Failures in Outlet Testing
A few months ago I was experimenting with electrical grounds and contemplating just how 3-light testers work. So I downloaded a schematic and took one apart. As I drew the diagram I noticed something very odd about its operation. While the 3-light tester would be able to identify many circuit problems such as a missing Ground or swapped Hot and Neutral wires, there didn’t seem to be any way for it to identify a situation where the Ground and Neutral were both at 120 volts and the Hot wire was at ground. How does this error occur? Let’s say you have ungrounded power outlets in your home, office, or campsite that never had a safety ground wire originally. This was common in pre 1970’s wiring so it’s often found in old buildings. You want “grounded” outlets, so you pay an electrician to replace the old “ungrounded” outlets with new “grounded” outlets.
(To see a demonstration video of what Mike is talking about, check out his video here! This should be required viewing by every RVer! Gary)