Wednesday, April 28, 2010

Electrical socket extension unit

Have you ever wondered how it looks inside the extension unit of electrical power socket? The following few pictures can help you appreciate what is going on inside this piece of common household items.

Picture 1 – The inside view of the electrical socket extension unit


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I think most readers can understand this picture clearly with the labels that I added.

For the absolute beginners that need explanations on what does what in this picture, let me just give brief descriptions.

Extension cord

I guess everyone knows this part. The extension cable has a three-pin plug at the other end of it. It is the plug that you insert into the wall socket.

Look at Picture 7 below to see the complete set of the extension socket and plug.

Extension cables

The extension cable that you see actually has three insulated cables inside it: the LIVE cable, the NEUTRAL cable and the EARTH cable.

Each of the three cables has their own color-coded insulation: Brown for LIVE; Blue for NEUTRAL and Green with yellow stripes for EARTH.

When you work on the connections of these cables, you have to make sure not to connect them in a wrong way.

If you connect in a wrong way, the electrical appliance that takes power from this extension sockets may still work.

For example, you mistakenly swap the connections of the blue and the brown cables.

However, the ON/OFF switch (the red colored piece in Picture 1) is located at the LIVE connection. Therefore, there is still a voltage going to the appliance connected to the socket.

Cable termination screws

There are 3 cables coming from the extension cord. So you have three connection points and therefore 3 connection screws.

The connection screw may seem simple enough, but not using it properly has been the cause of many house fires all over the world. See Picture 2 below for a closer view.

Picture 2 – Cable termination screws



This is one of the biggest problems with house electrical wiring: the electrical parts look simple enough that everybody thinks they can handle it.

Yes, it is easy. But you must know enough about how the electrical components works to be able to handle it SAFELY.

If you do your own wiring, and you happen to replace an extension cord like one in the picture, make sure the connection of the copper conductor to the termination screw is strong and tight.

If the connection is not tight, then connection surfaces between the copper conductor and the screw present a high resistance to the current flow when the electrical appliance is turned on.

This high resistance will cause a high-energy loss at the connection, which is dissipated in the form of heat.

Over time, if the appliance is in operation long enough, the extension socket unit may overheat and become a source of fire.

A combustible material nearby such as a window curtain, old newspapers, even carpets and rugs may catch fire.

That is how a house electrical fire can get started. It is one of the most common cause also.

LIVE and NEUTRAL busbars

Picture 3 below gives a better view of the three busbars.

Picture 3 – Busbar connections



As the cables are connected to the termination screws from the right side, the busbars are connected from the right side.

I know there are readers who are not very familiar with the word “busbar”. So let me just spend a few words on this part.

The purpose of a busbar is similar to electrical cables, which is to carry electric current.

In cables, we normally put insulation over the current carrying conductor. The reason to prevent touching of the conductor with other things and parts nearby.

However, at some places, there is already a very good place allocated to install the current carrying conductor. So the insulation may not be necessary.

The copper conductors inside the cables are flexible. This way it is easier to handle and bend around things.

However, making things flexible from metal materials cost money.

If at certain locations, the flexibility of the copper conductor is not necessary, then why waste money by using the flexible type, right?

Another advantage of using a solid conductor like busbar is that it is easier to make connection to it. In this case, multiple connections need to be made depending on how many socket points are needed.

I think the above description is enough to show what a busbar is.

It is “solid”, so it is a “bar”.

“Bus”? I am not that sure myself exactly why the this word is used here.

All the while, I only guessed that this word is used because in the old days, a “bus” is used to denote a main path, or a main road. That is where you could wait for a transport to go long distance.

You can also get the bus by waiting anywhere along the main road. My guess is that the public did not need to wait at the bus station or the “bus stop”.

That was the “bus transport”. This is the “bus bar”.

You can get power anywhere along the conductor part. There is no need to cut anything, or go to a terminal screw.

I am only guessing here. Your own guess is just as good as mine.

Now let’s go to the next component.

ON/OFF switch

Everybody knows what an ON/OFF switch is. It is exactly what the name says.

But there is one more component related to this on-off switch. It is called the pilot light.

Picture 4 – The pilot light



In picture above, the pilot light is labeled. When the on-off switch of a particular socket unit is switched on, this light turns on.

Trivial as it seems, this feature has a very important safety purpose on an electrical socket.

When the light is on, you know there is power going into your electrical appliance. Even when the appliance is not operating (maybe because the appliance built-in on-off swith has been turned off, or the equipment has a blown fuse), you know the power is there.

It is therefore still dangerous.

The pilot light helps train our habits about safety.

When it is ON, there is DANGER for sure. There is no way we can pretend the switch on the socket is OFF.

The pilot lamp is connected in parallel with the appliance (to be connected). So even when the appliance power cord is broken, the pilot lamp lights up when the socket switch is ON.

The earth connection piece

Please observe in Picture 4 above the connection pieces from all three busbars in side the pin sockets.

Notice that while inside the “LIVE pin socket” and the “NEUTRAL pin socket” the connection to the plugs pins are made using a separate piece, the connection piece inside the “EARTH pin socket” is NOT A SEPARATE PIECE.

Why?

Because it is EXTREMELY IMPORTANT that the grounding connection from the appliance to the electrical grounding system MUST NEVER FAIL.

Therefore, the connection piece for the earth pin is part of the earth busbar.

Both is made from one solid piece of conductor and then bent around to form the earth busbar and the earth contacts (three sets of earth contacts actually, because there are three socket outlets in this socket extension unit).

Picture 5 below shows how the plug pins are inserted into the sockets.

Picture 5 – 13A sockets and a plug



Picture 6 and 7 below just show the whole assembly for readers who need them.

Picture 6 – The cover for the cable termination compartment removed



Picture 7 – The whole 13A socket extension assembly



I will see you again in the next post.

Copyright http://electricalinstallationwiringpicture.blogspot.com Electrical socket extension unit

Monday, April 26, 2010

Feeder pillar hazard pictures

I think anybody with even a minimal amount of knowledge on the hazards presented by electrical equipment installed in public places know what is wrong with the feeder pillars in the picture below.

Picture 1 – Wrongly designed feeder pillar??



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I always avoid criticizing other people’s electrical designs based on evidence that is seen after installation has been completed because the outcome of a completed electrical installation is the products of many variables and factors.

Especially with the popularity of design-and-build and turnkeys types of contracts.

In these types of contracts, the main contractor is the boss and the employer of the professional consultants.

How professional can a consultant-engineer be when his paymaster is the main contractor?

Now let us get back to the picture above.

I do not know if the above electrical feeder pillars were constructed in a turnkey contract or not. I only passed by the area to find a place to eat.

However, the sight of these lovely feeder pillars caught my attention while I was looking for a parking space.

What is wrong with these feeder pillars?

I am not talking about age of the feeder pillars.

I know that everything gets old some day. Machines get worn out, the materials get deteriorated and the lovely paintwork fades out.

They do get old, just like us.

However, machines and equipment that can endanger people especially children should be designed and installed with safety as the most important criteria.

The feeder pillars above have failed in that respect. Look at Picture 2 below.

Picture 2 – Inadequate protection against electric shocks



Here you can see a hole at the feeder pillar front door.

The brownish rectangular material at the feeder pillar front door can only mean one thing: there is a kilowatt-hour (KWh) meter inside it.

The brownish material used to be a transparent material so someone could read the reading of the energy meter.

It is a usual practice to install a separate meter for the lighting of public spaces at a private compound because the owner or the property management could apply for a lower tariff on the electricity used by the carpark lights or road lights.

The feeder pillar that supplies the public lighting is where the authority KWh meter is installed.

At many installations, the design of these feeder pillars as shown in the above pictures should be adequate. It is actually one of the standard designs and therefore this design is widely used.

However, these particular feeder pillars were installed at open public spaces with open to public carpark and a number of recreational spots nearby.

In other words, now and then this place is crowded with children.

The design of the feeder pillars as installed here in the picture is wrong and dangerous

How should it be designed?

I will post a diagram of how it should be in another post. Maybe a picture or two of actual installations if I can steal a few hours to go take the pictures.

For now let me just point out a few points:

1: the front doors of the feeder pillars should be done in two layers, both having sufficient weatherproofing qualities.

The inside door protects the components inside the feeder pillar. The kilowatt-hour meter can also be installed behind this inner door.

If that is the choice, then a waterproofed viewing glass window needs to be provided at the inner door, and it should be at close distance to the meter dial.

The second layer of the feeder pillar door is the outer door. This door also has a glass-viewing window (the second layer of glass windows) directly in front of the inner viewing window.

The primary purpose of the outer door is to serve as an outer barricade against access to live parts if the outer viewing glass gets broken for whatever reason. Because of that, it is preferable if sufficient gap is provided between the outer and the inner doors. This will result in a more effective barricade.

2: The viewing windows for the kilowatt-hour meters should be of the correct materials.

Every time I looked at the feeder pillars in the above pictures, I always wonder about the cause of the damaged viewing windows.

Was it vandalism?

Or maybe it was the employees of the electricity supply company who broke the viewing window? With the windows turning so brownish, how could the “meter readers” (this is what we call the public utility workers who come to read the electricity meters and issue the bills for the month) read the readings?

But then the viewing window of the second feeder pillar was not broken. Maybe the door of this one was not locked so there was no need to break it.

It does not matter who did it. When it comes to safety of the members of the public especially children, the design and installation people in electrical installation works should ensure that the completed works is adequately safe.

Why do I put so much emphasize on children?

Because they are curious little creatures.

When they see holes like one in Picture 2 above, someday one of them may be tempted to put his hand inside.

Enough said.

I will see you again in the next post.

Copyright http://electricalinstallationwiringpicture.blogspot.com Feeder pillar hazard pictures

Friday, April 16, 2010

Building’s electrical rooms layout

During the design of an electrical installation for a building, spaces that are required as electrical rooms need to be provided for very early in the planning and design process.

I will try to present this in a form of a few basic concepts so that non-electrical readers can benefit from it.

There are also a few diagrams at the end of this post, but I do want to go too technical here as this may turn off the non-electrical readers.

If you need a more technical discussion, I will send a few posts of electrical substation layout and design in future.

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Sources of electrical supply

Two (or sometimes three) sources of electricity are normally required in high-rise buildings:

1) The normal mains supply from the electric supply authority or the local electricity supply company in some countries.

2) The standby or emergency supply for the standby electric generators. In most situations, this supply is not an option, but a mandatory requirement for buildings that exceed a certain size.

3) The uninterruptible power supplies, or commonly called UPS. This is only needed in certain types of office buildings and in some hospital buildings.

Voltage level of the incoming supply

The normal mains supply taken from the authority may be taken at HV (high voltage, normally 11 kV in this country), or LV (low voltage, 415 Volt, three-phase four-wire).

Whether it is the LV or HV supply depends on the size of the maximum electrical demand to be expected of the planned building when it is in full operation.

It also depends on the effects of voltage drops and the level of voltages that are currently available from the supply authority.

Authority’s HV room

When the incoming supply is HV, the authority usually only require a HV switch room to be built and handed over to them. This is where they house their high voltage switchgears and other equipment.

The location of the Authority’s HV room

The location of this room must allow for easy access by the authority’s maintenance people and it should not present an inconvenience to the occupants of the buildings or disrupts the building’s normal functions and operations.

(Separate meter room: At times, the local office of the electricity supply authority requires that a small meter room be provided and handed over to them. This is where they house the meter panel.)

Electrical distribution cables from the authority’s distribution network in the area will be tapped and looped to the HV switchgear panels in this room. They usually install a series of HV panels here.

Then from one of the HV panels, a supply feeder cable will be laid and connected to the consumer HV room.

Consumer HV room

A consumer HV room is generally a repeat of the authority’s HV room. The equipment and switchgears located in them are also similar.

The purpose of the consumer HV room is to house the equipment that are essential to the safe and proper handling of the electrical high voltage supply received from the authority’s HV room.

If the building management need to switch off the high voltage supply for some reasons, then this is where they do it.

Among the reasons may be if the transformer is faulty and need to be serviced ar checked.

Another reason may be if the transformer room is located at a separate location and the high voltage cables to the HV switchgear is by cables buried underground. Sometimes an excavation need to be carried out very close to the cable location that a complete shutdown to the supply carried by the cables is necessary.

The third scenario might be if the main low voltage switchboard (the electrical panels that receive the low voltage currents directly from the transformer) need maintenance or repair. Then the only way to make the main switchboard completely dead is by turning off the supply at the HV switchgears inside the consumer HV switchroom.

Can we turn off the supply by switching off the switchgears inside the authority’s HV room?

No, we can’t.

The room and all the equipment inside them are legally theirs now.

By transferring the HV electrical room to the authority, the building owner are actually required to sign some form of an agreement to transfer the ownership of the room to the electricity supply authority, or to lease it to them for a duration of 99 years I think.

It is like an embassy building in a foreign land.

Likewise, the supply authority is not allowed to freely access the consumer’s HV room or the equipment inside.


Metering CT

Buildings taking supply exceeding a certain amperes require the use of a set of CT’s (current transformers) in order to measure the energy consumption. The contractor of the new building will have to provide these CT’s.

However, the new CT’s also need to be sent for calibration and certification by the electric supply company before installation.

After the calibration, the CT’s are installed inside the consumer HV panels. A set of wiring are then installed to connect these measuring current transformers to the authority meter panel inside the meter room.

Authority’s transformer room

Sometimes during the negotiations on the application of the supply, the authority may require that a transformer room is also provided and handed over to them together with the HV room.

Usually this happens when there is no suitable site available for their substation in the vicinity of the area, such as when the planned building site is at a congested area of towns like the city center.

When transformer room(s) is required, the authority electrical substation would be a complete substation, not just a HV room.

This means that the substation may also be used to supply other buildings and properties nearby.

Distance from Authority HV room to Consumer HV room

As mentioned, the HV feeder cables that will carry the electric current to the planned building will need to connect to the consumer’s HV switchboard in the consumer HV room.

Part of the cost born by the authority in order to give supply to the new building are usually charged to the consumer (in what is usually called a “contribution fee”) and need to be paid before the authority commence their installation work.

Therefore, the nearer the consumer HV room is to the authority HV room, the shorter the HV cables that need to be laid and the lower the cost of the cables that need to be shared by both parties.

So in many cases, the consumer HV room needs to be nearer to the authority’s HV room.

In construction projects where the land space is limited such as building projects, it is highly recommended to locate the HV electrical rooms as close to each others for another reason.

Areas where high voltage equipment and cabling are installed need to be controlled as a restricted area. Locating the HV room near each other would make control easier and the restricted area would take less space.

Consumer’s transformer room, LV room, standby generator room and UPS room

Other than the HV room, the consumer also needs a transformer room, the LV room and the standby generator room. When a large UPS supply is used, then a UPS room may also be needed.

LV room and transformer room to be as close as possible

The consumer transformer room and the LV room need to be as close to each other as possible in order to minimize the voltage drop.

For every meter of extra distance between these two rooms, a significant cost needs to be spent to overcome the voltage drop to an acceptable level.

The cables used to carry the low voltage electrical supply also are usually of very large diameters.

Large diameter electrical cables are very difficult to maneuver and bend around corners and tight areas.

Keeping the two electrical rooms close to each other effectively reduces the bends needed of the electrical cables.

Supply intake at LV

If the electricity supply taken from the authority is LV (low voltage), then they will require a HV room and a transformer room to be provided. The two rooms must be situated adjacent to each other although sometimes they accept that the HV switchgear and the electrical transformers share the same room to save space.

The consumer is also required to provide a main switchroom adjacent to the transformer room. The standby generator room also needs to be near the main switchroom.

However, if the electrical energy required by the building is less that about 300 KVA, no electrical room is required to be prepared and handed over to the electrical authority.

They will tap off the supply from a nearby existing electrical substation or tap it off from an existing low voltage distribution network.

It is for this reason that some property developers submit their application of electric supply in stages with each stage requiring not more than 300kVA.

All the above electrical rooms are needed so we can receive supply from the public mains.

However, there is the second type of electrical supply in a building operation, which is the standby generator supply. I will not talk about the third type, the UPS supply (uninterruptible power supply) today because only certain types of buildings use it. I will address that topic in a separate post.

Standby diesel generator room

As I said earlier, no building exceeding a certain size or a certain height is allowed to be operated or occupied without some form of a standby emergency power.

The “emergency” here means when the public electrical supply is suddenly not available.

It also means a fire situation because a normal electric cable would fail under fire and the fire fighting equipment would need “emergency” power so the firemen could use them.

Now, this standby diesel generator and all its ancillary equipment need a room to house them in.

However, the electric generator is a bulky and noisy machine. It also produces very strong vibrations that can be transferred to the building walls and structure.

Therefore, a room for this electrical generator need to be specially designed and the room location need to be purposely located.

If you are given the freedom to make a decision, make a small separate building to house this noisy electrical generator, preferable somewhere hidden behind the main building.

Then build up all other main electrical rooms that I described earlier around the generator room.

If you start that way, you will have no problem later when the issues of noise level, engine exhaust, radiator exhaust, fresh air intake, maintenance access route and fuel storage tank come into play.

That is usually the time when the architect and the building owner start asking whether we can exhaust the radiator hot air at the third floor level 50 meters away.

Locations of substation rooms

The actual locations of the electrical rooms at the building complex are a major factor in the design of all types of electrical installations. There are a few major requirements that must be taken into account when deciding on the locations for these rooms.

1) They should be located inside the buildings, as near as possible to the load centers.

2) The electrical rooms should be as near as possible to each other.

3) The rooms need to be accessible by maintenance vehicles and maintenance people for purposes of installation, operation and maintenance works. This should be possible without disrupting the normal operation of the building.

4) They should be accessible by heavy vehicles during installation and when replacement of heavy equipment is necessary.

5) They should be adequately ventilated.

6) All electrical rooms should be adequately secured from possible disasters like flood, or even vandalism.

The above electrical rooms are in the category of substation rooms. For aesthetic reasons, layout of the buildings can be made such that the electrical rooms are located at a separate building adjacent or hidden behind the main buildings.

In fact, it is even preferable for the rooms to be secluded somewhere as long as all the above criteria are met because that would reduce the risks of interference to the functioning of the electrical system including accidents and even vandalism.

However, there are still a few more electrical rooms, which are needed for proper and efficient operation of an electrical installation in all buildings especially those of the multi storey and high rise types.

Other electrical rooms:

1) Electrical service ducts

Electrical service ducts or electrical riser rooms are used to house the submain cables that carry electricity supply to the upper floors of a building, which include the plants and machines at the roof top such as the chiller plants, cooling towers or the lift motor rooms.

The rising mains that supply the lateral distributions on individual floors are also located in these vertical ducts.

Often these concrete vertical ducts are as large as a small room. That is why it is often called electrical riser rooms.

The electrical riser rooms do not have to be stacked vertically like the toilet risers or wet stacks.

However, it is better to do so as it would minimize turns and sharp bends that can damage the cables.

Riser rooms stacked straight up from the lowest floor to the highest building floor would also minimize the length of the electrical cables required.

Minimum cable length not only reduces the cost directly. Longer route of an electrical cable run may cause too much voltage drop along its length that may require it to be changed to one or two size larger.

Larger cables cost more money.

2) Individual floor electrical rooms

Each individual floors of significant size will usually need at least one dedicated electrical room to house the electrical distribution equipment for that floor.

However, sometimes the vertical service ducts may be able to fulfill this function in which case a separate electrical room may not be necessary.

The architect may then need to make these service ducts bigger to give them enough space for proper operation and maintenance.

The electrical rooms at each floor house the electrical panels that serve the final circuit wiring.

Therefore, they should be as close as possible to the load center of the area that it serves.

Very tall buildings

If the planned building is very high (let’s say a 40 storey office building), or in cases where heavy loads are located at higher levels of the building, it may be necessary to provide substations at the higher levels of the building.

For the 40-storey office building, an 11/.415 kV substation may be necessary at one of the upper floor. It may be located at twentieth floor, for example.

All the electrical substation room spaces as explained earlier will then need to be provided except the authority’s electrical rooms.

The floors of this substation would then need to be specifically designed by the appointed structural consultants to handle the loads of all the substation equipment.

Electrical rooms must be planned for early in the design stage

The above requirements need to be planned for at the early stages of the design and coordinated with the architects and structural engineers.

In many projects, the room spaces and their locations as requested by the electrical engineers are subject to “negotiations” with the architects and structural engineers, not merely technical coordination and interfacing.

But that can turn to be a controversial subject so I think having a separate post on it will be better.

That is all I want to say on the electrical rooms today. I will continue again in the next post.

However, there are a few diagrams of electrical room layout that I think can help some readers make more sense of what I described above.

Diagrams of electrical rooms:

The first few diagrams show the core layout of a nurses' apartment building. The core layout means the layout of the building services infrastructure with the lift core at the center.

When the architect lays out the components of building services, this is what she need to place first.

Since this building is an eight storey building, I showed here the layouts of a few floors. This will help you see how the electrical rooms and the rooms of a few other building services go up the building floors.

I will not comment much on these diagrams today. Just observe the diagrams and you will be able to see the logic behind them.

Diagram 1 – Ground floor layout of building services



I will explain a little bit here to help the freshies get started.

ELEC – electrical riser room (I have uploaded some pictures of electrical riser rooms at this post: Electrical busduct installation pictures. Click the link and you can see what electrical rooms look like in an actual installation).

MATV - the riser room for the MATV (master antenna television) system. If the building has a CCTV (closed circuit television) system, the riser cables will run inside this riser shaft to connect to upper floors of the building.

In many building design, a single riser shaft is used to run all the ELV (extra low voltage) services to the upper floors.

(Note: When all the riser rooms at each floor are stacked up vertically straight up, then it forms a shaft. So it is called a riser shaft.

Put in another way, a long time ago when the ancient builders found out how to build a building with multiple floors one on top of the other, the riser started as shaft or a vertical wooden duct.

In order to make it safe for working inside it at each floor, they extended the floor into part of the riser. Then it became like a room. So it was called a riser room.)

TEL – for telephone cables and equipment.

DR – dry riser. A building exceeding a certain height is required to install vertical pipes with inlets at the ground level. These pipes will be used to pump water from fire engines to the upper floors so the firefighters can fight fire.

If the building height is even higher, dry pipe riser would not be accepted by the fire department. A wet riser system would then be required. This is the same piping as the dry riser but with water tanks to store water and sufficient number and horsepower of pumps to always keep the water under sufficient pressure in case there is a fire in the building.

WATER – Water is not available here. Just pipes that carries domestic water. Designers just label it WATER as a short form for COLD WATER.

ON CALL – You would only have this at residential buildings for hospital employees. They have a communication system that can call the employees on standby when they have to report for duty immediately.

The red rectangular symbol inside the electrical riser is the electrical panel. You will find one or more electrical panels at the upper floors also.

Diagram 2 – First floor layout



Diagram 3 – Sixth floor layout



Diagram 4 – Layout for seventh and eighth floor



The eighth floor is the highest occupied floor inside this building. The floor above is just a roof level that is normally used to locate some mechanical services and fire fighting equipment and plants.

If there is a centralized air conditioning system in this building, then the cooling tower may also be located here.

Diagram 5 – Closer view of the electrical riser room and the Main DB



I zoom specifically to this area to show you what is supposed to be inside the electrical riser room.

Observe the legend for the upper electrical panel symbol.

The symbol legend MDB ‘7F’ stands for Main Distribution Board No 7F. “7F” means Seventh Floor.

The lower electrical panel symbol represents two electrical panels, each with labels DB ‘CR-7’ and DB ‘ECR-3’.

So there are three electrical panels inside this riser room.

I will explain why one of the DB’s is called Main DB when I touched a little on the single line diagram of the MDB in Diagram 7 below.

Diagram 6 – Layout for roof level



Diagram 7 – The single line diagram for individual apartment’s electrical panel



The main electrical supply cables to the upper floors are run inside the riser shaft.

The electrical panel for each individual nurses’ apartment is inside the apartment unit itself.

Diagram 7 above shows a typical single line diagram of the wiring for each apartment.

Now in order to get the electrical power, each of these electrical panels needs to be connected to the riser cables.

There are eight apartment units at each floor. So there would be eight sets of tap off unit attached to the riser cable inside the electrical riser shaft.

This quantity of tap off units can present many maintenance problems during operation of the building.

Moreover, the cables connected to the tap off unit also need to be protected with a circuit breaker. That means we need a panel to house the circuit breakers.

With eight units of apartment needing supply, we might as well install a large electrical panel to house all the circuit breakers to protect all the supply cables to the eight apartments.

Then we can use a busbar to supply all the eight circuit breakers.

This way only one set of tap off unit is required, which is to supply the distribution busbar inside the panel.

This is what is represented by the schematic single line diagram in Diagram 9 below.

Diagram 8 – Single line diagram of Main DB



With the entire individual apartment DB’s taking supply from this electrical panel, it is called Main DB or MDB.

Don’t let all these names confuse you. Some would call this Main DB a sub-switchboard, or a floor DB.

It is just an electrical panel upstream of the other in the hierarchy of the electric power distribution system of the building.

Okay guys. I would love to continue this further as I have not yet touch on the diagrams of the substation rooms.

It’s already 3.30 in the morning. So I will continue with this in the next post, okay.

Copyright http://electricalinstallationwiringpicture.blogspot.com Building’s electrical rooms layout

Tuesday, April 13, 2010

Multi storey building electric closets

The electric closet in the following pictures has been done for a multi storey office building.

Picture 1 – Electric closet



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I wrote an article earlier on the protection of electrical panel at a multi storey office building. You can read the article here, Electric panel installation pictures.

In that article I gave a storey of how reluctant the main contractor was to provide an electrical room or cabinet in order to restrict access to the electrical panels and protect them from damages.

Access to the panel by unqualified people may lead to abuse, improper operation of the instruments inside the panels, or accidents by touching the LIVE parts inside the panels.

These panels were three-phase panels with 415V of voltage between the phases. Accidentally touching the live parts at this voltage would lead to very serious injuries. Electrocutions and immediate deaths are common results of electric shocks at this voltage.

You can see some pictures of electrical injuries and how the victim came to get them at this post, Electric shock injury pictures.

The second most important reason for having a box-up around the panels is to protect them from damages whether accidental or otherwise.

These electrical panels have not been designed for exposed installation to the general public.

The measuring instruments and indicating lamps accessible and visible at the front door of the panels are very fragile. Then can get easily damaged by accidental impact throughout the operation of the building.

When these measuring instruments and the indicating lamps are damaged, the live parts and wiring inside them would likely be exposed sooner or later.

Then you would have a very serious risk of electric shocks from the 415 volt supply.

You can see the picture of the earlier proposed mock-up below. It was the same photograph that I uploaded in the earlier article.

Picture 2 – The earlier box-up of the panels that I rejected




Even though the main contractor finally got their acts right by constructing a closet around the electrical panels as in Picture 1, it was not an easy task for me to force them to do so.

Even after I wrote my first article, there have been a few rounds of “fights”. Some main contractors are worse than car salesmen, I dare say, even though I have a lot of respect for both types of them.

I attach the following few more pictures to show you more details of the electric closet and how they are installed around the electrical panel.

Picture 3 - The lower groove for the closet sliding door



You can see here the 3 lines of groove to the sliding that would be installed later. Three groove means that the door would be split into 3 parts.

I assumed the sliding door was chosen to reduce the space taken along the corridor area.

With the width of access required to the two electrical panels and the telephone DP box, a normal swing door would need to open outside to reduce the space taken by the closet. This would block a large area of the office main corridor even when double leaf swing doors are used.

However, a contractor always thinks in terms of dollars and cents.

So I think I can pretty much make a good guess on the real reasons why they chose this type of construction for the electrical closet.

First of all, the closet walls were not actually a building construction; it was not even a dry wall type as were the rest of the internal walls of the multi storey office building.

The closet walls you see in Picture 1 were just built-in furniture constructed cheaply at site. The left and right walls were merely 1 layer of cheap plywood materials.

If normal swing doors are used, this type of construction of the wall would not be able to support the doors as they swing open.

So the contractor used sliding doors.

The closet walls are cheap and the sliding doors can be even cheaper.

Typical.

Picture 4 – Upper groove for the sliding door



Picture 5 – Access to the wiring trunking



Not only the electrical panels need to have proper access for operation and maintenance, the trunking into and out of the panels also need to have proper access.

With this arrangement, then all needed access are catered for.

Picture 6 – Ventilation through the ceiling opening



There is one last issue pending on this design: the matter of ventilation to the air surrounding the electrical panels.

During operation, the electrical panels generate heats which must be removed continuously to prevent overheating of the parts inside.

The panels themselves have been designed without ventilation opening. These are no air movement in and out of the panels.

Wouldn’t this cause the panels to overheat?

Nope.

The panel design is a fully field-tested design. The heat generated inside the panel are transferred to the air outside the panel because the panel cubicle is made of metal (i.e. sheets of mild steel materials). So the electrical panel is naturally cooled without the need for ventilation opening.

However, the electric closet in this case is not constructed of metals. So without sufficient ventilation opening, the air inside the closet would gradually get warmer.

Then slowly the dissipation of heat through steel material of the panel cubicle would gradually decrease until it finally stops when there is no more temperature gradient between the inside and outside of the electric panel.

Then you can imagine what will ultimately happen to the temperature inside the electrical panel and the electrical parts and components.

Overheat.

I raised this issue after seeing the work of the electric closet in progress.

The manager said that the sliding door would be provided with ventilation louvers below the door lockable key allowing for a path to the flow of cool air into the closet.

Then all the ceiling panels inside the closet (Picture 6) would be taken out. The hot air would be naturally routed into the ceiling space.

I would not think that the huge ceiling space would get overheated by the heat front a few electrical panels of this type.

Neat.

Now, I think I need to conclude the issue of protection and restricting access to the electric panels by saying this:

Cheap construction, but it will work. Even though I wonder how many years the wall of the closets would last, or the sliding doors.

Chiao…

P/S: See more pictures here, Electrical installation pictures.

Copyright http://electricalinstallationwiringpicture.blogspot.com Multi storey building electric closets

Sunday, April 11, 2010

Bollard light pictures

I do not have much to say about the bollard lighting in the pictures below. They are just pictures of existing lights that I saw on my way back from my workout routine at a local gym. However, for readers who have to deal with the installation of this type of landscape lighting, I did attach in this post a section diagram that shows a little bit more details. I hope it helps.

Picture 1 – Bollard light picture


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Well, I thought this bollard light looked nice at the children playground near at rest area and food stalls on my way from the gym.
Picture 2 – A closer view



This is just a closer view. It looked nice.

Landscape lighting falls within the jurisdiction of landscape architects. So I do not normally spend much time with them.

When I have to prepare an external lighting layout that also include the landscape lighting during a concept design stage, I usually just copied the general layout of a landscape lighting from previous projects, prepare the electrical distribution system for the lights and count the number of light fixtures.

The purpose was to capture a rough approximate of the cost for the landscape lighting works. We must get the money first. Once the money is available, there are so many ways to get the job done.

Picture 3 – Another view that I liked



Diagram 4 – Section diagram of a typical bollard light installation



This section diagram show a little bit more details of a typical bollard light fixture.

I use this to show the typical installation details so the contractor can price in their cost.

The actual look and design of the light are always decided by the architect or the landscape designer of the construction project.

The rating of the lamp inside does not have to be 70 watt. Depending on the architectural design, the wattage of the bulb can be as low as you can find in the market.

However, the underground cabling, the internal wiring and the bulb holder and accessories should be selected for the highest rating because the owner may decide to opt for much brighter lighting of the compound in future.

The smallest bulb wattage is usually installed where the bollard lights are meant as walk lights along garden paths.
In any case, all these architectural decisions should be done by qualified people. I never pretend to be good in these things.

Unless I am doing it for my own house, of course.

The size of the concrete stump in Diagram 4 is generally dictated by the diameter of the base plate of the bollard light. Allow for at least one inch between the mounting bolt and the edge of the stump.

The depth or the height of the stump would depend on the type of the soil and the environment where you install the light.

If there is a possibility that persons may be leaning to the light pole, then the stump should be made to give more stability.

An electrical contractor asked me this question a few days ago. I just said 500 mm would be nice and he did just that.

The mounting bolt was cast in to the concrete, not drilled in to avoid possible breakage if the quality of the concrete is poor.

Picture 5 – Another type of bollard light



This is another design of bollard light. It was installed not far from the above type. I assume this was done in the first phase of the construction there.

It does not look as cute as the first type above, but in my opinion it does suit the surrounding compound. Don’t you agree?

Picture 6 – Weather-proof feeder pillar



This last picture is to complete the bollard lighting topic.

The electricity to the light fixtures must come from somewhere and there has to be a distribution board and a control panel to control all the compound light fixtures including the bollard lights.

This weatherproof electrical panel is where the electric supply and the control were located.

Inside it were the circuit breakers, the electric shock protection devises and the timer control circuit that turns ON and OFF the lighting at specified times.

Take notice that the electric shock protection is an extremely important matter in the installation of a compound lighting including these bollard lights.

This is not a minor issue because now and then there are always members of the public who get electrocuted and died as a result of touching one of the landscape and compound lighting poles or fixtures.

However, this is a serious topic by itself and I will not discuss it here.


Copyright http://electricalinstallationwiringpicture.blogspot.com Bollard light pictures

Electric car pics

A number of people asked why I also have the “Electric car pics” in my blog description (Note: That is the description just below the blog title above) since the day I started this blog. My answer to them is always the same: We must move towards renewable energy if we want our grandchildren to inherit a planet earth that is still livable.

And we must move fast.

I am not giving you any electric car picture yet today, because I don’t have any. However, the pictures on the clickable image below are actual pictures of electric cars. Check it out and read. Saving the earth is not a one-man’s job. The good news is that some people are able to have a little bit of fun while doing it. Don’t worry. You do not have to buy anything.




Click on the above image to read on how easy it is to build your own electric cars.

Even if you have enough money to just buy the electric car instead of building it, or you already own a hybrid car, just read the e-book.

Knowledge is power. Knowing how easy to do it helps you persuade other people to build one if they cannot afford to buy.

I think a little correction is needed here: The e-book does not really teach you how to literally build the car, but to assemble some parts into an old car to convert it from petrol or diesel-powered vehicle into an electric powered vehicle that run on batteries. These batteries are just normal batteries you can easily buy or recycle, and they can be recharged from house electricity.

If you are the kind of guy or gal who reads sports car or auto repair manual, I think you should read this book.

Is the topic of electric cars relevant to this blog?

Yes it is. It is one hundred percent relevant.

Many people always think of cars and trucks as among the mechanical machines. So did I.

However, with these crises coming closer and the electric car technology getting more popular, I think now these machines should be in the domain of electricians and electrical engineers.

Maybe some of the readers need to be told that electric car is an old technology.

The technology that makes up an electric car system has been around a long time. I am not sure how long. By a blind guess, I would say 20 years or more. Please correct me if I am wrong here.

However, who cares for electric cars?

Why should we care for this “old technology” now?

We should care because the issue of renewable energy is not among typical issues that you normally see on television.

It is not an issue like who will win the next American Idol or how long President Barack Obama will last as the U.S. president.

The two global crises

A new global crisis has started; not just one crisis but two crises are coming up fast simultaneously – the global warming and the energy crises. Both of these are global crises and in this interconnected world, all peoples of this world will have to suffer the consequences.

Everybody must be concerned and everybody should do what he or she can. If we don’t do what we can, then how can we expect the world’s governments to do what they can in order to contain these crises? Those people care much less than we all do. The corporate leaders that play golf with their presidents will make tons of money no matter what situation the world is in.

Automobiles that we drive today are one of the contributors to the global warming. We can debate on how many percent are contributed by these machines, but where the emissions can be shut off, we should do it without talking too much. That is how to get things done.

Never mind the direct cash savings that you can get from the fuel consumption you no longer need to pay.

You can help save the world

We are lucky because the electric car technology has already been here a long time. This can help us shut down the car emissions fast. In my opinion, this is something that everybody can do relatively easy.

It was for this reason I have include the electric car pictures as one of the descriptions for this blog since the beginning.

The intention is to let the Google search engine know that the scope of this blog also covers the electric car technology and related electricity producing machines and technologies such as the solar panels and the wind-powered electric generators.

Therefore, from today on you can also read some articles on solar electrical installations and wind-powered electrical plants on this blog. I also wanted to cover bio-diesel fuels, but that is a bit out of my area. So I will probably “borrow” some articles from some of the article submission directories out there.

With that said, I am going to end this post by pointing out to the readers where you can get the reading materials and step-by-step instructions on how to build your own electric cars.

Click on the link and see what the advertiser have to say. You have nothing to lose. Advertisers’ online landing pages are always full of information even though you still have to filter out the ridiculous claims when you see them. Ridiculous claims or not, we still have to buy cars so we can go to work.

See you in the next post.

Copyright http://electricalinstallationwiringpicture.blogspot.com Electric car pics

Saturday, April 10, 2010

Temporary socket outlet pictures

The following are some pictures of temporary socket outlets and temporary electrical panels.

Picture 1 – Temporary distribution board


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This is a temporary distribution board installed outside of a building under construction.

I would say that by the way of its mounting and installation, this electrical panel was meant to operate as a weatherproof one.

But of course, it was not.

It is not installed directly under rain and sun. There is a roof above it.

Usually a fire alarm panel installed for an electrical substation is permanently mounted with similar conditions, just outside the entrance door of the substation.

The IP protection for the fire alarm panels is usually IP46 at least.

Picture 2 – Temporary electric sockets



Now let’s look at the socket outlet installed on the temporary panel.

Picture 2 above shows one socket that was being utilized to supply some electric tools that was being used by the workers inside the building under construction.

Readers not familiar with work conditions at construction sites may find the temporary panel and the was the socket is being used a little shocking. However, this is real construction habits in practice.

For the uninitiated, please notice that the practice in Picture 2 is on of those WHAT NOT TO DOS. Please do not get confused and follow this example.

The supply is taken from the socket without the use of proper plug. Some may argue that the size of the phase and neutral conductors may be large enough to handle the supply current from the corresponding protective MCB (miniature circuit breaker).

However, observe the socket outlet at the far right. A closer view is shown in Picture 3 below.

Picture 3 – Burned 13A socket outlet



Notice burn mark around one of the socket pin holes. This is the “LIVE” terminal of the socket.

You would get this mark if you use the socket the way photographed in Picture 2. It was cause by fire sparks when the live wire is pulled out of the socket without turning off the socket switch.

It can also be caused by fire or heat because the contact between the live conductor and the socket terminal inside was not good enough to handle the current taken by the electric tools being operated.

In any case, this would be a very good source of electrical fires.

This particular temporary was actually outside the building and there was not really anything that could catch fire. However, if it were inside the building, it would be a real fire hazard.

Picture 4 – Damaged socket outlet



This another type of damage caused by the method of taking supply shown by Picture 2.

I bet the worker who caused this would say there was not really a problem there. But if the socket pin hole could be damaged that way, then the conductors inside could also be shorted and become a real source of electrical fire.

Before I go on to another temporary electrical panel, notice that the green earth wire was not inserted into the Earth terminal in Picture 2.

This does not really need another reminder, but genuine beginners may interpret this the wrong way. ALWAYS CONNECT THE GROUNDING WIRES WHETHER YOUR EQUIPMENT IS EARTHED OR NOT.

Picture 5 – Another temporary distribution board



This one was installed inside the building under construction. Here the actual temporary DB itself was adequately installed. Only the 13A socket outlet was not properly used.

Notice the similar burn mark around the LIVE pin hole at one of the sockets (Picture 6).

Picture 6 – Another abused 13A socket outlet



I have been doing supervision works at construction sites for many, many years around this country. It is not easy to force the contractors to practice proper use of electricity at a construction site all the time.

This is made much worse by the practice of turnkey and design-and-build type of contracts.

There are many sub-contractors and sub-subcontractors involved. This makes the management of site safety a really challenging work.

What can be done effectively is to try to control the area around risky areas.

In the above examples, the best is to ensure the areas around the temporary electrical panels are clean, with no materials or debris that can catch fire if and when there are fire sparks from the improperly used temporary socket outlets.

The second thing you can do is to shut off the incoming supply to all the temporary electrical panels during lunchtime or after work hours.

Fires at construction sites are not rare incidents. These proactive actions can reduce those statistics.

I add one more picture below for the curious, in case he wants to know how the wiring is done for the temporary panel in Picture 5 above.

Picture 7 – "Internal" wiring of the temporary electrical panel



Isn't that one sexy-looking internal wiring work?

Visit this post, Temporary electrical installation pictures, for more pictures of temporary electrical installations.

If you are looking for the pictures of permanent installations, then visit Electrical installation pictures.

I have also sent some pictures on internal view of socket outlet extension unit. See them at this post, Electrical socket extension unit.

Copyright http://electricalinstallationwiringpicture.blogspot.com Temporary socket outlet pictures

Standby electric generator pictures

Today I am sharing with you a few pictures of a standby electric generator.

Picture 1 – 1000 KVA Standby Diesel Generator



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The generator room that houses this genset was not very large. All the equipment and support services for the standby diesel genset system were nicely laid out and installed, but there was not too much spare inside the room.

That was why I could not get a good overall picture of the generator unit.

Why do we a standby electrical generator?

No building of a significant size can be safely occupied without at least a small back-up electric generator installed.

The most important reason is the protection of lives in the case of fires. I think all fire departments in the world make the standby emergency generator a mandatory requirement for buildings with areas exceeding a certain size, or if the building exceeds a certain height.

Why diesel generators?

Oil is still a principal source of energy in our world today.

Even though for the past few years world government seemed to have put much greater emphasis on other sources of energy such as the solar energy, etc, we are still very much dependent on the fossil fuels as we have been for the past 100 years or so I think.

Because of that, diesel engine driven gensets system have been used on a large scale as a back-up electrical system to the public electricity supply.

These systems usually comprise of a diesel engine coupled to an electric alternator (also called electric generator) on a single chassis or a structural frame. Switchgears and control gears for operation, protection and instrumentation are also usually incorporated into the system.

The generator is set up so it is automatically started from a 12 V or 24 V batteries when the public mains supply fails. Then it takes over the electrical loads and shut down again after the mains electricity supply returns.

Usually not all of the building’s electrical loads are backed-up by this standby supply. Only the loads that are classified as part of the building’s fire protection system, and other loads that are categorized during the design as essential loads.

Picture 2 – Part view of the genset showing the alternator



It would be better of I can show the whole genset unit in a single picture but I can’t.

Here is the back end of the generator unit (assuming we can call the front of the radiator as the front). The diesel engine is coupled to this alternator (or electric generator), the part of the system that produces the electricity.

Notice on top of the alternator there are four flexible conductor connections.

Engines are machines that vibrate a lot. Everything that is connected to the diesel engine and the alternator should have considered the vibration in their design and installation. Picture 3 below shows one of the rubber absorbers installed below the engine chassis to absorb the effects of vibration between the genset unit and the building floor.

Picture 3 – Rubber vibration absorber



Picture 4 – Engine exhaust suspension hanger



Picture 5 – Spring absorber for the engine suspension hanger



As you can see from the above pictures, a lot of cost and efforts have been spent to handle the effects from the engine and alternator vibrations.

Picture 6 – Engine exhaust and silencer



An engine powered by fossil fuels need to exhaust the waste combustion gases. The picture above shows the exhaust gas pipe penetrating the generator room wall to discharge the hot gas outside.

The position of the outlet outside the building should be high enough above any possible walking pedestrians and passenger cars nearby.

Picture 7 below shows the position and height of the engine exhaust pipe outside the generator room wall.

Picture 7 – Engine exhaust and radiator exhaust outside the generator room wall



Both the engine exhaust and the hot air from the the radiator fan are shown in the above picture.

It happens that the side of the wall is right above the access route to the basement level of the building. Therefore, the engine exhaust is very well above the recommended level.

However, the radiator exhaust is at ground level.

But then the location of the radiator is not at any path way. In fact, a planter box has been constructed right in front of the radiator exhaust.

This would help not only keep the passer-bys away from the front of the exhaust grill, but also give a degree of camouflage which would make many architects a little bit happier.

I have a few more pictures to show you on this genset installation, but I am running late to a meeting now.

So I will upload the other pictures after a few days.

Visit this post, Electrical installation pictures, to see other photos that I have uploaded to this blog.



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