ELCB circuit diagram

This post will talk about the circuit diagram of house ELCB.

Picture 1 – House ELCB

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ELCBs are common household items. Most people know about them and every house has at least one, located inside the consumer electrical panel.

The above screenshot of the ELCB was taken from an old picture of the terrace house that I rented a few years ago when I was supervising a high-rise building construction project at the nearby town.

Picture 2 – A typical house electrical panel

The above picture shows the house electrical panel. Most of the readers should be able to find one similar to this in the house they live in.

Picture 3 – The electrical panel with the cover removed

Now I have removed the front cover of the “distribution” panel. I use the word distribution here because the electrical panel is actually a distribution center for the electric power for the whole house.

If you go to a new house and you need to know how the electricity is distributed in the house, you should look at this panel first.

I know many readers who already have some knowledge of electrical may question my choice of pictures to present in this blog.

Why do I show an electrical panel with a somewhat messy wiring?

There are websites who condemned my other blogs for showing these pictures. They said I promoted unsafe wiring practices.

I, however, have a slightly different opinion.

I believe that in order to educate the public on the skills of electrical safety, it is more effective to also show them the real life pictures instead of only some new and shining electrical panels for houses that have just been built.

Tenants who occupy such new houses do not face this kind of electrical hazards.

It is those who buy second-hand houses, or those who rent used apartments that face the electrical hazards due to bad electrical wiring or defective electrical parts.

Therefore, showing the readers only good wiring and neat electrical installation works are not good enough.

The not-so-good and the bad electrical works must also be shown because they are what the house users find most often in their daily lives.

With that said, let’s proceed further with the matters at hand.

There are so many that things I wish to say about the electrical parts and the wiring in the above pictures. However that will take so many pages that it is better to just concentrate on the “ELCB circuit” for now.

I will cover other topics on the electrical panel in future posts.

Diagram 4 – Typical ELCB Circuit Diagram

(Click on the image to enlarge it)

The above diagram shows how a single phase ELCB circuit looks like.

However, before I get down to explain more, please note that I am using the name “ELCB” as a generic name, just like a “circuit breaker”.

The rest of this article will be in point form so I can write faster. I am actually not much of a writer (if you don’t already know).

(a) ELCB is a short for Earth leakage Circuit Breaker.

When it first came to be used, the devise is actually a voltage-operated device that was designed to detect a current leaking through the earth path of electrical equipment and appliances.

I used to see the actual circuit during my college days, but I have to dig it up and redraw it for uploading. You will see it in one of my future posts.

(b)  The circuit that you see here is actually an RCD (residual current device), or RCCB (residual current circuit breaker).

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” earth leakage circuit breaker.

(c) In terms of performance, the residual current circuit breaker is definitely better.

The performance of the old ELCB did not have any problem, but the residual current device can do the same and more.

(d) I cannot remember when the residual current circuit breaker actually took over the whole wiring scene, but I cannot find the earth leakage circuit breaker in actual installation anymore.

Everywhere that I know is using the RCD, but in the field the terminology used have not changed at all.

Everywhere and in all design drawings the name ELCB has not been changed. Only some textbook and in the academic classes the RCD or RCCB terms has been used.

Therefore, the convention has not been changed. That is why throughout this blog I will keep on using the ELCB for this earth leakage device.

(e) Originally ELCB was designed to detect earth leakage current and to disconnect the circuit immediately when a certain limit was crossed.

Now RCD does the same. Therefore, the general practice to still call the residual devise an earth leakage circuit breaker is still correct.

It is still an ELCB by purpose and function even though the internal circuit design has actually changed.

(f) However, in certain scenarios both ELCB and RCD names need to be used for clarity.

The discussion on internal circuit design of the device like now is one of the scenarios.

That is why I will use the two names interchangeable in the following part of this post.

The circuit shown in Diagram 4 shows a typical single-phase double pole ELCB circuit.

I think it is better to first explain the components of the circuit one by one and explain the how the circuit works afterward.

(1) The supply coil, the neutral coil and the search coil all wound on a common transformer core.

Diagram 5 – The symbols of supply coil, neutral coil and search coil

(Click on the image to enlarge it)

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.

(2) In a situation when there is fault or a leakage to earth in the load circuit, or anywhere between the load circuit and the output connection of the ELCB circuit, the current returning through the neutral coil has been reduced.

Then the magnetic flux inside the transformer core is not balanced anymore. This unbalanced flux is what we call a residual flux.

(3) The residual flux will be detected by the will cross the winding of the search coil and produce a voltage that drives a current inside the wiring of the trip circuit.

It is this current that operates the trip coil of the circuit breaker. Since the current has been 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 full circuit, it is called residual current circuit breaker (RCCB) or residual current devise (RCD).

Diagram 6 – The circuit breaker symbol

(Click on the image to enlarge it)

(4) The incoming current will come through the circuit breaker first before going to the phase coil. The return neutral path passes through the second circuit breaker pole.

Diagram 7 – The incoming supply symbol

During tripping when a fault is detected, both the phase and neutral connection is isolated.

The circuit breaker can also be used to manually ON or OFF the circuit.

(5) The load circuit is not part of the ELCB circuit.

Diagram 8 – Symbol of the load circuit

(Click on the image to enlarge it)

However, notice the earthing symbol at the load circuit.

That is 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 fulfill its purpose of being in the electrical circuit.

You can have a good operational ELCB unit properly installed and wire at the electrical panel, but if the earthing connection is broken or missing, the ELCB will not trip during an actual earth leakage situation.

(6) The test pushbutton and the test resistor are arranged to provide a test function for the ELCB circuit.

Diagram 9 – The TEST PUSHBUTTON symbol

(Click on the image to enlarge it)

This part of the circuit bleeds away a fraction of the running current from the phase coil.

So the neutral coil current will be higher the phase coil current. Therefore, a residual current will be generated in the trip circuit and trips the circuit breaker.

Diagram 10 – Test resistor symbol

The above trip simulation tries to check the health of the ELCB circuit. In it works.

However, it does not test the complete operation of the protection system that the ELCB is supposed to serve.

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Electric circuit basic diagram

The diagram below is what I believe one of the most basic forms of electric circuits.

Diagram 1 – One of the most basic forms of electric circuits

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If you are a beginner on the subject of electric circuits and diagrams, and you have come to this blog looking for some materials that can help you understand electrical engineering better, then you have come to the right place.

I am starting this blog in my spare time for this purpose: to provide explanations on how electric circuits work.

In order to help you understand the materials easily, I will be using examples that are part of everybody’s normal lives.

House electrical wiring, automotive (e.g. Cars) electrical wiring, etc. Things like that.

Now and then I will still be using much more sophisticated examples such as the internal wiring of a building’s water pump control panel.

Some readers just don’t like simple examples. Therefore these types of examples are for them.

Electric, electrical or electronic?

Is a transistor radio (with alarm clock) that runs on mains power (240 volt house electricity supply) an electronic item or an electrical item?

What is the difference between electric, electrical and electronic?

Some beginners have these questions jumping around in their heads for quite some time before they can grasp the difference.

So I am going to give a short explanation here so that when I use these words, everybody will have at least a general idea of the difference and similarity of meanings between these three words.

Electric current and voltage

Now is the time to return to the above simple electrical diagram.

First, let’s go through the component one by one.

Image 2 – A symbol of the source of electricity, a 12 volt car battery

Well, my guess is that most people know what a car battery is. If you don’t, then open the hood or the engine compartment of your car, your father’s car, or your company’s car.

There you will definitely find a battery. Below is an example of a car battery.

Picture 3 – A 12V lead acid car battery (coming soon)

The battery is a source of electricity. Just like a house water tank at a roof-top (or above a toilet) is a source of water.

The height of the water tank provides the strength of the water pressure. The higher we locate the tank, the stronger the water pressure becomes.

If the height of the tank gives pressure to the water at a house, the chemical materials inside a battery provide the “electrical pressure”.

If “water pressure” forces the water fluid to flow inside the piping, the “electrical pressure” forces the electric charges to flow inside cables and metal wires.

What is voltage?

“12V” means 12 volt. This is the strength of the electricity source. “12” is a measure of the strength. Volt is just a name given. Instead of calling the battery “a 12-units strong battery”, we call it a “a 12 volt battery”, or “a 12V battery”.

I know the concept of the strength of an electricity source and the “voltage” unit can be confusing to some beginners. Others can grasp it easily at the first sight. I guess different persons have different talents.

At the end of this post, I attached an article that I have already published somewhere else.

I was trying to explain about Ohm’s Law, one of the most fundamental principles of electrical engineering. It was not fully completed yet when I published it.

It is, however, useful in understanding the concept of voltage, current, resistance and power.

Image 4 – Wiring cable symbol

The symbol is the line. It represents the conductor where the electric current is supposed to flow.

The strength of the battery is channeled through the electric cable so we can get some useful work done by the “electrical system”.

However, cables and metal wires are not the only way to channel the electric charges for some useful purposes. There are also other ways to do that.

Image 5 – A symbol of an electrical load

The 15 watt incandescent lamp is a “load” to the battery. It is a burden. When the lamp lights up after the circuit is wired as in the diagram, the battery uses up some of its stored chemical energy.

That is why it is called an “electrical load” or “burden”.

The three components of electric circuits

The above 3 components (four because there are two PVC insulated cables in the diagram) are the basic components of an electrical circuit.

You have the source, the load or burden, and the cables to channel electric charges between the source and the load.

So what is the difference between electric, electrical and electronic?

Only one different: The strength of the source.

In the above diagram, the strength of the source is 12 volt.

Many portable equipment and appliances use 12 batteries as the source. So you can call them electronic equipment.

On the other hand, in a house wiring, the source of electricity is the authority’s 240 volt supply.

240V, instead of 12V. So you can call house wiring an “electrical” system.

Electric?

This word is more of a generic term. It is for common uses.

“Electric heater” is an example. Would it sound right to call it “electrical heater”?

I don’t think so. Do you?

I am not trying to play with words here.

What I am trying to do is to twist and turn the basic terms of electrical engineering so you can “feel” their meaning.

Why it can be difficult to understand electricity

This is one of the root causes why many people have difficulties to understand electricity.

It cannot be seen. So it is difficult to know how it looks like. Not like water.

You may be able to feel it, but when you do feel it, then at that moment it is already about to seriously injure you, or kill you.

It is, however, very useful. It can even replace people.

For example, it can watch over your house for you. That is the burglar alarm system.

Human can fall asleep. An electronic burglar alarm does not.

So, electricity is like a loyal friend.

But a dangerous friend. Just like a wild beast.

My point is: BE WARNED. Electricity is useful, but IT KILLS.

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ADDITIONAL ARTICLE: Ohm’s Law (RE-PUBLISHED)

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Why would I post an article about Ohm's Law to a blog that contains advanced materials such as electrical specifications and temporary electrical supply? Isn’t that a bit out of place?

Nope. It is not out of place.

Ohm's Law is one of the most basic principles of electrical engineering. For beginners to have a sufficient understanding of electrical installations and electrical wiring, knowing and understanding Ohm's Law is a must.

For readers who have never heard of Ohm's law, please do not worry. It is just a name.

Many people who have already some practical skills of house electricity may also never hear about Ohm's law. Knowing the name is not really necessary. Knowing how things work is necessary.

However, if you wish to grow your knowledge of electricity, then you need to know what it is that electrical people call “Ohm's law”.

To grow knowledge, we need to be able to communicate with the language of that discipline. We need to understand what people are saying.

In electrical engineering, Ohm's law is like onions in cooking. Or PVC pipes in water supply.

Okey, enough on introduction.

Now let's go to the substance about the Ohm's law, one of the most basic of electrical principles.

Look at the simple electrical diagram below:

Diagram 1 - The simplest electrical circuit on earth

I have tried to make the above diagram self explanatory, but then maybe it is still not so self-explanatory yet.

How many components are there in the above circuit diagram? Four components: 1) The electricity source; 2) The 1.5 sq.mm PVC insulated wiring cable at the top; 3) The LOAD; 4) The 1.5 sq.mm PVC insulated wiring cable at the bottom.

There you have it. If you can get these four components, you can make a working electrical circuit and it will work.

For readers with even a minimal knowledge of electrical engineering, you may wish to visit other posts on this blog. There are quite a number of posts with advanced materials here.

This post is for true beginners only and the materials here will get more and more basic. This post is like a first day in a class of electrical engineering in college.

Now allow me to elaborate deeper into the above components for readers who still feel they do not yet understand fully about the above four components.

Components number (2) and (4) are the wiring cables. So you have two lengths of wiring cables here.

Component number (1) is called "Electricity source" because it is a source of electricity. A 1.5V cell battery size AA that we normally use to power a small pocket torch light is one source of electricity.

A car battery is also a source of electricity.

I could as well replace the word "Electricity source" with "Car battery" and our simple electric circuit in Diagram 1 will still work.

Component number (3) is an electrical "Load". It is called a "load" because it is a burden to the electricity source (or the car battery). I could just replace the word "Load" with the word "incandescent lamp".

If I replace the "Load" with "incandescent lamp", what will happen? Simple. The lamp will light up.

The word "Load" is used to represent all types of electrical loads, whether it is an incandescent lamp or a car radio.

I haven't really got to the Ohm's Law, have I?

I will get there soon. We are actually on the way.

Now look at Diagram 2 below:

Diagram 2 -A simple electric circuit

Here I have replaced the "Electricity source" with "12 V car battery" and the "Load" with "15 Watt (12V) incandescent lamp".

I have also added the capital letter "I" after "Electric current" above the top wiring cable.

And also a capital letter "V" on the right side of the electricity source, opposite to the "12 V car battery"

Also the capital letter "P" on the left side of the electrical load, opposite of the "15 Watt (12V) incandescent lamp".

Now our electrical circuit is detailed enough. If you get these four components: a 12 Volt car battery, two lengths of 1.5 sq.mm PVC insulated wiring cable and a 15 Watt incandescent lamp, you can easily put them together and see the result.

The 10 watt incandescent lamp will light up.

The above is very basic and I believe anybody can see the common sense logic there. I can go even deeper and MUCH MORE basic, but that will take more time. We now need to get back to the direction of the Ohm's Law.

Now if the above electrical components are assembled and connected as shown, we will get a lighted incandescent lamp.

As students of electrical engineering (you are now if you have read through this post this far), you should be asking yourself what are the numbers that makes the lamp light up.

Let me help you here. These are the numbers:

A. 15 watt divided by 12 volt = 1.25 ampere. The 1.25 ampere here is what we call the electric current. It is how we give a quantity to the flow of electrons that flow through the wiring cables.

This current flows from the positive side of the car battery (marked + ) travel along the top wiring cable, and pass through the incandescent lamp.

It then continue the travel through the bottom wiring cable, return to the car battery on the negative side (marked - ), and pass through the battery to the positive side and keep circulating the loop in the same direction.

The material that the lamp is made of heats up and produces light when the electric current flows through it.

B. Now we have three numbers: 12 is the strength of the car battery.

People in electrical engineering called it "volt" to honor one of the scientists who discovered and developed electricity into the form that we can use today.

A few hundred years ago, people still used candles to light up their whole house, not just the dinner tables. Imagine that.

We can consider ourselves very lucky.

C. Then we have number 1.25 for the current that flows through the lamp and the two wiring cables.

This number has been called ampere, also for the same reason that the name volt was given.

1.25 is generally the volume of electrons that flow through the wiring cables and the lamp.

When you think of electric current, think of the water current in a river or at a beach. The water current can be strong enough to sweep you away and drown you.

If the river floods, it can even sweep away houses and cars, etc. The electric current can be just as strong as the water current.

To bring it closer to home, think of the water flow in a water hose when you wash your car.

D. Another number is 15.

That is from the incandescent lamp. It is the amount of energy that is used by the lamp while producing the light.

The name watt is given to just give a name to the quantity. Watt is also a given name just like volt and ampere.

Now we have three numbers with a name to label each one of them.

Ampere for the volume of electric current that flows through the "loop" (or "circuit", just like circuit in a race car track).

In our electrical circuit in Diagram 2, the current is 1.25 Amperes.

Now please do not get confused about this quantity. When I say volume of current, it is like 1.25 liters of water per second, not 1.25 Liter in quantity.

So it is more like “speed” of electron flow, not the quantity of electrons.

The second number is 12.

As I said above, this number is a measure of the strength of the car battery.

Trucks usually have a battery with the strength of 24. That is twice the strength of a car battery.

Even some cars have batteries with the strength of 24. A stronger battery can force the electrons to flow faster.

Therefore, we can get a higher volume of electron per second passing through the cables and the lamp.

A stronger battery is like a bigger water pump. A bigger pump can push more liter of water per second through a water hose. The car battery functions the same way.

The name "volt" is just name that has been given to call the quantity. It could have been 12 Lucy instead of 12 Volt if there was a scientist by that name during the period of discovery of electricity.

The third number, 15, is a measure of the strength of an electric machine in doing work.

The incandescent lamp in our electric circuit can be called a machine also if we like. The work of the lamp is to produce light.

15 is a measure of that strength. A similar lamp with the strength of 30 would produce a light twice as strong or double the brightness.

You can get creative here and maybe use two lamps with the strength of 15. Then you can get the same amount of light.

Again one scientist got lucky and his name was used to name this strength. The name is "Watt".

Is this tiring?

If it is, then that is good.

That means your mind has been trying to adapt itself to this logic of electrical quantities. If it is a consolation, please know that if you can follow this through and understand these three quantities as I explain them, then you are already on your way to become a good electrician.

Not an engineer yet, but you just showed to yourself that you have the capacity to handle one of the most powerful invisible powers on earth, ELECTRICITY.

Where is the Ohm's Law?

Please be patient. There is one more number, the fourth number, which you need to understand before I show you the Ohm's Law.

If you are feeling really impatient already, then I should tell you that learning electricity is like learning magic. I mean real magic, not the "mind trick" types that you can see on TV every day.

Before a sorcerer can teach her powerful magic to her student, she must first teach the student the knowledge of defense against magic. This includes measuring how strong a magic is.

Only after mastering the knowledge and skills in the defense against magic, then only one is prepared enough to learn how to use magic.

Without the knowledge in defense, the magic itself can hurt or seriously injure the student.

Enough metaphors.

Now the fourth number.

Before the invention of automobiles (or cars as we call them today), people use horses to pull carts so they could deliver goods to distant places.

They actually didn't have to use the horses to move the carts; they could just push or pull the cart themselves.

However, that would be a lot of work. Men were smart. They wanted results the easy way. So they enslaved the wild horses and train them the skills of pulling the carts.

Being less smart than men, some of the horses happily do the task while men sit on horses with the goods. Guess who got rich...

Imagine a scenario when a horse (This one man could only afford one horse and a cart. The rest of his money went to the cost of purchasing the goods.) was about to pull a cart.

Before the horse starts pulling, the cart was not moving. It was stationary. The cart was loaded with goods and the man, the owner.

The moment the horse starts pulling, the cart starts to move.

Slowly in the beginning moments but it accelerate faster and faster. After a while the horse and the cart travels at a steady speed.

Now if the man suddenly cuts the ropes that tie the horse to the cart, what would happen?

The cart would slow down gradually, right? And eventually the cart would come to a stop.

In order to keep the cart moving, the horse, the source of strength need to be constantly tied to the cart.

Of course the man can also order the horse to stop thereby causing the cart to stop also.

I know what you are thinking. The man need to have some means of braking the cart.

Otherwise the cart would hit the back of the horse because the natural stopping of the cart would not be immediate. It would be a gradual stop, naturally.

That is the point I am trying to make.

NATURALLY.

It is the nature of things to stay still, stationary, unless there is a source of strength that forces it into motion.

Even after it has been moved into speed, the source of the strength must stay connected. Otherwise the moving object will gradually come to a stop.

This tendency to stay still, and to gradually come to a stop if the driving force is cut loose, is the way things are in this world.

This RESISTANCE to motion is the way of nature.

If we need to light up the lamp in Diagram 2, we need to overcome the RESISTANCE against the flow of electrons that is in the nature of the materials that make up the electric circuit.

Have I made this point clear?

The speed of the cart is dependent on a number of things.

The strength of the horse and the combined weight of the cart, the goods and the man, the owner.

However, the type of ground surface also plays an important role.

Also the quality of contact surfaces between the moving "tires" of the cart and other mechanical parts that don not move.

All this factors combines together to determine the TOTAL or overall RESISTANCE of the LOAD that is being pulled by the horse, the SOURCE OF STRENGTH.

This overall resistance dictates how fast the horse can drive the load.

In our simple electric circuit above, the overall RESISTANCE dictates how much electrons per second can flow through the lamp and the wiring cables.

The car battery is the SOURCE OF ELECTRICITY, OR THE SOURCE OF STRENGTH.

Hey! Where is the Ohm's Law?

Let's not waste everybody's time. The Ohm's Law is here.

With the STRENGTH of the car battery, the STRENGTH of the light producing lamp, the SPEED of the electron flow inside the wiring cables, and the total RESISTANCE of all materials along the path of the electron flow, you now know HOW THE OHM'S LAW WORKS.

The Ohm's Law

Please... do not get intimidated by engineering names such as this Ohm's Law here. It is just a name.

However, nobody can learn engineering without some use of mathematics.

Here you do not need much. There will more as the subject gets more advanced.

V = I x R

R = V / I

I = V / R

P = V x I; P = I x I x R; P = V x V / R

There you have it. The mighty Ohm's Law.

What does it mean? How does it relate to the cart, the horse, the car battery and the circuit in Diagram 2?

The above formulas are a representation of the natural behaviors of the things and quantities that I explained above, when they are electrically connected as shown in Diagram 2.

Let me explain..

(a) Mathematical symbols V, I and P are already shown in Diagram 2.

(b) The symbol R represents RESISTANCE. This is the resistance against the flow of electrons that is what we normally call electric current.

(c) If you refer to other websites about Ohm's Law, most websites (not all) usually only show the first three formulas as the immediate components of Ohm's law.

However, if you recall how I explained the logic about the current, the voltage and the wattage of the incandescent lamp, you will notice that the RESISTANCE only emerged at the end, which was at the end of the horse's story.

This is my own way of introducing the concept to you. I start with what is real and visible. Then use them to explain those that are invisible.

(d) The resistance is invisible. You cannot see the resistance, the "R".

(e) The volt is visible as the voltage of the battery.

Take or buy any battery and you will see the voltage clearly written on it.

A cell battery size AA will have 1.5V written, plus the positive (+) and negative (-) labels clearly indicated on each end of the terminals.

A car battery would have 12V or 24V label plus the positive and negative terminal labels. These are all VISIBLE and REAL. That volt is the "V" in the formulas.

(f) The watt of the incandescent lamp would be clearly embossed or printed on the crystal glass, or the metal base of the bulb.

A 15 watt incandescent bulb in the above circuit diagram would have 15W and 12V DC written on it.

The label 12V DC indicates that the bulb has been manufactured to be used on a 12V direct current battery.

The label DC is additional information so that consumers do not connect it to some other types of voltage supply such as a 12V alternative current in a laboratory or in an electrical workshop.

The bulb is real and the information on the bulb is visible. The watt is represented by symbol "P" in the formulas.

(g) What about the electric current?

The magnitude of the current is represented by the symbol "I" in the formulas.

But is the current real? Is it visible?

Yes, the current is real but it not visible anywhere. I had to do a calculation to know the magnitude of the current in the above circuit.

(h) And the resistance R?

Now do you feel that I am going in a circle?

That has been done on purpose. Electricity is invisible. That is the reason some people just cannot understand enough to be comfortable about it.

That is the very reason a beginner need to appreciate and "feel" the logic between the four quantities of electricity: voltage (V), wattage or power (P), current (I) and resistance (R).

I ran you around in circles to train your mind to the logic and relationships between these four quantitities.

I used analogies such as horses and carts to give you a picture that you can put to the logic and the relationships.

If you have difficulties in following on the train of the logic, keep reading this post. You will feel tired mentally.

However, if you persist, sooner or later you will be able to "see" the electricity: the invisible current, the invisible resistance, the invisible power and the invisible voltage.

It is the relationships between these electrical quantities that is called the Ohm's Law. The above formulas only help to summarize it.

I will end this post here. It is not yet finished. We need to play with numbers in order to have more "feel" for the formulas in the Ohm's Law.

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See you in the next post.

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