TNB denies certifying power saving devices

TNB denies certifying power saving devices

KUALA LUMPUR: Tenaga Nasional Bhd (TNB) has never provided any certification to individuals or companies offering power-saving devices on business premises or on social media.

TNB senior General manager of Corporate Affairs and Communications Datuk Mohd Aminuddin Mohd Amin said in a statement today that those selling such products are using false testimonials, purportedly from TNB or its staff.

He urged consumers to use energy wisely and efficiently Aminuddin said they can verify the authenticity of products by contacting the nearest Energy Commission of Malaysia office or surf the TNB website at for further information.

Malaysian Standards for Electrical Equipment

Standards for Electrical Equipment that Requires Certificate of Approval to Manufacture, Import, Display, Sell or Advertise

  1. Plug Top/Plug (15A and below)
  2. Switch and Dimmer
  3. Socket Outlet (15A and below)
  4. Fluorescent Lampholder/ Starter Holder
  5. Ceiling Rose
  6. Bayonet Cap and Multiways Adaptor
  7. Fluorescent Lampfitting Excluding Tubes if Imported Separately
  8. Capacitor for Fluorescent Lamp
  9. Ballast for Fluorescent Lamp
  10. Circuit Breaker Including AC Current Operated Earth Leakage Circuit Breaker and Miniature Circuit Breaker
  11. Water Heater Including Heating Elements if Imported Separately
  12. Hand Operated Hair Drayer/Haircare
  13. Table Lamps Having Accessible Metal Part
  14. Kettle Including Heating Elements if Imported Separately
  15. Iron
  16. Shaver
  17. Food Mixer/Blender (Kitchen Machine)
  18. Immersion Water Heater
  19. HI-Fidelity Set
  20. Mosquito Matt Vaporizer
  21. Toaster / Oven (Cooking Appliance)
  22. Fan
  23. Television
  24. Vacum Cleaner
  25. Video Player
  26. Washing Machine
  27. Refrigerator
  28. Rice Cooker
  29. Christmas Light
  30. Domestic Power Tools (Portable Type)
  31. Wire / Cable / Cord (non-armoured) 0.5mm² to 35mm²

Reference: Energy Commission of Malaysia | Standards

The AC/DC War

Which is the better way to go: AC or DC? Ask three power engineers this question and you will likely get three different answers.

Of course, everyone views the AC/DC debate in the context of their own power engineering culture or operating experience. But their responses generally break down into two main camps:

Telco DC power engineers have had years of experience with lead-acid batteries. Batteries are reliable for long outages up to eight hours or more and, in fact, are always on so that service is never interrupted. Consequently, they rely very little on backup engine generators that may not always start when needed. Moreover, delivering DC power involves only one main conversion step from AC to DC, which minimizes potential points of failure.

AC power engineers believe that the combination of relatively reliable AC conversion equipment, which has a minimal battery reserve of only 15 minutes and is backed by standby engine-generator systems, affords a level of availability that is acceptable to most users. Furthermore, using batteries with long reserve times for large loads involves a big up-front investment, requires special handling and needs a lot of maintenance to ensure performance reliably.

There is not one right answer. The classical telephone central office (CO) environments will continue to be served by DC power systems. Enterprise data centers will remain the AC power systems domain. The arguments get interesting, however, as telecommunications and information technology converge. In these scenarios, critical loads in a single facility likely will require -48 VDC power and one or more commercial AC voltages. Here again, one solution does not fit all.

The new public network

Telecom facilities that can deliver multimedia voice, data and video are no longer confined to the CO. The new public network comprises facilities that house multimedia equipment and that are located close to customers with connections to backbone networks, as required.

The result is new types of buildings designed specifically for the new public network, or a refurbishing of existing commercial structures for telecom applications. The industry refers to these new facilities by various names such as Internet data centers, co-location or tele-hosting sites, and carrier hotels. Despite the nomenclature, each type of facility serves the needs of different service providers. Like the CO, these facilities are groomed for space, power, environmental control and security. It is perhaps the power aspects that are the most challenging for the operators and represent a significant portion of the total facility investment.

According to Nicholas Osifchin of International Power Strategies, there are three categories of new public network equipment.

Category I comprises large buildings that comply with the same new equipment building standards that apply to telephone equipment buildings. These buildings, primarily data centers, are designed mainly for Internet servers and data storage systems. They are equipped with protected power systems that can range up to 40 megawatts; many often require their own substation. Moreover, these are large sites ranging from 50,000 sq. ft. to more than 100,000 sq. ft. Category I sites deliver predominantly AC and a lesser amount of DC power with AC UPS, gen-sets, DC power plants with battery backup, and power subsystem monitoring and management systems. Target customers for this type of facility include enterprises, international ISPs, interexchange carriers (IXCs), and global service providers. Exodus Communications is the largest independent operator in this category.

Category II companies are co-location sites (or tele-hosting sites) that provide comparable but less extensive facilities and support services than Category I companies. These sites are also located close to incumbent local exchange carriers’ (ILECs’) COs and IXCs’ points of presence. They serve a more diverse market of medium- and large-sized competitive local exchange carriers (CLECs), application service providers and ISPs. Typical sites range from 10,000 sq. ft. to 30,000 sq. ft. There is a different balance between AC and DC that is dependent of the mix of customers in the site. DC is increasingly predominant and is supplied by the facility operator. Switch and Data and are examples of companies in this category.

Category III are carrier hotels that are mainly a real estate play. These companies serve a diverse group of small to medium-sized ISPs and niche local service providers. Carrier hotels provide basic co-location facilities and services that include protected power equipment, modem pools, voice and data switches, transmission equipment and in-building connectivity to ILEC and CLEC local loops. The Dallas ComCenter is an example of this type of facility provider.

The growth of these facilities has been driven by a steady outsourcing trend by the new carriers and at the same time an ongoing shakeout among the facility providers that will result in fewer but larger hosting companies serving these carriers.

Comparative issues

Category I sites predominantly use AC much along the lines of the classical corporate data center. Power is delivered from AC uninterruptible power supplies (UPSs) through power distribution units (PDUs) to the load with generator backup for the UPSs, lighting and heating, ventilation and air conditioning (HVAC) units. DC power required for carrier transmission equipment is supplied by a separate DC power plant with batteries. The DC component is relatively small in the data center model, perhaps comprising 5% to 15% of the total power, depending on the size of the site.

A few distinguishing features are associated with these very large data centers. Power density is increasing with each generation of server technology, packing more processing power into smaller spaces. This plays into the user’s desire to get more productivity out of leased real estate. Some data centers are running 100 watts/sq. ft. to 200 watts/sq. ft. This means, however, that in addition to the power draw increasing, the need to cool this equipment intensifies. So HVAC operation is critical and must be constant.

It is this latter point that keeps data center operations managers awake at night. They know that if the AC fails and the back-up generators then fail to start, their customers’ revenue-producing servers will fail because of overheating, even though the servers themselves may still be running off battery back-up. Either way, the customer is out of service and maybe even out of business.

Category II sites generally have a higher proportion of DC power requirements because of a greater mix of telecom carriers such as CLECs along with smaller ISPs and ASPs. Accordingly, many of these sites are designed with DC power to serve a larger part of the load. In the case of Switch and Data, about 80% of its customer load is served by -48 VDC even though the company caters to a mix of CLECs, ISPs and ASPs. The company points out that a lot of new IT equipment can run on DC. This plays into Switch and Data’s advantage to offer high reliability as a selling point.

Moreover, the DC power system can be configured in a highly distributed fashion to serve a variety of accounts. Switch and Data will sell DC power to its customers in increments of no less than 20-amp distribution feeds. The company points out that distributing DC throughout a site is not as economical as with AC. For example, at 10 kilowatts on a dollar per watt basis, DC is more expensive than AC.

But when compared on the basis of dollar per watt per minute of backup, DC costs come down substantially. “Plus we can charge a premium for DC feeds,” says James Lavin, Switch and Data founder and chairman. “Power is a significant percentage of our revenues.” Switch and Data designs its sites for 85 watts/sq. ft. and handles cooling on a modular basis using a distributed HVAC approach so that lightly used units can be shut off until needed.

A blended approach

Liebert, in a paper presented at the September 2000 Intelec conference, advocated a combined AC/DC architecture. Liebert’s concept is to maximize the best attributes of AC- and DC-predominant architectures while increasing overall system reliability and lowering upfront and operating costs.

To do this, Liebert has coined the term “hybrid distributed redundant power system”

This hybrid system delivers AC to key computing gear from AC UPSs and PDUs that are backed up by standby generators. The UPSs have a small battery plant with about a 15 minute reserve, enough time for the generators to start. Any requirement for DC loads is served from “battery-less” DC rectifier plants that act like DC PDUs. The key here is that the DC plants are not equipped with large battery strings that are expensive, need heavy floor support and require a lot of maintenance.

Rather, all the battery backup resides at the UPS, which is small in comparison to a DC battery installation. A greater reliance, however, is placed on the performance of the standby generators and the automatic transfer switches when a commercial AC power outage occurs. Such hybrid AC/DC configurations are really intended for large data centers in which AC still dominates the power requirements. Liebert calculates that overall system reliability from such a hybrid configuration is on par with the highly reliable DC-only approach that has been used in COs for decades but at overall lower capital investment.

Strategic considerations

The evolution to the new public network is already affecting power in ways AC and DC power engineers had never anticipated. These changes have significant implications for power equipment vendors and hosting facility providers.

Count uptime, not reliability. As much as we debate the merits of 99.9%, 99.99%, or 99.999% reliability, what really counts in the customer’s mind is: “How long can I keep my equipment running?” Reliability calculations are only that-calculations. In large scale networks involving multiple sites, there are just too many variables and intangibles to make a reliability calculation stick. When it comes to making performance guarantees, hosting companies must keep it simple, and their vendors must provide appropriate support. Switch and Data, for example, guarantees four hours of redundant backup and two hours of non-redundant backup if the utility AC fails.

Address system solutions. Power equipment vendors must ensure they fully understand their hosting customers’ system requirements for a given site. One hosting manager at a long-distance carrier lamented that his DC power equipment vendors “needed three times the field force and twice the time” to commission the large DC plants they were installing. Basic installation steps such as torquing lugs and tightening crimps properly can make a difference between uninterrupted service and an outage even with sophisticated power conversion equipment.

Sell price/performance. New public network hosting companies are installing DC and AC UPS power systems in accordance with their assessment of cost, risk and quality of service. Many hosting companies like to adopt a “template” approach to developing their sites in different locations. Level 3 Communications calls it a “cookie-cutter” approach; Genuity refers to it as the “build unit.” This way, these carriers hedge against provisioning too much power ahead of demand.

This provisioning methodology minimizes capital expenditure and disruptions to customers. In reality, many hosting companies have found it is difficult to predict the mix of customers that will show up in the various locales and what their individual AC and DC power requirements will be. So the onus is on power system vendors to deliver flexible solutions that meet customer expectations for high availability and capital conservation.

The debate will continue about the relative cost and performance trade-offs between AC and DC powering methods. To make an informed decision about a given application, hosting companies need to know the comparative AC vs. DC data such as the cost per watt and the cost per watt per minute of backup. In the end, power equipment vendors must offer hosting companies cost-effective solutions while helping them manage the risks for their customers.

How Transformers Work?

A Transformer does not generate electrical power, it transfers electrical power. A transformer is a voltage changer. Most transformers are designed to either step voltage up or to step it down, although some are used only to isolate one voltage from another. The transformer works on the principle that energy can be efficiently transferred by magnetic induction from one winding to another winding by a varying magnetic field produced by alternating current . An electrical voltage is induced when there is a relative motion between a wire and a magnetic field. Alternating current (AC) provides the motion required by changing direction which creates a collapsing and expanding magnetic field.

NOTE: Direct current (DC) is not transformed, as DC does not vary its magnetic fields
A transformer usually consists of two insulated windings on a common iron (steel) core.

The two windings are linked together with a magnetic circuit which must be common to both windings. The link connecting the two windings in the magnetic circuit is the iron core on which both windings are wound. Iron is an extremely good conductor for magnetic fields. The core is not a solid bar of steel, but is constructed of many layers of thin steel called laminations. One of the windings is designated as the primary and the other winding as the secondary. Since the primary and secondary are wound the on the same iron core, when the primary winding is energized by an AC source, an alternating magnetic field called flux is established in the transformer core. The flux created by the applied voltage on the primary winding induces a voltage on the secondary winding. The primary winding receives the energy and is called the input. The secondary winding is discharges the energy and is called the output.


The primary and secondary windings consist of aluminum or copper conductors wound in coils around an iron core and the number of turns in each coil will determine the voltage transformation of the transformer. Each turn of wire in the primary winding has an equal share of the primary voltage . The same is induced in each turn of the secondary. Therefore, any difference in the number of turns in the secondary as compared to the primary will produce a voltage change.

Step Down Transformers
If there are fewer turns in the secondary winding than in
the primary winding, the secondary voltage will be lower than the primary.


Step Up Transformers
If there are fewer turns in the primary winding than in the secondary winding, the secondary voltage will be higher than the secondary circuit.


Note: The primary winding is the winding which receives the energy; it is not always the high-voltage winding. When the primary winding and the secondary winding have
the same amount of turns there is no change voltage, the ratio is 1/1 unity.


Common single-Phase Voltage Combinations:
120 x 240 to 120/240; 480 to 120/240; 4160 to 240/480
208 to 120/240; 480 to 120/240; 4160 to 240/480
277 to 120/240; 2400 to 120/240
240 x 480 to 120/240; 2400 to 240/480
This relationship between the number of turns in the secondary and primary is often called the turns ratio (also referred to as the voltage ratio). It is customary to specify the turns ratio by writing the primary (input) number first.

Example: 30 to 1 is a step-down transformer, whereas a 1 to 30 would be a step-up transformer.


Winding Physical Location: In most transformers the high voltage winding is wound directly over the low voltage winding to create efficient coupling of the two windings.

Note: Other Designs may have the high voltage winding wound inside, side-by-side or sandwiched between layers of the low voltage winding to meet special requirements.

As stated previously, the voltage transformation is a function of the turns ratio. It may be desirable to change the ratio in order to get rated output voltage when the incoming voltage is slightly different than the normal voltage. As an example, suppose we have a transformer with a 4 to 1 turns ratio. With 480 volts input, the output would be 120 volts. Suppose the line voltage is less than the normal or 456 volts. This would produce an output voltage of 114 volts which is not desirable. By placing a tap in the primary winding, we could change the turns ratio so that with 456 volts input we could still get 120 volts output. This is called primary output voltage tap and standard transformers may have from two to six taps for the purpose of the adjusting to actual line voltages.


The above transformer has a tap (2) 2 1/2% below normal and one at 5% below , it is said to have (2) 2 1/2% full capacity below normal taps (FCBN). This would give a 5% voltage range. When the transformer has taps above normal as shown, they would be full capacity above normal (FCAN).

For Standardization purposes, these taps are in 2 1/2% or 5% steps. The taps are so designed that full capacity output can be obtained when the transformer is set on any of these taps. The universal tap arrangement used on many of our transformers ((2) 2 1/2% FCAN and (4) 2 1/2% FCBN) provides a 15% range of tap voltage adjustments.

Note: taps are only to be used for steady state input line variations. They are not designed to provide a constant secondary voltage when the input line is constantly fluctuating.

Series-Multiple Windings (Reconnectable Transformers)

To make the basic single-phase transformer move versatile, both the primary and secondary windings can be made in two equal parts. The two parts can be reconnected either in a series or in parallel . This provides added versatility as the primary winding can be connected for either 480 volts or 240 volts and the secondary winding can likewise be divided into two equal parts providing either 120 or 240 volts. (note: there will be four leads per winding brought out to the terminal compartment rather than two). Either arrangement will not affect the capacity of the transformer. Secondary windings are rated with a slant such as 120/240 and can be connected in a series for 240V or in a parallel for 120V or 240/120V (for 3-wire operation). Primary windings rated with an X such as 240X480 can operate in series or parallel but are not designed for 3-wire operation. A transformer rated 240X480V primary, 120/240V secondary could be operated in 6 different voltage combinations. Transformers are designed and cataloged by KVA ratings. Just as horsepower ratings designate the power capacity of an electric motor, a transformer’s KVA rating indicates its maximum power output capacity. The higher the transformers KVA rating for a specific input and output voltage, the larger transformer.
What does KVA mean? K= Abbreviation of the Greek word kilo, meaning ‘times 1000 V= Volts A= Amperes or Amp

Have a class for the history of Electric Power

Benjamin Franklin is known for his discovery of electricity. Born in 1706, he began studying electricity in the early 1750s. His observations, including his kite experiment, verified the nature of electricity. He knew that lightning was very powerful and dangerous. The famous 1752 kite experiment featured a pointed metal piece on the top of the kite and a metal key at the base end of the kite string. The string went through the key and attached to a Leyden jar. (A Leyden jar consists of two metal conductors separated by an insulator.) He held the string with a short section of dry silk as insulation from the lightning energy. He then flew the kite in a thunderstorm. He first noticed that some loose strands of the hemp string stood erect, avoiding one another. (Hemp is a perennial American plant used in rope making by the Indians.) He proceeded to touch the key with his knuckle and received a small electrical shock.

Between 1750 and 1850 there were many great discoveries in the principles of electricity and magnetism by Volta, Coulomb, Gauss, Henry, Faraday, and others. It was found that electric current produces a magnetic field and that a moving magnetic field produces electricity in a wire. This led to many inventions such as the battery (1800), generator (1831), electric motor (1831), telegraph (1837), and telephone (1876), plus many other intriguing inventions.


In 1879, Thomas Edison invented a more efficient lightbulb, similar to those in use today. In 1882, he placed into operation the historic Pearl Street steam–electric plant and the first direct current (dc) distribution system in New York City, powering over 10,000 electric lightbulbs. By the late 1880s, power demand for electric motors required 24-hour service and dramatically raised electricity demand for transportation and other industry needs. By the end of the 1880s, small, centralized areas of electrical power distribution were sprinkled across U.S. cities. Each distribution center was limited to a service range of a few blocks because of the inefficiencies of transmitting direct current. Voltage could not be increased or decreased using direct current systems, and a way to to transport power longer distances was needed.

To solve the problem of transporting electrical power over long distances, George Westinghouse developed a device called the “transformer.” The transformer allowed electrical energy to be transported over long distances efficiently. This made it possible to supply electric power to homes and businesses located far from the electric generating plants. The application of transformers required the distribution system to be of the alternating current (ac) type as opposed to direct current (dc) type.

The development of the Niagara Falls hydroelectric power plant in 1896 initiated the practice of placing electric power generating plants far from consumption areas. The Niagara plant provided electricity to Buffalo, New York, more than 20 miles away. With the Niagara plant, Westinghouse convincingly demonstrated the superiority of transporting electric power over long distances using alternating current (ac). Niagara was the first large power system to supply multiple large consumers with only one power line.

Since the early 1900s alternating current power systems began appearing throughout the United States. These power systems became interconnected to form what we know today as the three major power grids in the United States and Canada. The remainder of this chapter discusses the fundamental terms used in today’s electric power systems based on this history.

Three Phase Voltage

The relationship between magnetism and electrical current was discovered and documented by Oerstad in 1819. He found that if an electric current was caused to flow through a conductor that a magnetic field was produced around that conductor. In 1831, Michael Faraday discovered that if a conductor is moved through a magnetic field, an electrical voltage is induced in the conductor. The magnitude of this generated voltage is directly proportional to the strength of the magnetic field and the rate at which the conductor crosses the magnetic field. The induced voltage has a polarity that will oppose the change causing the induction – Lenz’s law. This natural phenomenon is known as Generator Action and is described today by Faraday’s Law of
Electro Magnetic Induction: (Vind = ∆Ø/∆t), where Vind = induced voltage, ∆Ø = change in flux density, ∆t = change in time All rotary generators built today use the basic principles of Generator Action.

Three phase voltage is developed using the same principles as the development of single phase voltage. Three (3) coils are required positioned 120 electrical degrees apart. A rotating magnetic field induces voltage in the coils which when aggregated produce the familiar three phase voltage pattern.

three phase voltage

British Standard Electrical Wiring

In England and Wales, the Building Regulations (Approved Document: Part P) require domestic electrical installations to be designed and installed safely according to the “fundamental principles” given in British Standard BS 7671 Chapter 13. These are very similar to the fundamental principles defined in international standardIEC 60364-1 and equivalent national standards in other countries. Accepted ways for fulfilling this legal requirement include:

  • the rules of the IEE (IET) wiring regulations (BS 7671), colloquially referred to as “the regs” (BS 7671: 2008, 17th Edition).;
  • the rules of an equivalent standard approved by a member of the EEA (e.g., DIN/VDE 0100);
  • guidance given in installation manuals that are consistent with BS 7671, such as the IET On-Site Guide and IET Guidance Notes Nos 1 to 8.

In Scotland the Building (Scotland) Regulations 2004 apply.

Installations in commercial and industrial premises must satisfy various safety legislation, such as the Electricity at Work Regulations 1989. Again, recognised standards and practices, such as BS 7671 “Wiring Regulations”, are used to help meet the legislative requirements.

Wiring colours

The standard wiring colours in the UK are (as of 2006) the same as elsewhere in Europe, Australia, and New Zealand and follow international standard IEC 60446. This colour scheme had already been introduced for appliance flexes in the UK in the early 1970s, however the original colour scheme recommended by the IEE for fixed wiring was permitted until 2006. As a result, the international standard blue/brown scheme is as of 2006 found in most appliance flexes. In fixed wiring, the blue/brown scheme is only found in very new (post-2004) installations, and the old IEE black/red scheme is likely to be encountered in existing installations for many more decades.

The standard colours in fixed wiring were harmonized in 2004 with the regulations in other European countries and the international IEC 60446 standard. For a transitional period (April 2004 – March 2006) either set of colours were allowed (but not both), provided that any changes in the colour scheme are clearly labelled. From April 2006, only the new colours should be used for any new wiring.

The UK changed colour codes three decades after most other European countries, as the change in standard was not considered safe. Blue, previously used as a phase colour, is now the colour for neutral. Black, which was previously used for neutral, now indicates a phase.

Household wiring does not usually use three-phase supplies and the clash only occurs in three-phase systems. Wiring to the old standard can be detected by use of a red wire. The new standard colour code does not use red. Where new wiring is mixed with old, cables must be clearly marked to prevent interchange of phase and neutral.

Circuit design

UK electrical circuits are normally described as either radial or ring. A radial circuit is one where power is transmitted from point to point by a single length of cable linking each point to the next. It starts at the distribution board and simply terminates at the last connected device. It may branch at a connection point. Lighting circuits are normally wired in this way, but it may also be used for low power socket circuits.

In a ring circuit, a cable starts at the distribution board and goes to each device in the same way as a radial circuit, but the last device is connected back to the supply so that the whole circuit forms a continuous ring. This means that there are two independent paths from the supply to every device. Ideally, the ring acts like two radial circuits proceeding in opposite directions around the ring, the dividing point between them dependent on the distribution of load in the ring. If the load is evenly split across the two directions, the current in each direction is half of the total, allowing the use of wire with half the current-carrying capacity. In practice, the load does not always split evenly, so thicker wire is used. This practice was adopted in Britain to save on copper during the shortages after World War II. It is unknown in other national wiring codes.

Cables are most commonly a single outer sheath containing separately-insulated line and neutral wires, and a non-insulated protective earth to which sleeving is added when exposed. Standard sizes have a conductor cross sectional area of 1, 1.5, 2.5, 4, 6 and 10 mm2. Sizes of 1 or 1.5 mm2 are typically used for 6 or 10 ampere lighting circuits and 2.5 mm2 for socket circuits. The protective earth conductor in older cables was normally one standard size smaller than the main conductors but is now specified to be the same size.

The earthing conductor is uninsulated since it is not intended to have any voltage difference to surrounding earthed articles. Additionally, if the insulation of a line or neutral wire becomes damaged, then the wire is more likely to earth itself on the bare earth conductor and in doing so either trip the RCD or burn the fuse out by drawing too much current.


Earthing refers to connecting the exposed conductive part of electrical equipment and also the extraneous conductive parts of earthed bodies like water pipe to the general mass of the earth to carry away safely any fault current that may arise due to ground faults. This is done to minimize the danger of electric shock due to human contact with live parts which could result from bad insulation and insulation failures. In domestic wiring earthing of equipment is done by bonding together the earth points and metallic parts of the appliances and earthed bodies using Green/Yellow wire coming from the consumer main earthing terminal. The earth terminal is in turn connected to either consumer’s earth electrode (TT system) or to the earth point given by the supplier (TN system).


All new electrical work in England and Wales within a domestic setting must comply with Part P of the Building Regulations first introduced on 1 January 2005, which are legally enforceable. One way of achieving this is to apply British Standard BS7671 (the “Wiring Regulations”), including carrying out adequate inspection and testing to this standard of the completed works. British Standard BS 7671 (the “Wiring Regulations”) is not statutory, thus someone doing electrical work is allowed to deviate from the wiring regulations to some degree, but it is generally accepted that it is best to follow the wiring regulations to the highest standard possible. Electrical work does not have to be compliant with BS7671, but if a casualty or fatality occurs as a direct result of that electrical work, and this results in a legal action, then it may be necessary to justify major deviations from the principles of BS7671 and/or other appropriate standards.

Some of the restrictions first introduced with the 2005 version Part P were highly controversial, especially the rules surrounding work carried out by unregistered electricians, builders and DIYers. Under the new regulations, commencement of any work other than simple changes became notifiable to the local building control authority; “other than simple” in this context meant any work in a kitchen or bathroom other than like-for-like replacement, work in other areas more than just adding extra lights or sockets to an existing circuit or meeting certain other criteria, such as outdoor wiring. To coincide with the new regulations, the Government approved several professional bodies to award “competent persons” status to enterprises which meet the minimum agreed criteria for Scheme entry:

(The minimum criteria for Scheme entry is set by the EAS Committee, on which all of the commercial enterprises running Competent Persons Schemes are actively represented).

Scheme membership allows an enterprise to “self-certify” work that they carry out without the requirement to have undergone any formal installation training or to hold relevant qualifications in electrical installation practices – since practical competence can be assessment-based only.

The building control authority must be informed of any notifiable work carried out by someone not registered under this scheme before it is started (unless it is an emergency) and must subsequently be approved by them. Originally, it was widely understood by some local authorities that inspection by a qualified person (leading to authority approval) must be organised and paid for by the home-owner or person responsible for the site and this caused some considerable criticism.

On 6 April 2006, Part P was amended to clarify the actual requirements around certification of DIY work (or work completed by someone otherwise unable to self-certify) and to “make enforcement more proportionate to the risk”.

The 2006 amendment made it clear that it is the responsibility of the building control authority to issue the necessary certificate (a Building Regulations Completion Certificate) once work has been completed. Any inspection required to safely issue that certificate must be determined by, and paid for by, the building control authority. This can be done “in house” or they may contract the work out to specialist body. Note that although any inspections are at the expense of the building authority, notification of building work is a formal process and a building control fee is payable.

In some cases the installation of 12 V down-lighters is notifiable whereas the installation of 230 V mains down-lighters is not. This is because 12 V down-lighters draw high currents, in comparison with a mains voltage lamp with the same power rating, and that combined with the wrong choice of cable could lead to a fire.

Additionally, whilst the Building Regulations apply equally to anyone carrying out electrical work in dwellings, without appropriate knowledge and test equipment it is not possible to ensure that the work carried out is safe. Registered Scheme members must issue appropriate certification, yet many DIY- householders will be unable to do so.

Another element of confusion is that the term “Special Locations” has different meanings in Part P of the Building Regulations and BS7671 (the “Wiring Regulations”).

Later revisions of part P (latest is 2013) retain the requirement to work to an appropriate standard, but have relaxed the requirements on both certification and notification for many more types of minor works, and crucially also permit a member of an approved body to inspect and ‘sign off’ notifiable aspects of any work of a third party such as DIYer whose work is of a suitable standard. This is intended to free up local authorities, who often do not have suitably qualified building control staff themselves. Due to uncertainty about who then becomes be responsible for any hidden wiring, very few electricians are happy to sign off an installation that they have not been party to from the outset, and been able to agree stages to inspect and test before any covering in.

Installation accessories

Many accessories for electrical installations (e.g., wall sockets, switches) sold in the UK are designed to fit into the mounting boxes defined in BS 4662:2006 – Boxes for flush mounting of electrical accessories – Requirements, test methods and dimensions, with an 86 mm×86 mm square face plate that is fixed to the rest of the enclosure by two M3.5 screws (typ. 25 mm or 40 mm long) located on a horizontal center line, 60.3 mm apart. Double face plates for BS 4662 boxes measure 147 mm×86 mm and have the two screws 120.6 mm apart.

Accessories in the BS 4662 format are only available in a comparatively limited range of designs and lack the product diversity and design sophistication found in other European markets. The UK installation-accessory industry is therefore occasionally criticized for being overly conservative. As many modern types of electrical accessories (e.g., home automation control elements from non-UK manufacturers) are not available in BS 4662 format, other standard mounting boxes are increasingly used as well, such as those defined in DIN 49073-1 (60 mm diameter, 45 mm deep, fixing screws 60 mm apart) or, less commonly in the UK, ANSI/NEMA OS-1.

The commonly used domestic wall-mount socket used in the UK for currents up to 13 A is defined in BS 1363-2 and normally includes a switch. For higher currents or three-phase supplies, IEC 60309 sockets are to be used instead.

Note that many high load non-UK-sourced appliances need IEC 60309 connectors (or wiring via a British Standard “20 A connection unit”) in the UK because of the lower plug rating.

Isolating devices

Single-pole switches are most commonly used to control circuits. These switches isolate only the line conductor feeding the load and are used for lighting and other smaller loads. For larger loads like air conditioners, cookers, water heaters and other fixed appliances a double-pole switch is used, which isolates also the neutral, for more safety. A three-pole isolator or circuit breaker is used for three-phase loads, and also at the distribution board to isolate all the phases as well as the neutral.

Plug and accessory fuses

Flexible appliance cords require protection at a lower current than that provided by the ring circuit over-current protection device. The protection device may be contained within the appliance plug or connection unit, and is normally a ceramic cartridge fuse to BS 1362:1973, commonly rated at 3 A (red), 5 A (black), or 13 A (brown), but some accessories and adapters use a ceramic cartridge fuse to BS 646:1958.

In the case of permanently connected equipment a Fused Connection Unit to BS 1363-4 is used, this may include an isolator switch and a neon bulb to indicate if the equipment is powered.

In the case of non-permanently connected domestic equipment, a BS 1363-2 socket rated at 13 A is attached to the ring circuit, into which a fused plug may be inserted. (Note, it is not intended that the fuse should protect the appliance itself, for which it is still necessary for the appliance designer to take the necessary precautions.) Multiple socket accessories may be protected with a fuse within the socket assembly.

Consumer supply, metering and distribution

A domestic supply typically consists of a large cable connected to a service head, a sealed box containing the main supply fuse. This will typically have a value from 40–100 A. Separate line and neutral cables (‘tails’) go from here to an electricity meter, and often an earth conductor too. More tails proceed from the meter into the consumer side of the installation and into a consumer unit (distribution board), or in some cases to a Henley block (a splitter box used in low voltage electrical engineering) and thence to more than one distribution board.

The distribution board (aka fuse-box) contains one or more main switches and an individual fuse or miniature circuit breaker (MCB) for each final circuit. Modern installations may use residual-current devices (RCDs) or residual current breakers with over-current protection (RCBOs). The RCDs are used for earth leakage protection, while RCBOs combine earth leakage protection with over-current protection. In a UK-style board, breaker positions are numbered top to bottom in the left-hand column, then top to bottom in the right column.

Residential wiring

Cable types

In domestic wiring, the following cable types are typically used:

Pre-1977 IEE Pre-2004 IEE Current IEC
Protective earth (PE) Color wire green.svg Color wire green yellow.svg Color wire green yellow.svg
Neutral (N) Color wire black.svg Color wire black.svg Color wire blue.svg
Single phase: Line (L) Color wire red.svg Color wire red.svg Color wire brown.svg
Three-phase: L1 Color wire red.svg Color wire red.svg Color wire brown.svg
Three-phase: L2 Color wire yellow.svg Color wire yellow.svg Color wire black.svg
Three-phase: L3 Color wire blue.svg Color wire blue.svg Color wire grey.svg

Internal wiring

  • Single core PVC insulated cables (fixed internal wiring)
  • Flexible cords

Supply side wiring

  • 2/3/4 core PVC insulated, SWA, PVC sheathed cables
  • PVC Insulated, PVC sheathed (Unarmored cables)
  • Three and four cores XLPE insulated, SWA, PVC sheathed cables

Selection of conductors and circuit breakers

The selection of conductors must be done taking into consideration both maximum voltage drop allowed at the load end and also the current carrying capacity of the conductor. Conductor size and voltage drop tables are available to do the selection, which is based on the load current supplied.

The choice of circuit breaker is also based on the normal rated current of the circuit. Modern circuit breakers have overload and short circuit current protection combined. The overload protection is for protection of the equipment against sustained small to medium increase in current above the rated current while short circuit protection is for the protection of the conductors against high over currents due to short circuits.

For domestic circuits the following choices are typically adopted for selecting conductor and circuit breaker sizes.

CB and conductor selection
Capacity Main conductor size;
copper (mm2)
Earth conductor
size (mm2)
Circuit breaker
capacity (A)
Up to 600 W 1.5 1.5 5
600–1,200 W 1.5/2.5 1.5 10
1,200–1,800 W 2.5/4 2.5 15
Ring circuit
(floor area 100 m2)
2.5 2.5 30/32
A2 radial circuit
(floor area 75 m2)
4.0 2.5 30/32
A3 radial circuit
(floor area 50 m2)
2.5 1.5 20
Air conditioner (1.5 tonne) 6.0 6.0 30/32
Cooker 6.0 6.0 30/32
Water heater 4.0 4.0 20

For distribution boards the incomer circuit breaker rating depends on the actual current demand at that board. For this the maximum demand and diversity is taken into consideration based on which the probable current is calculated. Diversity refers to the condition that all appliances are not likely to be working all at the same time or at their maximum ratings. From this the maximum demand is calculated and the currents are added to determine the load current and hence the rating of the circuit breaker.

IEE recommends these current demands and diversity factors for various loads to determine the load current and rating of overcurrent protective device.

Outlet point or
Assumed load Diversity factor
Socket outlet 2 A 0.5 A 25%
Other socket outlets Rated current 50%
Light outlet
(per lamp holder)
100 W 50%
Domestic cooker 10 A, 30% remainder,
and 5 A for auxiliary socket
Other stationary
BS current rating or normal current

Supply voltage

Since 1960, the supply voltage in UK domestic premises has been 240 V AC (RMS) at 50 Hz. In 1988, a Europe-wide agreement was reached to unify the various national voltages, which ranged at the time from 220 V to 240 V, to a common European standard of 230 V (CENELEC Harmonization Document HD 472 S1:1988).

The standard nominal supply voltage in domestic single-phase 50 Hz installations in the UK is still 240 V AC (RMS), but since 1 January 1995 (Electricity Supply Regulations, SI 1994, No. 3021) this has an asymmetric voltage tolerance of 230 V+10%−6% (253–216.2 V), which covers the same voltage range as continental 220 V supplies to the new unified 230 V standard. This was supposed to be widened to 230 V ±10% (253–207 V), but the time of this change has been put back repeatedly and as of December 2012 there is no definitive date. The old standard was 240 V ±6% (254.4–225.6 V), which is mostly contained within the new range, and so in practice suppliers have had no reason to actually change voltages.

Application of Wastage Eliminator Technology

Wastage eliminator technology have many potential applications where its use can offer plenty of benefits. Wastage eliminator have been proven to provide lowered disturbances, lower carbon dioxide emissions through improved energy efficiency, lower current consumption and increased production stability to name a few. Just as other technology has evolved, so have various production technologies. Today’s semiconductor loads require far more sophisticated solutions than was necessary in the past.

Welding Plants

Electrical welding systems place uneven demands with extremely high peaks in current demand during short periods. The resulting highly fluctuating voltage levels cause flicker. Flicker emissions can cause disturbances with other electrical consumers such as neighboring industries or residential areas and can cause reliability issues with nearby equipment.


Furnaces and casting processes are known to give rise to both flicker and instability. This is largely due to being some of the most energy intensive production processes today. Wastage eliminator technology is ideal to combat both of these issues to increase production stability and reduce effects on the grid.

Wind and Solar Power Systems

A major problem inherent in many renewable energy sources today is the inconstant load delivered to the grid. Both wind and solar energy is delivered as wind and sun is available, causing surges of energy that the existing grid is usually not built for. The remote location of these energy plants also means that grid connections are sub-optimal.

Wind power systems and solar power plants cause flicker,instability as well as other problems. In some cases, especially in weaker networks, resonances may be excited by the output of the solar inverter. Wastage eliminator technology is very effective in combating these problems; reducing the stress placed on the grid and making these renewable energy sources more effective and widely viable.


Light systems can cause heat neutral conductors and disturb nearby equipment. This can mean production disturbances and unnecessary maintenance costs. Modern energy saving lamps may be more likely to cause disturbances depending on type. The worst type of lighting system will be LED. Wastage eliminator are well suited to combat these problems.