The Basics of Electrical Shocks in the Home
Most of the receptacles in a typical house are wired for 120 volt AC electrical power. The power/current flows between the 'hot' and 'neutral'
wires (equivalent to + and - in a DC circuit). To reduce the risk of surges and unstable voltage, the neutral side of utility power is connected to
earth ground using a copper rod driven into the soil near the main electrical panel. The downside of doing this is that the entire earth
becomes a potential conductor. To get an electrical shock you need to make contact with both electrical polarities (hot & neutral). Typically
electrical shocks happen when a persons body is 'grounded' (the worst case is standing barefoot on the damp ground/soil or concrete) and
they come in contact with the 'hot' side of the electrical power. There are many ways this can happen. One of the more dangerous instances
is if a metal cased appliance (e.g. washing machine) has a defect which allows the case to become energized (e.g. insulation on the power
cord is damaged) and a person touches the appliance. It takes very little electrical current to cause death or serious injury. Connecting the
metal case of the appliance to ground, which will happen with a properly installed receptacle and plug, will greatly reduce the risk of electrical
shocks. On houses built before the mid 1960's, the wiring did not incorporate a separate ground conductor. Appliances sold with 3-prong
plugs typically have a warning label indicating that the appliance must be plugged into a properly grounded receptacle. If you have an older
home, you may have to provide a ground to reduce risk of electrical shock. See the chart below for information on 2-prong and 3-prong plugs
3-prong receptacles are the standard type
in use today. The smaller slot is designed
to be connected to the 'hot' (or 'live') side of
the house wiring. The longer slot is
designed to be connected to the 'neutral'
side of the house wiring. The semi-round
hole is for the ground connection (the
Appliances which have a 3-prong plug must
be plugged into a properly wired receptacle to
provide the intended protection against
electrical shock and damage to sensitive
electronic equipment. Typically these are
supplied with metal cased appliances or
appliances that are used with or near water.
They are also used on equipment with
sensitive electronics and surge protectors.
|GFCI & AFCI Protection
GFCI receptacles and breakers are
used to provide additional protection
against dangerous electrical shocks.
See more about GFCI here
AFCI receptacles and breakers are
used to reduce the risk of electrical fire.
See more about AFCI here.
2-prong receptacles were widely used until
the mid 1960's. Until then, most of the
wiring in a typical house did not include a
grounding conductor. The narrow slot is
designed to be connected to the hot side of
the electrical power. Most household
appliances have 2-prong plugs and are not
affected by the lack of the ground
|2-Prong Polarized Plug
There are two types of 2-prong plugs,
polarized & non-polarized. Polarized plugs
are used on some appliances to ensure that
the hot side of the electrical power is
connected correctly to reduce the risk of
electrical shock and/or damage to the
appliance. A non-polarized plug can be
plugged in either way.
|3-Prong to 2-Prong Adapter
An adapter is designed to allow a
3-prong plug to be connected to a
2-prong receptacle. These are typically
misused due to the fact that the green
tab or wire is usually not connected to
ground. To provide the intended
protection the green tab/wire must be
connected to ground.
Typical Defects Noted During Inspections:
- Open Ground - A 3-prong receptacle where the ground connection is not attached. This typically occurs on a house where the older
wiring does not have a ground conductor. Without the ground connection, an appliance with a 3-prong plug will not have the intended
protection. Also, surge protectors require the ground connection to protect sensitive equipment from spikes/surges. Most surge
protectors have a light to indicate lack of grounding and the warranty would be void without grounding.
- Reverse Polarity - The hot and neutral connections are reversed at the receptacle. An appliance with a 3-prong plug or a polarized 2-
prong plug is designed to have the hot side connected properly. A typical lamp can become much more dangerous when plugged into
a reverse polarity receptacle because the switch is no longer turning off the 'hot' connection to the bulb and the outer screw part of the
bulb becomes 'hot'. Because of this, a reverse polarity condition should be corrected.
BRADY HOME INSPECTION
HOUSEHOLD WIRING AND GROUNDING