Bare in mind that even when your ground circuit is in good shape, you can be electrocuted! The ONLY thing that will save you from electrocution is a GFCI. Every growroom should have all power GFCI protected!
Good Point HD, and one I try to stress to everyone as much as possible. My point is that a safety ground is the bare minimum.
For those that don't know, a GFI is a Ground Fault Interrupt.
Without getting all technical, a fact in electrical flow is that the current (amps) are the same throughout the circuit. It is a physical law.
What a GFI does is measure the current in both sides (the black and the white) and if they are not equal it opens up the circuit or turns it off.
What can happen in an electrical circuit is a wire nut can come off, vibration, UV light rays or HEAT can wear insulation, or a connection can come undone. This live wire can touch the metal housing of a fan or light or touch you personally. What the GFI does is senses current going into one line (black for instance) and not the same going back through the white. When the GFI senses this it opens the circuit or shuts it down.
HD is sounds like an electrician that installs these things in his work, per code. Code requires GFI or GFCI circuit breakers or outlets in wet places like kitchens, laundries, bathroom or outdoors. Think of an indoor grow as a wet place.
One of the problems with GFI outlets is that they are sensitive and will shut down. Something like a worn fan that arcs to the chassis will shut you down. Worn insulation will cause some current leakage and shut it down too. People do not get shocked and everything works and they get frustrated and take the GFI out. That is not advised.
My wife had all these animated Christmas decorations, moving rain deer out in the yard. It rains a lot in the winter and those things would trip the GFI. She got a giant extension cord and put power strip on it around the GFI. I freaked out when I seen that. Funny thing is she loved her decorations more than her own our our pets safety and refused to use the outlets that were protected by GFI.
In a typical GFI installation you have one outlet that is GFI and it protects all the outlets in the circuit that Are Down Stream. If you have say 5 outlets coming from a circuit breaker the outlet closest to the panel has to be GFI. If you pick the second or third outlet those closer to the panel are not protected. This seems to only happen when people retrofit a GFI into a circuit in an existing home. Do not assume all the outlets have GFI protection. It is conceivable that an outlet that appears closer to the panel is not. Know what you have and do not assume.