Monday, January 30, 2012

MATV trunking riser

Below is a picture of an MATV trunking riser. I have also shown a closer view of how the trunking is firmly fixed to the ELV riser reinforced concrete wall.

Picture 1 - MATV trunking riser

(Click on the image to enlarge it)

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Location: Inside the ELV riser

TYpe of building: Office building

Other description:

MATV is an acronym of Master Antenna Television. Nowadays this name is often changed to SMATV, with the letter S added to show that the system can also receive the satellite with just the addition of a satellite dish antenna and a suitable head-end amplifier module.

No other additional parts are needed.

Even though the vertical distribution of the television signal is carried from top or roof of the building downward, it is quite common to call the vertical MATV cabling as the riser cable.

The vertical cables are actually down-feed cables, similar to the distribution of the drinking water supply from water storage tank mounted at the roof a a building.

The water is then fed to individual floors through one or more "main cold water riser pipes".

For electrical cables, it is more common to run vertical main cables on trays.

When trunking are used in ways similar to the MATV trunking is the above picture, they usually are used to carry wiring cables, not the vertical distribution cables.

I guess it is just easir to handle and manage the small wiring cables if the steel trunking is used.

But when the main vertical cables are involved, cable trays are the preferred method most of the time.

Notice also I have marked the enclosure that has been used to mount accesories for the distribution of the TV signals. Things such as the signal boosters, the splitters, etc.

Having the accessories mounted inside the riser next to the riser trunking is not just for the ease of cable connection, but also for the protection of these accessories from damage, theft and vandalism.

This may sound trivial sometimes, but in some buildings these issues are ongoing major problems.

I have also zoomed in to the mounting bracket for the trunking riser as shown in the following picture:

Picture 2 - The mounting bracket for the MATV riser trunking

(Click on the image to enlarge it)

Observe how a set of screw stud is used with a few nut and washers to provide a reliable and easy to implement mounting method for the vertical trunking.

Notice also how the angle iron is extended at this location to provide a nice mounting base for the PVC enclosure.

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Friday, January 27, 2012

Lift car lighting

Lift car lighting inside a 21-storey high rise office building.

Picture 1 - Lift car fluorescent light inside a passenger lift under construction


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Location: Passenger lift car

Type of building: 21-storey office building

Other description:

This view is a upward view, meaning that I was looking up while taking this photograph. It was inside one of the pasesenger lifts.

The building was in the testing and commissioning stage. Actually all the lift were already tested and commissioned. However, there was some issues on the warranty and the insurance coverage of the equipment if the lift were operated before the building was handed over to the owner.

Therefore, all the lifts for the building were not turned.

However this one was operational to fulfil the needs of the main contractor as all the temporary construction lifts were already dismantled at this time.

Author's note:

Regular visitors to this blog may surprised by this new format of my posts.

This will the format for all my future posts.

Nowadays I find it more and more difficult to find spare time for my blogs. Unless I can write and send up a post within fifteen minutes or so, this blog will be dead.

It will go down  so deep in the Google's ranking that nobody will be able to find it (except the regular readers, of course).

So this will be my new format. Simple and fast, plus one or two photos or diagrams.

Believe it or not, today alone I already send up four posts with this new format.

Impressive, huh?

Ciao.

Jimmy Lee Wan Seng
(Information Trader)

Copyright http://electricalinstallationwiringpicture.blogspot.com/ Lift car lighting

Tuesday, January 24, 2012

Lighting flexible conduits

Why do we need flexible conduits for the wiring to lighting fixtures?

Picture 1 – A lighting flexible conduit above a false ceiling (Click on the image to enlarge it)

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Conduits provide the mechanical protection for electrical wiring cables that are run inside them.

Without this protection, sooner or later the wiring cables are liable to get damaged which can expose the live conductors that can lead to electrical fires and risks of electrical shocks.

Picture 2 – Rigid metal conduits running on surface below the concrete slab

(Click on the image to enlarge it)
As shown above, the rigid metal conduits are clipped directly to the concrete slab. This method allows for easy adaptation of the conduit run so that the end of a rigid conduit can be installed directly to the exact location of the light fixture, or directly above it.

If the light fixture is also surface mounted similar to that in the picture below, then the rigid conduit can be run directly to the light fixture.

Picture 3 – Rigid conduit direct connection to a light fixture

(Click on the image to enlarge it)
This installation is inside a plant room. So this method of installation can be done easily.

However, when an installation is above a false ceiling, as they usually are in large office buildings, then it is not really practical to run the rigid conduit directly to the light fixture because there is usually a significant distance between the surface of the concrete slab and the level of the false ceiling is obvious in Picture 1 above.

Well, to be precise, it can actually be done but in large installation works this method demands a very close control of the workers and slows down the speed of installation.

To say it simply, it cost too much extra while not adding anything of real value.

The practice is to use a length of flexible conduit to protect the wiring cables between the end of the rigid conduit and the light fixture as shown below.

Picture 4 – Flexible conduit connections to ceiling-recessed down lights

(Click on the image to enlarge it)
I know you cannot see the concrete slab in the above picture but together with the flexible conduit in Picture 1 you should be able to see the connection.

From the way the flexible conduits sagged vertically downward, you know the ends of the rigid conduits are directly above them.

However, I did not write this post just to explain to the above use of the flexible conduits.

Look at the following picture:

Picture 5 – Excessive length of flexible conduits

(Click on the image to enlarge it)
However, life is never simple.

This is especially true for construction works, and it is also true for the design works that precedes the construction.

In many cases, the layout design of the office (Note: I just pick office buildings as an example. Other types of buildings can suffer exactly the same type of problems) cannot be finalized on time for some reasons. This drastically affects the work of the electrical contractor who needs to run the conduits for the office lighting system.

In fast track projects, or design-and-build types of contract, postponing the conduit installation works just because the architects or the building owner need more time to finalize the office layout design (or to make another “minor” revision to the “final layout”) is not a good idea and a very risky one for the electrical contractor.

The wisest choice is usually to just proceed with the installation of the rigid conduit works based on whatever construction drawings available at the time.

Of course after completion you may get installation works that look like Picture 5 above.

Definitely not a good job, I agree with you. However, as some people say, it “still fits the purpose”.

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Sunday, January 22, 2012

Metal-clad socket outlets

Many people consider exposed and metal-clad electrical socket outlets as one of those unnecessary objectionable sights in a building and practically put them in almost the same category as rain water down pipes and sanitary plumbing. If we have to have them, they need to be hidden away.


Photo 1 – Metal-clad electrical outlets


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In order to make these people happy, designers only use them in plant rooms, substations, mechanical and electrical risers, those kind of spaces.

The two 13A switched socket outlets in the above picture were installed inside an AHU room in an office building.

The logic behind having metal clad wall fittings inside such building spaces is obvious: toughness.

The metal casing of the unit provides better protection against possible damage caused by accidents and frequent usage.

The fact that the orange-colored wiring conduit have also been installed exposed here have nothing to do with toughness. In fact it is more to do with efficiency: technical efficiency and more importantly COST efficiency.

Normal users of the building, AND people who think of metal clad electrical sockets like rain water down pipes, rarely or never come into the plant rooms once the building construction has been completed and it is operational.

Therefore it is theoretically not cost efficient for the owner or the electrical contractor to spend the extra cost of hiding the steel conduit into the plant room concrete wall.

Then again some managers and engineers representing the owner may want only the best for the new building and would be willing to pay the little extra dollars to conceal the wiring conduit.

However, if I was in the picture and I could have my way, I would object to such move.

Personally I like exposed things. Exposed and protected.

Photo 2 – A zoomed out view

Photo 3 – Metal-clad light switch

No, this one is not a 13A socket outlet. It is a light switch that is also of a metal clad type.

It was installed in the same room as the metal clad power outlet.

So you can see that in plant rooms and non-public service areas, we go for toughness, practicality and ease of maintenance.

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