My experience is less than 30% of electricians get this right.

That statement is a little harsh, but it not all their fault:

1. Lack of Safety Policy is probably number one

2. Lack of proper tools

3. Lack of Training (All Electricians should have been trained, but refreshers never go a miss).

Remember “OFF AIN’T OFF UNTIL TESTED”

The Procedure is:

Identify ALL sources of supply are OFF

Visual Inspection of Test Instrument

Test Instrument for Function on known Supply

Conduct Measurement on Asset wearing Insulating Gloves & Face/Eye Protection

ReTest Test Instrument for Function on known Supply

If you leave the Work Area ReTest.

Some of the problems occur finding a “Known Supply” if the board has been Isolated. This forces the Test to be conducted on upstream known supply and higher fault current (Not Good).

Once a Test is skipped because of Production pressures this reinforces a “Trust its OFF” culture.

I like Proving Units, they provide a known supply right at the Work Area, they eliminate testing on higher fault currents, and they help to reinforce a Safety Culture.

Maintenance Managers its Cheap, Easy to Implement, and Significantly Improves Safety.

3Phi Reliability Ask for a Lock Out Tag Procedure.