Electrical Notes & Articles

Which Class of Wire need to be used for House Wiring

Different Class of Conductor

• As per IEC 60228, Electrical wires/cables are classified into different classes according to the conductor’s flexibility, conductor hardness & thermal effects.
• There are four classes of flexibility for electrical cables
• Class 1 = Solid conductor= ideal conductors for permanent installations.
• Class 2 =Stranded conductor= conductors designed for fixed installation.
• Class 5 =Flexible conductor= preferred to used where flexibility is required, for movable equipment , where there is vibration in equipment.
• Class 6 =Very Flexible conductor= highly flexible conductors used in robotics, flexible codes.
• Classes 3 and 4 are not described in IEC 60228.
• The most basic type of conductor is a single, solid wire (Class 1). It provides a smaller diameter, the largest Cross-Sectional Area (CSA), and the clearest signal, it is mechanically fragile and susceptible to breakage after repeated bending cycles.
• To improve flexibility, wires are stranded together (Class-2, Class-5, Class-6). Class 2 is a multi-wired conductor, while classes 5 and 6 are fine or ultra-fine wired conductors. The IEC standard specifies values such as the maximum diameter and maximum resistance for the individual wires.
• The more wires that are stranded together to make a given size, the more flexible the conductor will be. This indicates that a higher class corresponds to a greater number of strands within the conductor. Additionally, stranded wires are significantly easier to manipulate and bend during installation compared to a single wire of equivalent cross-section.
• Classes 1 and 2 are intended for use in cables for fixed installations. On the other hand, Classes 5 and 6 are designed for use in flexible cables and cords but may also be used for fixed installations.

(A) Class 1: Solid Conductors

• Construction: Single Conductor, solid copper wire.
• Flexibility: Rigid and non-flexible. the cable should not be bent more than about four times its diameter
• Characteristics: High electrical conductivity and resistance to corrosion, but less suitable for environments requiring flexibility.
• Advantages: Less expensive than cables with multiple wires
• Disadvantages: Less suitable for applications involving movement.
• Heat and Losses: Class 1 wires are more efficient for fixed wiring due to lower resistance and heat generation. 
• Applications: Typically used in permanent, stationary installations, House wiring where the conductor will not be subject to frequent movement or low flexibility is not a problem such as in building wiring and power distribution.
• They are often used when cables with larger cross-sections are required for fixed installations. They are not suitable for very flexible cables, which are used, for example, in continuously moving objects such as robotic arms in industrial production

(B) Class 2: Stranded Conductors

• Construction: Composed of multiple smaller copper wires twisted or braided together to form a single conductor.
• Flexibility: More flexible than Class 1, allowing for some movement without breaking or damaging the wire.
• Characteristics: Offers a balance of flexibility and durability but may not be as conductive as a solid conductor of the same gauge.
• Advantages:Lower electrical resistance and less heat buildup under load.
• Disadvantages:Less suitable for applications involving movement.
• Heat and Losses:Class 2 wires are more efficient for fixed wiring due to lower resistance and heat generation. 
• Applications: Primarily used for fixed installations like permanent building and house wiring and for industrial applications with increased cable flexibility requirements.

(C) Class 5: Flexible Conductors

• Construction: Consists of many fine copper wires (often tinned for corrosion resistance) twisted together, making the conductor highly flexible.
• Flexibility: Extremely flexible, designed for applications where the conductor needs to withstand frequent movement, bending, or vibration without damage.
• Characteristics: High flexibility, durable against wear and tear, but may have slightly lower conductivity compared to solid conductors due to the finer strands.
• Advantages:Superior flexibility.
• Disadvantages:Higher electrical resistance, which can result in greater heat loss and voltage drops.
• Heat and Losses:Class 5 wires are not efficient for fixed wiring due to higher resistance and heat generation compared to Class-2. 
• Applications: Used in situations where more flexibility is required, such as in circuits that may need to be bent, coiled, or moved occasionally. Ideal for portable appliances and equipment that move constantly like portable cords, flexible cables, and power tools that require a durable, yet highly flexible conductor.

(D) Class 6: Extra Flexible Conductors

• Construction: Made up of very fine copper wires, typically tinned, twisted into a very flexible configuration.
• Compared to class 5, the number of strands and wires arranged around each other is even larger, which can further increase the flexibility of the wire
• Flexibility: The highest level of flexibility among copper conductors, suitable for applications requiring frequent movement or twisting.
• Characteristics: Very high flexibility, ideal for dynamic applications, but may have lower conductivity due to the fine strands.
• Applications: Used in highly flexible cable assemblies, robotics, automobile, machine and tool construction and flexible power cables where the conductor will experience constant movement and mechanical stress.

Which Class of Conductor Used for House hold Wiring:

• To reduce power consumption, eliminate heating of wires, The Selection of House wire is most important.
• The selection of Wires broadly depends on conductor Resistance, Current, Quality of conductor material, Cross section area and power consumption.
• Resistance: A conductor with higher resistance will consume more power (P = I²R, where P is power, I is current, and R is resistance).
• Current: If both conductors are used in the same application with the same current, the one with the higher resistance will consume more power.
• Conductor Quality: Many people believe that wire quality simply by measuring its diameter and doing a mathematical calculation to estimate resistance. Conductor resistance is not just about the size of copper but it also depends on copper purity. For example, impure or recycled copper may have a bigger cross-sectional area but still higher resistance, which means more heat, more energy loss and shorter wire life.
• Conductor Size: The material (copper, aluminum, etc.) and the cross-sectional area of the conductor also significantly affect resistance and power consumption.
• Power Consumption: The power consumption of a conductor is primarily determined by its resistance and the current flowing through it, rather than its classification (Class 2 or Class 5). However, the classification itself does provide some context regarding the conductor’s characteristics:
• There are mainly two types of Conductors solid (Class-1) and stranded (Class-2 & Class-5).

(A) Selection between Class-1 or Class-2 (Solid or Standard):

• Solid conductor (Class-1) has less flexibility hence not easily passing in conceal conduits of house wires and making hot spots at conductor bends. Due to less flexibility easily break conductor at its termination location.
• The cables used in Building wiring switched to Class 2 copper conductors as it offered better flexibility over the Class 1 solid copper conductors. It is also technically superior and avoid hot spots at bends without compromising the current carrying capacity on account of its resistance being the same as specified for Class 1 copper conductors.
• Multi-stranded conductor (Class-2) shall be replaced to single solid conductors (Class-1) for all the House wiring.

(B) Selection between Class-2 & Class-5 (Standard or fine Standard):

• Stranded conductor can be divided broadly in two types one is multi-strand conductor (known as class-2 conductor) other is Flexible stranded conductor (known as class-5 conductor).
• The difference between Class-2 & Class-5 Wires are as under
• Resistance: The conductor resistance of class 5 is high compared to class 2 conductor, the heat generated for the same current loading will be different on both class of conductors

• Insulation: The insulation thickness for the class 5 conductor cable is lesser than specified for class 2, not better for higher load conditions
• Mechanical Strength: The mechanical strength of insulation for class 5 is lesser in comparison to class 2, this can lead to issues during conduit pull.
• Flexibility: The difference lies mainly in flexibility.
• Class 2 wires have fewer strands (Conductor) of more diameter. Example :14/0.31mm(max.) 14 strands each of 0.31 mm (max.). typically, 7 strands are used which makes them less flexible and more suitable for fixed installations.
• Class 5 wires have more strands (Conductor) of less diameter. Example: 32/0.21mm(max.) 32 strands each of 0.21 mm (max.). Typically, 30 to 50 strands are used, which makes them more flexible and easier to bend.
• Application: For fixed wiring application conductors with Class 2 copper shall be used. Worldwide the usage of class 2 conductors is specified for building wires as it offers lower resistance, mechanical strength is higher.
• Class 5 wires are commonly used in applications where flexibility is important, such as in portable appliances and equipment where the lengths are preferably 1.5 to 2-meter, power tools, panel wiring (As bending and routing of such cables in constricted paths do not stress on the cable and handling and installation of such conductors in confined areas is easier).
• Amount of Copper content: Actually, in class 5 conductors, copper content is less than that of class 2 conductor which make them more flexible wires. The reason is copper wires with class 5 conductor are cheaper.
• Lesser copper content in wire leads to increased cable resistance and which may in turn increase power consumption and loss. on the other side these coper wires with class 5 conductor can bring disaster in a building as it increases the disconnection time of protective device due to its increased resistance. The power loss of class 5 conductor is higher and is against the concepts of energy conservation or sustainability.

• Multi-stranded conductor (Class-2) shall be used for house wiring due to its Less Resistance, Less heat loss, Low Power consumption, better insulation, higher mechanical Strength.

Conclusion:

• Actually, Wires with Class-5 copper are used for appliance wiring and panel wiring (Not Fixed Wiring) only and they are also manufactured accordingly. Wiring with Class-5 copper conductors do not conform to the code of practice of wiring and hence it’s illegal to use them in fixed wiring and In IS 694 specifies panel wire and building wire as a similar group of functioning. This created a confusion and an create opportunity to misuse of Class 5 conductors as building wires because Class-5 Wires are 8 % cheaper than wires with Class-2 copper conductor.
• However, we must avoid to use Class-5 Wires for Wiring Application due to its less copper content (due to its more flexibility) in wire will lead to increase cable resistance and which may in turn increase the power consumption, higher watt loss, higher voltage drops, higher fault loop impedance.
• Higher impedance of the circuit may lead to accidents due to higher disconnection time of protective device. Less mechanical strength, less insulation hence heats up in load and not safe in continuous load.
• For fixed wiring application, House Wiring conductors with Class 2 copper shall be used.