Electric Distribution Systems Guidelines

OMB Control Number 3041-0029

Investigation Guideline
PRODUCT: HOME ELECTRICAL DISTRIBUTION SYSTEM COMPONENTS
15- AND 20-AMPERE ELECTRICAL RECEPTACLES
Appendix: 86
Date Amended:January 9, 2004
I. INTRODUCTION
A. Background Information
According to the 1998 Residential Fire Loss Estimates, receptacles were associated with an
estimated 3,800 fires resulting in 30 deaths, 120 injuries, and $52.6 million in property losses.
Despite the CPSC staff-proposed changes to Underwriters Laboratories (UL) Standard 498
(covering electrical receptacles) which became effective in 1995, the number of fire deaths and
injuries (40 deaths and 120 injuries) remain similar to those estimated in 1994.
The purpose of this investigation is to learn more about the characteristics of electrical
receptacles that overheat, arc, smoke or start fires and the circumstances under which such fires
occur. The causes of receptacle fires may be many and varied; we would like as much detail as
possible regarding the cause for each case. We are interested in data that capture (1) the
physical characteristics of the electrical receptacle and (2) the design or installation features,
including the outlet box, pigtail wiring, terminations, branch circuit wiring, and loading that
may have contributed to the failure of the receptacle. The data collected may be drawn from a
variety of sources, for instance, from: interviews, news clips, fire investigation reports, other
official reports, and other relevant materials. We are interested in any information that is
relevant to understanding the cause of the fire or fire hazard as well as environmental
information in the immediate area around the receptacle.
Please remember that no guideline can cover all the pertinent factors that may apply to a
particular incident. Include an explanation in your narrative of all factors that you believe to be
relevant, even when these factors have not been specifically mentioned in this guideline.

B. Product Description
The National Electrical Code (NEC) in Article 100, defines a receptacle as a "contact
device installed for the connection of an attachment plug. A single receptacle is a single
contact device with no other contact device on the same yoke. A [duplex or] multiple
receptacle is two or more contact devices on the same yoke." Consumers variously call them
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Investigation Guideline
by a range of names: wall socket, wall plug, electric or electrical outlet or, simply, outlet. The
NEC is more specific in its distinctions:
•An outlet is "a point on the wiring system at which current is taken to supply utilization
equipment [any equipment or apparatus that uses electric energy for some purpose]"
•A receptacle outlet is an outlet where one or more receptacles are installed.

Figure 1 - Side-wired Grounded Duplex 15A Receptacle (front view)

Figure 2 - Back-wire Receptacle (rear view)
The push-in terminals on the back (4 shown, or
sometimes 8) are typically sized to accept 14AWG or
12AWG copper wire as appropriate for 15A or 20A
receptacles. A slot next to each terminal hole allows
inserting a flat-blade screwdriver to release wires from
the terminals. Note here that a 1989 CPSC report
suggested that removing wires and replacing them in the
push-in terminals may reduce retention forces and
weaken the electrical connection.

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Investigation Guideline
Outlet boxes: Receptacles, switches, and fixtures (ceiling- or wall-mounted luminaires, for
example) are typically required to be installed in outlet boxes that provide safe means to
assemble and protect the electrical connections and to support the electrical device. The boxes
may be either metal or non-metallic but should always be certified by a recognized national
testing laboratory (such as Underwriters Laboratories, Inc. (UL), among others). The figure
below shows a back-wired, grounded duplex receptacle installed in a molded, non-metallic
outlet box (on the left) and two others, side-wired with screw terminals, ready to be installed
in metal boxes (below and right). Notice that the center outlet is the end of a circuit while the
outlet on the right is "daisy-chained." Power comes into the receptacle from one set of
conductors. A second set of conductors, which is attached to the second set of terminal on the
receptacle, supplies power to another outlet "downstream" on the same branch circuit. Notice
that the grounding wires are spliced together with a “pigtail" wire that is attached to the single
grounding terminal on the receptacle.

Figure 3 - Outlet Boxes with Installed Grounded Receptacle
Although grounded receptacles are typically installed with the ground pin contact beneath the
plug blade line contacts, no requirement exists in the NEC for either orientation. Some have
argued that the orientation illustrated in Figure 3 may allow the "knife-edge" of a fallen metal
object to come across both blades of the loosened plug of an electrical cord and cause serious
arcing that could ignite adjacent combustibles or may permit easier accidental contact with
and electrical shock from the ungrounded plug blade. It is unknown if any studies have been
done on this issue.
In addition to the typical wall-mounted receptacle, which may have one, two, four, or even
more receptacles installed, single receptacles may be installed on the floor of a room in "floor
box assemblies," such as the unit shown below.
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Investigation Guideline

Figure 4 - 15 Ampere Floor Box Assembly

Receptacle Identification: The National Electrical Manufacturers Association (NEMA) has
established a coding scheme for various receptacle and plug configurations. These can be
used to identify and distinguish between 15- and 20-ampere-rated receptacles. Complete
tables of NEMA configurations are in many references, including
http://www.gwi.net/images/nema.pdf . The receptacles of primary concern to this
investigation are the typical 115VAC (or NEMA 125V) outlets used in homes. The current
NEMA configurations, typically found in household settings, are shown in Figure 5; their
designations may be used in official reports.

<1-15R

<5-15R

<5-20R

Figure 5-NEMA Receptacle Configurations (found in typical household use)
Not shown in the figure are the older, non-polarized receptacles in which the ungrounded
(HOT) and grounded (NEUTRAL--labeled "W" on the NEMA configuration drawings)
receptacle slots are the same size . For the sake of convenience, the designations "1-15NR"
and "5-15NR" may be used to describe 2-wire and 3-wire receptacles that have flat blade
openings the same size. (Note that 3-wire receptacles are, by default, polarized; a plug may be
inserted in only one orientation, so the Hot and Neutral slots may be the same size in some
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Investigation Guideline
older receptacles. If the receptacle and power cord are properly wired, there is no likelihood of
accidentally plugging the cord in reversed polarity. )
In addition to conventional receptacles, UL also certifies two specialized types of receptacles
that should be used in residential areas. One is Ground Fault Circuit Interrupter (GFCI), which
provides protection against severe electrical shock, especially in damp or wet areas. The other
type is Arc Fault Circuit Interrupter (AFCI), which provides a degree of protection against
electrical fires caused by arcing in electrical devices and installed wiring systems. The NEC
code requires that GFCIs and AFCIs be installed in new homes and during residential
renovations that involve the electrical wiring. GFCIs must be installed in every location (such
as bathrooms, kitchens, basements, garages, outdoors, etc.) where water, moisture, and
dampness may increase the risk of electrical shock and AFCIs must be installed to protect
receptacles in bedrooms. While GFCI receptacles are widely available for a variety of
manufacturers, AFCI receptacles are rare, almost nonexistent. This may be because of the
current interpretation of the NEC requirements concerning AFCI protection. UL lists
receptacle-type AFCIs made only by two manufacturers. However, neither one appears to be
available in the United States in 2003-2004.
Summary of Receptacles: There are a wide variety of 15- and 20-ampere receptacles that can
be used in residential structures. The table below shows a summary of the receptacles
discussed above. AFCI receptacles are included for completeness, although we are not likely
to encounter them in current (2003 and earlier) installations.
Type
Single
Duplex
GFCI
AFCI
(rare)

Characteristics
1 connection point
2 connection points
“Test” and “Reset” Buttons
and additional white wire
“Test” and “Reset” Buttons
and additional white wire

Typical Use
Floor Outlet, Dedicated appliance
Most general-purpose residential applications
Kitchen, Bathroom, Basement and Outdoor
Receptacles (esp. around water and moisture)
Required in Bedrooms per NEC 2002.
Requirement probably met using circuit
breaker AFCIs.

C. Specific Items of Interest
CPSC staff wants to learn as much as possible about receptacles that have suffered fire,
overheating, or arc damage and the circumstances that led to the damage. Contact CPSC
headquarters staff listed below if there are questions about the need for sample collection of
damaged receptacles and/or identical exemplars. Because the receptacle is a mechanical and
electrical point of interaction between the residential installed wiring and the electrical
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Investigation Guideline
appliances or tools being used by the consumer, the process of incident investigation and
sample collection must explore the full range of the receptacle's installation and use.
WARNING: If conducting an on-site investigation, do not disturb or
otherwise attempt to disassemble the receptacle and outlet box yourself. It is
possible for such equipment to sustain internal damage that may not be
visually obvious. Parts of such equipment may be energized even if other
investigators have taken what they believe to be the steps necessary to remove
power. Items in the data record sheet that require access to the interior of
outlet boxes are to be addressed either by obtaining the information from the
fire investigators, electricians, or others involved in the investigation and
repair of incident damage or when accompanied by a qualified electrician
who will disassemble the equipment when necessary for your inspection and
collection. In some cases, you may be limited to recording and
photographing markings and evidence that is visible from the outside.
Photograph the receptacle and the area surrounding the installation if possible. It is best to
capture a sequence of photographs of the device. Start with a panoramic view to show
physical relationships and gradually move in to close-ups. If a power cord or extension cord
plug that was involved in the incident under investigation is still attached to the receptacle, do
not remove it until photos are taken, and then, only if the receptacle face is undamaged and the
plug can be removed without causing additional damage to either the plug or receptacle. After
close-up images have been captured of the front of the receptacle, remove the cover plate (if
you can do so without damaging physical evidence). Attempt to photograph the interior and
determine whether the receptacle has been side wired with the screw terminals or back-wired
with the push-in terminals. If a plug and cord are still attached to the receptacle, slide the
cover plate over the cord to clear the receptacle. DO NOT TOUCH the electrical components
or loosen the receptacle from its mounting until you are certain that the circuit has been deenergized by removing the fuse or turning off the circuit breaker. Always TEST THE
CIRCUIT with needle-point probes connected to a meter or test
lamp, but not a "plug-in" tester. Touch the probes across all three
combinations: Hot-to-Neutral, Hot-to-Ground, and Neutral-toGround to be sure the light stays off, meaning that power is off.

Figure 6 - Test FIRST!

•Visible evidence of damage -- Observing and documenting
external signs of damage may offer clues to what sort of internal
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Investigation Guideline
damage may exist or what caused the events that led to the incident. External
signs of mechanical damage may include a cracked, warped or broken cover
plate or similar damage to the face of the receptacle. Of special concern is
damage that may expose energized, ungrounded conductors, such as the wiring
in the outlet box or internal components of the receptacle. Overheating related
physical damage such as melting or bubbling, pyrolization (darkening, charring,
other evidence of burning), ash or soot, is also important to note. Because UL
generally requires thermoset (non-melting) plastic as construction material for
receptacles and covers, evidence of melting may show that material other than
the receptacle were involved in the fire--typically a power cord, plug, or a direct
plug-in electrical device.
•Concealed damage – There may be internal damage such as poor or
weakened electrical connections, which may be hidden from view while the
receptacle remains installed in its outlet box. If the receptacle is not collected
carefully, the evidence may be irretrievably lost. See detailed instructions in
Section IV, pages 10 and 11 for possible methods of exposing concealed
damage and collecting the incident sample.
D. Headquarters Contacts
Robert Garrett, ES, 301 504-7563, [email protected]
Richard Stern, CRC, 301 504-7620, [email protected]
Risana Chowdhury, EPHA, 301 504-7334, [email protected]

II. INSTRUCTIONS FOR COLLECTING SPECIFIC INFORMATION
A. Synopsis
Use the product code 4061 and use keyword electrical receptacle to ease the computer-based
data retrieval process.
B. Description of the Incident Environment
• Describe the structure where the receptacle fire (or overheating) occurred. What was the age
and renovation history of the structure, the electrical wiring, and receptacles? Where was the
receptacle located? Had there been problems with the device before the incident (for instance,
portable lamp flickered or went out but bulb was good, outlet lost power or felt warm,
complainant heard buzzing, hissing or crackling or saw arcing)?

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Investigation Guideline
• Describe the course of related activities before the receptacle failure and the course of events
directly prior to the fire breaking out. Include the electrical devices in use at the time, such as,
the hair dryer, lamp, TV, or power tool, and whether the receptacle was installed indoors or
outdoors, within the wall, surface-mounted, in a stud-mounted box or open (i.e. not in an
outlet box). The photos below show some examples. Note the environmental (indoor and
outside) conditions immediately before the incident. Describe, also, the historical
environment/climate where the receptacle was located. (For example, was the structure ever
flooded?)

Fig. 7 -- Surface Mounted Fig. 8 -- Stud-mounted Fig. 9 -- Open, unmounted receptacle

• Record statements concerning the suspected cause of the receptacle failure. State who made
the determination of cause. Try to determine exactly what happened to precipitate the fire.
Describe the way the fire unfolded.
• Did anyone witness the fire event? Was anyone in the room with the receptacle when the fire
started? Did anyone enter the room while the fire was already in progress?
• Once the fire started, did the user try to extinguish the fire (him)(her)self? If so, how
successful was the attempt? What means did (s)he use to extinguish the fire? Was the fire
department called? Did the fire department respond? If so, what was the extent of the fire
department’s involvement?
• Describe any damage done to the area where the receptacle was located, e.g., burn marks,
scorch marks, blistering, etc.
• Recount who was injured and how badly. Did anyone require hospital care? Was anyone
permanently injured? Did anyone die? Please record the age, sex, and general health of the
injured persons. Briefly describe the treatments the injuries required and whether any
permanent injuries were incurred.
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Investigation Guideline
• How severe was the property damage and loss? Please provide an estimated dollar value for
destroyed or damaged property and possessions and the source of the estimate.
• Was the receptacle installed in a bedroom and protected by an AFCI?

C. Description of Product
(Full description of the physical receptacle to be collected on the Data Record Sheet.)
• Describe use patterns and characteristics.
• What company manufactured the receptacle? What was the model number, UL markings?
• When was the receptacle installed (or replaced)?
• Describe how the receptacle was installed and the material it was attached to (for example,
flush- or surface-mounted and drywall, concrete block, wooden or metal stud, etc ).
• Did the consumer notice any unusual characteristics about the way receptacle performed?
For instance, did the branch circuit breaker or fuse trip often, or did the receptacle ever seem
warm?

D. Product Safety Standards
UL 498 – Attachment Plugs and Receptacles
UL 514A – Metallic Outlet Boxes
UL 514C – Nonmetallic Outlet Boxes, Flush-Mounted Boxes and Covers
UL 943 – Ground-Fault Circuit-Interrupters
UL 1699 – Arc-Fault Circuit-Interrupters

III.

PHOTOGRAPHS/DIAGRAMS OF INCIDENT SCENE
If the incident receptacle or any remnants are available, conduct a physical investigation. In
order to document the condition of the receptacle and/or outlet box, take as many photographs
as possible before it is removed. These photographs should include close-ups of any
markings/labels on the receptacle as well as clear illustrations of where and how the receptacle
was installed and what damage was done to the room or structure by the event involving the
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Investigation Guideline
receptacle. If the user/owner/complainant took pictures or videotapes of the receptacle, obtain
copies of them. Diagram the room where the receptacle was located, if possible, showing
attached electrical appliances and nearby combustibles.

IV. OBTAINING SAMPLES AND DOCUMENTS RELATED TO THE INVESTIGATION
•Samples: Samples of receptacles and attached plugs are critical to the investigation.
However, due to the nature of receptacle failures, the best samples may be difficult to collect.
Severely damaged receptacles will be the most readily available for collection but will provide
the least amount of information as to the cause of the failure. Nevertheless, it is important to
collect these samples when available.
Incidents where the failure was detected early and minimal damage occurred to the receptacle
and surrounding area would provide the most useful information. It may be more difficult to
collect the slightly damaged sample because careful collection methods may cause some
damage to finished areas where the receptacle is installed. In some cases, purchasing the
sample and repairing the damage incidental to its collection will be necessary. Contact CPSC
staff listed in section I to determine whether the sample should be purchased or not.
When a sample is collected, it is best to retrieve the receptacle intact and still installed in the
outlet box, including portions of the attached electrical appliances (or, at least, their power
cord plugs) by cutting their wires approximately six inches away from the receptacle and
outlet box or from the damaged portion of the power cord. Then the entire outlet box can be
removed from its mounting location. This should not be a problem for severely damaged
samples but for moderately damaged samples, an additional cost to replace the power cord
plug(s), receptacle, outlet box, installed wiring, and some wall board may be required.
Package the sample in a manner that will not further damage the sample or lose any loose
parts.
Detailed Collection Instructions:
Sample collection will require the services of a licensed electrician unlessthe
investigator is properly qualified to perform the needed electrical work. If it is
possible to do so, collect the receptacle and box with the branch circuit wiring
and connected appliance or extension cords undisturbed and still attached to it.
Be certain that electrical power is removed from the circuit before starting.
TEST THE CIRCUIT!

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Investigation Guideline
1)

2)

3)

4)

With side-wired receptacles, if you can not also collect the outlet box,
receptacle-only collection may be accomplished by removing the screws
above and below the receptacle, which secure it to the outlet box. Gently
pull the receptacle from the box to avoid altering the quality of the
electrical connections. Be particularly careful if any wires appear to be
loose under the terminal screw heads. Cut the wires (noting whether
they are copper or aluminum) at least 2 inches or more from the
connections. If the insulation is damaged, cut the wires at least 2 inches
back from the damage.
With back-wired receptacles, removing the receptacle from the outlet
box can significantly alter the condition of the connections and destroy
evidence. If enough residential wiring is left in the wall to replace a new
outlet box (if necessary), dismounting and collecting the entire box is the
best approach. Some of the wall board around the outlet box will likely
have to be removed to get full access to the box unless it is a surface
mounted box (Figure 7). After removing the nails or screws that hold the
box in place, cut the sheathed branch circuit wiring at least 2 inches,
preferably 6 inches, from its entry into the box.
If collecting the entire outlet box is not feasible, first use a similar
approach as with the side-wired receptacle to loosen the mounting of the
back-wired receptacle.
a. Once the mounting screws are removed, try to reach in
behind the receptacle with needle-nose pliers to grasp the
BLACK (Hot) and WHITE (Neutral) wires that are
connected to the back of the receptacle.
b. Pull on the wires (NOT the body of the receptacle) to
draw the receptacle very gently out of the box.
c. If you can not initially reach the wires and there is no other
way to get it clear of the box, pull as gently and slowly as
possible on the receptacle to expose them. Then grasp the
wires as soon as they are accessible to reach with needlenose pliers and pull the receptacle clear of the box.
d. Holding each wire with pliers to absorb mechanical shock,
use diagonal cutters or a similar tool to cut the wires at
least 2 inches from their terminations on the back of the
receptacle.
Protect the exposed wires of a removed receptacle from contact and
bending by forming a shell with stiff cardboard of other similarly rigid
material around the receptacle so that the wires are suspended in space,
not touching the walls of the shell.
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Investigation Guideline
5)

Pack the enclosed receptacle in a larger box, well-surrounded with
loose-fill styrofoam packing material to absorb impacts from shipping.
Label the box for special handling (Handle Like Glass!) before
shipping it to the Sample Custodian.

•Documents: Obtain copies of the fire incident report, insurance documents, and any other
investigative reports of the incident. If the incident site is a school, church, or some other type
of institution, attempt to obtain their official records

V. CORONER’S REPORT AND DEATH CERTIFICATE
In cases that involve death(s), procure the coroner’s report and the death certificate(s).

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Investigation Guideline
DATA RECORD SHEET FOR RECEPTACLE OVERHEATING AND FIRES
1. Task Number _______________________________________________________________
2. Sample Number _______________________________________________________________
3. Date of incident _____________________________________________________________
4. Date purchased / installed _______________________________________________________
5. Characteristics of receptacle:
a. Manufacturer/Model number: ______________________________________________
b. Type (single / duplex) and NEMA designation: (Circle choices and add "N" for nonpolarized)

1-15R >

5-15R >

5-20R >

c.

Marked Rating (Volts/Amps/Hz)? _____________________________________________

d.

Terminations used?: Screw

e.

Properly polarized (Black = HOT, White = NEUTRAL)? Y N

f.

Was Ground Wire Terminal (NEMA 5-) used? Y N Bare Copper? Green Insulated?

Push-in Both (Circle choice)

g. Condition of receptacle (Brief description):____________________________________
____________________________________________________________________________
h.

Is the receptacle a GFCI type? Y

N

6. Characteristics of Installation:
a. Location of Outlet Box and Receptacle: _________________________________________
b. Environmental Conditions and History: ________________________________________
__________________________________________________________________________
__________________________________________________________________________
c. Outlet Box dimensions (L x W x D): _________________________________________

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Investigation Guideline
d. Outlet Box Material: Metal Plastic (Circle choice)
e. Condition of Outlet Box: ____________________________________________________
(dirt, heat, moisture, mechanical or other damage)
f. Outlet Box Fill? No. of wires_______ No. of Splices _______
Type : Wire Nut, Crimp, Solder and Tape, Other ______________________________
g. Wire Type: Copper Aluminum Mixed Other (circle choice) Comments:
___________________________________________________________________________
h. Feed-through Wiring:
Is receptacle at the end of the circuit, connected to one set of two or three wires? Yes/No
Or
Is there a second set of wires connected to the second set of terminals --daisy-chained-- to
carry power out of the box to another location? ___ Yes / No ___
If yes, how many additional outlets (including lighting fixtures) were connected
downstream? ______________________________________________________________
i. No. of wires directly attached to the receptacle? HOT___ NEUTRAL___ GROUND___
j. Over current protection provided by: Fuse Circuit Breaker GFCI CB AFCI CB
(circle choice)
Brand/Model:__________________________________
Rating: _____/_____Volts/Amps .
Was device open after incident? Yes/ No
k. Receptacle installed by: Unknown Electrician Homeowner Other ______________
(circle choice)

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Investigation Guideline
7. Electrical Load on Damaged Receptacle:
a. Describe what was connected (plugged into) Receptacle:
Appliance Type
Ampere Rating
On/Off Switch?
No. of Daily Uses

Yes

No

Yes

No

Smoke /sparks
seen?
Did Power Cord
Plug Fit
Properly?

Yes

No

Yes

No

Too tight
Tight enough
Too loose

Too tight
Tight enough
Too loose

Yes

Yes

No

No

Too tight
Tight enough
Too loose

Yes

No

Yes

No

Too tight
Tight enough
Too loose

b. If the receptacle was daisy-chained and fed power to other outlet, what was the
downstream load? ________________ (Amperes)
8. Had there been any additions, modifications, or repairs made to the receptacle or outlet
prior to the incident? Yes No
9. If so, what was done? ________________________________________________________
________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
10. By whom? _________________________________________________________________
11. Contact the person(s) who did the work described in Item 9 to determine the reason(s) for
the work. If repairs were necessary to correct a prior incident, obtain a detailed explanation
of the repairperson’s opinion as to the cause of the previous incident. Obtain any
information which may be available to support that opinion, e.g., an invoice listing the parts
that were replaced, etc. _______________________________________________________
12. For the incident under investigation, determine if the fire investigators, electricians, or other
involved in the investigation or repair of the incident damage have developed opinions on
the cause(s) of the incident. Obtain and attach detailed explanation of the opinion(s) and the
information on which the opinion(s) is/are based. __________________________________
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Investigation Guideline
13. Were there smoke detectors in the home? Yes / No
14. If yes, how many and where? __________________________________________________
15. Did it sound an alarm? _______________________________________________________
16.Was there a sprinkler system in the home? Yes / No
17.If yes, did it operate? _________________________________________________________
18. Identify the source(s) of information used to answer the above questions ______________
______________________________________________________________________________
19. Please refer to the articles attached in the Appendix for more detailed safety information.
Additional Comments ( If continuing answers from above, include Question Number at left
margin) _________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
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Investigation Guideline
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________

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Investigation Guideline
Appendix
Article 1

Article 2

Article 3

Article 4

Acrobat DocumentAcrobat DocumentAcrobat DocumentAcrobat Document

Page 18 of 18

Appliance Safety Information - ACME HOW TO.com

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Electrical Guide: How To Check for Proper Grounding - ACME HOW TO.com

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How To Check for Proper Wiring

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How-To > Home Maint > Electrical

Caution: Read our advisory about working with electricity
Items Needed:

The wiring in your home consists of the "line" or "hot" wire, the neutral wire
and in for at least the past couple decades, a ground wire. In the United
States the common color coding for these wires are black or red for the hot
wire, white for the neutral wire and green for the ground wire.

Multimeter
or
Continuity tester
Click to add to your
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To test whether an outlet is properly grounded, you will need an
inexpensive tool called a circuit tester (you can also use a multimeter set to
AC voltage appropriate for the outlet you are testing). Standard outlets
have a large slot, a small slot and a "U" shaped hole. In a properly wired
outlet, the smaller slot is "hot", the large slot is neutral and the "U" shaped
hole is ground.

Insert one probe of the circuit tester into the small slot and the other probe
into the large probe. If the circuit tester lights up, you have power to the
outlet. Now place one probe in the small slot and the other probe into the
"U" shaped ground hole. The indicator should light up if the outlet is
grounded. Test both outlets because they can be wired separately. The fact
that one is properly wired does not guarantee that they are both properly
wired.
If the tester does not light, then place one probe into the large slot and the
other probe in the ground hole. If it does light, then the outlet is grounded
but the "hot" and neutral wires are reversed. If it still does not light, then the
outlet is NOT grounded. If the outlet is miswired or not grounded, it should
NOT be used until the problem is corrected.

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Electrical Guide: How To Test an Electrical Outlet for Current - ACME HOW TO.com

How To

Parts Store

Ask the Expert

How To Test an Outlet for Current

Page 1 of 2

Help
How-To > Home Maint > Electrical

Caution: Read our advisory about working with electricity
Items Needed:

You can test an outlet to determine if current is present with a current
tester. If you don't have a current tester, simply use a shop light or other
convenient electrical device. Start by making sure the tester is working and
plug it into a circuit you know is working. Note that if you need to test a
220v outlet, use only a device rated for that voltage.

Multimeter
or
Circuit tester
or
Shop light

Be sure to test both outlets, sometimes only one of the two will work. To
test whether the outlet is properly grounded, follow this link to the article on
grounding .

If there is no current, make certain that the outlet isn't controlled by a
switch. Try all nearby switches and check whether the tester lights up.
Another possibility, if there is no current, is that the fuse has blown or the
circuit breaker has tripped. Click on the links below for more information on
checking fuses and circuit breakers .
If the circuit breakers were not tripped, the outlet may be in a circuit with a
GFCI outlet (ground fault circuit interrupt). If the GFCI outlet has been
tripped, it may cause other outlets on the same circuit to lose current. Look
for an outlet that has a "Test" and "Reset" button. They are often located
near water such as in a bathroom or kitchen. If the outlet has been tripped,
unplug anything that may have caused the fault and then press the "Reset"
button.

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Electrical #1
nal screw on the right side of the outlet. (Be careful not to touch the terminals with your fingers or
any part of your hand.) You should read about 120
volts ac on the meter. If you do, repeat step “4” or
“5” above. If you do not measure voltage at the
slots of the outlet, but you do measure voltage at
the terminals, the outlet is damaged and should be
replaced. Turn OFF the power at the panel before
replacing the outlet.

Problem:
Problem:

Have you ever plugged a radio or lamp into the wall only to find
it didn’t work? Your natural reaction may be to assume the radio
is broken, but it could also be a faulty outlet, a tripped circuit
breaker, broken wiring, or some other failure.

7. Where To Go From Here.
Hopefully by now you have found and fixed the
problem. However, if you still do not measure any
voltage at the terminal screws on the sides of the
outlet, the problem is likely either in the wiring, or
the circuit breaker. You should contact a qualified,
licensed electrician to troubleshoot and repair the
wiring. You can also read the booklet “How to
Troubleshoot Circuit Breakers” for information on
things you can do to check the circuit breaker.

Meterman
How-to
Test it
Yourself

Task Summary:

Illustrations of
recommended
tools (What
tool should be
shown?)

This booklet will lead you through the steps to safely test for
power at a wall outlet then troubleshoot and fix the common
causes if there isn’t. To properly repair or replace an electrical
outlet, first check the outlet for power, then for proper grounding
and polarity (making sure the wires are connected to the proper
terminals). If the outlet checks out OK, the next step is to check
the wiring. Note: These same basic procedures can be used to test
ceiling fixtures and wall switches.

Illustrations of
recommended
tools (What tool
should be
shown?)

Task Summary:

Recommended Tools:
Recommended Tools:

For this project you will need a basic digital multimeter (DMM)
that measures ac voltage and resistance. You should also consider
using a DMM that has a built-in Safety Tester. This is an extra
feature that gives a quick indication whether voltage is present or
not, even if the DMM batteries are dead. This booklet assumes
you already know how to use a DMM to make basic voltage and
resistance measurements. If not, read the booklet “Basic DMM
Measurements” and your DMM owner’s manual before you start
this project.

®

Electrical outlets
Meterman Test Tools
P.O. Box 9090
Everett, WA 98206
tel: 877-596-2680
fax: 425-446-4882
web: www.metermantesttools.com
16435347 B-ENG-N Rev. A

®

®

TM

Helpful tips from Meterman Test Tools

Illustrations of
recommended
tools (What tool
should be
shown?)

Step by step
troubleshooting:

Work
safely!

1. Check the Device.

Electricity can be
dangerous. Protect
yourself and your
home by remembering
to follow a few simple
rules when working
with electrical circuits:

Before you spend a lot of time
troubleshooting the outlet, make
sure the device you are plugging
in to the outlet is working. Try
plugging the device into an outlet
that you know is working. If it
still doesn’t work, the problem is
most likely with the device. (See
the booklet “How to Troubleshoot
Common Household Appliances”
for more information.)

3. Check for Power.
To check an electrical outlet for
power, first make sure the breaker is not tripped. (If the breaker
is tripped, or trips again when
you reset it, read the booklet
“How to Troubleshoot Circuit
Breakers” for more information.)
If the outlet is controlled by a
wall switch, make sure the
switch is in the ON position.

750 OFF 1000

200

750 OFF 1000

200

50V

2000
k

24V

200
k

50V

2000
k

24V

200
k

figure 1

figure 2

2k
200

5V

+ –
MAX

Ω

figure 3

2k
200

5V

+ –

200
10A 200
20m 2m

Ω

200
2

200
m
20
M

110V

2000
k

50V

200
k

24V

figure 4

20k
12V

2k
200

5V

10A

V

20

220V

20k
12V

750 OFF 1000

SAFETY
TESTERTM

200
m
20
M

110V

20k
12V

200

2

220V

10XL

V

V

20

SAFETY
TESTERTM

200
m
20
M

110V

10XL

V
200

V

20
2

220V

200

+ –

10A

Ω

200

How-to safely test electrical outlets

2. Check for Damage.
Inspect the outlet for signs of
damage, such as burn marks,
soot, melted plastic, or cracked
or broken plastic. These are
indications there may be a short
inside the outlet, or that the
receptacle is broken. It is best to
replace any outlet that shows
visible signs of damage. Turn the
power OFF at the breaker panel
before attempting to replace an
outlet.

10XL

V
200
SAFETY
TESTERTM

Set the multimeter to the ac voltage function, 200 volt range
(ranges may vary on different
meters, check your meter manual
if you are unsure of settings),
and connect the test leads to the
COM and V inputs. Insert the
probes, one at a time, into the
long and short slots of the outlet.
(See figure 1.) Make sure the
probes make contact with the
metal conductors inside the outlet slots. Check both the top and
bottom receptacle. With some
outlets, the top and bottom
receptacles are wired separately
from each other – one may work
while the other does not.
The voltage on an electrical outlet is usually about 120 volts. If
the circuit is disconnected or
turned off at the electrical panel
or wall switch then the voltage
should be less than 1 volt.

4. Testing for Grounding and
Polarity on a 3-Slot Outlet:
A 3-slot outlet has a “hot” slot,
a neutral slot and a grounding
slot as shown in Figure 2. The
short slot should be the hot, the
long slot should be the neutral,
and the U-shaped slot should be
the ground. Incorrect wiring on
an electrical outlet not only
leads to problems with electronic equipment and appliances, it
can also present a safety hazard.
With the meter set to the
200 volt ac range, place one
probe in the U-shaped slot and
the other in the long slot. The
meter should read less than 1
volt. Move the probe from the
long slot to the short one. (See
Figure 3) The meter should now
show about 120 volts. If your
readings are the opposite, the

hot and neutral wires are
reversed. Turn OFF the power at
the panel and re-wire the outlet.
5. Testing for Grounding and
Polarity on a 2-Slot Outlet:
While most homes are equipped
with 3-slot electrical outlet,
some older homes still have 2slot. In these homes the outlet
box should be grounded. In
order to test for grounding and
polarity you’ll have to make sure
that there is no paint on the
cover plate screw (if the screw
has paint on it, temporarily
replace it with an unpainted
screw to conduct this test).
With the meter set to the 200
volt ac range, place one probe in
the long slot. Hold the other
probe on the screw head. You
should read less than 1 volt.

Move the probe from the long
slot to the short one. You should
now read about 120 volts on the
meter. (See Figure 4) If your
readings are the opposite, the
hot and neutral wires are
reversed. Turn OFF the power at
the panel and re-wire the outlet.
6. Check the Wiring.
If your readings so far still show
no voltage, you’ll have to test the
wiring inside the junction box.
First, turn OFF the power at the
circuit breaker panel. Remove the
outlet cover plate and remove the
screws at the top and bottom of
the outlet bracket. If your DMM
has a Safety Tester™
feature, use it to check for voltage at the screw terminals on
either side of the outlet to make
sure the power is turned OFF.
Otherwise use your meter in the

200 volt ac range and probe the
screw terminals to verify that
power is OFF. Carefully pull the
outlet out of the junction box.
Look for broken or loose wires
going to the receptacle. Tighten
any loose connections on the
outlet or in the wire nuts inside
the junction box. Replace any
broken wires.
Set the outlet aside making sure
the side terminal screws are not
touching anything inside or outside the junction box. Turn ON
the power at the circuit breaker
panel (remember to also turn on
the wall switch if there is one).
With the meter set to the 200
volt ac range, place one probe
on the head of the terminal
screw on the left side of the
receptacle. Touch the other
probe on the head of the termi(continued on back)

• Always turn the power
off at the electrical
panel before handling
wires or terminals.
Don’t assume that you
know which wire is hot!
Use your meter to
verify the power is off
before handling any
wires or terminals.

• Make sure your meter
is working with a 3point check: Measure a
known live circuit, next
measure the circuit
you’re working on and
finally re-check the
known live circuit.

• Use caution when
measuring live circuits.
Don’t stand in water,
use one hand to probe
whenever possible,
and don’t wear metal
jewelry.

• Only use a meter that
has the proper voltage
ranges for the job at
hand and make sure
the meter has the
proper safety ratings
and protection.