Reverse Polarity

By Frank G. Ross

Improper or careless wiring of receptacles (outlets) is the most common electrical defect found in a typical home.  Improperly wired outlets are a potential shock hazard and can cause electrical equipment to work harder.  Much of today’s electronic devices such as TVs stereos, VCRs, and computers have a 3-prong receptacle with the device wiring looking for power from one direction of the outlet – improper wiring may cause the device to prematurely fail.

All receptacles should be wired such that the hot or live (black) lead is connected to a specific side of the outlet, and the neutral (white) lead to the other.  A switch on an appliance you plug into the outlet, as well as your home, will open and close on the hot side – so when the switch is off, there will be no voltage inside the device or receptacle.  On the typical receptacle, the hot side is the smaller of the two openings.  Likewise the neutral is the wider of the two.  A cord, where it mates to the appliance, will have one of the prongs wider so the hot and the neutral sides line up correctly.

Reverse polarity or hot-neutral reverse occurs when the hot (black) and neutral (white) wire connections are reversed.  The hot wire must be connected to the brass screw, while the neutral wire is connected to the silver screw.  Some older outlets do not have these colored screws, consider upgrading to avoid confusion.

Open ground receptacles indicate that the bare copper wire in the sheathed cable is not connected to the green screw on the receptacle.  It also occurs frequently in older homes originally wired with a 2-wire system (knob and tube or duplex wiring) where an upgrade has included a 3-prong receptacle.  This is an unsafe practice and does not comply with current Electrical Codes – which requires that original and replacement outlet be grounded correctly.  If grounding does not exist, the outlet must be replaced with a 2-prong (non-grounding) receptacle or with a 3-prong GFCI (ground fault circuit interrupter) receptacle.  The 3-prong GFCI receptacle must also be marked as “No Equipment Ground”.

In some installations, the ground (bare copper) wire may have been connected to the metal receptacle box in which case some homeowners use an adapter connected to the cover screw of the outlet to achieve ground.  This is an unreliable method.  It is much safer to upgrade to a 3-prong receptacle with the ground wire connected directly to the receptacle.  Note that some small appliances such as radios and lamps do not require a ground.

An open neutral receptacle does not have a neutral wire connected.  Electrical current works on the simple principle that the hot carries current to the receptacle and back via the neutral wire in a closed system. In open neutral installations, the circuit is completed through the ground wire – which is intended to be the secondary path.  In older installations, the neutral is shared by the opposing hot leg of the 240-volt service.  This results in erratic voltages which could damage electronic equipment and pose a potential shock hazard.

Where the hot and ground wires are reversed you find a very dangerous situation.  The receptacle enclosure and housing of the equipment plug into the receptacle may be energized.  In this case, should you come in close contact; your body will complete the circuit to ground!

Each of these conditions can be tested for and corrected. Although some homeowners may feel confident performing this work themselves, in most cases, electrical work is best left to a qualified professional electrician.

Frank Ross is a Certified Utah Home Inspector for Pillar to Post Professional Home Inspection and a full member of the National Association of Certified Home Inspectors.  Readers may contact Mr. Ross at (435) 867-6400 or frank.ross@pillartopost.com.  You can learn more about Pillar To Post Professional Home Inspection at www.pillarposthomeinspection.com