Grounded vs. Ungrounded Electrical Devices, and Outlet Testers

Please note: All persons using power tools on a new site should always use a power cord with a GFCI Ground Fault Circuit Interrupter. Outlet testers will not necessarily inform you if you are protected from a possible lethal shock.

This article pertains to equipment and electronics powered by a battery or AC electrical power using a power cord with an internal ground wire connected to its third-prong grounding conductor pin. This ground conductor wire, which should be termed a bonding wire, inside the power cord is then bonded to some part of the equipment’s metal casing and connects to the ground conductor in the electrical wall outlet and then continues onto the ground bus bar in the electrical mains panel and ultimately to the Earth ground (soil) using a ground rod, ground grid, etc.

Any ungrounded device, termed “floating, that is plugged into a wall outlet receptacle is a possible shock hazard if shorted. Floating devices will also emit a 6-8 foot electric field (in theory, emanating to infinity) from their power cord and the powered device itself, even when the power switch is off.

A two-prong plug on the left and a three-prong plug on the right.Please note: Inserting a two-prong plug into a three-prong power strip will not ground your device because the grounding wire needs to run all the way to the device to be properly grounded. — Photo: A two-prong plug on the left and a three-prong plug on the right. *(Compliant with DOJ requirements.)*
Please note: Inserting a two-prong plug into a three-prong power strip will not ground your device because the grounding wire needs to run to the device to be properly grounded.

While standing within a 6-8 foot radius of any ungrounded electrical device (the reactive near-field), the corresponding E-Field emitted by this “floating” ungrounded device and its cord will couple onto any metallic objects within this radius. This coupling includes any metal enclosures, metal structures, and your epidermis. The closer any of these conductive objects are to electrically floating equipment, the higher the capacitively coupled voltage will be to the receptor, you, also electrically termed the “victim.”

Depending on the resistance of your skin’s natural insulators (usually between 1,000-100,000 ohms differing from one person to another) and the voltage frequency, your resistance to any nearby voltage will vary. However, it is common to all of us that our natural insulation begins to break down once its frequency exceeds 1.7 kHz (Applied Bioelectricity, From Electrical Stimulation to Electropathology, by J. Patrick Reilly, Ph.D., MIT, Johns Hopkins University.)

Battery-powered devices emit DC electric fields. Devices that use an electrical cord emit AC electric fields. Most people do not know that DC static electricity can have a more interruptive effect on electrical equipment than an AC electric field. Anyone who uses an oscilloscope will eventually learn this fact, hopefully not the hard way.

If a third-pronged power cord is plugged into a wall outlet with “open” ground, meaning the ground conductor is not connected (wired incorrectly,) that tool is considered electrically floating.

(Please, do NOT bend a ground pin so your tool can plug into an ungrounded receptacle. And, again, always use an outlet tester to verify if the ground tail is connected.)

We occasionally find homes and offices with unconnected grounding ground tails. It’s always good to have your electrician check that your ground tails are correctly connected to avoid potential shock from a short circuit. While you are at it, check that your GFCIs (Ground fault Circuit Interrupters) are functioning correctly, too. You can easily find an outlet tested that has this function. Here is a good one: Sperry GFI6302 GFCI Outlet/Receptacle Tester

Please, know that an outlet tester will only inform you if the ground conductor is connected to the outlet receptacle via a mechanical ground. It will not indicate whether your electrical safety system EGC, Equipment Ground Conductor, is functioning correctly. You also need to be sure that your circuit breakers are in good working order. We recommend yearly electrical inspections by your licensed electrician and that you maintain all of your electrical equipment and panels.

Schedule an annual checkup of your EGC, Equipment Ground Conductor, the Overcurrent Protection System, and all GFCIs. Elexana LLC can conduct these checks. Generally, electricians do not have the tools to measure ground resistance/impedance. Hopefully, someday, this will change.