How To Test An Emergency Light

An emergency light (EL) is an emergency equipment.

Like all emergency equipment, we do not need it unless we are in a state of emergency.

Picture 1 – An emergency light fixture

It is also a safety equipment, which means that we need it to prevent danger, to reduce the risk of personal injuries, to prevent loss of lives or properties.

There is a problem common to most emergency or safety equipment. It is not used or not in operation most the time. In other words, it is always on standby.

This is how the problems develop.

When an equipment is seldom used or operated, it may not work at the moment it is supposed to work.

Poor workmanship during installation, low quality components, etc may cause failures in parts of the equipment.

These failures are not noticed until an emergency situation arises. Then it would already be too late.

Another example is the standby electric generator. Many buildings rely on the standby generator as part of the fire protection system for the building.

However, because it is seldom used, many times the generator cannot start when there is a fire and the main supply fails.

Of course, we have the emergency lighting to aid us in evacuating the building.

But then again, what if the emergency light also fails at some place in the building?

The occupants in the room can be left in total darkness. Accidents can happen which will make the situation much worse.

This is why the emergency light should be checked regularly and it is easy to do it.

How to test an emergency light

Picture 2 – A close up view of a surface-mounted emergency light



Picture 2 above shows the close up view of the emergency light in Picture 1.

MAINS HEALTHY light

The MAINS HEALTY light is an LED light. Under normal condition, this LED would give out red light. I took this picture while the building is under construction. The mains electricity from the public supply is still not connected. That is why this LED did not light up yet.

If the red LED lights up, that means the building supply is connected to the EL light unit. Therefore, the rechargeable battery inside the unit is charging.

The battery is always charging to keep it at full charge all the time. There is an electronic circuitry inside the fixture that automatically charges the battery to keep it full all the time.

However, even when the battery is fully charged, the LED stays ON. Do not expect the LED to light off when the battery charge is full. This light only says that the electricity supply is available.

In some design, the LED may also be used to say that the internal electronic charging circuit is also working properly. In other words, it summarized the status of the health of the charging part of the EL light fixture.

The TEST pushbutton

This pushbutton switch allows you to check if the lamp would light up when the building electricity supply really fails.

To test it, just press the red pushbutton switch.

The EL lamp will light up.

With the charging circuit healthy and the operation test of the lamp also okay, you now have no worry about your emergency lighting.

With recessed mounted EL lights, the test is also similar. Picture 3 below shows a ceiling-recessed EL light.

Picture 3 – Ceiling-recessed emergency light




You can see more pictures of the emergency lights at this post, Emergency lighting installation pictures.

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Bare fluorescent light pictures

This post contains a few pictures of bare fluorescent lighting as part of a series of posts on pictures of basic components of electrical systems. These series of short posts will be part of the building blocks that can help me present materials so they are easily digestible by beginners in electrical works.

Picture 1 – Normal view of 4-ft inch diameter bare-channel fluorescent light fixture


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Bare channel (Picture 1 above) fluorescent light fixtures has been one of the most low cost and energy efficient type of lighting that is available today.

The above picture shows an example of a bare channel fluorescent light fixture. This one was installed inside a substation room. That is why you can see that the wiring conduit is run on surface of the wall instead of concealed into the concrete wall.

However, the above light fixture does not have the fluorescent tube installed. The electrical substation is still under construction. Many workers were still in and out of the place. Lighting lamps and tubes were one of the most frequently stolen items at a construction site. It is for that reason that they are usually not installed until just before the commissioning stage of the installation works.

Picture 2 below had the fluorescent tube on. But the fixture is inside the Sample Room of the project.

The picture was taken during materials inspection of some of the fixtures. I was checking on the components of the light fixture. You can below a few other pictures that show the components of the light fitting.

The light fitting in Picture 2 is a slightly different type than that in Picture 1.

In Picture 1, the fixture is a bare channel type. The fluorescent tube is just exposed. It is a very efficient type of lighting assembly.

While in Picture 2, the fitting is provided with a wire guard. Other than that, it is almost the same design.

This type of design is usually installed at locations where theft of the fluorescent tube and vandalism of likely, such as at unprotected public corridors.

Picture 2 – Bare-channel fluorescent light fixture with wire guard




If you look closely there are more than one type of light fittings in the picture. They are all the fluorescent types.

Picture 3 – The fluorescent ballast




This is a 36-watt low loss fluorescent ballast.

You can also see painted onto the body of the ballast how it should be connected in the fluorescent light internal circuitry.

I will send a post how the fluorescent lighting works with detail descriptions on the operations of the internal circuitry. There are actually a number of variations to the basic circuitry that you see painted there.

Picture 4 – 240 volt fluorescent starter unit



This is the automatic fluorescent starter unit. The fluorescent lighting is an electronic device. The starter provides a short circuit to cause a high current to flow in the ballast coil of Picture 3 above.

The high current heats up the filaments at both ends of the fluorescent tube. The heated filaments release electrons into the lamp tube.

The starter unit is actually an automatic bimetallic heat switch. After a few seconds at most, the starter switch open-circuit, stopping the current flow through the ballast coil.

A strong magnetic field is developed in the iron core of the ballast coil due the high current flow.

When the current flow suddenly stops, energy of the magnetic field turns the coil into a source of electric voltage. Actually, the voltage developed there can be a few thousands of volts.

This high voltage, with the connections as painted on the ballast body, causes the gases inside the fluorescent tube in to break down and become a conductor.

As explained above, the operation of a fluorescent lighting uses a ballast coil in order to create a high voltage to break the gases in the tube into a conductor.

However, the strong magnetic coil also presents a very high inductive effect into the electricity supply circuit.

Due to this inductive effect, the current in the wiring becomes higher than the actual consumption of the light fixture.

This is what is called “low power factor”, or simply low PF.

Where many of these light fixtures are used, such as in large hospitals which has thousands of lights turned on simultaneously day and night, the difference between the total current drawn by the lights and the actual power rating can be hundreds of amperes.

Many electrical cables and equipment need to be sized much bigger, and therefore much more expensive, because of this simple reason.

More than that, the electricity supply authority would penalize an installation that has a low PF. That is because their cabling and equipment also need to be sized bigger.

In order to avoid all these problems, a device to turn the fluorescent lighting fixture from low PF to a higher PF is installed.

It is called “power factor correction” capacitor, or PF capacitor. Picture 5 below show the one installed inside all the fluorescent lighting in this project.

Picture 5 – Power factor correction capacitor




This blog is for beginners. I try as best as I can to turn complicated electrical subjects into easily digestible chunks of general knowledge. That is the highest objective of this blog.

However, it is not always easy to convert a highly technical subject such as this one into a general knowledge that is practically useful to everyone.

Therefore, every post that I send here will evolve as I constantly modify them and build them up in order to achieve this objective.

If there is anything that you would like me to explain sooner, that please do leave a comment. I may make your question a priority topic for my future posts.

See you in the next post.


(Lee Wan Seng)


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Most Basic Principles of House Electricity

This post will try to make you understand the most basic principles of house electricity. Since this blog is intended for beginners in electrical works, and for readers who seek to understand electrical system enough so they can do their own work, I think it should start with materials that can help readers understand whatever materials I post here as smoothly as possible.

It is actually quite easy to understand electrical and the simple diagrams below will show that.

Diagram 1 – The most basic principle of electricity
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What does this diagram say?

It says that there is a battery, a length of wiring cable connecting the positive terminal of the battery to one of the incandescent lamp terminal.

Then there is another length of cable connecting the other terminal of the lamp back to the battery at the negative terminal.

You may have played with toys that work with this very basic electric circuit when you were young.

You take one AA-size battery, a pair of whatever metal wires you can lay your hands on and a small bulb. Any bulb you can dig out of battery-powered electric toys will do.

Connect the battery and the bulb with the metal wires as in shown the diagram.

The electricity will flow and the bulb will light up.

There you have it, a working electric circuit.

Electrons flow from the positive terminal of the battery through the upper metal wire (shown by the red-colored arrow) to the top terminal of the bulb (i.e. load).

They flow through the bulb and come out of the lower terminal to the lower metal wire to go back to the battery but at the negative terminal.

Then they flow out through the battery positive terminal again, and the same process repeats.

These electrons flow round and round in the “loop” continuously.

The flow of electrons carries energy just like the water flow carry energy at the hydroelectric power station.

The filament inside the incandescent lamp converts the energy contained in the continuous electron flow into heat and light.

Such a long story, but where is the principle, right?

The principle is that there must be a complete circuit path or a loop for the electrons to circle around in a continuous stream between the source of electricity (i.e. the battery) and the electric load (i.e. the incandescent lamp).

If you break the loop at any point along this path, then the electrons will stop flowing. Therefore, the lamp will stop glowing.

Just like I said, it is easy. The only problem is that you cannot see the electrons flowing in an electric circuit like you see race cars racing (flowing continuously in a loop) in a Formula 1 race circuit. But it is very similar. No flow, no show.

Now let go to the second principle shown by the following diagram. Don’t worry. This is the last one.

Diagram 2 – The most basic principle of electrical power wiring



This one is the most basic principle of a house wiring installation.

Picture 3 below shows a typical house electric meter.

Picture 3 – House electric meter


If you look closely at the picture of the electric meter, you will notice that there is actually a pair of electric cables connecting to the meter panel. These electric cables come from the electric poles in front of the house (See Picture 4 below).

Picture 4 – Electric poles


So this satisfies the first principle above – the electrons need a complete loop path.

Now your source of electricity in Diagram 2 is the electric supply company who gives you the two terminal connections, just like the battery gives you two terminal connections.

With these two connections to the power source, you can make electricity work for you, right?

Well, not so right. Because this time the source of electricity is so strong, it can burn a house and kill the house occupants, literally.

It can kill without even causing the fire first.

Therefore, to make this strong power source work for you, you need to be able to control it any time you like.

You also need to be able to kill it before it causes danger or damages.

You need also the ability to shut off the flow of this dangerous energy into your house if your house wiring is not prepared enough to receive it safely, or to handle it.

That is the second principle, as shown by the diagram:

1. The switch gives you the ability to control. You can turn the lamp on and off with the switch.

2. While the fuse will automatically shut off the dangerous energy flow into the house when the energy flow behavior exceeds certain limits that you have set into the fuse.

These two make up the principles of a house wiring system. If you understand this, then you can understand any house electrical wiring.

However, the above is not yet enough to keep users from getting electric shock.

So, there is a third principle which I will continue here in a few days. But you can read the long version of at this post, 1-Phase ELCB Connection Pictures. If the materials there are too technical for you, there are a number of ELCB pictures there that you can see.

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