What is the differences between ELCB and RCCB

What are the differences between ELCB and RCCB

ELCB - Earth Leakage Circuit Breaker

  Characteristics. 

• Phase (line), Neutral and Earth wire connected through ELCB.
• ELCB is working based on Earth leakage current.
• Operating Time of ELCB: 

• The safest limit of Current which Human Body can withstand is 30ma sec.
• Suppose Human Body Resistance is 500Ω and Voltage to ground is 230 Volt.
• The Body current will be 500/230=460mA.
• Hence ELCB must be operated in  30maSec/460mA = 0.65msec

RCCB - Residual Current Circuit Breaker.

Characteristics. 

• Phase (line) and Neutral both wires connected through RCD

• It trips the circuit when there is earth fault current.

• The amount of current flows through the phase (line) should return through neutral 

• It detects by RCD. any mismatch between two currents flowing through phase and neutral detect by -RCD and trip the circuit within 30 Millisecond. 

• If a house has an earth system connected to an earth rod and not the main incoming cable, then it must have all circuits protected by an RCD (because u mite not be able to get enough fault current to trip a MCB)

• RCDs are an extremely effective form of shock protection

     The most widely used are 30 mA (milliamp) and 100 mA devices. A current flow of 30 mA (or 0.03 amps) is sufficiently small that it makes it very difficult to receive a dangerous shock. Even 100 mA is a relatively small figure when compared to the current that may flow in an earth fault without such protection (hundred of amps)

A 300/500 mA RCCB may be used where only fire protection is required. eg., on lighting circuits, where the risk of electric shock is small.

Limitation of RCCB

• Standard electromechanical RCCBs are designed to operate on normal supplywaveforms and cannot be guaranteed to operate where none standard waveforms are generated by loads. The most common is the half wave rectified waveform sometimes called pulsating dc generated by speed control devices, semi conductors, computers and even dimmers.

• Specially modified RCCBs are available which will operate on normal ac and pulsating dc.

• RCDs don’t offer protection against current overloads: RCDs detect an imbalance in the live and neutral currents. A current overload, however large, cannot be detected. It is a frequent cause of problems with novices to replace an MCB in a fuse box with an RCD. This may be done in an attempt to increase shock protection. If a live-neutral fault occurs (a short circuit, or an overload), the RCD won’t trip, and may be damaged. In practice, the main MCB for the premises will probably trip, or the service fuse, so the situation is unlikely to lead to catastrophe; but it may be inconvenient.

• It is now possible to get an MCB and and RCD in a single unit, called an RCBO (see below). Replacing an MCB with an RCBO of the same rating is generally safe.

• Nuisance tripping of RCCB: Sudden changes in electrical load can cause a small, brief current flow to earth, especially in old appliances. RCDs are very sensitive and operate very quickly; they may well trip when the motor of an old freezer switches off. Some equipment is notoriously `leaky’, that is, generate a small, constant current flow to earth. Some types of computer equipment, and large television sets, are widely reported to cause problems.

• RCD will not protect against a socket outlet being wired with its live and neutral terminals the wrong way round.

• RCD will not protect against the overheating that results when conductors are not properly screwed into their terminals.

• RCD will not protect against live-neutral shocks, because the current in the live and neutral is balanced. So if you touch live and neutral conductors at the same time (e.g., both terminals of a light fitting), you may still get a nasty shock.

Difference between ELCB and RCCB

• ELCB is the old name and often refers to voltage operated devices that are no longer available and it is advised you replace them if you find one.

• RCCB or RCD is the new name that specifies current operated (hence the new name to distinguish from voltage operated).

• The new RCCB is best because it will detect any earth fault. The voltage type only detects earth faults that flow back through the main earth wire so this is why they stopped being used.

• The easy way to tell an old voltage operated trip is to look for the main earth wire connected through it.

• RCCB will only have the line and neutral connections.

• ELCB is working based on Earth leakage current. But RCCB is not having sensing or connectivity of Earth, because fundamentally Phase current is equal to the neutral current in single phase. That’s why RCCB can trip when the both currents are deferent and it withstand up to both the currents are same. Both the neutral and phase currents are different that means current is flowing through the Earth.

• Finally both are working for same, but the thing is connectivity is difference.

• RCD does not necessarily require an earth connection itself (it monitors only the live and neutral).In addition it detects current flows to earth even in equipment without an earth of its own.

• This means that an RCD will continue to give shock protection in equipment that has a faulty earth. It is these properties that have made the RCD more popular than its rivals. For example, earth-leakage circuit breakers (ELCBs) were widely used about ten years ago. These devices measured the voltage on the earth conductor; if this voltage was not zero this indicated a current leakage to earth. The problem is that ELCBs need a sound earth connection, as does the equipment it protects. As a result, the use of ELCBs is no longer recommended.

Click here to Watch : How to work earth leakage circuit breaker