Flush Floor Trunking ; The Wrong Things That Most People Do!

This is the things that engineers and site workers must avoid when installing flush floor trunking (FFT); cable congested in FFT.

FFT normally consist of single, 2 compartments and 3 compartments of internal trunking. These compartments are segregated between each other and each compartment shall not be shared together.

Based on IEE Wiring Regulation, cabling in enclose enclosure should comply with 40% space factor.

Meaning to say, all cables should only occupy only 60% of overall internal dimension of FFT.

However, designer must consider the internal flyover inside three compartments in FFT. This area can be considered as unused space in FFT. Therefore, the actual usable space is much lesser than 60%.

Calculating the space factor without considering this unused space will result congested cable in FFT (see figure below).

Light Fitting Categories (Cat 1, Cat 2 and Cat 3).

There are three categories of light fitting listed in The Chartered Institution of Building Services Engineer (CIBSE’s) namely Category 1, Category 2 and Category 3.  These types of lighting are differed according to their luminance limit angle.   Category 1 limit angle is 55, Category 2 is 65 and Category 3 is 75 as shown in figure below;

Categorizing these light fitting is not indicating that category 1 is not ‘better’ than category 2 ‘better’ than category 3. The correct category must be selected for each individual installation otherwise undue installation and energy costs are likely to be incurred.

Light output ratio is another aspect of the installation when choosing the ‘right’ category. This ratio must be determined so that the luminance is evenly distributed as can be seen in the figure below.

From this information it can be ascertained that in general Category 1 (reflector luminance less than 200cd per sq.m from an angle of 55^o)luminaires are recommended where there were a high density of VDU (Video Display Terminal) in an area, and where usage is sustained over long periods of time, or is of an intensive nature or where errors are critical.

Category 2 luminaires (reflector luminance less than 200 cd per sq.m from an angle of 65°) are recommended where there would be fairly wide spread use of VDT in an area where one VDT per desk for general use.

Category 3 luminaires (reflector luminance less than 200 cd per sq.m from an angle of 75°) are recommended where the density of VDT is low and where computer use is casual. 

Credit to PCO Lighting

How To Identify Faulty Underground Cable

It happens at one of my project....the underground cable from main substation experience a faulty.

This faulty cable causing the Main Switch Board to trip over certain period of energizing (not an instantaneous tripping).

Since the underground cable are laid over more than 150 meter, the location of the faulty cable may not be seen through naked eye.

In order to identify the fault location, voltage injection need to be apply to the faulty cable. This is to ensure the faulty cable will produce spark.

The spark that appear below ground will produce sound (sounds like dup...dup..dup). The sound was so soft that you need microscopic equipment to hear it.

By using that microscopic equipment, place the equipment on the ground and walk along the routing of the faulty cable until the sound are stronger. Once the fault location are found, the digging process started and cable rectification to be done.

This is how the video look like during the process.

Enjoy....