Distribution boards are the central hub of a building's electrical system, splitting the main supply into individual circuits. Installing, wiring, and commissioning distribution boards involves working with potentially high fault currents and requires strict isolation procedures. Arc flash during testing or commissioning can cause severe burns and blast injuries. Only qualified and authorised electricians should carry out distribution board work, following approved procedures at every stage.
Key Hazards
Arc flash causing severe burns and blast injuries during commissioning
Electric shock from contact with live busbars during installation and wiring
Incorrect circuit labelling causing wrong circuits to be isolated or energised
Short circuits from tools or loose components contacting live busbars
Control Measures
Ensure the main supply is isolated and locked off before starting any work on the distribution board.
Prove dead at the board using a voltage indicator tested on a known live source before and after.
Use insulated tools and wear arc-flash rated PPE during all distribution board work.
Follow the approved wiring diagram and label every circuit accurately during installation.
Keep the board interior clean and free from cable off-cuts, dust, and loose components.
Torque all connections to the manufacturer's specification and record the values.
Carry out commissioning in accordance with BS 7671 with clear exclusion zones during testing.
Ensure all covers and enclosure panels are refitted and secured before the board is energised.
Complete all required test certificates and records before handing the installation to the client.
Emergency / Rescue
If an arc flash occurs, isolate the supply immediately if safe to do so. Cool any burns with water for at least 20 minutes. Call 999. Do not touch the casualty if they remain in contact with a live source.
Remember
Distribution boards handle the full building supply current and present serious arc flash risk.
Always isolate, lock off, and prove dead before opening or working on any distribution board.
Arc flash during commissioning can produce temperatures exceeding 19,000°C in milliseconds.
Every circuit must be labelled accurately because incorrect labelling causes dangerous errors.
Torque all connections to specification — loose connections cause overheating and fire.
Only qualified electricians following BS 7671 procedures should commission distribution boards.
Applicable Legislation: Electricity at Work Regulations 1989 · BS 7671 (IET Wiring Regulations) · HSG85 (Electricity at Work) · Health and Safety at Work etc. Act 1974