What's the Big Deal About Reversed Polarity?

Posted by: Elementary Property Inspections |

When inspecting homes in the Niagara Region and beyond, we often come across one or more outlets that have reverse polarity, especially in older homes. When we inspect houses where an amateur has been doing electrical work, there’s a good chance we’ll find outlets with reversed polarity. This happens when the hot and neutral wires get flipped around at an outlet, or upstream from an outlet. Reversed polarity creates a potential shock hazard, but it’s usually an easy repair.

For a standard outlet, there are two wires. There’s a white wire that is grounded (or connected) to the Earth and is often called a neutral wire. There is also a wire behind the outlet that isn’t grounded, it’s called the hot wire and it carries electricity. On a two-pronged plug, that’s what the smaller slot on your outlet is for. This wire can be any color except white, usually, it is red or black. A circuit is completed by a hot wire coming in contact with the ground, you will get shocked if you touch a hot wire while standing on the ground because you have now become part of the circuit.

To help make electrical devices safer, some plugs are polarized. This means that one blade is larger than the other, and the larger blade will only fit into the neutral side of an outlet.

Let’s look at the example of a slice of bread that gets stuck in the toaster. If you look in the toaster and see that the heating elements are off, you may assume it’s safe to stick a knife in the toaster to your bread. You *should *be safe doing this because the switch that controls the flow of electricity to the heating elements in the toaster shuts off the hot wire. Unfortunately, your toaster is plugged into an outlet with reversed polarity, so the switch on my toaster is shutting off the neutral wire instead of the hot. This means there is always electricity at the heating elements. As soon as somebody sticks a knife into the toaster, electricity will travel up the knife, through their body, and back to the earth. Mom was right all along.

To correct reversed polarity outlets, hire an electrician. Although it is often as simple a swapping the wires at the outlet, that’s not always the case. If the wiring appears to be correct, then the wiring error happened somewhere upstream from the outlet. Now the electrician needs to trace down the wires to figure out exactly where things went wrong and fix it there. Simply swapping the wires at the outlet would not be an acceptable fix.

The bottom line is that reversed polarity at outlets is a shock hazard, but electronic equipment plugged into an outlet with reversed polarity will still function. Don’t assume that your outlet is wired properly just because it “works”. You can test for reversed polarity at your outlets with an inexpensive outlet tester you’ll find at any home improvement store. And if your home inspection reports that you have outlets with reversed polarity, have the wiring repaired by a licensed electrician.