What is an RCD ( Residual Current Device ) ?Further information:

What is an RCD?

Circuit breakers, surge protectors and RCDs Types of RCDs

Testing

RCD Laws

homeowners real estate agents, landlords and tenants electrical contractors

Frequently asked questions

RCD - new laws (Factsheet PDF)

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Circuit breakers, surge protectors and RCDsCircuit breakers and fuses are designed to protect electrical cables and fittings installed in the home from overloading and short circuits. They cut the power when electrical wiring in the home has too much current flowing through it. They are designed to prevent electrical fires, not electrocution.

Some meter boxes have surge protectors fitted to safeguard appliances against a spike in electrical voltage, such as a lightning strike. Some power boards or extension leads also have surge protectors fitted. These devices do not offer any protection against electrocution.

Only RCDs will prevent electrocution by cutting the power to a circuit in the event of an earth leakage.

RCDs are the only device that can give you or a family member a second chance.

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Types of RCDs

Meter box mounted RCDs

RCDs are required by law to be fitted to the power and lighting circuits of new homes and houses for sale or lease.

They are generally located alongside circuit breakers in the main meter box or distribution board of the residence. They can be distinguished from the circuit breakers by the test button.

A minimum of two RCDs are required to ensure some light and power remains if one operates. Two RCDs also reduces the possibility of tripping due to some appliances which have low levels of earth leakage.

Combination RCD and circuit breakers

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Home owners can choose to install combined circuit breaker and RCDs. These devices protect the electrical circuits and appliances as well as preventing electrocution. Various brands are available.

These combination RCDs are an attractive option for retro-fitting into existing meter boxes with little or no spare space.

Portable RCDs

Portable RCDs attached to a power board or extension lead are available. RCDs on power boards and extension leads only protect the circuits of appliances connected to them. They are essential for people using power tools or electrical appliances outside that are not protected by a meter box RCD or power point RCD.

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Power point RCDs

RCDs may be fitted to a power point and can be distinguished by the test button on the face plate. They must be fitted to the first power point after the meter box. They are suitable for protecting electrical appliances in specific areas such as bathrooms and workshops.

An RCD is a safety device that disconnects a circuit when it detects an imbalance of the electric current. It works on the principle that the electricity flowing into a circuit must be equal to the current flowing out of a circuit. When a person receives a shock, it means some current is diverted through the body directly to earth.

If the RCD detects an imbalance in the electrical current, indicating a leakage to earth, it immediately cuts the electricity supply to prevent electrocution.

An RCD cannot detect all types of faults, for example if a person receives a shock between the active and neutral conductors. However, these circumstances are rare and the vast majority of incidents occur between the active conductor and earth, which is protected by an RCD.

If a person comes in contact with a live electrical conductor, electricity flows through their body, causing an electric shock. Effects can vary from a tingling sensation or muscular pain to breathing difficulties, burns and heart failure.

RCDs are extremely sensitive, disconnecting within 10 to 50 milliseconds of detecting a leakage current. This is usually 30 milliamps for domestic residences but may be lower in other locations such as hospitals. This stops the flow of electricity through someone’s body to earth. Importantly, this response time is much faster than the critical section of the cardiac cycle and therefore significantly reduces the risk of death or serious injury.

RCDs also protect against fire caused by faults in appliances, tools and wiring. If these faults go undetected they could cause a fire or personal injury. RCDs provide a means of early fault detection.

RCDs are required to be fitted at the meter box (main switchboard) or distribution board for the residence.

Various brands of RCDs are available; however they can all be identified by the test button located on the front of the device.

If you press the ‘test’ button, or the RCD has detected an imbalance, the on/off switch will jump to the “off” position.

Checking and testing RCDs

Checking if you have RCDs installed

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RCDs will be installed in your home’s meter box or distribution board and can be identified by the test button on the front of the device.

Your meter box may only have one RCD installed if your home was constructed between 1992 and 1999 when it was a requirement to have one RCD installed on the power outlet circuits only. Since 2000 it has been compulsory for all new homes to have two RCDs fitted to protect the power and lighting circuits as part of the electrical installation.

One RCD will not ensure complete protection for your family. One RCD is likely to protect only the power circuits and leaves the lighting circuits unprotected.

If you are unsure whether you have RCDs installed contact a licensed electrical contractor.

Testing RCDs

To ensure that the RCDs fitted to your home perform correctly, they must be tested at regular intervals. EnergySafety recommends that each RCD be tested every three months.

To test your RCD press the ‘test’ button on the front of the device quickly and then release it. The button will only test the RCD if an electricity supply is connected.

Pressing the test button will simulate an earth leakage fault and indicates whether the device is operating correctly. When an RCD operates all power is lost to the equipment, power point or circuit protected by the RCD. To restore power simply move the “on/off” switch back to the “on” position. Electrical clocks and timing devices may have to be reset.

If the RCD fails to operate a licensed electrical contractor must be engaged to test the RCD and replace it if necessary.

Follow these simple steps to ensure your RCDs are operating correctly:

1. Plug a small lamp into a power point and make sure it works. Leave it turned on.2. Make sure that electricity is connected to the property and the main switch is in the on position. The lamp should be on.3. Turn off all electronic equipment (computers and televisions) etc4. Push the test button on each RCD. Do not hold your finger on the test button. The RCD should operate (turn off). If it does not operate, it must be checked by an electrical contractor.5. After pushing the test button and the RCDs have turned off check that the small lamp is now off. Also check that all the lights and power points do not operate. To do this, plug the small lamp

into all the power points and turn the power point on. If the lamp turns on a licensed electrical contractor must be engaged to correct the wiring.6. When finished testing, turn the RCDs back on and check that the lamp works when plugged into a power point.

Nuisance Tripping

Some electrical appliances and old wiring may have a normal small amount of earth leakage current which can trip an RCD.

Earth leakage increases with each additional electrical appliance plugged in, so a single meter box RCD protecting all household wiring is more likely to experience nuisance tripping.

If an RCD trips twice for no apparent reason, have your wiring and appliances tested by a licensed electrical contractor.

 Residual-current deviceFrom Wikipedia, the free encyclopedia

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A two-pole residual-current device

A residual-current device (RCD), or residual-current circuit breaker (RCCB), is an electrical wiring device that disconnects a circuit whenever it detects that theelectric current is not balanced between the energized conductor and the

return neutral conductor. Such an imbalance may indicate current leakage through the body of a person who is grounded and accidentally touching the energized part of the circuit. A lethal shock can result from these conditions. RCCBs are designed

to disconnect quickly enough to prevent injury caused by such shocks. They are not intended to provide protection against overcurrent (overload) or short-circuitconditions.

In the United States and Canada, a residual-current device is most commonly known as a ground fault circuit interrupter (GFCI), ground fault interrupter (GFI) or an appliance leakage current interrupter (ALCI). In Australia they are

sometimes known as "safety switches" or simply "RCD" and in the United Kingdom, along with circuit breakers, they can be referred to as "trips" or "trip switches".

A residual-current circuit breaker with overload protection (RCBO) combines the functions of overcurrent protection and leakage detection. An earth leakage circuit breaker (ELCB) may be a residual-current device, although an older type of

voltage-operated earth leakage circuit breaker exists.

Residual-current device is a generic term covering both RCCBs and RCBOs.

Contents

  [hide]

1 Purpose and operation

2 Typical features

3 Form factors

4 Combined with overcurrent devices

5 Testing

6 Limitations

7 Technical characteristics

o 7.1 Number of poles

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o 7.2 Rated current

o 7.3 Sensitivity

o 7.4 Type

o 7.5 Break time

o 7.6 Surge current resistance

8 History and nomenclature

9 Regulation and adoption

o 9.1 Australia

o 9.2 Europe

9.2.1 Italy

9.2.2 Germany

9.2.3 Norway

9.2.4 United Kingdom

o 9.3 North America

10 See also

11 References

12 External links

[edit]Purpose and operation

Principle of operation.

1. Electromagnet with help electronics

2. Current transformer secondary winding

3. Transformer core

4. Test switch

L live conductor

N neutral conductor.

RCDs are designed to disconnect the circuit if there is a leakage current. By detecting small leakage currents (typically 5–30 milliamperes) and disconnecting quickly enough (<30 ms), they may prevent electrocution. There are also RCDs with

intentionally slower responses and lower sensitivities, designed to protect equipment or avoid starting electrical fires, but not disconnect unnecessarily for equipment which has greater leakage currents in normal operation. To prevent electrocution,

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RCDs should operate within 25-40 milliseconds at leakage currents (through a person) of 30 milliamperes, before electric shock can drive the heart into ventricular fibrillation, the most common cause of death through electric shock. By contrast,

conventional circuit breakers or fuses only break the circuit when the total current is excessive (which may be thousands of times the leakage current an RCD responds to). A small leakage current, such as through a person, can be a very serious

fault, but would not cause the total current to become high enough for a fuse or circuit breaker to break the circuit, let alone do so fast enough to save a life.

RCDs operate by measuring the current balance between two conductors using a differential current transformer. This measures the difference between the current flowing through the live conductor and that returning through the neutral conductor. If

these do not sum to zero, there is a leakage of current to somewhere else (to earth/ground, or to another circuit), and the device will open its contacts.

Residual current detection is complementary to over-current detection. Residual current detection cannot provide protection for overload or short-circuit currents, except for the special case of a short circuit from live to ground (not live to neutral).

Animated 3-phase RCD schematic.

For a RCD used with three-phase power, all live conductors and the neutral must pass through the current transformer.

[edit]Typical features

Internal mechanism of RCD

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Opened 3-phase residual-current device

The photograph depicts the internal mechanism of a residual-current device (RCD). The device pictured is designed to be wired in-line in an appliance power cord. It is rated to carry a maximum current of 13 amperes and is designed to trip on a

leakage current of 30 mA. This is an active RCD; that is, it latches mechanically and therefore trips on power failure, a useful feature for equipment that could be dangerous on unexpected re-energisation.

The incoming supply and the neutral conductors are connected to the terminals at (1) and the outgoing load conductors are connected to the terminals at (2). The earth conductor (not shown) is connected through from supply to load uninterrupted.

When the reset button (3) is pressed the contacts ((4) and hidden behind (5)) close, allowing current to pass. The solenoid (5) keeps the contacts closed when the reset button is released.

The sense coil (6) is a differential current transformer which surrounds (but is not electrically connected to) the live and neutral conductors. In normal operation, all the current down the live conductor returns up the neutral conductor. The currents in

the two conductors are therefore equal and opposite and cancel each other out.

Any fault to earth (for example caused by a person touching a live component in the attached appliance) causes some of the current to take a different return path which means there is an imbalance (difference) in the current in the two conductors

(single phase case), or, more generally, a nonzero sum of currents from among various conductors (for example, three phase conductors and one neutral conductor).

This difference causes a current in the sense coil (6) which is picked up by the sense circuitry (7). The sense circuitry then removes power from the solenoid (5) and the contacts (4) are forced apart by a spring, cutting off the electricity supply to the

appliance.

The device is designed so that the current is interrupted in milliseconds, greatly reducing the chances of a dangerous electric shock being received.

The test button (8) allows the correct operation of the device to be verified by passing a small current through the orange test wire (9). This simulates a fault by creating an imbalance in the sense coil. If the RCD does not trip when this button is

pressed then the device must be replaced

[edit]Form factors

A ground fault circuit interrupter circuit breaker (GFCI in USA and Canada) and residual-current breaker with overload (RCBO in Europe) are devices which combine the functions of a residual-current device with a circuit breaker. They detect both

supply imbalance and overload current.

In Europe RCDs can fit on the same DIN rail as the MCBs, however the busbar arrangements in consumer units and distribution boards can make it awkward to use them in this way. If it is desired to protect an individual circuit an RCBO (Residual-

current Circuit Breaker with Overcurrent protection) can be used. This incorporates an RCD and a miniature circuit breaker in one device.

Electrical plugs which incorporate an RCD are sometimes installed on appliances which might be considered to pose a particular safety hazard, for example long extension leads which might be used outdoors or garden equipment or hair dryers

which may be used near a tub or sink. Occasionally an in-line RCD may be used to serve a similar function to one in a plug. By putting the RCD in the extension lead protection is provided at whatever outlet is used even if the building has old wiring,

such as knob and tube, or wiring that does not contain a grounding conductor.

GFI receptacles can be used in cases where there is no grounding conductor, but must be labeled as "Ungrounded". An ungrounded GFI receptacle will trip using the built in Test button, but will not trip using a GFI test plug, because the plug tests by

shorting a small current from line to the non existent ground.

Electrical sockets with included RCDs are becoming common.

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[edit]Combined with overcurrent devices

RCBO

Residual-current and overcurrent protection may be combined in one device for installation into the service panel; this device is known as a GFCI breaker (Ground Fault Circuit Interrupter) in USA/Canada and as an RCBO (residual-current circuit

breaker with overload protection) in Europe. In the US, RCBOs are more expensive than RCD outlets.

As well as requiring both line and neutral (or 3-phase) input and output, GFCI/RCBO devices require a functional earth (FE) connection. For reasons of space some devices use flying leads rather than screw terminals, especially for the neutral input

and FE connections.

More than one RCD feeding another is unnecessary, provided they have been wired properly. One exception is the case of a TT earthing system where the earth loop impedance may be high, meaning that a ground fault might not cause sufficient

current to trip an ordinary circuit breaker or fuse. In this case a special 100 mA (or greater) trip current time-delayed RCD is installed covering the whole installation and then more sensitive RCDs should be installed downstream of it for sockets and

other circuits which are considered high risk.

[edit]Testing

This RCD contains a resistor with an improper value in the test circuit, which gives incorrect results for testing. Under certain circumstances it may prove lethal because it will not trip when expected. That is why RCDs should

be tested by the socket tester with calibrated leakage.

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RCDs can be tested with the built-in test button to confirm functionality on a regular basis. RCDs if wired improperly may not operate correctly and are generally tested by the installer to verify correct operation. Use of a solenoid voltmeter from live to

earth provides a external path and can test the wiring to the RCD. Such a test may be performed on installation of the device and at any "downstream" outlet.

[edit]Limitations

A residual-current circuit breaker cannot remove all risk of electric shock or fire. In particular, an RCD alone will not detect overload conditions, phase to neutral short circuits or phase-to-phase short circuits (see three phase electric power). Over-

current protection (fuses or circuit breakers) must be provided. Circuit breakers that combine the functions of an RCD with overcurrent protection respond to both types of fault. These are known as RCBOs, and are available in 1, 2, 3 and 4 pole

configurations. RCBOs will typically have separate circuits for detecting current imbalance and for overload current but will have a common interrupting mechanism.

An RCD will help to protect against electric shock where current flows through a person from a phase (live / line / hot) to earth. It cannot protect against electric shock where current flows through a person from phase to neutral or phase to phase, for

example where a finger touches both live and neutral contacts in a light fitting; a device can not differentiate between current flow through an intended load from flow through a person.

Whole installations on a single RCD, common in the UK, are prone to nuisance trips that can cause safety problems with loss of lighting and defrosting of food. RCDs also cause nuisance trips with appliances where earth leakage is common and not

a cause of injury or mortality, such as water heaters.

A dangerous condition can arise if the neutral wire is broken or switched off on the supply side of the RCD, while the corresponding live wire remains uninterrupted. If the tripping circuit needs power to work, it cannot operate. Connected equipment

will not work without a neutral, but the RCD cannot protect people from contact with the energized wire. For this reason circuit breakers must be installed in a way that ensures that the neutral wire cannot be switched off unless the live wire is also

switched off at the same time. Where there is a requirement for switching off the neutral wire, two-pole breakers (or four-pole for 3-phase) must be used. To provide some protection with an interrupted neutral, some RCDs and RCBOs are equipped

with an auxiliary connection wire that must be connected to the earth busbar of the distribution board. This either enables the device to detect the missing neutral of the supply, causing the device to trip, or provides an alternative supply path for the

tripping circuitry, enabling it to continue to function normally in the absence of the supply neutral.

[edit]Technical characteristics

[edit]Number of poles

RCDs may comprise two poles for use on single phase supplies (two current paths), three poles for use on three phase supplies (three current paths) or four poles for use on three phase & neutral supplies

[edit]Rated current

The rated current of an RCD is chosen according to the maximum sustained load current it will carry (if the RCD is connected in series with, and downstream of a circuit-breaker, the rated current of both items shall be the same).

[edit]Sensitivity

RCD sensitivity is expressed as the rated residual operating current, noted IΔn. Preferred values have been defined by the IEC, thus making it possible to divide RCDs into three groups according to their IΔn value.

High sensitivity (HS): 6 – 10 – 30 mA (for direct-contact / life injury protection)

Medium sensitivity (MS): 100 – 300 – 500 – 1000 mA (for fire protection)

Low sensitivity (LS): 3 – 10 – 30 A (typically for protection of machine)

Note that (in the UK at least) these nominal values are not in fact the residual current values at which the devices trip. 30mA RCDs typically trip at around 20mA.??

Up Date Sept 2012 reference document UK IET Wiring Regulations / Chaz Andrews Technical Manager Doepke UK

For the UK the required tripping values and times are defined in EN61008(RCCBs) and EN61009(RCBOs), summarized in the IET 17th Edition Wiring Regulations Amd. 1 Appendix 3 table 3A. For example a 30mA device must not trip with a current

value less than 50% IΔn, but must trip within a defined period at current greater than 50% IΔn. At IΔn the device must trip within 300mS. At 5 x IΔn the device must trip within 40ms see link to article giving basic overview of UK requirements for type

of RCCB http://www.doepke.co.uk/download/Techpub-08.pdf

[edit]Type

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Standard IEC 60755 (General requirements for residual current operated protective devices) defines three types of RCD depending on the characteristics of the fault current.

Type AC: RCD for which tripping is ensured for residual sinusoidal alternating currents

Type A: RCD for which tripping is ensured

for residual sinusoidal alternating currents

for residual pulsating direct currents

for residual pulsating direct currents superimposed by a smooth direct current of 0.006 A, with or without phase-angle control, independent of the polarity

Type B: RCD for which tripping is ensured

as for type A

for residual sinusoidal currents up to 1000 Hz

for residual sinusoidal currents superposed by a pure direct current

for pulsating direct currents superposed by a pure direct current

for residual currents which may result from rectifying circuits

three pulse star connection or six pulse bridge connection

two pulse bridge connection line-to-line with or without phase-angle monitoring, independently of the polarity

[edit]Break time

There are two groups of devices:

G (general use) for instantaneous RCDs (i.e. without a time delay).

Minimum break time: immediate

Maximum break time: 200 ms for 1x IΔn, 150 ms for 2x IΔn, and 40 ms for 5x IΔn

S (selective) or T (time delayed) for RCDs with a short time delay (typically used in circuits containing surge suppressors)

Minimum break time: 130 ms for 1x IΔn, 60 ms for 2x IΔn, and 50 ms for 5x IΔn

Maximum break time: 500 ms for 1x IΔn, 200 ms for 2x IΔn, and 150 ms for 5x IΔn

[edit]Surge current resistance

The surge current refers to the peak current an RCD is designed to withstand using a test impulse of specified characteristics ( an 8/20 µs impulse, named after the time constants of the rise and fall of current).

The IEC 61008 and IEC 61009 standards impose the use of a 0.5 µs/ 100 kHz damped oscillator wave (ring wave) to test the ability of residual-current protection devices to withstand operational discharges with a peak current equal to 200 A. With

regard to atmospheric discharges, IEC 61008 and 61009 standards establish the 8/20 µs surge current test with 3000 A peak current but limit the requirement to RCDs classified as Selective.

[edit]History and nomenclature

The world’s first high-sensitivity earth leakage protection system (i.e. a system capable of protecting people from the hazards of direct contact between a live conductor and earth), was a second-harmonic magnetic amplifier core-balance system,

known as the magamp, developed in South Africa by Henri Rubin. Electrical hazards were of great concern in South African gold mines, and Rubin, an engineer at the company F.W.J. Electrical Industries, initially developed a cold-cathode system in

1955 which operated at 525 V and had a tripping sensitivity of 250 mA. Prior to this, core balance earth leakage protection systems operated at sensitivities of about 10 A.

The cold cathode system was installed in a number of gold mines and worked reliably. However, Rubin began working on a completely novel system with greatly improved sensitivity, and by early 1956, he had produced a prototype second-harmonic

magnetic amplifier-type core balance system (South African Patent No. 2268/56 and Australian Patent No. 218360). The prototype magamp was rated at 220V 60A and had an internally adjustable tripping sensitivity of 12.5 to 17.5 mA. Very rapid

tripping times were achieved through a novel design, and this combined with the high sensitivity was well within the safe current-time envelope for ventricular fibrillation determined by Charles Dalziel of the University of California, Berkeley, USA, who

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had estimated electrical shock hazards in humans. This system, with its associated circuit breaker, included overcurrent and short-circuit protection. In addition, the original prototype was able to trip at a lower sensitivity in the presence of an

interrupted neutral, thus protecting against an important cause of electrical fire.

Following the accidental electrocution of a woman in a domestic accident at the Stilfontein gold mining village near Johannesburg, a few hundred F.W.J. 20 mA magamp earth leakage protection units were installed in the homes of the mining village

during 1957 and 1958. F.W.J. Electrical Industries, which later changed its name to FW Electrical Industries, continued to manufacture 20 mA single phase and three phase magamp units.

At the time that he worked on the magamp, Rubin also considered using transistors in this application, but concluded that the early transistors then available were too unreliable. However, with the advent of improved transistors, the company that he

worked for and other companies later produced transistorized versions of earth leakage protection.

In 1961, Charles F. Dalziel, working with Rucker Manufacturing Co., developed a transistorized device for earth leakage protection which became known as a Ground Fault Circuit Interrupter (GFCI), sometimes colloquially shortened to Ground Fault

Interrupter (GFI). This name for high-sensitivity earth leakage protection is still in common use in the U.S.A.[1][2][3][4][5]

In the early 1970s most GFCI devices were of the circuit breaker type. However the most commonly used in the USA since the early 1980s are built into outlet receptacles. The problem with those of the circuit breaker type was that of many false trips

due to the poor alternating current characteristics of 120 volt insulations, especially in circuits having longer cable lengths. So much current leaked along the length of the conductors' insulation that the breaker might trip with the slightest increase of

current imbalance.

]Regulation and adoption

Regulations differ widely from country to country. In most countries, not all circuits in a home are protected by RCDs. If a single RCD is installed for an entire electrical installation, any fault may cut all power to the premises.

[edit]Australia

In Australia, residual current devices have been mandatory since 1991 in new houses on all power and lighting circuits.[6]

[edit]Italy

The Italian law (n. 46 March 1990) prescribes RCDs with no more than 30mA residual current (colloquially called "salvavita", although incorrectly[citation needed] ) for all domestic installations to protect all the lines. The law was recently updated to mandate

at least two separate RCDs for separate domestic circuits. Magnetic and thermal protection has been compulsory since 1968.

[edit]Germany

Germany requires the use of RCDs with no more than 30mA on sockets up to 20A which are for general use. This rule was introduced in June 2007 (DIN VDE 0100-410 Nr. 411.3.3).

[edit]Norway

In Norway, it has been required in all new homes since 2002, and on all new sockets since 2006.

[edit]United Kingdom

The former 16th Edition of the IEE Electrical Wiring Regulations required use of RCDs for socket outlets that were liable to be used by outdoor appliances. Normal practice in domestic installations[citation needed] was to use a single RCD to cover all the

circuits requiring RCD protection (typically sockets and showers) but to have some circuits (typically lighting) not RCD protected. This was to avoid a potentially dangerous loss of lighting should the RCD trip. Protection arrangements for other circuits

varied. To implement this arrangement it was common to install a consumer unitincorporating an RCD in what is known as a split load configuration, where one group of circuit breakers is supplied direct from the main switch (or time delay RCD in the

case of a TT earth) and a second group of circuits is supplied via the RCD. This arrangement had the recognised problems that cumulative earth leakage currents from the normal operation of many items of equipment could cause spurious tripping

of the RCD, and that tripping of the RCD would disconnect power from all the protected circuits.

The current edition (17th) of the regulations requires that all socket outlets in most domestic installations have RCD protection, though there are exemptions. Cables buried in walls must also be RCD protected (again with some specific exemptions).

{Refer to 17th Edition Amendment 1 effective from January 2012} Provision of RCD protection for circuits present in bathrooms and shower rooms reduces the requirement for supplementary bonding in those locations. The regulations also require

that the circuits are arranged to avoid spurious tripping due to normal earth leakage currents. Two RCDs may be used to cover the installation, with upstairs and downstairs lighting and power circuits spread across both RCDs. When one RCD trips,

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power is maintained to at least one lighting and power circuit. Other arrangements, such as the use of RCBOs, may be employed to meet the regulations. The new requirements for RCDs do not affect most existing installations unless they are

rewired, the distribution board is changed, a new circuit is installed, or alterations are made such as additional socket outlets or new cables buried in walls.

RCDs used for shock protection must be of the 'immediate' operation type (not time-delayed) and must have a residual current rating of no greater than 30 mA.

In certain commercial and industrial installations of RCDs may be omitted.

[edit]North America

In North America, RCD (“GFCI”) receptacles invariably have rectangular faces and accept so-called decorator face plates. GFCI outlets can be mixed with regular outlets or with switches in a multigang box with a standard cover plate. GFCI circuit

breakers for load centers are less common in residential applications due to their higher cost.

A Leviton GFCI "DecoraTM" receptacle in a North American kitchen. Local electrical code requires tamper-resistant receptacles in homes, and requires a GFCI for receptacles within 1 metre of a sink. The T-slot indicates this

device is rated 20 amps and can take either a NEMA 5-15 or a NEMA 5-20 plug, though the latter type is rare on household appliances.

In Canada and the United States, two-wire (ungrounded) (NEMA-1) outlets may be replaced with GFCIs to protect against electrocution, and a grounding wire does not need to be supplied to that GFCI. The outlet must be labeled as such. The GFCI

manufacturers provide tags for the appropriate installation description. GFCI receptacles can be connected to also protect all the downstream receptacles on that circuit.

GFCI devices approved for protection against electric shock trip at 5 mA within 25 ms. A GFCI device which protects equipment (not people) is allowed to trip as high as 30 mA of current; this is known as an Equipment Protective Device (EPD).

"RCDs" with trip currents as high as 500 mA are sometimes deployed in environments (such as computing centers) where a lower threshold would carry an unacceptable risk of accidental trips. These high-current RCDs serve for equipment and fire

protection instead of protection against the risks of electrical shocks.

GFCI outlets are required by code in most places where an easy path to ground exists, such as wet areas, rooms with uncovered concrete floors and outdoor areas. In the U.S., successive editions of the National Electrical Code required GFCIs for

additional areas: underwater swimming pool lights (1968); construction sites (1974); bathrooms and outdoor areas (1975); garages (1978); near hot tubs or spas (1981); hotel bathrooms (1984); kitchen counter receptacles (1987); crawl spaces and

unfinished basements (1990); wet bar sinks (1993); and laundry sinks (2005).[7]

[edit]See also

Arc-fault circuit interrupter  (AFCI)

Earth leakage circuit breaker

Insulation monitoring device

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Domestic AC power plugs and sockets

[edit]References

1. ̂  Charles F. Dalziel, Transistorized ground-fault interrupter reduces shock hazard, IEEE Spectrum, January 1970

2. ̂  The Professional Engineer, Official Journal of the Federation of Societies of Professional Engineers of South Africa, pp 67, Vol 6(2) 1977

3. ̂  Earl W. Roberts, Overcurrents and Undercurrents – All about GFCIs: Electrical Safety Advances through Electronics, Mystic Publications, Mystic CT, 1996

4. ̂  Edward L. Owen, Power System Grounding Part II: RCD & GFCI, IEEE Industry Applications Magazine, July/August 1996

5. ̂  Forging ahead: South Africa’s Pioneering Engineers, G R Bozzoli, Witwatersrand University Press, 1997

6. ̂  SAA Wiring Rules AS/NZS 3000:2000, SAI Global Limited

7. ̂  "GFCIs Fact Sheet". US Consumer Product Safety Commission. Retrieved 2009-06-28.

[edit]External links

GFCIs Fact Sheet (Consumer Product Safety Commission)

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File:Siemens lethal RCD.jpgFrom Wikipedia, the free encyclopedia

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Description English: Testing this RCD on 4,7kΩ resistor (when I wanted to do photo showing how does it work), I've found, that resistor still warm but this RCD doesn't trip at all. I pushed "test" button and it disenergized circuit. One more time I shorted cicuit to the ground, but it hadn't triped at all. OK, I decided to find out, what's wrong here. Imagine, how I was surprised, when have found out, that testing resistor has improper value and giving improper results. Especially instruction "test half yearly" surprised me.

Well, Siemens produced protective appliance, which material of cover and dimensions satisfy European standarts. But it doesn't protect human against lethal shock when it will be need.

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Important mission of this device is lost.

Who hadn't understood: pushing "TEST" button RCD will trip even if it is broken. Resistor over limits leakage current 6.5 times, so result of testing will be wrong. If this RCD (which is

created to protect people against electric shock) doesn't work correct, "TEST" button will always show that RCD working properly. As result, someone may be harmed by electric shock

according to spurious result of the test, which has formed during tests.

To check those RCDs I recommend to use professional testing device, which you can find in electrical storey. It looks like power strip with lights and buttons. You put it into the

socket and push "TEST" button, which will make 30mA of leakage and test your RCD. If you have any doubts, you may always check it using multimeter.

Date 10 December 2010

Source Own work

Author Dmitry G

RESIDUAL CURRENT DEVICES

Residual Current Devices

Earth Leakage Detectors for EN/IEC Applications

The Bulletin 1492-RCD line includes Residual Current Devices for earth leakage detection to EN/IEC standards. These devices are used in association with miniature circuit breakers (1492-SP).

Features

True IP2X Finger-Safe Design (Front) Undelayed Tripping Time Line-Voltage Independent Tripping (Suitable for Residual Current & Additional Protection) Rated Tripping Current: 30, 100, 300, 500 mA For Applications in which AC and Pulsating DC Fault Currents are Likely to Appear, Non-Selective and Non-Delayed Designed to Prevent Unwanted Tripping Caused by Switching Electronic Circuit Devices Mounts on DIN Rail Busbar Position on Top or Bottom Conditionally Surge Current Proof 250 A Rated Short-Circuit Strength: 10 kA with 63 A gG/gL Back-Up Fuse, 10 kA with 80 A gG/gL Back-Up Fuse for 80 A Device Auxiliary and Signal Contacts May Be Added

Standards Compliance

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Product

Overview

IEC/EN 61008

Certifications

VDE CertifiedCE Marked

The Bulletin 1492 Residual Current Devices are available in 2- or 4-pole construction with (4) sensitivity settings to detect earth leakage to EN/IEC standards. Bulletin 1492-RCDs are designed to provide a degree of safety⋆  in the sensing of earth leakage that can be hazardous to personnel or machinery. Both line and load terminals accept 1.5…35 mm2 copper wire.

⋆ It is recommended that the devices be tested monthly by using the “TEST” button to check for proper operation of the device.

Bulletin 1492-RCD Product Selection Table

Rated Tripping Current (mA)

Rated Current (A)

2-Pole (1-Pole + Neutral)

4-Pole (3-Pole + Neutral)

Standard With Delay

30 16 1492-RCD2A16 — —

25 1492-RCD2A25 1492-RCD4A25

—

40 1492-RCD2A40 1492-RCD4A40

—

63 — 1492-RCD4A63

—

80 — 1492-RCD4A80

—

100 25 1492-RCD2B25 1492-RCD4B25

—

40 1492-RCD2B40 1492-RCD4B40

1492-RCD4B40D

63 — 1492-RCD4B63

1492-RCD4B63D

300 16 — 1492-RCD4C16

—

25 1492-RCD2C25 1492-RCD4C25

—

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40 1492-RCD2C40 1492-RCD4C40

1492-RCD4C40D

63 — 1492-RCD4C63

1492-RCD4C63D

80 — 1492-RCD4C80

—

500 16 — 1492-RCD4D16

—

25 — 1492-RCD4D25

—

40 — 1492-RCD4D40

—

63 — 1492-RCD4D63

—

80 — 1492-RCD4D80

—

Operational Voltage 230/400V, 50 Hz

Pieces per Carton 1 1 1

Diagram

Note: Dimensions are shown in millimeters unless otherwise noted. Dimensions are not intended to be used for manufacturing purposes.

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Auxiliary Devices

Device Description Diagram Cat. No.

Dual auxiliary contact moduleSwitches when protective device is operated manually or tripped electrically2 N.O. – 2 N.C. 2 Form C Contact

1492-ASPHH3

Auxiliary/signal alarm contact module1 Auxiliary Contact switches when protective device is operated manually or tripped electrically1 N.O. – 1 N.C. Form C Contact1 Signal Contact switches when protective device is tripped electrically1 N.O. – 1 N.C. Form C Contact

1492-ASPHS3

Design according to: IEC/EN 61008

Certifications VDE, CE Marked

Tripping Time Undelayed; 40 ms for "D" suffix

Rated Voltage 230/400V, 50 Hz

Rated Tripping Current 30, 100, 300, 500 mA

Sensitivity AC and Pulsating DC

Rated Short Circuit Capability 10 kA with 63 A gG/gL Back-Up Fuse for up to 63 A10 kA with 80 A gG/gL Back-Up Fuse for 80 A

Maximum Back-Up Fuse for Short Circuit Protection

63 A gG/gL for up to 63 A80 A gG/gL for 80

Maximum Back-Up Fuse for Overload Protection

25 A gG/gL (25 A and 40 A devices)40 A gG/gL (63 A device)50 A gG/gL (80 A device)

Resistance to Climatic Conditions Per IEC/EN 61008

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Degree of Protection Built-in switch IP40

Electrical Life  4000 change-overs

Mechanical Life  10000 change-overs

Mounting DIN Rail

Housing Material Halogen-Free

Electrical Life  4000 change-overs

Operating Temperature -25°C…+40°C (Non-Condensing)

Shipment and Short-Term Storage Limits -35°C…+60°C

Wire Size 1.5…35 mm2 Copper

Terminal Torque 2.4 N•m  40 A, 3.0 N•m  63 A

Recommended Wire Strip Length 13 mm

Heat Loss Due to Current

At rated current in Watts

Rated Current

Rated Tripping Current

30 mA

100 mA

300 mA

500 mA

2-Pole 16 A 1.2 — — —

25 A 2 1.3 1.3 —

40 A 5.8 5.4 5.4 —

63 A — — — —

80 A — — — —

Rated Current

Rated Tripping Current

30 mA

100 mA

300 mA

500 mA

4-pole 16 A — — 1.8 1.8

25 A 3.1 2.8 2.8 2.8

40 A 9.6 8.4 8.4 8.4

63 A 10.5 10.5 10.5 10.5

80 A 11.4 — 11.4 11.4

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