Picture 1 – FR cables installed on tray
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This picture shows two circuits employing FR electric cables installed on a vertical cable tray. These cables were taken in a cable riser at a multi-storey building.
All these cables are single-cores. The circuit on the right (with the smaller cables) was supplying the lift motor room at the roof level of the building.
The copper tape on the right edge of the vertical cable tray is the common earth and it is connected to the main electric grounding bar at the LV Room on the ground floor of the building.
The LV Room houses all main switchboards (MSB’s) for the building.
The circuit on the left edge of the cable tray was supplying two fan rooms, which were also at the roof level.
The loads of the fan rooms were mostly electric driven motors that run fire protection fans. These include smoke spill fans, staircase pressurization fans, etc.
These fan loads are significantly large. That is why the cables are of bigger size than those for the lift motor room electrical panel.
The color of FR cables
You can see in the picture that all the outer sheath of the FR cables are red colored.
I think the manufacturer can manufacture the cables to any color you wish. In this project the red color has been chosen because these FR cables supplies the equipment of the building’s fire fighting system.
Red is the standard color code for all fire fighting and fire protection systems and equipment as far as I know.
Fire sprinkler pipes, wet riser pipes, hose reel pump control panels, etc are all painted with red color.
Standby electric generators are part of the fire protection system
All the FR cables in picture 1 are supplied from the Essential MSB (EMSB) inside the LV Room at the ground floor.
The electric supply of the essential MSB in turn is backed by the standby electric generator of the building.
For readers with minimal background knowledge in the design of high-rise buildings, a standby electric generator is part of the fire protection system of a high rise building. Many fire fighting equipment and systems depend on the electricity supplied by this generator (or generators, often more than one electric generator are needed when the building’s total floor areas are very large, or if the building complex is spread over a very wide land area).
Fire lift is a classic example. Even though lift are designed as a means of vertical transportation for multi-storey buildings, a minimum of one lift is required to be designed and equipped as a fire fighting lift.
That means to say one of the lift will be used by the firemen to fight fire during fire emergency.
That is why the cables that supply the lift electrical panel should have the properties that can withstand fire condition for a few hours. That is also the reason the cables supplying the lift panels in picture 1 are colored red.
Essential supply cables are also colored red
Because electricity supply from the standby diesel generators is part of the building’s fire protection system, it follows that all cables from the generators must be colored red. This is assuming that the building’s color code for fire fighting equipment is red.
However, the supply from the standby generators is not only used for the fire protection. There are also other types of equipment in the building that need supply from the generators for other reasons.
These are equipment, lighting and socket outlets that need to run even when the mains supply from the public supply network is down.
We call the supply to these types of equipment “Essential Supply”. It is an essential electricity need of the building. Which equipment, lighting and power sockets need to be provided with the essential supply is usually defined by the owner of the building, assisted by professional architects, engineers and building managers. That is why the advice of at least one of these professionals is always needed during the planning of any new building.
Even though the is not fire fighting equipment connected to a circuit supplying essential supply, the supply cables are usually colored red. This is the common practice.
FR cable installation pictures
The foregoing general brief was given to fill in the gaps some readers may have when looking at the pictures of FR cable installations in this post and in other posts here.
I would need a separate and dedicated post to discuss the fire-related electrical systems in building works, which I may actually do some time in the near future. However, for now let just stick to the pictures.
Picture 2 – More fire-rated (FR) cables
Here there are more FR cables in the electrical riser.
Actually, this electrical riser is at the same building, but it is in a different riser room.
This building actually has two tower blocks: one tall and one a lower tower attached to each other.
Most of the mechanical plant and fire-related equipment for the both building towers are located at the roof of the lower tower. The cables on this cable riser tray supply emergency power to the lower roof.
That is the reason you seem more FR cables here.
Separate supply cables for each fire fighting system
A note for genuine beginners: it is usually a common practice to install a totally separate supply circuit for each system of fire fighting equipment and other mechanical systems from the Essential MSB (EMSB) at the LV Room.
Even the earthing cables are usually independent. That is why you can see the smaller green cables bunched together with each of the four circuits in picture 2.
However, you do not see the green earth cables in Picture 1 even though there are 2 separate circuits going up to the roof.
You see, the designers were not being very strict here.
I personally supervised the installation in this project, but it was a design-and-build contract. In this kind of contract, the professional design consultants are part of the main contractor’s team.
Because of that, the consultants must support the main contractor’s continuing effort to reduce costs and maximize profits.
They call this “value engineering”.
I apologize for the “negative tone” there, but I have been involved in many “turnkey contracts” and “design-and-build contracts” either as design engineers, consultant’s project managers and construction supervision engineers.
I think I have earned the right to insert the “negative tone” there.
Picture 3 – Normal supply cables
This picture shows a circuit employing normal supply cables on a separate vertical cable tray alongside the cable tray carrying the FR cables.
Notice the 3mm x 25mm earthing copper tape clipped to the cable tray along the single-core cables.
The normal supply cables here uses XLPE type cables for all submain cables. Only the final wiring circuits were allowed to use PVC insulated cables.
What is a “submain” cable?
I bold this item for the benefit of beginners in electrical installation works and building services engineering.
A submain cable is a cable that feeds supply from the main distribution equipment of an electrical system to an electrical panel that further distributes that electric power to current-using equipment or other electrical panel downstream of the distribution hierarchy.
The term can actually be used rather loosely.
In contrast to this term, a final wiring circuit cannot be called a submain cable even though the circuit may use exactly the same type and size of cables.
A set of cables supplying power ‘into’ the main distribution board are usually called main cables. I think that is why the distribution cables coming out of the main switchboard are called submain cables.
There is nobody out there going around enforcing rules about what you should call these cables. It is just a widely practiced way of categorizing these cables in real installations. If you call them the way other people in the industry call them, then you are using the same language.
If not, other people may get confused about what you were trying to say. That’s all.
Picture 4 – FR cable termination to busduct feed in box
This picture shows the termination of a busduct riser.
A busduct is a set of electrical conductors (usually copper or aluminium conductors) enclosed inside metal trunking.
The assembly is usually factory-manufactured and sold in ready-made length complete with integral earthing conductors.
You only need to purchase the number of lengths necessary to cover the distance from the source of supply to the destination.
Bends and angle pieces are also available from the manufacturers.
If you wish to know more about busduct installations, read this post, Electrical busduct installation pictures. There are more pictures there too.
Picture 5 – Fixing of the FR cables to cable tray
There is nothing special about the cable tie used to fix the FR cables to the cable tray. It is just the same type used to tie normal supply cables (i.e. PVC cables or XLPE cables).
Steel bolt and nuts are used to hold and tighten the steel cable tie to the tray.
Picture 6 – Copper tape fixing to the cable tray
This is just a closer view to show how the 3mm x 25mm earthing copper tape is fixed to the cable tray.
It is actually not necessary to use separate copper tape or the green earth cables to provide the electrical grounding for the electrical system.
The steel wire armor of multi-core submain cables can also be used to provide the electric grounding path.
Proper calculations should be done however, in order to ensure the cross-sectional area of the conductor is adequate for the protection system to operate properly. Also to ensure the requirements of the relevant codes are complied with.
Using separate 3mm x 25mm copper tapes is widely practiced in good installations because it is easy to monitor the quality of the earthing system and minimize the possibility of the contractor doing “value engineering” to this most important part of shock protection in an electrical installation.
That is all the time I can spare today for blogging.
I will see you again in the next post.
If you need more pictures, just visit Electrical installation pictures. There are links there that will take you the various posts with the pictures you are looking for.
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