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What is CP5:1998 and why is it important for electrical installations?

What is CP5:1998 and why is it important for electrical installations?

CP5:1998 is a Singapore Standard that provides the code of practice for electrical installations. It is a modified adoption of BS 7671:2008, which is the British Standard for wiring regulations. CP5:1998 covers the design, selection, erection, inspection, testing and maintenance of low voltage electrical installations up to 1000 V AC or 1500 V DC.


CP5:1998 is important for electrical installations because it ensures the safety and functionality of the electrical systems and equipment. It also helps to prevent fire hazards, electric shocks, overloading, short circuits and other faults that may cause damage or injury. CP5:1998 also complies with the relevant statutory requirements and regulations in Singapore, such as the Electricity Act and the Electricity (Electrical Installations) Regulations.

CP5:1998 was first published in 1977 and has undergone three revisions since then. The latest revision was in 2018, when it was re-designated as SS 638:2018. The new standard incorporates the amendments and updates from BS 7671:2008 and reflects the changes in technology and industry practices. Some of the key changes include:

  • The introduction of new protective devices such as arc fault detection devices (AFDDs) and surge protection devices (SPDs).

  • The expansion of the scope to cover special locations such as medical locations, marinas, caravan parks, photovoltaic systems and electric vehicle charging points.

  • The alignment of the terminology and definitions with the international standards such as IEC 60364.

  • The clarification of the requirements for earthing and bonding, cable sizing, circuit design, inspection and testing.

CP5:1998 or SS 638:2018 is a useful reference for electrical contractors, engineers, consultants, designers, installers, inspectors, testers and students who are involved in electrical installations. It provides the best practices and guidelines for ensuring safe and reliable electrical systems in various types of premises and applications.

To access the full standard document, you can purchase it from the Singapore Standards eShop at You can also find more information about the standard from the following sources:

  • SINGAPORE STANDARD Code of practice for electrical installations SS 638 : 2018 (Formerly CP 5) [^1^]

  • SINGAPORE STANDARD CP 5 : 1998 CODE OF PRACTICE FOR Electrical installations [^2^]

  • Amendment no. 1 to CP 5 : 1998 : code of practice for electrical installations (incorporating erratum no. 1, March 2012) [^3^]

How to apply CP5:1998 or SS 638:2018 for electrical installations?

To apply CP5:1998 or SS 638:2018 for electrical installations, you need to follow the steps below:

  • Identify the type and purpose of the electrical installation, such as domestic, commercial, industrial, agricultural, public or special.

  • Determine the characteristics and requirements of the electrical supply, such as voltage, frequency, current, power factor and harmonics.

  • Select the appropriate wiring system and materials, such as cables, conduits, trunking, switches, sockets, outlets and fittings.

  • Design the electrical circuits and layout, taking into account the load diversity, demand factor, diversity factor and maximum demand.

  • Calculate the cable size and rating, based on the current carrying capacity, voltage drop, short circuit capacity and thermal effects.

  • Provide adequate protection against electric shock, overcurrent, earth fault, overload and short circuit, using devices such as fuses, circuit breakers, residual current devices (RCDs), AFDDs and SPDs.

  • Provide proper earthing and bonding of the electrical installation, using methods such as TN-S, TN-C-S or TT systems.

  • Erect and install the electrical equipment and wiring according to the manufacturer's instructions and specifications.

  • Inspect and test the electrical installation before energizing it, using instruments such as multimeters, insulation testers, earth testers and loop impedance testers.

  • Record the results of the inspection and testing in a certificate or report, and label the electrical installation with relevant information such as ratings, ratings and warnings.

What are the benefits of complying with CP5:1998 or SS 638:2018 for electrical installations?

Complying with CP5:1998 or SS 638:2018 for electrical installations has many benefits, such as:

  • Ensuring the safety of people and property from electrical hazards.

  • Improving the efficiency and reliability of the electrical systems and equipment.

  • Reducing the energy consumption and carbon footprint of the electrical installations.

  • Minimizing the maintenance costs and downtime of the electrical installations.

  • Enhancing the aesthetics and functionality of the electrical installations.

  • Meeting the legal obligations and standards requirements in Singapore.

What are the challenges of complying with CP5:1998 or SS 638:2018 for electrical installations?

Complying with CP5:1998 or SS 638:2018 for electrical installations may also pose some challenges, such as:

  • Keeping up with the changes and updates in the standard and regulations.

  • Obtaining the necessary permits and approvals from the authorities and stakeholders.

  • Finding qualified and competent personnel to design, install, inspect and test the electrical installations.

  • Sourcing for suitable and quality materials and equipment for the electrical installations.

  • Balancing between cost-effectiveness and performance of the electrical installations.



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