tables have assumed flat twin and earth cable to BS 6400 with reduced cpc size and installed as Table 4A2 of BS 7671 with current rating.
We recommend, if this applies to you, that you get an electrician immediately for a full rewire.Insulation and sheathing can deteriorate with age, but also with excessive temperatures and overloading, as well as the rubber deteriorating if it has been exposed to direct sunlight.When cables deteriorate, it means they lose their insulation and flexibility, becoming dry and more like to crumble away and break. Lead Sheathed cablesPre-1950s saw lead-sheathed cables (see above) being used more in domestic dwellings. They are rubber insulated, copper conductors, with an outer sheath of lead. Just like TRS cables, lead sheathed cables deteriorate over time as they are rubber insulated.Lead sheathing is still used in some older properties and could be gradually deteriorating without you knowing. If you spot any lead sheathed cables, please be warned that these cables are past their expected working life and should be inspected by an electrician immediately for safety.
Despite the obvious importance of maintaining and updating electrical wiring, faulty wiring remainsone of the most common causes of fire in historic buildings. A surprisinglylarge number of buildings still retain wiring installed in the mid 19thcentury and, in some cases, the earliest forms of wiring are still inuse, presenting a constant threat not only to the building and its contents,but also its occupants. It is an unseen problem, and often not eventhe owners are aware of the situation. In churches, which are subjectto regular architectural quinquennial surveys but not always to electricalquinquennial surveys, the risk may be understood but may not be dealtwith due to a lack of funds. The situation is not helped by EnglishHeritage and the Heritage Lottery rarely providing funds for the replacementof old, dangerous electrical wiring unless it can be claimed as partof the building work. However, wiring within a listed historic buildingis now not subject to VAT providing that listed building consent hasbeen granted for the work.
ASSESSINGTHE PROBLEMThe Electrical Regulations,BS 7671: 2001 state that electrical wiring should be regularly tested.In Guidance Notes Number 3, a supplement of BS 7671:2001, a table givesrecommended frequency of testing for various buildings. In ecclesiasticaland secular historic buildings it is generally accepted that if a buildinghas been rewired, the first periodic test should be after five years;for wiring older than five years, periodic tests should be carried outevery 2½ years. In practice, however, the periodic testing of electricalwiring rarely takes place, as it is considered to be a very costly anddisruptive exercise. As a result, the scale of the threat to historicbuildings has never been fully quantified.The wiring in historicbuildings generally falls into one of three categories.
Where wiring fallsin the first category, the existing wiring in VIR cables and lead sheathedVIR cables will have long passed the end of its productive life. Itwould not be a good idea to carry out any electrical testing of thecircuits, as the rubber sheath would now be so old and perished thatharm would be done to the installation, thus leaving the installationin a more dangerous state than existed before the insulation resistancetests were undertaken.Statisticscollated by the Ecclesiastical Insurance Group indicate that electricalfaults in churches cost £5 million each year.