Originally Posted By: rpalac
This post was automatically imported from our archived forum.
Some receptacles are ground rated:
This means that mechanically you can complete the ground by the receptacle box being grounded and when you attach the receptacle to the box the frame of the box and the skeleton of the receptacle mechanically are grounded to each other. typically there is a metal spring clip of sort were the 10/32 screw is connected to the receptacle so it has a zero impedance and good connection.
If your tester shows a good ground, that is why.
If your tester shows a receptacle with a bad ground and when you observe a ground wire connected. You need to take caution. This means that ahead of that receptacle the ground id not complete.
* 1.) The best way to ground a receptacle is by the use of a ground wire from the incoming cable being directly wrapped around the ground screw . Such as what you were looking for.
* 2.) Some receptacles that you will see have the incoming ground wire connected to the back of the metal box and a short wire also grounded to the box and connected to the receptacle. This is also a continuity situation and is also acceptable.
* 3.) Some metal boxes are fed with pipe. Although piping is a great method and is mostly always acceptable as a ground continuity some installations are not acceptable. If the connectors are set screw type. That is okay. If they are compression type they are probably not rated for grounding and are not acceptable. Most piped installations are in commercial locations. These would also have a grounding tail connection between the back of the box and the receptacle or a grounding type receptacle.
* 4.) Of course as previously described, the receptacle can be ground rated. That screw that connects the receptacle to the box is the continuos path of the ground. The caution is that the box must also be properly grounded.
In all cases most people would insert the testing module and see if it shows a good ground. If it does, they accept it.
If it doesn't, It Must be Examined more closely by a qualified electrical to determine why the grounding conductor is not showing continuity.