Picture a1 - A site temporary lighting with mobile generator
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Arguably more important than the light levels, the temporary lighting installation should be sufficiently safe for use and provided with adequate protection to prevent electrical shocks.
A. SITE TEMPORARY LIGHTING
Picture 1 – Indoor temporary lighting and wiring
Picture 1a – Temporary lighting – Bad cabling installation
Picture 2 – Another temporary lighting and wiring indoor
Picture 3 – External site floodlight
1) Mechanical protection
In general, equipment for use at construction sites should be tough enough to withstand the abuses of work area where they are installed. Damaged light
fittings not only result in the repair cost, but they also present risks of electrical shocks to workers using them or those who are nearby.
For temporary lighting, they can be installed out of reach of human hands or any construction materials that are handled in the area. Also from equipment and
machines being operated there.
Another easy measure is to use wire cages type of lighting fixtures.
Precautions should also be taken against the danger of electrical fires that may result because of damaged lighting fixtures or the temporary supply wiring.
2) Supply from a separate section of the distribution panel
The temporary wiring supplying the lighting circuits should be connected to the special lighting section on the temporary switchboard. These circuits should
be protected by 100 mA RCD (residual current circuit breakers).
3) Mechanical support of the wiring
The installation of wiring for the temporary lighting should be carried out with proper supports and fittings to allow for wiring cables to be routed in ways
that minimize obstructions, which can results in damage to the luminaries and wiring.
These damages can present shock risks to the works and possibilities of electrical fires.
4) Normal duty lighting
Normal duty lighting circuits are installed to provide general illumination for work and allow safe movement inside and around the construction site.
5) Lighting levels
An illumination level of 10 lux is adequate for general movement within a building under construction.
As a simple example, one length of 100 meter festoon light string fitted with 20 nos 100 watt lamps at 5 meter intervals will give a 10 lux over a
rectangular area of 25 meter x 30 meter.
6) Use of festoon lighting
Festoon lighting should only be used strictly in underground shafts, wells and tunnels.
When this type of lighting is used, the lamp holders should only be the moulded, non-removable type (the lamp holders are bonded or moulded to the wiring
cables) and the lighting supply voltage is 32 Volts or below.
7) Supply to lift shaft temporary lighting
Either a temporary wiring or the newly installed permanent electrical wiring may be used to supply a lift shaft temporary lighting.
However, the light fittings used should be properly guarded against accidental mechanical damage and they should only be connected to the wiring using a
lighting plug and socket.
These lights should be installed at intervals of less than nine meters along the vertical length of the lift shaft.
The control of the lift shaft lighting should be by means of two-way switches located near the shaft access points.
8) Use of SELV voltage
The use of lighting circuits supplied at safe extra low voltage levels (SELV - voltages less than 50 volts ac or 120 volts dc) is highly recommended for
working in confined spaces where workers faces high possibilities of frequent contacts with temporary electrical equipment and wiring.
B. TEMPORARY SITE FLOOD LIGHTING
Large construction sites usually need temporary floodlight towers (in addition to the temporary lighting inside the new buildings) to provide lighting
efficiently for the general movement, safety and security on the external areas of buildings under construction.
The lighting towers will usually takes the form of fixed tower or mobile tower units. Which one to use usually depends on the siting positions available for
the lighting tower units and the duration of the contract.
For contracts with construction periods of relatively short durations, it may be much more economical to use mobile tower units.
However, if contract period is long, then it may be worth some considerations to use fixed height tower units. In any case, the fixed height towers can still
be reused on future projects. Careful dismantle the fixed height static towers at the end of the contract. Then the only extra material that is required in
at the next construction site is the foundation.
Static floodlighting tower units are normally available up to 18 meter high. They can be powered from the mains supply and they can be provided with their
own electric generator.
The external areas of a construction site usually need a lighting level of around 20 lux average. This is the level sufficient of for the handling of
construction materials and site clearing works.
A rectangular area of 60 meter by 60 meter can be lighted up to this light level by a typical 18 m tower carrying four units of 400 watt high pressure sodium
fittings.
A main contractor with larger contracts and relatively longer contract period may want to consider a more elaborate study on their site lighting
requirements. If there is enough space to mount these floodlighting tower units, a proper lighting engineering study can be carried out together with the
overall temporary electrical installation.
The exercise would employ the floodlight lamp data, the aiming angles of the light fittings, and the mounting heights of the individual fittings to arrive at
the required overall illuminance.
These static towers would normally employ high intensity luminaries and with the type of equipment available today, the contractor can now light areas to
sufficient level so the works can continue in evenings of the darker months. This is significant because it can considerably reduce the contract time.
Light fittings used in this application would necessarily be high intensity discharge type and the high pressure sodium lantern have become the more dominant
type due to its high lighting output per kW of power usage (approximately 125 lumens per watt).
A tungsten filament lamp would give only 22 lumens per watt.
The capital cost of choosing the high-pressure sodium equipment is considerably higher than the tungsten halogen, but the main contractor may do well to
consider other factors also such as the running cost, installation cost and the lamp life.
At the end of the construction work, all these equipment except the tower foundation can be dismantled and transported to other project sites for reuse.
You can see below a few pictures of a small mobile floodlight unit and other types of temporary site floodlights:
Picture 4 - Mobile site floodlight unit
Picture 5 – Luminaries of mobile flood lights
Picture 6 – This is a permanent floodlight, not a temporary one
Picture 7 – A closer view of the 400 watt temporary floodlight in Picture 3
C. SITE TEMPORARY ELECTRIC SUPPLY
A site temporary lighting is actually part of its temporary electric supply installation.
The term ‘temporary’ brings up a vision of a length of twin and earth cable, or a four-core twisted cable and an undersized green earth wire, that is connected into a 30A single or 4-phase and neutral switch-fuse, trailing across the rough ground of the construction site to terminate into a seasoned self-fabricated distributed (with or without metal-clad enclosure).
On the so-called ‘distribution board’, a length of three flexible extension cord is connected to a clumsily assembled socket outlet with or without the use of a three-pin plug.
How would you connect a three-core extension cord to a three-pin 13 A socket outlet?
Somewhere on this blog, you can see clearly how it is done. It even has had various ways of doing it.
The extension cord run at high level near the soffit of floor slab, or some just run on the scattered floor to a temporary metal-clad 13A switched socket outlet some 30 meters away.
The construction contract cost hundreds of millions, but the temporary electric supply system has been ‘engineered’ to fulfill all the site electrical requirements for the minimum price possible.
The main contractor has the responsibility to ensure the temporary electricity supply system installed is not only functional and meets all his electrical needs, but also safe for all involved in the construction work.
The supply system need to be good enough to provide reliable power distribution, whether that period of the construction contract is three months or three years.
Or whether the site supply requirement is 4 kVA or 3-megawatt supply.
What specifications to use for the temporary electric supply equipment?
Generally, what applied to low voltage installation is in the IEE Wiring regulations also apply to the temporary supply system.
However, two more British standards should be used to cover the gaps not covered there: BS 4363 (Specification for distribution units and electric supplies for construction sites and building sites) and BS 7375 (Code of practice for distribution of electricity in construction and building sites).
Source of the temporary supply
The temporary electric supply can be obtained from either the distribution network of the local electric supply authority or an independent electric generator installed at the site. Which one to use is usually just a matter of judgment on the cost involved.
However a few other factors may also need to be carefully considered which include practical problems that are usually associated with the distribution of the electric power safely and effectively throughout the site.
If the supply is taken from the local electric supply authority, a lead-time is usually required, as the authority would need time to arrange for the connection.
The main contractor also need to submit sufficient details on the peak demand that will be required during the course of the contract, the positions of the point of supply intake and also the estimated contract period.
The authority usually requires enough details on the types and size of electrical load, e.g. lighting, heating, motors, etc. Motor loads usually need more details such as types of motors and the method of starting (direct-online, auto-transformer starting, etc).
Update (March 15, 2014): I have a collection of pictures on temporary lighting that I have not yet uploaded anywhere. I plan to just progressively attach the pictures below in this post with a brief comment for each picture.
This way I do not need to write a post just for the purpose of sharing the pictures.
xxx MORE TEMPORARY LIGHTING INSTALLATION PICTURES xxx
Picture 08 - Temporary flood light installed at high level of a rail workshop under construction
This picture show flood lights installed at the high level of a rail workshop under construction.
Actually this temporary lighting has only recently been installed. Electrical supply wires were still dangling around and not properly fixed.
However, the main contractor were pressing for progress and I did not wish to look like a bad guy there. So I just let them use them first to help them gain some additional progress before I apply more pressure for the temporary cable to be properly fixed.
In any case, the dangling cabling were mostly at the higher level of the work area.
This is not to say that the risk of accident was minimal. As you can see in the background of the picture, there was a mobile sky-lift being used to install the fighting pipes just below the roofing of the workshop.
In some days, there were quite a number of the sky-lifts throughout the workshop floors.
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