If you feel that the following materials are too highly technical, read this post,. You may find out that house electricity is really quite easy to understand. As you can see in the above picture, it is one of the standard components inside a house electrical panel. This component is designed to detect electric current leakage in a house wiring and appliances connected to the wiring. The circuit that you see here is actually a residual current devise RCD , or residual current circuit breaker RCCB. This circuit is like a second generation of ELCB design. It is based on the principle of magnetic core balance and the trigger core is current operated instead of voltage operated as in the original design of ELCB. Even though the original ELCB design is no longer used, the name stuck. Some textbooks now use the term RCD or RCCB to refer to this shock protection devise. Therefore, the convention has not been changed. Diagram 3 — Typical ELCB circuit a. Observe that the supply coil, the neutral coil and the search coil all wound on a common transformer core. On a healthy circuit the same current passes through the phase coil, the load and return back through the neutral coil. Both the phase and the neutral coils are wound in such a way that they will produce an opposing magnetic flux. With the same current passing through both coils, their magnetic effect will cancel out under a healthy circuit condition. The periodically changing residual flux inside the transformer core crosses path with the winding of the search coil. This action produces an electromotive force e. An electromotive force is actually an alternating voltage. The induced voltage across the search coil produces a current inside the wiring of the trip circuit. It is this current that operates the trip coil of the circuit breaker. Since the trip current is driven by the residual magnetic flux the resulting flux, the net effect between both fluxes between the phase and the neutral coils, it is called the residual current devise. With a circuit breaker incorporated as part of the circuit, the assembled system is called residual current circuit breaker RCCB or residual current devise RCD. The load is not part of the internal ELCB circuit. However, notice that there is an earthing symbol at the exposed casing of the load. That symbol represents the earthing connection from the exposed metal parts of the electrical equipment or appliance to the electrical earth. This earthing connection will allow the ELCB to fulfill its purpose of being in the electrical circuit. You can have a good operational ELCB unit properly installed and wired at the electrical panel, but if the earthing connection is broken or missing, the ELCB will not trip during an actual earth leakage situation. When the pushbutton is operated i. This is because of the additional current supplied by the test resistor. Therefore, there is an imbalance between the two fluxes and this generates a residual current in the trip circuit, which trips the circuit breaker. The above trip simulation attempts to check the health of the ELCB device. However, the TEST pushbutton cannot test the complete operation of the electric shock protection system. As mentioned above, the protection system can only be effective if the grounding part of the electrical wiring is adequately functional. I will spend an entire post on electrical grounding soon. However, I already have a post on the electrical earthing for a very simple installation. The pictures there also show very clearly the connections and the path of the grounding cables. The electrical earthing for your house wiring is probably very similar to this one. Read the post here,. If your interest is temporary electrical installations, I have also uploaded a couple of pictures here,. How to connect ELCB or RCD The single line diagram provides an overall picture of the wiring system for the whole house into in easy to understand view. Remember, this is not a wiring diagram. A single line diagram is a representation of the whole system by showing the interrelationships between all major components that are assembled to produce the system. It is just like a block diagram. She actually did not know the exact load for sure because the precise electric load imposed by some appliances such as the air conditioning units was unknown yet at the time. It may also change from time to time. Notice that the cable sizes for the wiring circuits are also indicated in Diagram 9 at the top left corner, as shown below: Diagram 9 — Wiring circuit cable sizes Notice that the wiring cables to one of the 20A Air-conditioning Panels are 2 cables of 4 mm square in size, and the circuit breaker i. MCB protecting these cables is rated 20A. These 4 mm square can handle more than 20A of electric current. However, if the air conditioning unit is faulty, the current flow may rise dramatically to a value that the cables cannot handle. The cables may overheat and cause fire to the house. The 20A rating would prevent that by limiting the current flow to just 20A. If the flow exceeds 20A, the MCB would trip and this prevents overheating and any other types of damages and fire risks. Have I strayed from the ELCB topic again? Yes, but I did it on purpose. I briefly explained on components around the ELCB unit and their purposes. This clarifies that those functions are not the purpose of the ELCB unit. For example, the protection of the house wiring cables from overheat above is done by the MCB circuit breakers. The supply current at the LIVE busbar is protected by the ELCB On the other hand, the supply that is distributed by the LIVE busbar to the wiring circuit breakers is taken from the ELCB. Therefore, any leakage of current or voltage from the live busbar to electric panel casing would be detected by the ELCB and the ELCB unit would cut off the supply if the leakage exceeds a preset leakage level which is 100 mA in this case. The supply from the meter goes through the switch-fuse first, and then come out of the second terminal to go to the ELCB. Therefore, the electric voltage at the switch-fuse is has no shock protection. A person can suffer severe injuries due to shorted connections to the switch-fuse terminals even though the ELCB and the house elect
