Lock Off / LOTO Procedure: The Complete Guide for Electricians

• Electricity at Work Regulations 1989 (Regulation 12) — requires that adequate precautions shall be taken to prevent electrical equipment from becoming electrically charged during work where this would give rise to danger. This is the primary legal basis for lock off procedures. Regulation 13 further requires adequate precautions for work on or near live conductors, reinforcing the need for proper isolation.
• Health and Safety at Work etc. Act 1974 (Sections 2 and 3) — places a general duty on employers to ensure the health, safety, and welfare of employees and anyone else who may be affected by the work. Implementing LOTO procedures is part of this duty.
• Management of Health and Safety at Work Regulations 1999 — Regulation 3 requires risk assessments that identify the need for safe systems of work including LOTO. Regulation 4 requires the implementation of preventive and protective measures identified by the risk assessment.
• HSE Guidance Note GS 38 — while primarily about test equipment, GS 38 is integral to the safe isolation and proving dead process that forms part of the LOTO procedure. It sets the standard for voltage indicators and proving units used during the prove-test-prove sequence.
• BS 7671:2018+A4:2026 — Chapter 46 (Isolation and Switching) sets out the requirements for isolation, switching off for mechanical maintenance, emergency switching, and functional switching. Regulation 462.2 specifically requires that a means of isolation shall be provided to enable the installer or user to disconnect the installation from every source of supply.

• MCB lock off devices — clip over the MCB toggle in the OFF position and accept a padlock through the hasp. Available in universal designs that fit most brands (MK, Hager, Schneider, Wylex, Crabtree) and brand-specific designs for a tighter fit. Typically made from glass-filled nylon for durability. Cost around two to five pounds each.
• Fuse carrier lock off bags — for rewireable fuse boards, the fuse carrier is removed and placed in a lockable bag or pouch that accepts a padlock. This prevents anyone from reinserting the fuse carrier while you are working on the circuit. The bag should be clearly labelled and visible at the distribution board.
• MCCB lock off devices — moulded case circuit breakers are larger than MCBs and require dedicated lock off devices. These typically fit over the MCCB handle mechanism and accept a padlock. Some MCCBs have built-in lock off facilities with a padlock hasp integrated into the breaker design.
• Isolator switch lock off devices — for rotary isolators, handle- operated switches, and main switches. These typically clamp around the handle or fit over the switch mechanism to prevent operation. Multi-point lock off hasps allow several padlocks to be applied to a single isolator.
• Plug lock off devices — for locking off plug-connected equipment. The plug is enclosed in a lockable box or pouch that prevents it from being reinserted into the socket. Used for portable appliances and plug-in equipment.
• Personal padlocks — each electrician must have their own personal padlock with a unique key. Padlocks should be non-conductive (nylon body) or insulated, with a hardened steel shackle. Red is the standard colour for danger/ electrical isolation padlocks. Keep the key on your person at all times — never leave it in the lock or give it to someone else.
• Warning tags — pre-printed "DANGER — DO NOT SWITCH ON" tags with space for your name, date, circuit details, and contact information. Available in PVC or laminated card for durability. Attach with a cable tie or integral loop through the padlock shackle.

Individual Circuit Isolation

• Switch off the individual MCB protecting the circuit you are working on.
• Apply an MCB lock off device and your personal padlock.
• Attach a warning tag with your details.
• Prove dead at the point of work using GS 38 compliant equipment (prove-test-prove).
• If the circuit may have multiple supplies (e.g., ring final with a spur from another board), identify and isolate all supply points.

Full Board Isolation (Consumer Unit Change)

• Isolate the supply to the board at the upstream point — the main switch, the service head isolator, or the DNO cut-out (if a registered electrician authorised to work on the supply side).
• Apply a lock off device and personal padlock to the upstream isolator.
• Attach a warning tag. Consider also locking off the main switch on the board itself as a secondary precaution.
• Prove dead on the supply tails at the board — both line and neutral, between all conductors.
• For consumer unit changes, consider energy stored in capacitors or batteries (e.g., UPS or EV charger systems) that may maintain voltage even after the mains supply is isolated.

• Multi-lock hasp — a device that accepts multiple padlocks (typically 4, 6, or 8). The hasp is fitted to the lock off device at the point of isolation. Each person working on the circuit applies their own personal padlock to the hasp. The isolating device cannot be operated until all padlocks have been removed. This ensures that no one can re-energise the circuit while any person is still working on it.
• Group lock box — for complex isolations involving multiple points of isolation (e.g., a machine with several electrical, pneumatic, and hydraulic supplies), a group lock box is used. The keys from all the isolation point padlocks are placed in a lock box, and each person working on the equipment applies their personal padlock to the lock box. The isolation point padlocks cannot be removed until the lock box is opened, which requires all personal padlocks to be removed first.
• Permit to work system — on commercial and industrial sites, multi-lock LOTO is often managed through a formal permit to work (PTW) system. The responsible person (authorised person) issues a permit that specifies the isolation points, the lock off requirements, the people authorised to work, and the conditions for re-energisation. The permit is not cancelled until all locks have been removed and all persons have signed off.

• Safe isolation method statements — step-by-step procedures tailored to the specific installation, covering circuit identification, isolation points, lock off device selection, proving dead sequence, and re-energisation.
• Risk assessments — covering the specific hazards of the isolation process, including electric shock from incorrect isolation, arc flash from operating switchgear, and stored energy hazards.
• Permit to work templates — for commercial and industrial work requiring formal permits, the AI generates pre-filled permits with the correct isolation points, safety precautions, and authorisation fields.
• Training and competence records — Elec-Mate's training courses include working at height, manual handling, asbestos awareness, and site safety — all of which contribute to the competence needed to carry out safe isolation and LOTO procedures.