Reverse Polarity Electrical Outlets
What is Reverse Polarity
"Reverse polarity" is the term used to describe a situation where electrical wires are
connected to the wrong terminals of a receptacle, basically it means that the current is
coming in through the "back door" of your appliance.
I test for reverse polarity during a home inspection and if any outlets are found with this
condition I always discuss the implications with my client. However, there are many
outlets that are hidden behind furnishings or other obstacles during a typical inspection
so I may not find all of them.
Dangers of Reverse Polarity
The reverse flow of the current turns the appliance into a receptacle of electrical heat
and can even spark a fire. Because many appliances will continue to work in this
condition, you may not even know there is a problem. Another danger is that during an
electrical storm when there is a power surge from the utility company, any equipment
that has solid state electronics (such as a computer) may be permanently damaged. Not
all surge protectors will protect you from reverse polarity.
Detecting the Problem
The best way to test for reverse polarity is to use a plug-in voltage tester, which you can
find at most hardware stores for less than $10. The tester plugs into any home outlet and
a chart on the device indicates whether the wiring is correct. Plug the tester into each of
the outlets in the home to conduct a thorough check of the home's receptacles.
Fixing the Problem
After you have determined where the polarity problem exists, turn off the circuit breaker
that supplies that outlet or receptacle. Unscrew the wall cover and use the circuit tester
to be sure none of the wires in the electrical box is still receiving power. Remove the
wiring and reconnect to the proper terminals. Generally this means the white neutral wire
goes to the silver terminal (wide slot) and the black hot wire to the brass terminal (narrow
slot). The green or bare wire (the ground) should connect to the green screw. Put the
wall cover back on and turn on the circuit breaker. Use the plug-in tester again to be
sure the polarity is correct. If it is still not correct, call an electrician, as the faulty
condition lies elsewhere in the electrical system.