Technical Bulletin 118 (TB118) issued by the Gas Safe Register, last updated on January 30, 2018, outlines the necessary measures that gas engineers must take to appropriately isolate appliances utilising electrical power. This applies to a wide array of appliances found in both residential and commercial settings. Ensuring secure electrical isolation is crucial to preventing gas engineers from being exposed to potentially hazardous electric shocks, which can range from mild discomfort to fatal consequences.

Legal Considerations

In addition to addressing the repercussions of electric shocks, TB118 highlights the relevant legislation concerning the safe isolation of gas appliances. Specifically, the Health and Safety at Work Act 1974 mandates employers to ensure the safety of employees and others, while the Electricity at Work Regulations 1989 states that all conductors must be inactive during work unless impractical, with engineers taking reasonable precautions. The Health and Safety Executive offers additional information on electrical testing for servicing and repairs of domestic appliances in Engineering Information Sheet No. 35 Revision 1.

Establishing a Secure Working Environment

Maintaining a safe work area is paramount, and TB118 offers specific guidance on electrical isolation procedures. For instance, restricting access to appliances by third parties is crucial, often achieved by setting up a temporary barrier. Other recommendations include preventing the presence of children and pets, informing property occupants of potential testing dangers, and ensuring appliances in a hazardous state are never left unattended. Additionally, providing sufficient space around an appliance is advised to allow quick movement away from live conductors in the event of an electric shock.

TB118 also suggests thoroughly testing the earth path of Class 1 appliances before commencing work to ensure adequate protective earthing in fault conditions. Performing an earth loop impedance test using an instrument providing a numeric reading is recommended, with any identified issues communicated to the customer before proceeding with the work.

A Safe Isolation Procedure

TB118 outlines a guide for a safe isolation process and provides specific advice on various aspects of the procedure. Notably, single-pole or non-contact voltage testers are only suitable for locating live conductors and do not confirm equipment deactivation. Instead, a two-pole voltage detector complying with BS EN 610101-1 is recommended. The bulletin emphasises the importance of isolating equipment to prevent re-energisation, which may involve warning signs, locking devices, fuse removal, or locking fuses and switches open.

Summary of TB118 Guide to Safe Isolation Procedure:

1. Obtain permission and ensure safe isolation of the gas appliance.
2. Remove all load by switching off switches and removing fuse carriers and/or fuses.
3. Test the two-pole voltage indicator on a known voltage source before use.
4. Test for voltage between E-L, N-L, and E-N with the voltage detector, ensuring all other terminals are proven dead.
5. Reprove the voltage indicator by testing on a known voltage source.
6. Conduct a risk assessment before testing and utilise appropriate PPE for safety.

Various instruments are available for locking out and voltage detection, with our specific TB118 Gas Engineer’s Electrical Test Kit meeting all the bulletin’s recommendations.

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