Recessed down lights installation

I have a few pictures on installation of recessed down lights. I do not intend to write much on this today, but readers who have never seen how it looks above the ceiling may find these pictures interesting.

Picture 1 – The normal view of a recessed down light


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This is the normal view of a recessed down light. This one has two PLC type fluorescent tubes; each has a rating of 18 watt.

With the two tubes, one unit of the down light fixtures would give

2 x 18W = 36 Watt of lighting power in layman terms.

That is the same power rating to the standard single tube 4 feet fluorescent light fitting of 36 Watt.

PLC down lights used to be more of an architectural type of lighting fixture. They were usually installed at lift lobbies, main entrances and corridors of buildings.

Now that seems to have changed somewhat.

Many clients choose down lights even for general lighting of office areas, which used to be the domain of standard fluorescent lighting fixture and the PL fluorescent light fixtures.

Picture 2 and Picture 3 below show examples of a standard fluorescent light fixture and a PL fluorescent light fitting.

Picture 2 – Standard 4 ft x 2 ft fluorescent light fixture



Picture 3 – 2 ft x 2 ft standard fluorescent light fixture



Between the 4 ft fluorescent and the 2 ft PL light, which type to use is normally a choice dictated by the Architect and the owner of the building.

However, the most dominant factor that affects the choice seems to be the ceiling pattern.

If the ceiling pattern is two feet by two feet, the choice is almost always the 2 ft x 2 ft PL fluorescent.

If the ceiling is 2 ft by 4 ft, then majority of the time the 4 ft standard fluorescent is chosen.

However, when the area uses plaster ceiling, the architect usually choose down lights.

Indirect lighting using 4 ft or 2 ft standard fluorescent tubes is also commonly used to complement the down lights at lift lobbies and meeting rooms to give deeper and more elaborate architectural effects.

Whichever choice is made by the architect and the client, the electrical engineers still have to recheck the adequacy of the lighting level for the particular tasks the space is designed for.

Also not less important is the practicality of the design from the safety aspects and the maintenance point of view.

The above is just a few introductory points that I think relevant to readers who would be interested in these pictures.

I will spend a few posts on the title of interior lighting in the future. This post is just a starter to get my mind rolling in that direction.

I have however sent a post on lighting one or two weeks ago, Light switch installation pictures. Check it out. It contains some pictures of down lights and also a few design issues.

There are also other posts relevant to lighting that you may want to check out:

Temporary lighting installation pictures;
Pictures of electrical wiring;
Electrical installation pictures.

Now let’s go back to other pictures of down light installation.

Picture 4 – View of installed down light from above ceiling



This is how the recessed light fixture looks from above the ceiling.

Observe the control-gear compartment, the flexible conduit and the fixture hanger wires.

The control gear compartment

The control-gear compartment is where the starter ballast coils are located. It also houses the starter unit and the power factor correction capacitor.

Notice also the lamp holders for the PLC lamps. With this construction all components are outside the light unit except the PLC lamps.

In fact the light fixture that is visible from the normal view (i.e. below the ceiling) is just the light reflector, nothing more.

I would say this design is very cheap, but this is how to make it low-cost.

The flexible conduit

Why do we need the flexible conduit?

This is a question I would ask a beginner in the wiring works.

A cable, an insulated wire, or any conductor at all carrying electricity need to be protected from damage.

A damaged cable can cause further damages to itself and other electrical parts and equipment.

The damage cable can also cause electrical fires and electric shock injuries to humans and animals.

Therefore, all electrical wiring cables must be physically protected from damage.

The wiring installation here has been specified to be installed inside G.I. (galvanized iron) conduit. The conduit provides the mechanical protection as explained above.

When the conduit is installed hidden from normal view, they are allowed to be installed on the surface of walls or concrete slab.

Above ceiling is considered hidden so the conduits are installed on the surface of the concrete slab. You can see the wiring conduits in Picture 6 below.

Now, the concrete conduits are installed in rigid lengths.

However, the precise location of the light fittings above the ceiling cannot be determined before the ceiling construction commenced.

This means that exact positions of the light fixtures are also undetermined.

Yet the rigid wiring conduit must be installed before the ceiling contractor starts his works. This is the nature of wiring works in building construction.

By using the flexible conduit at the last stretch to connect to the light fixtures, fluidity of the final positions of the light fittings would not cause major problem to the wiring contractor.

That is the purpose of the flexible conduit.

Of course, there is a limit to the maximum length the flexible conduit is allowed for each lighting point. Otherwise, we would have the flexible conduits running all over the place above the ceiling.

The fixture hanger wires

The hanger wires take most of the weight of the lighting fixture.

Often many contractors take this issue too lightly.

As a result, there have been many cases where the ceiling suspension system failed and the whole ceiling installation collapsed because of weight overload from the fittings of building’s mechanical and electrical services.

Not all cases have been this severe, but these types of incidents can only be blamed to inadequate design or construction qualities.

Because of this, many clients and design consultants have become very stringent on these matters.

One of the end results is what you see in this picture. The two hanger wires are for the less than 1 KG down light.

Actually this client demanded that 4 hanger wires (I do not remember the wire gauge) be used for all fittings installed on the ceiling panels.

Only after some considerable persuasion efforts and time did the client accepts the use of only two hanger wires for very light fittings such as the down lights and ceiling speakers.

Picture 5 and Picture 6 below give broader views of the installation above the ceiling.

Picture 5 – Another type of down light and a 2 ft by 2 ft fluorescent light



Picture 6 – A broader view of the above ceiling installation



I will come back with more pictures of above ceiling wiring works and lighting installation in future.

You can also check for more pictures and posts on lighting and wiring issues at this post, Pictures of electrical wiring.


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Emergency lighting (EL) installation pictures

You will find below a few pictures of emergency lighting installation.

Most countries have statutory provisions that require the installation of emergency lights in all buildings exceeding certain sizes. These lights need to be provided at strategic locations throughout the building to assist in the evacuation of the building occupants during fire situations or other types of emergencies.

Picture 1 – Surface-mounted emergency light (EL light)



Picture 2 – EL light unit close up view



Picture 3 – Ceiling-recessed emergency light



Practically this emergency lighting is useful even without the emergency and during daytime.

Time gap between mains failure and standby generator supply

When the mains power fails, there is a certain time delay before the backup power supply can take over. The standby electric generator, the most usual form of backup emergency power in normal buildings, takes quite a few seconds to warm up before it can provide the electricity supply to essential services inside the building.

Windowless rooms and corridors can be dangerous

Some internal corridors in large buildings can be very dark without electric lighting. Serious accidents can happen if the corridor suddenly becomes dark. Even with a little stray lights from windows somewhere, the eyes take a little bit of time to adjust to the sudden change of light level.

Some internal rooms inside large air-conditioned buildings are totally windowless.

Even with windows, the daylight from outside the building may not reach the rooms.

During power failures, these rooms can be darker than nighttime out in the open air outside. At least outside there you can rely on a little light from the stars or the moon. Again, in this type of darkness, anything can happen.

Locations of the emergency lights

The self-contained emergency light fittings are usually installed at all exit routes and at all places where uninterrupted lighting is required. In the second situation this lights serve the dual functions of a fire related equipment and a normal lighting (with much reduced lighting level).

The emergency light fittings are connected to the essential supply of the building electrical system. This way the rechargeable storage battery is charged even during normal power failure (i.e. when the standby electrical generator is running).

The purpose of emergency lights

The self-contained emergency lights need to be provided at strategic places throughout the building in order to aid the evacuation of the building occupants out of the building in the event of failure of the mains supply.

The need for these emergency lighting is real even during daytime because some internal corridors inside the building are actually too dark without some form of lighting. The emergency lights are meant to provide the minimum brightness needed for a safe and orderly movement of the people.

Who is responsible for the design of the emergency lighting layout?

The exact quantity and the exact locations of these emergency light fittings are usually recommended by the Fire Department. In practice, a licensed architect is required by law to submit the building design plans to the Fire Department for approval before the building construction commences. The architect would need to incorporate these lighting into their fire protection design schemes in order to obtain the Fire Department’s approval.

Static Fire Protection System

This layout is part of what is normally called the “static fire protection”. Those services like the wet risers, etc are called active fire protection and they will need to be submitted by licensed professional mechanical engineers to the Fire Department after the passive fire protection schemes (submitted by the architects) have been approved.

Prior to the submission by the architect, the electrical engineer’s input may be requested by the architect with respect to the quantities and locations of the emergency lights.

However, this task has become so routine that the engineer’s advice on this aspect is rarely necessary.

After the approval has been obtained, the approved layout of the emergency lighting is binding and it has become an input and a minimum design requirement for the electrical engineer. She can add more of the emergency light fittings into the design, but she cannot omit or change what has been approved in the submitted drawings.

That is the principle behind the layout and locations of the emergency lighting fixtures.

General lighting on Essential Supply

In addition to the self contained emergency lights that are required by the fire department, some of the general lighting luminaries are also connected to the essential supply that has been backed by the standby generator.

This is sometimes done to supplement the lighting provided by the self-contained emergency lights. More often, however, this is done to provide some level of general lighting that can allow normal work to continue even in the event of normal power failure. Of course, power failures that are caused by fire conditions demand a different course of actions immediately from all the building occupants.

Self-contained lighted EXIT signs

One more lighting component that is closely related to the self-contained emergency lights is the lighted “EXIT” sign.

The Exit signs are also required by law similar to the emergency lights. They must be provided at all exit doors of all buildings and all floors, and at each location where the fire emergency exit routes change direction.

Similar to the emergency lights, these components of the building fire protection are included in the proposed static fire protection submitted by the architects to the Fire Department. An approved layout of this fire component will become a minimum design requirement to the electrical engineer. She can add more of the lighted Exit signs, but she cannot reduce them or change them.

Like the emergency lights also, the Exit signs are self-contained, battery operated. The difference between the two is that the Exit signs are always on.

The installation

The following pictures show how a ceiling-recessed emergency light is mounted to the ceiling panel.

Picture 4 – Side view of the ceiling-recessed emergency light installation



Picture 5 – Rear view, from above the ceiling panel, to show how it is fixed to the board



Picture 6 – Normal view



An emergency light is a very important standby equipment. Therefore, it should be regularly checked and tested. Fortunately, that is not difficult to do. Read this post, How To Test An Emergency Light, to know more.

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Temporary lighting installation pictures

A construction site’s temporary electrical installation must provide adequate lighting for the activities that are carried out at a particular workspace whether indoor or outdoor.

Picture a1 - A site temporary lighting with mobile generator

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Arguably more important than the light levels, the temporary lighting installation should be sufficiently safe for use and provided with adequate protection to prevent electrical shocks.

A. SITE TEMPORARY LIGHTING

Picture 1 – Indoor temporary lighting and wiring

Picture 1a – Temporary lighting – Bad cabling installation


Picture 2 – Another temporary lighting and wiring indoor



Picture 3 – External site floodlight



1) Mechanical protection

In general, equipment for use at construction sites should be tough enough to withstand the abuses of work area where they are installed. Damaged light

fittings not only result in the repair cost, but they also present risks of electrical shocks to workers using them or those who are nearby.

For temporary lighting, they can be installed out of reach of human hands or any construction materials that are handled in the area. Also from equipment and

machines being operated there.

Another easy measure is to use wire cages type of lighting fixtures.

Precautions should also be taken against the danger of electrical fires that may result because of damaged lighting fixtures or the temporary supply wiring.

2) Supply from a separate section of the distribution panel

The temporary wiring supplying the lighting circuits should be connected to the special lighting section on the temporary switchboard. These circuits should

be protected by 100 mA RCD (residual current circuit breakers).

3) Mechanical support of the wiring

The installation of wiring for the temporary lighting should be carried out with proper supports and fittings to allow for wiring cables to be routed in ways

that minimize obstructions, which can results in damage to the luminaries and wiring.

These damages can present shock risks to the works and possibilities of electrical fires.

4) Normal duty lighting

Normal duty lighting circuits are installed to provide general illumination for work and allow safe movement inside and around the construction site.

5) Lighting levels

An illumination level of 10 lux is adequate for general movement within a building under construction.

As a simple example, one length of 100 meter festoon light string fitted with 20 nos 100 watt lamps at 5 meter intervals will give a 10 lux over a

rectangular area of 25 meter x 30 meter.

6) Use of festoon lighting

Festoon lighting should only be used strictly in underground shafts, wells and tunnels.

When this type of lighting is used, the lamp holders should only be the moulded, non-removable type (the lamp holders are bonded or moulded to the wiring

cables) and the lighting supply voltage is 32 Volts or below.

7) Supply to lift shaft temporary lighting

Either a temporary wiring or the newly installed permanent electrical wiring may be used to supply a lift shaft temporary lighting.

However, the light fittings used should be properly guarded against accidental mechanical damage and they should only be connected to the wiring using a

lighting plug and socket.

These lights should be installed at intervals of less than nine meters along the vertical length of the lift shaft.

The control of the lift shaft lighting should be by means of two-way switches located near the shaft access points.

8) Use of SELV voltage

The use of lighting circuits supplied at safe extra low voltage levels (SELV - voltages less than 50 volts ac or 120 volts dc) is highly recommended for

working in confined spaces where workers faces high possibilities of frequent contacts with temporary electrical equipment and wiring.

B. TEMPORARY SITE FLOOD LIGHTING

Large construction sites usually need temporary floodlight towers (in addition to the temporary lighting inside the new buildings) to provide lighting

efficiently for the general movement, safety and security on the external areas of buildings under construction.

The lighting towers will usually takes the form of fixed tower or mobile tower units. Which one to use usually depends on the siting positions available for

the lighting tower units and the duration of the contract.

For contracts with construction periods of relatively short durations, it may be much more economical to use mobile tower units.

However, if contract period is long, then it may be worth some considerations to use fixed height tower units. In any case, the fixed height towers can still

be reused on future projects. Careful dismantle the fixed height static towers at the end of the contract. Then the only extra material that is required in

at the next construction site is the foundation.

Static floodlighting tower units are normally available up to 18 meter high. They can be powered from the mains supply and they can be provided with their

own electric generator.

The external areas of a construction site usually need a lighting level of around 20 lux average. This is the level sufficient of for the handling of

construction materials and site clearing works.

A rectangular area of 60 meter by 60 meter can be lighted up to this light level by a typical 18 m tower carrying four units of 400 watt high pressure sodium

fittings.

A main contractor with larger contracts and relatively longer contract period may want to consider a more elaborate study on their site lighting

requirements. If there is enough space to mount these floodlighting tower units, a proper lighting engineering study can be carried out together with the

overall temporary electrical installation.

The exercise would employ the floodlight lamp data, the aiming angles of the light fittings, and the mounting heights of the individual fittings to arrive at

the required overall illuminance.

These static towers would normally employ high intensity luminaries and with the type of equipment available today, the contractor can now light areas to

sufficient level so the works can continue in evenings of the darker months. This is significant because it can considerably reduce the contract time.

Light fittings used in this application would necessarily be high intensity discharge type and the high pressure sodium lantern have become the more dominant

type due to its high lighting output per kW of power usage (approximately 125 lumens per watt).

A tungsten filament lamp would give only 22 lumens per watt.

The capital cost of choosing the high-pressure sodium equipment is considerably higher than the tungsten halogen, but the main contractor may do well to

consider other factors also such as the running cost, installation cost and the lamp life.

At the end of the construction work, all these equipment except the tower foundation can be dismantled and transported to other project sites for reuse.

You can see below a few pictures of a small mobile floodlight unit and other types of temporary site floodlights:

Picture 4 - Mobile site floodlight unit


Picture 5 – Luminaries of mobile flood lights


Picture 6 – This is a permanent floodlight, not a temporary one



Picture 7 – A closer view of the 400 watt temporary floodlight in Picture 3



C. SITE TEMPORARY ELECTRIC SUPPLY

A site temporary lighting is actually part of its temporary electric supply installation.

The term ‘temporary’ brings up a vision of a length of twin and earth cable, or a four-core twisted cable and an undersized green earth wire, that is connected into a 30A single or 4-phase and neutral switch-fuse, trailing across the rough ground of the construction site to terminate into a seasoned self-fabricated distributed (with or without metal-clad enclosure).

On the so-called ‘distribution board’, a length of three flexible extension cord is connected to a clumsily assembled socket outlet with or without the use of a three-pin plug.

How would you connect a three-core extension cord to a three-pin 13 A socket outlet?

Somewhere on this blog, you can see clearly how it is done. It even has had various ways of doing it.

The extension cord run at high level near the soffit of floor slab, or some just run on the scattered floor to a temporary metal-clad 13A switched socket outlet some 30 meters away.

The construction contract cost hundreds of millions, but the temporary electric supply system has been ‘engineered’ to fulfill all the site electrical requirements for the minimum price possible.

The main contractor has the responsibility to ensure the temporary electricity supply system installed is not only functional and meets all his electrical needs, but also safe for all involved in the construction work.

The supply system need to be good enough to provide reliable power distribution, whether that period of the construction contract is three months or three years.

Or whether the site supply requirement is 4 kVA or 3-megawatt supply.

What specifications to use for the temporary electric supply equipment?

Generally, what applied to low voltage installation is in the IEE Wiring regulations also apply to the temporary supply system.

However, two more British standards should be used to cover the gaps not covered there: BS 4363 (Specification for distribution units and electric supplies for construction sites and building sites) and BS 7375 (Code of practice for distribution of electricity in construction and building sites).

Source of the temporary supply

The temporary electric supply can be obtained from either the distribution network of the local electric supply authority or an independent electric generator installed at the site. Which one to use is usually just a matter of judgment on the cost involved.

However a few other factors may also need to be carefully considered which include practical problems that are usually associated with the distribution of the electric power safely and effectively throughout the site.

If the supply is taken from the local electric supply authority, a lead-time is usually required, as the authority would need time to arrange for the connection.

The main contractor also need to submit sufficient details on the peak demand that will be required during the course of the contract, the positions of the point of supply intake and also the estimated contract period.

The authority usually requires enough details on the types and size of electrical load, e.g. lighting, heating, motors, etc. Motor loads usually need more details such as types of motors and the method of starting (direct-online, auto-transformer starting, etc).

Update (March 15, 2014): I have a collection of pictures on temporary lighting that I have not yet uploaded anywhere. I plan to just progressively attach the pictures below in this post with a brief comment for each picture.

This way I do not need to write a post just for the purpose of sharing the pictures.

xxx MORE TEMPORARY LIGHTING INSTALLATION PICTURES xxx

Picture 08 - Temporary flood light installed at high level of a rail workshop under construction

This picture show flood lights installed at the high level of a rail workshop under construction.

Actually this temporary lighting has only recently been installed. Electrical supply wires were still dangling around and not properly fixed.

However, the main contractor were pressing for progress and I did not wish to look like a bad guy there. So I just let them use them first to help them gain some additional progress before I apply more pressure for the temporary cable to be properly fixed.

In any case, the dangling cabling were mostly at the higher level of the work area.

This is not to say that the risk of accident was minimal. As you can see in the background of the picture, there was a mobile sky-lift being used to install the fighting pipes just below the roofing of the workshop.

In some days, there were quite a number of the sky-lifts throughout the workshop floors.

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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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