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LO 6-3 Identify and describe the safety hazards associated with high-voltage chassis systems and outline control practices

1. High-Voltage Hazards and Safety

1.1. Practices to Minimize Electrical Hazards

LO 6-03: Identify and describe the safety hazards associated with high-voltage chassis systems and outline control practices.

 

Practices to Minimize Electrical Hazards

To minimize electrical hazards on most vehicles, technicians should observe the following precautions:

  1. Switch off the main power at vehicle battery boxes. Lock and tag disconnect switches during shift.
  2. Disconnect battery cables on conventional vehicles with 12 or 24 volt electrical systems.
  3. Press the starter button or turn the ignition switch to the START position to verify that correct systems are locked out.
  4. If a machine or piece of equipment contains capacitors, they must be drained of stored energy.
  5. If the vehicle or equipment has an electric motor isolating shutoff switch, shut it off and lock and tag the switch.

High-Voltage Service Tools

All electrical meters and test equipment used on high-voltage systems must be rated to a minimum of CAT III. This standard is set by the International Electrotechnical Commission (IEC). Meter operation should be validated before using. An acceptable procedure is to measure a known low voltage with an auto ranging meter and then use it to test for high voltage without changing the settings. Testing for high voltage is primarily used to confirm that the system is not live before beginning any work. Note that rather than using meters, it is much safer to use OEM software or scan tools. Software-based electronic service tools should be used to monitor live, high-voltage readings. This ensures that there is no connection between the high-voltage circuits and the vehicle technician. Insulated tools to prevent conduction of high voltage should be used when working on circuits with any potential for high-voltage electrical current Figure 20.

   Fig06_20

FIGURE 06-20: Hand tools, with electrically insulated handles, to minimize exposure to electric shocks.

 

Fig06_21

FIGURE 06-21: Leather over rubber ANSI Class 0 gloves.

  
  Technicians Tip  
  High-voltage circuits are not always connected with large cables. The safest way to identify high-voltage equipment or circuits is to first identify high-voltage components and circuits using OEM service literature. Look for high-voltage warning labels and brightly colored orange insulation of the electrical conduit. Inspect the vehicle for any equipment or circuits that may have been added after the truck was built, which could potentially interfere with high-voltage circuit isolation.  

 

High High-Voltage Hazards and Personal Protective Equipment

When working with high voltage, protective, insulating linesperson gloves are recommended. Gloves should be rated for a minimum of 1000 volts. According to the American National Standards Institute (ANSI), Class 0 is the accepted standard when working on electric vehicles. Leather “over gloves” can be used to protect the rubber gloves. Gloves need to be inspected before using and tested in accordance with manufacturer procedures each time they are used Figure 21.

 

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