Ground-fault circuit interrupters (GFCIs) limit the available shock current to personnel by sensing current flow in the neutral and interrupting the circuit at a predetermined value (typically 6mA) that is well below the “let go” threshold.
Let’s take a quick look at the hierarchy of risk control methods [NFPA 70E. Informative Annex F, Table F3]:
- Elimination. The surest method: If you eliminate the existence of 120V circuits, you eliminate the shock hazard that comes with using things that plug into 120V circuits. This simply is not practical.
- Substitution. An example is using a 24V drill instead of a 120V drill. Battery-powered tools carry their own risks and additional costs, plus not all 120V items can be replaced by battery-powered ones. Many kinds of test equipment require 120V power, for example.
- Engineering controls. This means using guards to reduce the chance of electrical contact or arcing faults. A double-insulated tool is an example of where this is done.
- Awareness. A warning sign is an example of something used to raise awareness of a shock hazard. Can you think of any example where this is done with cord-connected equipment?
- Administrative controls. Procedures and job planning tools are used for this purpose. Much can be done here. For example, the procedure calls for inspecting power cords before use and also for routing them so as to avoid damage to them (and not running them through puddles).
- PPE. When all else fails, your personal protective equipment is your last line of defense.
Can you see where GFCI fits in here? It functions like a cross between engineering controls and PPE. Either of these can be defeated by misuse or simply failure of the device. So, don’t rely totally on GFCI protection. Use as many of the other risk control methods as you can. In particular, take a moment to be aware (No. 4) of any shock hazards and adjust your work methods (No. 5) and other factors to reduce the risk. For example, the task is to be done outdoors, but it is now raining. Maybe you can eliminate the hazard (No. 1) by postponing the work until the rain has passed, and things have dried out a bit.
The employer must provide GFCI protection to comply with applicable state, federal, or local codes and standards [110.10(A)]. NFPA 70E is one of those standards, and it requires GFCI protection for maintenance and construction [110.10(B)] or outdoor use [110.10(C)]:
GFCI protection must be provided for equipment supplied by a 125V circuit rated up to 30A. If over 30A, an assured grounding program is an alternative to GFCI protection (see Informative Annex O).
And GFCI protection must be tested per the manufacturer’s instructions [110.10(D)]. Games can be played to avoid work and perhaps reduce some cost. Yep, not having to replace a defective GFCI receptacle can save a company a whopping $16, and not replacing a defective GFCI cord can save an astounding $25.
You could play games with GFCI requirements in general and provide GFCI protection only where absolutely required by law. But since you already have GFCI equipment for compliance purposes, why not use it in all cases? By always ensuring GFCI is provided, you don’t have to worry about inadvertently violating a law or code — and you get the additional safety factor.
It’s not about determining where you don’t have to use GFCI. It’s about using this technology wherever it can help protect people from being exposed to lethal current on 120V circuits. Wherever that risk exists, and it’s greater than the risk involved in resetting the GFCI protection (see the exception in 525.23(B), for example), provide GFCI protection. But also make it clear to users that they have responsibility for testing GFCIs and reducing the likelihood the GFCI will ever need to interrupt the circuit in the first place.
