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
