Temporary electrical cabling

Today readers get to see a few pictures of bad practices in the utilization of temporary electrical supply at a building construction site.

Picture 1 – Temporary electrical panel



===== RELATED ARTICLES:  Temporary electrical installation pictures | Temporary electrical installation pictures  |   Temporary Electrical Earthing Pictures  |   Temporary electrical panel and cords pictures   |
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I got involved with this new building project since a few weeks ago.

After reporting to work at the construction site, I spent the first few days attending a few meetings and on the fourth day I took my first round of general inspection around the building under construction.

I went out alone on that first inspection, bringing with me my old and cheap Canon digital camera. It was really a cheap camera and that is probably the reason the picture quality here are not so good.

My previous digital camera was much better but it got stolen when my car was broken into.

First things first

The first thing that I look for when starting on a new project site is always the temporary electricity supply equipment and their associated temporary cabling and wiring works.

There can be hundreds of workers are involved during peak period of activities in a building job of a few million dollars.

With a bad temporary supply installation and with most workers being generally ignorant of the dangers of temporary electricity, the risk of fatal electrical accidents is always high.

I did my round and took a few pictures of temporary electrical panels being used, the temporary supply cabling, wiring, and extension cords that were taking supply from temporary panels.

I selected a few of the picture shots that I took and sent it to the Main Contractor’s Project Manager together with the following Site Memo.

You can see a few of the pictures of the temporary electricity supply DB and their cabling works toward the end of this post.

SITE MEMO:

Dear Sir,

Re: Temporary electricity supply: Electric shock hazards

As I have explained on Saturday last week, please find attached photographs of the temporary electrical cabling.

I believe the photos are self-explanatory. However, I wish to highlight the following points:

Many extension cords do not have the grounding cable.

The extension cords are laid on the floor along main work traffic. Cables can be damaged leading to exposures of LIVE cables. A few have already been damaged and improperly patched up.

Observe that the area is a very wet area. The risks of electrocution here is very high.

I suggest the following action be taken IMMEDIATELY:

If possible, the temporary DB is relocated to a more suitable and DRY area.

Enforce the rules that all subcontractors run their extension cords at high level along walls or columns.

Enforce the rules that all extension cords have a working grounding conductor.
It is my opinion that the present situation is VERY DANGEROUS and a fatal electric shock accident can happen any time.

Regards,



Lee Wan Seng
Resident Electrical Engineer

Picture 2 – Temporary electrical cabinet



Picture 2 above shows the overall view of the temporary electrical cabinet where the temporary electric panel is located.

I know that many electrical readers are surprised by the way I accept these equipments and installations.

The temporary panel in the pictures is not what I would use if I am in charge.

Here I was not in charge. I was the resident engineer representing the professional electrical consultant in a design-and-build contract.

In this type of contract, the main contractor is the boss and the paymaster.

And this project was in a “third world country".

We in the construction and engineering consultant industry cannot turn the standard of our construction practices overnight, especially not in the design-and-build or turnkey types of contracts.

What we can do is to set out priorities in an order that can still be implemented on the ground within a particular contract scenario.

In this case, it was an issue of safety of human lives.

Even in this matter of life and death of many human lives, priorities must be set properly so that it can be implemented.

I could have rejected the whole temporary electrical DB and the temporary cabling in the picture.

In many situations, I have done so.

However, in real life situations, political factors are always present and everywhere, especially where there is a lot of money involved. That is the nature of life that I know.

To say it simply, if I rejected the makeshift temporary electrical DB, I would have been kicked out of the project in a matter of a few weeks and the main contractor would have easily found a replacement that would bend to their wills.

Of course I could easily find myself another job, even with much better paychecks and benefits if I want to.

However, nothing good would come out as far as the electrical safety at this construction site is concerned. It may even get worse.

That is why I sent out the above Site Memo.

If the Main Contractor take action as I advised (which they did immediately after receiving the memo) in the above Site Memo, then I would have made a strong improvement. That was a good first step.

The point here is that handling construction issues on the ground has as much to do with diplomacy and PR works as with technical issues.

One has to properly balance a number of top priority matters in order to get things improved enough.

That is a measure of effectiveness of the site supervision team in the real construction world.

Going back to the reason I made this blog, its objective is mainly to share pictures. With this method, I share my experience with the readers. Good experience, and the bad ones.

You will find lots of pictures showing good electrical installations here. You will also find tons of bad installations. I am not recommending anything by showing all these pictures, unless I specifically say so.

As long as readers find some uses from the pictures, then I would have accomplished my purpose by sharing the pictures that I have in this blog.

Enough said. Now let’s get back to the pictures.

Picture 3 – A view of the wet area around the electrical panel



This picture shows one situation was with a wet area around the temporary panel and unsuitable extension cords laying around on the building's ground floor.

From the point of view of safety practices and regulations, I think this real life example has broken about all the relevant codes in the book.

Picture 4 – Damaged extension cord



This shows a closer view of the extension cords laying on the work floor. They have no armor and could be easily be damaged.

A few have been already damaged and improperly patched up.

Picture 5 – Closer view of the repaired extension cables



Picture 6 – One of the portable electric tools



Picture 7 – Extension cords on the floor



Picture 8 – An example of electrical plug without earthing connection



I wish to emphasize a little bit here.

Why do you think the workers did not connect the green earth cable to the plug?

The extension cord already has 3 cables one of which was meant for grounding.

So why such a reluctance to do it?

The reason is almost the same most of the time. The ELCB on the electrical panel may trip if the green earthing cable is connected.

Portable electrical tools used at construction sites are mostly motorized tools (e.g. Drills, grinders, electric hammers, etc).

These tools always have an electric motor underneath the casing.

An electric motor always has a coil that transforms the electrical energy into the mechanical energy that do the work.

That is where the problem comes from.

Motor coils have a tendency to leak electrical voltage. Other moving parts behave similarly also.

The leaked electric voltage (Note: an electric voltage is an electrical pressure much like a water pressure inside a water pipe) would turn into a leakage current if the electric tool is properly earthed or grounded.

The flow of the leakage current would be detected by the ELCB (earth leakage circuit breaker) unit on the electrical panel and the ELCB would trip.

If the grounding conductor is not connected as shown in Picture 8, then the ELCB would not trip. So the worker using the portable electric tool could keep on working.

In another word, frequent trippings of the ELCB is a nuisance to the workers.

That is why they disconnect the green grounding conductor of the extension cord.

But then, without the grounding cable, the worker has zero protection against the risk of electric shock.

By that, I really mean absolutely NO PROTECTION AT ALL AGAINST ELECTRIC SHOCKS.

Picture 9 – Grounding of the temporary supply through the steel wire armor of the multi-core armored distribution cable



That is all I have for today. See you again in the next post.

Copyright http://electricalinstallationwiringpicture.blogspot.com Temporary electrical cabling

Temporary electrical distribution

Would you believe it if I say that the picture below is a distribution system for a temporary electrical supply at a building under construction?

Picture 1 – A method(?) for a temporary electrical distribution



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I have been away for a few days. So I cannot write long posts yet.

Therefore, I will only give you pictures for a while. You have to interpret what they mean.

I took the above picture quite a while back. I thought I was interesting.

This distribution system was supplied from a temporary electrical panel nearby (see Picture 2 below).

Picture 2 – Temporary electrical panel



I was wondering why the worker needed to create such a distribution “harness”.

But I guess the answer was clear.

Notice the burn marks on one of the socket outlet at the temporary electrical panel (see Picture 3 below).

Picture 3 – Damaged electrical socket



A clearer view of the damaged outlet can be seen in Picture 4 below.

Picture 4 – Clearer view of the temporary socket outlets



You can see more pictures of electrical installations at this post, Temporary electrical installation pictures.


Copyright http://electricalinstallationwiringpicture.blogspot.com Temporary electrical distribution

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

Temporary electrical installation pictures

I have uploaded so many pictures of temporary electrical installations to this blog that I think it is time to give the subject a separate post title of its own. This post will be an anchor post for all pictures that I uploaded on temporary electrical installations.

Picture 1 – Temporary electrical submain cables




===== RELATED ARTICLES:   Temporary Electrical Earthing Pictures  |  Electrical grounding electrode pictures |  Electrical installation pictures

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I wish to make one thing very clear on temporary electrical installations.

The installations for purposes of temporary electricity supply are not "nice" installations in majority of construction scenarios.

If I am to show only the nice and proper temporary supply installations on this blog, then I only serve the readers with only less than half of my experience on this matter.

With that also it means that only less than half of the lessons can be learned by beginners of electrical installations.

With all these good and bad examples of electrical installations, beginners can learn more of the real life scenarios that they will face when they start work at real construction sites.

Now back to the pictures.

Picture 1 above shows how the low voltage (LV) submain cables are installed in this project.

These cables are 4-core, steel-wire-armored copper cables. They connect the temporary main switchboard to individual sub-switchboard inside the building under construction.

Personally I do not really have any objection to the way the contractor installed these cables because they are steel wire armored cables even though they look a little unsightly.

They however should be protected from accidental damage. Some sort of barricade should be installed because one of the main construction roads is just a few feet away from the steel fence.

An alternative might be to raise the temporary cables higher so that any possible accidents by construction vehicles would not hit the electric cables.

Notice the picture label that I put on the right of the picture: temporary earthing electrode. The indication pointed to a white signboard.

Actually this was one of a few improvements made by the main contractor to the temporary electrical installation at this project site. I have sent a post earlier on this issue, which you can read here, Temporary electrical panel and cord pictures.

The warning sign indicating the location of temporary electrical grounding is a very important safety matter. If the earthing is damaged and not functioning well enough, hundreds of workers at the job site faced risks of electrocution or serious injuries from electric shocks every day.

If you have not seen these sorts of injuries before, you can see them see them at this post, Electric shock injury pictures. If you have seen then, then don’t. Once should be enough. I lose my appetite for food almost a whole day every time I look at those pictures.

The temporary grounding electrode should have also been barricaded for protection from damage, which was also carried out one or two weeks after this photograph was taken.

Later the temporary submain cables on the fence were also provided with some DANGER warning signs.

Picture 2 – Temporary site flood lighting



This flood light was installed on the fence not far from the sub-main cables in Picture 1.

If I remember it correctly, this flood light fixture was 400 watt, IP 65 metal halide.

You can see more photographs of temporary lighting at another post, Temporary lighting installation pictures.

Picture 3 – Temporary electrical panel without earthing connection



This electrical panel was installed to operate a machinery at a very wet condition and outdoor.

The electric panel was very neat and of a high quality.

A brief look inside might not alarm you at all. It did look good.

However, a closer observation revealed something sinister. The panel did not have the electric shock protection at all.

In case some readers may wonder, the machinery supplied by this panel was not an automated machine. It was a manned at the machine itself with the motor near the operator and in a very wet area.

You can read the post here, Electrical panel pictures. There are more pictures of this electric panel there also.

Picture 4 – Burned 13A socket outlet



This is a temporary switched 13A socket out installed on a temporary electrical panel at a construction site.

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 (check the photo at the post link below). It could have been caused by fire sparks when the live wire was pulled out of the socket without turning off the socket switch.

It could 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 temporary DB was actually installed outside of the new building and there was not really anything that could catch fire. However, if it were inside the building, it would be also a real fire hazard.

Visit this post, Temporary socket outlet pictures, to see more photos of temporary electrical panels and temporary socket outlets.

Picture 5 – A method(?) for a temporary electrical distribution



Would you believe it if I say that the above picture was a distribution system for a temporary electrical supply at a building under construction?

I took the above picture quite a while back. I thought it was interesting.

You can see the rest of the pictures here, Temporary electrical distribution.

Picture 6 - Another temporary electrical panel



I saw the above temporary installation at a new project I just get involved in. So I took some pictures and sent out the following Site Memo:

SITE MEMO:

Dear Sir,

Re: Temporary electricity supply: Electric shock hazards

As I have explained on Saturday last week, please find attached photographs of the temporary electrical cabling.
I believe the photos are self-explanatory. However, I wish to highlight the following points:

1. Many extension cords do not have the grounding cable.
2. The extension cords are laid on the floor along main work traffic. Cables can be damaged leading to exposures of LIVE cables. A few have already been damaged and improperly patched up.
3. Observe that the area is a very wet area. The risks of electrocution here is very high.

I suggest the following action be taken IMMEDIATELY:

1. If possible, the temporary DB is relocated to a more suitable and DRY area.
2. Enforce the rules that all subcontractors run their extension cords at high level along walls or columns.
3. Enforce the rules that all extension cords have a working grounding conductor.

It is my opinion that the present situation is VERY DANGEROUS and a fatal electric shock accident can happen any time.

Regards,

Lee Wan Seng
Resident Electrical Engineer

Visit this post, Temporary electrical cabling, to see the rest of the pictures.

That’s all I have time for today. I will update this post with more pictures soon.

Chiao.

Copyright http://electricalinstallationwiringpicture.blogspot.com Temporary electrical installation pictures

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.

Copyright http://electricalinstallationwiringpicture.blogspot.com Temporary lighting installation pictures

Temporary Electrical Earthing Pictures

This post shows a few pictures on the earthing of temporary electric supply installations. However, before you see the pictures, remember that I am sharing here pictures of real life electrical installations. By showing them on this blog, I am sharing my experience with the readers.

It does not mean that I am recommending what is shown on a picture as a good or correct way to do something, unless I specifically say so, of course.

Beginners, please take note. The pictures that I show on this blog are materials for you to see and think. These are real life pictures from real construction sites, and construction industry is a really complex world by itself.

Picture 1 – The earthing of temporary supply DB using the cable’s wire armor



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Picture 2 – A closer view on the termination of the cable armor



The safe utilization of a temporary electric supply often depends on the existence of an effective electrical earth.

It is the responsibility of the person in charge of a construction site to ensure that the earthing of the electric supply system is working effectively. The site’s electricity supplier (the electric supply authority) has nothing to do with this part of the electric supply.

Many electricity supply authorities use protective multiple earthing (PME) system. With this method, the electrical system’s neutral and earth are combined.

When this method is used, all metalworks including structural metalwork must be bonded together in such a way to make all metal parts electrically continuous.

However, in most real life construction sites, this bonding is hard to do and almost impossible to maintain properly throughout the duration of the construction period.

So usually, the public utility supplier will not connect the supply until an alternative electrical earth is provided and fully tested.

They also insist that evidence of the earthing test results endorsed by a competent electrician is submitted together with the completed application forms for the temporary electricity supply to the site.

Independent earth electrodes

Several methods are used to provide the alternative electrical earth. The most commonly used method is to use independent earth electrodes installed at the location near the main intake temporary switchboard (this is usually the location where the temporary meter is installed).

This will ensure that the protection fuses will operate and disconnect the site electrical installation from the incoming public supply in the event of a fault.

This disconnection is an absolute must in order to minimize the damages to the site’s electrical system due to the fault.

It is also to prevent the fault from spreading upstream to the electric supplier’s distribution network. The latter is the main reason the electricity supplier is worried about this aspect of the temporary installations.

Picture 3 – Temporary electric supply: A poor man's complete system


I will devote a whole post in the future for this subject of earthing.

For now, I have a few picture of temporary electrical grounding for your viewing pleasures. I seek an apology from those readers who already have some electrical knowledge. These pictures are not for you guys. They are just too simple.

However for those managers and construction people who have always been intimidated by those colleagues on these sorts of issues, let me assure you that if you understand what these three lousy pictures say, then you already understand what an electrical grounding is.

Picture 4 – Temporary incoming cables, kWh meter, DB, earth wire and protective PVC conduit


Picture 5 – Temporary earth grounding



Now lets start with picture 10. You may need to click on the picture to see it in full size.

The black case on the wooden panel there is the temporary electric meter supplied by the electric authority. Below it in white PVC casing is the temporary distribution board.

You can also see a piece of wire in green insulation coming out downward from the distribution board.

This wire goes straight into a two-meter length white PVC conduit, and (if you watch it closely) it comes out of the vertical PVC conduit at the bottom and goes straight into the concrete floor just beside the plywood partition wall.

All these you can see much more clearly in Pictures 11 and 12.

Now let’s get back to the black energy meter.

Above it you can see two lengths of black insulated cables coming down from high level (below the roof level of the temporary wooden structure).

One cable terminates at a black piece of component just above the meter, while the other one terminates at a cheap white plastic terminal block.

The two components each have a cable of the same size coming out at the bottom connection and terminate at the temporary kilo-watt-hour meter.

Now lets get a little bit more technical.

Single-phase electrical installation

This is what we call a single-phase electrical installation (a three-phase supply would have four black cables coming down from the roof level – three phase cables and one neutral cable).

Therefore, the incoming supply from the authority is also a single-phase supply (we apply single-phase supply, so they give us a single phase supply).

An electric supply from the authority can be one of a few types.

Single-phase two-wire system

The type as recorded in the pictures is the single-phase two-wire type (three-phase 4-wire if we apply three-phase supply). This type will have two incoming cables from the authority’s distribution network – one live or phase cable and one neutral cable.

Other types may have three incoming cables from the distribution network for the same one-phase supply – the same live and neutral cables, plus a third cable, which is the earthing cable.

A construction site needs an independent, reliable electrical earthing

Now as I said earlier in this post, a construction site really needs an independent and reliable earthing, an electrical grounding that is not dependent on any third party’s grounding or even the electricity supplier’s grounding.

Failure to provide this can result in fatal injuries from electric shocks, even multiple casualties in a single accident.

Never mind my emotions on this (if you can sense them), but an electrical accident is that dangerous and electrical shocks can strike silently without warning.

Because of the need for that independent and reliable earth for the temporary site supply, the green electric cable is installed below the white PVC distribution board (Picture 11 shows this more clearly).

What if this earthing is not working?

The electrical earthing is important so that the electric shock protection device (ELCB or RCD) can operate and isolate the incoming supply from the temporary installation. (I have uploaded a few ELCB pictures at this post, 1-Phase ELCB Connection Pictures, for the readers who wish to see them).

Without this cable, the electrical system can still work. The workers can still use their tools and do a good job for their employers so the construction venture can end up being very profitable for the shareholders of the company.

However, one fine day, the extension cord that carries current to the electric drill one of the workers has been using gets damaged, exposing the live wire to an unintentional contact with any of the workers around the area.

Being hard at work, the workers bodies and clothes are usually very damp or very wet with sweat, and human sweat is a good conductor of electricity just like the electrolyte in your car battery.

In this situation, all that is needed is one accidental contact at any part of a worker’s body with the exposed live conductor of the damaged extension cord. Then he would receive a severe electric shock injury. Even death is highly likely depending on where on the worker’s body the contact to the live wire happens.

Severity of electric shock injuries depend on the location of the contact

If the contact is at the hands, then the electric shock current will travel through the chest and the workers heart before going down to the legs and the ground. Then you may have a case of fatal injuries there.

Sorry for the diversion. This electrical earthing matter is so simple that I have to drag the stories into the injury aspects to make it a bit longer ;-)).

Not only it is simple, it is also plain cheap and low cost.

Look at the picture again. You have a short length of the green wire and two meters of the white PVC pipe.

Wait… I know what a few of you are thinking…

Yes, there is copper earth electrode in the concrete, which goes straight down below the concrete about 1.5 to three meters into the ground.

Cheap in price, costly in lives

The above example is a very small installation, so it looks simple. This wooden structure only draws a few amperes. However, even for a large installation, the grounding is relatively just as simple.

The point that I am trying to make in here is that providing an independent and effective earth is not a challenge at all in most construction site situations.

So, do not risk human lives just to save some construction cost there.

Update February 11, 2010:

The challenge of a site electric supply

It is always a challenge to provide the electricity supply to the site people safely. Construction sites are among the most challenging environments to the safe use of electricity.

A lot of works are done outdoors, in all sorts of weather conditions. Wet and damp conditions present very high risks of severe electric shocks.

The workflow of site works is constantly changing as the construction work progresses. Therefore, the temptations to improvise the electrical distribution system are often too great to resist.

Routine construction activities, the demolition and excavation works may all result in damages to both the temporary supply and the newly fixed permanent supply systems.

When the activities at a site are at its peak with hundreds or thousands of workers ,not to mention construction vehicles and machineries, the site usually become congested.

This sort of situations makes the control of risks very difficult. Temporary cables and electric construction tools and equipment are very likely to be damaged by the movement of heavy machines and materials.

The people who use electricity at site have various needs, and sometimes conflicting interests and expectations. The workers and team leaders themselves work for different subcontractors and suppliers.

In order to maintain any reasonable degree of safety and control of risks, a effective site management is an absolute must-have for the site main contractor or the client’s people who are in charge at the construction site.

Due to the nature of construction works, a risk-free environment is impossible to attain most of the time. However, some risks can be avoided by careful planning before the work commences at the site.

Protect the earthing system

The protection of workers against electric shocks and injuries depends so much on the integrity of the earthing part of the electrical grounding system.

The earthing part, as shown in the above pictures, includes the grounding electrodes and all the underground conductors or cables that form part of the earth grounding network.

However, that is easier said than done.

These networks of electrodes and the connecting conductors are almost always installed at the ground level. They can easily be damaged by uncontrolled excavation works construction vehicles.

The personnel in charge of safety aspects of the construction site should include it their daily routing to patrol this part of the site temporary supply installation.

Other than that, it always a good idea to install some highly visible warning signs to warn workers and drivers of construction vehicles of these critical electrical supply safety parts.

The following are two pictures show the temporary warning signs put up by the contractor indicating the location of the temporary earthing electrodes.

They rushed up to install this after I found out in my second day of assignment at the construction site that the temporary supply at the building under construction has been operating for many months without earthing connection at all.

I have sent a post earlier about this temporary installation. Read it here, Temporary Electrical Panel Pictures.

Picture 6 – Temporary electrical earthing warning sign


Picture 7 – Notice the temporary supply cables at the fence, but that is a topic for another post.



There were 250 to 400 construction workers at site daily. Luckily there was no electrical accident yet. Really, really lucky.

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