Electrical Safety
& Lockout/Tagout

Electrical Hazards in HVAC

HVAC technicians work daily with 24V, 120V, 240V, and sometimes 480V three-phase equipment. Understanding the hazards and safe work practices is fundamental - not just for OSHA compliance, but for going home safely every day.

The Four Main Electrical Hazards

Electric shock - Current passing through the body. As little as 100 milliamps can cause cardiac arrest.
Arc flash - An explosive electrical discharge that releases intense heat (up to 35,000?F), light, and pressure. Can cause severe burns even without direct contact with the arc.
Arc blast - The pressure wave from an arc flash. Can throw workers, collapse eardrums, and destroy equipment.
Electrical fire - Overloaded circuits, poor connections, and insulation failures cause building fires.

? Current Kills - Not Voltage

It is the amount of current through your body that kills, not the voltage alone. However, higher voltage drives more current through body resistance. 100 milliamps (0.1A) through the chest cavity is potentially fatal - that's 150 times less than a standard 15-amp breaker, which is why breakers do NOT protect against electrocution.

Safe Electrical Work Practices

The Most Important Rule: Test Before You Touch

Always verify that a circuit is de-energized using a properly functioning voltmeter BEFORE touching any conductors. Do this every single time - even on a circuit you just turned off. Never assume.

Additional Safe Work Practices

One-hand rule - When working near energized circuits during diagnostics, keep one hand in your pocket or behind your back. This prevents current from crossing your chest and heart if accidental contact occurs.
Insulated tools - Use tools with 1000V-rated insulated handles for HVAC electrical work
Dry footing - Never stand on wet surfaces or in water when working near electrical equipment
Safety glasses - Wear eye protection when working near energized equipment - arc flash can cause permanent eye damage even from a distance
Check the work area - Remove loose tools, materials, and trip hazards before energizing a circuit

Lockout/Tagout (LOTO) - OSHA 29 CFR 1910.147

LOTO prevents the unexpected energization, startup, or release of stored energy during service and maintenance. It is required whenever a technician is exposed to hazardous energy while servicing equipment.

LOTO Six-Step Procedure

Notify - Inform all workers in the area that LOTO is being applied
Identify - Locate ALL energy sources (electrical breakers, disconnect switches, plus pneumatic, hydraulic, or thermal sources)
Shutdown - Use normal stopping procedure to shut down the equipment
Isolate - Open the disconnect switch or breaker to isolate electrical energy
Lock and Tag - Apply your personal padlock to the isolated disconnect. Each technician gets their OWN lock. Apply a warning tag identifying you, date, and reason.
Verify - Try to start the equipment (it should not start). Then use a voltmeter to confirm zero voltage on all isolated conductors before touching anything.

? Restoring Energy After LOTO

When service is complete: (1) Remove all tools and materials from the equipment. (2) Replace all guards and covers. (3) Notify all affected workers. (4) Have all workers remove their own locks and tags. (5) Restore energy. Never remove another person's lock - only the individual who installed it should remove it.

Stored Energy - Beyond Electrical

LOTO covers all forms of hazardous energy, not just electrical:

Capacitors - Store electrical charge and can deliver a dangerous shock even after power is disconnected. Discharge with a 20,000? discharge tool before handling.
Springs under tension - Damper actuators, valve operators
Pressurized refrigerant - Refrigerant under pressure can cause injury if a fitting is opened unexpectedly
Gravity (suspended loads) - Heavy components that could drop if not supported
Thermal energy - Hot surfaces (heat exchangers, heating elements) after shutdown

? Module 1 Module 3: Wiring Diagrams ?