Tuesday, March 2, 2010

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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