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Wiring Systems: Refurbishment of older wiring systems

One of the first types of wiring incorporated insulated spacers supporting conductors, in the early stages these were often bare conductors. This was a relatively easy type of installation not ideally suited for homes because electric shock was a great risk.

Often when carrying out refurbishment or repairs on an existing building, older wiring systems are sometimes encountered by electricians. For the new generation of electrical installers this can be the first time they have encountered an older wiring system in working operation. It is quite difficult to explain the nature of a wiring system when there is little or no practical information available. An older wiring system does not necessarily mean the installation is unsafe.

Lead-sheathed cables were another type utilized, which consisted of tinned copper conductors with rubber insulation, often having a cloth covering, then an outer lead sheath. This proved to be a popular type, due to the ease and speed of the installation methods. The fixing methods were bottle- style clips which were prefixed along the route and then the lead- sheathed cable was laid along the route and the clips used to secure the cable in place.

The lead sheath formed the circuit protective conductor and it was essential that this was maintained to ensure that the sheath could not become live. At each termination there was a clamp system that secured the lead sheath to a metal box.

This type of cable offered an element of mechanical protection but the rubber insulation was liable to deterioration over a period of time, often due to excessive heat or overloading at the terminations of accessories. If lead-sheathed cable is found within an installation, it can be inspected and tested to determine the condition of the lead sheath and the rubber insulated conductors, but it is advisable to leave it undisturbed until such time as the wiring system can be replaced.

Wooden trunking
Vulcanized India rubber insulated cloth covered conductors encapsulated in a wooden- style trunking system, which had normally two grooves for the conductors to be located. This was a time- consuming process where usually carpenters were used to complete the system for the early electricians. The rubber insulation was liable to cracking over a period of time, often due to excessive heat or overloading at the terminations of accessories and there was the inherent fire risk associated with the wooden system.

Should this type of system be encountered, the only course of action would be replacement, although a detailed description including photographs and the retention of the system for display purposes would be greatly appreciated.

Tough rubber sheath
Another popular type was, rubber insulated, tough rubber sheath cable (TRS) which was easily recognized by the black coloring, similar to the modern PVC cable. This once again proved popular because the flexible nature of the cable assisted the speed of the installation.

However, the mechanical protection for this cable was almost nonexistent. Also, the rubber was liable to deterioration depending on whether it was being subjected to overloading and/or high ambient temperatures. This cable type was also susceptible to damage from exposure to direct sunlight. The resultant deterioration often led to the loss of the insulating properties where the rubber became dry and inflexible, normally resulting in cracking of the sheath and inner core.

When the TRS cable is discovered, it can be inspected and tested to determine the condition but it is advisable to leave undisturbed until such time as the TRS wiring system can be replaced.
Polyvinyl chloride

The introduction of polyvinyl chloride as a means of insulation revolutionized the electrical wiring industry by providing an insulation product with a long lifespan originally expected to be approximately 25 years but is now still undetermined.

The initial PVC cables were installed utilizing imperial- sized conductors, 1/.044, 3/.029, 7/.029 and 19/.044 for those who remember them, and it can be difficult to determine their cross sectional area.

The introduction of low smoke and fume (LSF) cable to the PVC cable market removed the danger from fire hazards associated with electrical installation fires.

When old wiring systems are encountered, it is extremely important to determine the type of system you are dealing with. Failure to be aware of the dangers can lead to an increased risk of electric shock or the risk of fire to the building.

Mr. Gregory Raffaele, Vice President of Sales and Marketing at EMSI insists that, temperature resistance, flexibility, new fiber optic and mechanical resistance are important factors to consider when repairing old wiring systems. “But besides all the existing approvals or standards, a contractors and their client should always consider the practical requirements which do not always fall within existing standards,” he adds.

“The cable industry is a very traditional industry and trends vary on the applications and products. Chinese competition has been a challenge which has forced some manufacturers to increase their efficiencies and reduce their costs, but has also raised new concerns due to quality issues,” reiterates Mr. Raffaele.

Mr. A. V. Shah the General Manager at Coast Cables Limited (CCL) advises that, customers must always look for the best quality when it comes to cables it will power their homes, businesses and livelihood for decades. “They must do their research and purchase original cables from officially appointed distributors. Cheap counterfeit cables can be attractive to consumers until it leads to high costs when they are forced to replace their wiring due to shorts or being under-powered,” he adds.

Coast Cables Limited is a local manufacturer of house and underground cables; plus they import intensely technical and specialized cables from reputable cable manufacturers globally.

“We have noticed CCL counterfeit cables countrywide and urge consumers to avoid these by knowing who to purchase original cables from. Eyeballing our cables, one can notice that CCL cables are differentiated from counterfeit by our skin coating technology whereby our original cables are coated with a white PVC on the inside layer and colored on the outside layer,” affirms Mr. Shah.

The Administration Manager at Metsec Cables Limited Mr. Davis Ndonye, a local manufacturer of Power Transmission and Distribution Cables; insists that, KEBS needs to be stricter in ensuring compliance by imported cables. Customer awareness should be heightened to counter counterfeit and substandard products. “Competition is high to entry of new manufacturers and imports while consumer awareness is low to medium. Consumers should go for products with extensive variety and sizes, countrywide availability high quality, ISO Certification and Environmental Certification,” he adds. “Metsec cables embody all these quality,” he asserts.

In addition, Stephen Liasides of alverncables is of the opinion that the world is advancing in leaps and bounds with regard to technology and this move tends to be more electronic and thus sensitive, automation, interfacing, prohibiting of harmful lead and gasses, to mention just a few. “This makes the products available much better quality and although more difficult to manufacture something one can be proud to put your name to,” he adds.

He further advises consumers to consider more than just price since price is only one factor and not the key factor. “Use reputable companies and products. Where electricity is concerned lives are often at stake plus endless costs in downtime,” he reiterates.


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