What is SS 638?
SS 638 is the Singapore Standard for the Code of Practice for Electrical Installations. Published by Enterprise Singapore (formerly SPRING Singapore), it sets out the technical requirements for how electrical installations in Singapore must be designed, installed, tested, and maintained.
Think of it as the rulebook that every electrical contractor and licensed electrical worker (LEW) in Singapore must follow. When testing is said to be done "to SS 638," it means the inspection and test methods follow this standard.
In short: SS 638 is to Singapore electrical work what the Highway Code is to driving — it defines what is safe, legal, and required.
Who Does SS 638 Apply To?
SS 638 applies to virtually all new and modified electrical installations in Singapore, including:
- New buildings and fit-outs (commercial, industrial, and residential)
- Extensions or modifications to existing electrical installations
- Temporary electrical installations on construction sites
- Electrical installations in industrial premises
- Periodic re-inspection of existing installations
If you are applying for a new electricity supply connection from SP Group, or getting a TOP (Temporary Occupation Permit) from BCA, you will need a test report that complies with SS 638.
What Tests Are Carried Out Under SS 638?
A full SS 638 inspection and test typically covers the following:
1. Insulation Resistance Test
This test checks that the electrical insulation on all wiring is intact and not degraded. A high voltage is applied between conductors and between conductors and earth, and the resistance is measured. Low insulation resistance can indicate damaged cables that could cause electric shocks or fires.
2. Continuity of Protective Conductors
This verifies that all earth (protective) conductors are properly connected throughout the installation — from the main earthing point all the way to every socket and appliance point. A break in the earth conductor means a fault current may not trip the circuit breaker, creating a shock hazard.
3. Earth Fault Loop Impedance Test
This measures the total impedance of the earth fault loop — the path that a fault current would take from the point of fault, through the earthing system, and back to the source. The result determines whether the circuit breaker or fuse will disconnect fast enough in the event of a fault to protect people from electric shock.
4. RCD / ELCB Trip Time Test
Residual Current Devices (RCDs) and Earth Leakage Circuit Breakers (ELCBs) are life-saving devices that detect small leakage currents and disconnect the supply within milliseconds. This test verifies that they operate within the required time limits — typically 30ms for 30mA RCDs protecting socket outlets.
5. Polarity Test
This confirms that single-pole switches and fuses are connected in the live conductor only, and that socket outlets are wired with the correct polarity (live, neutral, and earth in the right terminals). Reversed polarity is a common and dangerous wiring error.
6. Prospective Short-Circuit Current (PSCC)
This test measures the maximum current that would flow in the event of a short circuit at the origin of the installation. This value is needed to verify that the circuit breakers installed have sufficient breaking capacity.
Who Can Carry Out SS 638 Testing?
Under Singapore's Electricity Act, testing of electrical installations must be carried out by or under the supervision of a Licensed Electrical Worker (LEW) holding a valid EMA licence. The LEW signs and certifies the test report, which is a legally binding document.
Using an unlicensed individual to carry out testing is illegal and can result in your test report being rejected, your electricity supply not being connected, and potential prosecution under the Electricity Act.
What Happens After Testing?
If the installation passes all tests, the LEW issues a signed Electrical Installation Test Report (EITR). This document is required for:
- Applying for a new electricity supply from SP Group
- Obtaining a Temporary Occupation Permit (TOP) from BCA
- Renewing your Electrical Installation Licence (EIL) with EMA
- Demonstrating due diligence in the event of an electrical incident
If defects are found, the LEW will document them and the installation owner must arrange for rectification before a pass certificate can be issued.
Need SS 638 testing? RES Engineering Services carries out electrical testing for all types of premises across Singapore. Contact us for a quote — we typically respond within one business day.