ELE/Specific Hazards/TBT-ELE-010

Generator Connection and Backfeed Risk

Electrical Safety › Specific Hazards › Generator Connection and Backfeed Risk

Presenter		Project
Location		Date

Backfeed occurs when a generator energises a circuit thought to be dead, putting workers at risk of electrocution.
Connecting a generator directly to a building electrical system without a transfer switch causes backfeed.
Backfed electricity can travel through transformers and energise the public supply network at lethal voltages.
Network engineers and linesmen have been killed by backfed generators connected by untrained persons.
A properly installed changeover switch prevents simultaneous connection of the generator and mains supply.
Portable generators on construction sites must be connected through distribution boards with RCD protection.
The Electricity at Work Regulations 1989 require all electrical connections to be safe and properly made.
Only competent electricians should connect generators to any fixed electrical installation or distribution system.
Generator earthing is critical; incorrect earthing causes the frame to become live during a fault.
Fuel storage for generators must comply with fire safety requirements and be properly bunded.

Kill remote workers	Backfed generators energise circuits that linesmen believe are dead, causing fatal electrocution miles from the generator.
Electrocution on site	Incorrectly connected generators energise exposed metalwork and cables, electrocuting workers who touch them.
Legal compliance	The Electricity at Work Regulations 1989 make it a criminal offence to create dangerous electrical conditions.

Don't

Use a properly installed changeover switch to prevent generator backfeed.
Have all generator connections made by a competent qualified electrician only.
Connect portable generators through distribution boards with RCD protection.
Earth the generator correctly following the manufacturer instructions.
Isolate the mains supply before connecting a generator to any building circuit.
Test the installation after connection to verify correct polarity and earthing.
Position generators outdoors in ventilated areas to prevent carbon monoxide buildup.
Store generator fuel in bunded containers away from the exhaust and ignition sources.
Label the changeover switch clearly showing mains and generator positions.
Inspect generator connections, cables, and earthing before each use.

DON'T connect a generator directly to a building socket or consumer unit.
DON'T energise a generator without confirming the mains supply is isolated first.
DON'T allow unqualified persons to make generator electrical connections.
DON'T operate a generator indoors or in poorly ventilated enclosed spaces.
DON'T use a generator without proper earthing connected and verified.
DON'T bypass the changeover switch to connect generator and mains simultaneously.
DON'T refuel a running generator; shut it down and let it cool first.
DON'T assume a portable generator is safe because it is small and temporary.
DON'T ignore RCD protection requirements for generator-fed distribution boards.
DON'T leave generator cables trailing across walkways without cable protection.

See also: Electrical Safety Awareness | Temporary Electrical Installations

Generate professional Risk Assessment and Method Statements in minutes. 10 document formats, site-specific content, instant Word download.

Toolbox Talk Record