A trunking is a larger size of a conduit. When you need to run a number of electric conduits along each other for a significant distance, then consider using a trunking in place of the conduits. There are so many sizes you can choose from.
Picture 1 – Electric trunking running below soffit of floor concrete slab
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This is an example of a trunking installation above ceiling level, under the soffit of the concrete floor slab.
I also labeled some of the other services there for the benefit of those non-electrical readers who need pictures like this for reference, to know what is what among the myriads of pipes and wires running above the ceiling level.
Notice the label “E” and “N” on the electric trunking. “E” means Essential Supply and “N” Normal Supply.
All large buildings need labels of some sort to distinguish two types of electric supply: the “normal” electricity supply and “essential” electricity supply.
The normal supply means the supply that is obtained from the public electricity supply. When the public supply fails, then your have a black-out.
If you live at a higher floor of a flat building, then you have to walk down the emergency staircase to leave the building.
That is why an “essential” supply is provided. This is normally generated by one of more standby diesel generators.
When the public supply fails, the standby generator automatically kicks in and provides the electricity to the building through the cables run inside the “E” trunking.
If you wall socket is supplied from these cable, then you have electricity even during a black out.
Picture 2 below shows how the electric trunking is installed at location like this.
Picture 2 – Hanger rod
Two hanger rods and a length of angle iron are normally used to support the trunking at these types of location. The angle iron can be as long as is necessary to accommodate the number of trunking it will support.
The hanger rods would be as long as needed to position the height of the trunking to a level that would necessitate a minimum number of bends.
Bends are more expensive than the straight piece regardless of whether you buy it ready made from factory or fabricated at the site from a straight piece.
Custom made at site means labor costs, which can even result in a much higher cost in the end.
So far all the clients of the projects that I was involved in did not accept custom made trunking bends. Neither do I.
Custom made bends tend to have sharp edges that injures the insulation and protective outer sheath of electric cables.
Injured cables can cause many problems during the operation of the installation even though they normally seem to pass all tests and inspection during construction.
I always warn contractors not to use custom made trunking or cable tray bends. When they have to, they are required to notify me or my staff in advance and specific locations where they are used should be identified and permission granted for each one on case by case basis.
Picture 3 – Vertically mounted trunking
This picture shows electric trunking when they are mounted vertically.
This installation was inside a fan room at the roof of a multi storey building. A number of electrical panels would be located on that wall later. That is the reason for the multiple trunking installed.
This room was basically a machine room. It housed many of the smoke control and ventilation fans of the building.
As usual, wiring to machines and electrical equipment requires frequent maintenance due to overheated cables, addition of new machines, replacement or upgrading to bigger machines, etc.
All these reasons require frequent troubleshooting and rewiring of electric cables. The use of trunking makes the maintenance and upgrading work much easier. That is why trunking are used in these sorts of locations even though there would only be just a few small electric cables to be installed inside them.
The following pictures show how the trunking are fixed to the wall, the types of mounting brackets used, etc.
Picture 4 – Mounting bracket for wall mounted trunking
The above picture and the one below show two types of mounting brackets. These two are the low cost types.
Picture 5 – Another type of vertical mounting bracket
Same method, only different materials.
The type shown in Picture 6 would cost more, but it can provided higher strength which is needed for long vertical trunking such as those inside electrical risers in a multi storey buildings.
Picture 6 – Mounting bracket for long vertical trunking
This type also is suitable for large trunking sizes, which can carry more cables.
Picture 7 – Trunking 90 degree bend
This is an example of a bend. This one was factory-manufactured.
Picture 8 – A hanger rod support bracket installed by the air-conditioning contractor
This trunking and the hanger rod support were installed by the air-conditioning contractor. It is exactly the same as the method used in Picture 2.
However, I show this picture for a different reason.
Notice the white label “AC” painted under the trunking. This label is painted to all electric trunking installed by the air-conditioning contractor to distinguish them from electrical trunking installed by the electrical contractor.
It is a common practice that all electrical conduit and trunking are required to be painted orange color.
An air conditioning system runs throughout all floors of a modern high rise building. The locations of air-conditioning electrical equipment are not restricted to just inside the AHU rooms of a building floor.
There are numerous fan coil unit (FCU) throughout the floor area. Where individual control of the air temperature and quality inside a room is required, an FCU unit is needed.
So, an electric circuit need too be run there.
Many times, especially in large buildings, the works of electrical wiring to all these air-conditioning electrical equipment are located inside the air-conditioning works contract.
If for nothing else, this arrangement eliminates many coordination problems that usually occur when too much interfacing is required between different trade contractors.
The electrical contractor is then just required to run supply cable to the main electrical panel of the air-conditioning system at each floor. The electrical panel and all downstream cabling and wiring are parked under the air-conditioning contract.
Neat.
Okay. This is all I have time for today. We will meet again in the next post.
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