Before working on electrical equipment why is it good practice to isolate fixed equipment at the circuit breaker and not at the local on - off switch?

What are the hazards of working on fixed electrical gear when isolated only at the local on-off switch ?

 

Hello,

Lock-out / tag-out is a system to have a safe way of working on an electrical / chemical installation.

see the attached PDF for more info, as an example.

Greetings,
Bertus

 

Thank you sir for the prompt reply. Excellent attachment. Will put it to good use.

 

bertus' document contains information that's often used in industry where elaborate procedures are used to protect workers. And rightly so, as most of the stuff is written in blood (like the US national electrical codes and fire codes) -- meaning the rules that evolve are based on situations that resulted in someone's death.

I'd like to suggest that similar techniques and thinking also be used in the home. Those of us who work on things ourselves to fix them often need to e.g. shut off electrical power, water pressure, air pressure, etc. It's a good idea to clearly mark these situations in the event that another household member isn't aware of the work and accidentally turns something back on that shouldn't be on. Thus, for example, when I'm working on an AC electrical circuit in the home, I put red tape over the circuit breaker so that it can't be moved without removing the tape. I also write a warning on it. If I was really paranoid and the circuit was going to be exposed for quite a while, I'd remove the breaker box cover and remove the circuit breaker or disconnect the branch circuit wire.

Simple things, no doubt. But they have protected me against shocks for quite a while. I remember the last 120 VAC shock I got due to my own shoddy procedures -- it was in 1970 and I was visiting my parents in their just-built new house and I wired a fan for my dad under the house -- and neglected to turn off the power. Though that was 40 years ago, it's burned into my memory -- I can still see the bundle of wires I was working on and remember the damp smell of the dirt.