Megger PAT450 User Manual
WWW.MEGGER.COM
Guide to
Portable Appliance Testing
The word “Megger” is a registered trademark
Table of Contents
Introduction ....................................... 2
What is Portable Appliance
Testing? ............................................... 2
Why Should Electrical Equipment and
Appliances be Tested? ...................... 4
What Inspection and Testing
Needs to be Done? ............................ 6
What Types of Electrical Equipment
Need Visual Examination and
Electrical Testing? .............................. 6
Multiway adapters and GFCI
Adapters ........................................ 7
Extension Cords and GFCI-
protected Extension Cords ........... 7
Hand-held Equipment .................. 7
Portable Appliances ...................... 7
Information Technology (IT)
Equipment ..................................... 7
Portable Equipment ...................... 7
Static Equipment ........................... 8
Fixed Appliances ........................... 8
Built-in Equipment ........................ 8
Construction of Electrical
Equipment ......................................... 8
Class I Equipment ........................ 8
Class II Equipment ....................... 8
Class III Equipment ........................ 9
Visual Examination and
Electrical Testing ................................ 9
Frequency of Visual Examination
and Electrical Testing .................... 9
Operator Checks (Procedure) ..... 10
Formal Visual Inspection
(Procedure) .................................. 12
Combined Visual Examination
and Electrical Testing
Procedure .................................... 15
Electrical Tests .................................. 16
Earth Bond/Continuity Test ........17
Insulation Test .............................19
Protective Conductor/Touch
Current Measurement ................ 20
Differential Leakage Test............ 21
Substitute/Alternative
Leakage Test ................................ 21
Load Test ...................................... 22
Flash Testing ................................ 23
Faulty or Damaged Equipment ...... 23
Missing Equipment .......................... 23
Labelling ........................................... 24
Documentation ................................ 24
Portable Appliance Testers
Available from Megger ................... 25
Megger PAT320 ........................... 25
Megger PAT450 ........................... 26
www.megger.com A Guide to PAT Testing 1
Introduction
We live and operate in a world filled with electrical equipment and
appliances. Electrical “things” fill our homes, our offices, our manufacturing
facilities and the places we go for leisure activity. Electricity poses dangers.
Personnel can be injured, sometimes fatally, by malfunctioning electrical
equipment. Fires caused by defective electrical equipment and appliances
damage property and cause large financial losses for companies. In addition,
ours is a litigious society and lawyers are waiting for opportunities to file
lawsuits.
How does an equipment rental company ensure that a piece of electrical
equipment is electrically sound/safe every time it goes out to a customer?
How do in-house tool cribs ensure that their electrical equipment is safe for
the next person to use it? How do manufacturing companies ensure that the
appliances and equipment they make have no dangerous electrical faults?
Beyond the challenges of protecting personnel and property, many of
our manufacturing plants produce electrical equipment for sale into
the European Union that must meet European standards. While it is the
responsibility of the European importer to ensure that imported items
are safe to European standards, any testing done at the destination can
prove quite costly for the manufacturer when faults are found. Identifying
problems at the manufacturing plant allows for faults to be fixed prior to
shipping and export.
A number of European countries, including the UK, make extensive use of
portable appliance testing to ensure the safety of electrical equipment and
appliances. This booklet will provide a guide to understanding portable
appliance testing and how/where it fits as part of an overall electrical safety
program. While we use the term “portable appliance testing”, a better
description might be portable electrical equipment testing.
What is Portable Appliance Testing?
Portable appliance testing is the visual examination and electrical testing of
portable electrical equipment used in industrial, commercial or public access
areas and locations (including rented property) to ensure they are safe to
use, and cannot present an electrical hazard to the operator or anyone in
their vicinity. Among the issues that can arise are:
2 A Guide to PAT Testing
n Exposure to live, conductive parts due to damage to the outer casing of
the equipment.
n Worn and/or frayed power cord.
n Defective, loose or missing earth/ground connections.
n Failure to identify and correct problems such as those listed above can
result in the electrical equipment becoming a shock hazard or a fire risk.
Many of these problems can be identified visually, but still often go
unreported. Internal faults often go undetected. Portable appliance testing
involves performing a series of tests that, taken together, are designed to
identify any faults or product defects that would otherwise not be detected.
In addition to protecting personnel, regular safety checks of electrical
equipment tend to increase the operational life of that equipment. A
portable appliance tester (PAT) allows the operator to make a number of
safety tests with a single instrument, including:
Earth Bond and Continuity Tests
To verify the integrity of exposed metalwork on grounded appliances.
Insulation Test
To check that equipment conductors are isolated from earth.
Touch Current Test
To check that the equipment case and all exposed metal parts are isolated
from earth/ground.
Differential Leakage Test
To measure the difference in current between live and neutral conductor
during operation.
Substitute/Alternative Leakage Test
To check that the equipment case and all exposed metal parts are isolated
from earth/ground, by use of a safe test voltages as an added protection
against seriously faulted test items.
Functional Load Test
An operational test to ensure the asset works as it should without drawing
excessive current from the supply.
www.megger.com A Guide to PAT Testing 3
Extension Cord and IEC Power Cord Tests
To check extension cords and line cords for safe operation.
In addition to these standard tests, some instruments will perform a flash test
(hipot or dielectric strength test) to test breakdown voltage levels. This test is
normally done on new equipment, articles that have had a major overhaul,
or equipment in the rental industry.
Why Should Electrical Equipment and Appliances be Tested?
The key word is liability. An employer or manufacturer should show as
much concern about safety as does the legal system. The liability is with the
employer or owner of a place of business, or public place, to ensure that all
electrical equipment accessible by employees or the public is maintained in a
safe condition. The liability is with the manufacturer of electrical equipment
to ensure that the equipment is safe for those who operate it. The best way
to ensure electrical safety is by routine visual examination, electrical testing
and documentation.
In the UK, the Health and Safety at Work Act and the Electricity at Work
Regulations, while not specifically dictating that portable appliance testing
must be carried out, do state that all electrical systems (which include
appliances) must be maintained to prevent injury and danger. The Provision
and Use of Work Equipment Regulations 1998 (PUWER 98), made under
the HSW 1974 act, states: “the provision and maintenance of a working
environment for his employees that is, so far as reasonably practicable, safe,
without risks to health, and adequate as regards facilities and arrangements
for their welfare at work”. Regulation 4(1) of PUWER 98 has a more direct
meaning to portable appliances, it states: “Every employer shall ensure
that work equipment is so constructed or adapted as to be suitable for the
purpose for which it is used or provided.” In the USA, the Department of
Labor governs the Occupational Safety and Health Administration (OSHA).
Electrical safety is addressed in rule 72:7135-7221 and the NFPA 70E Electrical
Safety Requirements for Employee Workplaces. The purpose of the OSH
(Occupational Safety & Health) Act, 29 U.S.C. 651 et seq., is “…To assure
so far as possible every working man and woman in the Nation safe and
healthful working conditions and to preserve our human resources.” The
requirements are regularly revised in accordance with the most current
4 A Guide to PAT Testing
practices and technologies, and in response to a request by those concerned
to reflect the most recent editions of NFPA 70E and the NEC. The stated
goal is to “…provide nationally recognized safe electrical installation
requirements,” and to assure that “…the requirements contained in that
standard are current and at the forefront of electrical safety technology.”
The standard states that “…electricity is widely recognized as a serious
workplace hazard, exposing employees to electric shock, burns, fires, and
explosions.” Underlying causes are listed as “...work involving unsafe
equipment and installations, workplaces made unsafe by the environment,
and unsafe work performance.” Hazards stemming from faulty equipment
are further identified as “…faulty insulation, improper grounding, loose
connections, defective parts, ground faults in equipment, unguarded live
parts, and underrated equipment.”
Detailed information on all the definitions and full requirements of portable
appliance testing can be found in the Code of Practice for In-Service
Inspection and Testing of Electrical Equipment (3rd Edition) (ISBN 978-086341-833-4) available from the Institution of Engineering and Technology
(www.theiet.org). Those environments where these regulations are
applicable include any place where someone is employed, areas of public
access, and rented accommodation of all kinds. The Code of Practice for InService Inspection and Testing of Electrical Equipment identifies that regular
visual examination and electrical testing of equipment is an essential part
of any preventive maintenance program. Records of maintenance, including
test results, should be kept throughout the working life of the equipment to
enable the condition of the electrical equipment to be regularly monitored.
While the USA does not have the level of regulation found in the UK, we
are far more litigious. Implementing a regular inspection program that
includes PAT testing of electrical equipment and appliances will help protect
personnel from shock hazards, facilities from electrically induced fires
and businesses from litigation. For businesses that manufacture and ship
electrical products to the European Union, PAT testing at the factory will
ensure that products shipped will pass import testing and not become a
costly problem.
www.megger.com A Guide to PAT Testing 5
What Inspection and Testing Needs to be Done?
The dangers of contact with live electrical parts need no explanation to an
electrician. However, the environments in which the majority of portable
appliances are used are not necessarily where operators would be aware
of the dangers or the implications of damage to equipment. The point of
routine visual inspection and electrical testing is to identify potential hazards
and actual dangers before they turn into an accident.
The hazards that must be identified include:
n Personal exposure to live conductors — electrocution.
n High current faults causing excessive heat — fire.
n Intermittent connection — arcing causing heat and potential ignition.
These hazards can be identified by performing in-service:
n Regular electrical tests.
n Visual examination.
n Combined visual examination and electrical tests.
Various people have responsibility for electrical equipment, including:
n Property owners, equipment owners, company owners, directors, and line
managers etc.
n The person undertaking the formal visual examination and electrical
testing.
n Maintenance managers.
n Operators of the equipment.
What Types of Electrical Equipment Need Visual Examination
and Electrical Testing?
Everything portable or transportable, whether fitted with a plug for
connection to a socket-outlet or connected directly to a fused spur, requires
visual inspection and testing. Such items include:
6 A Guide to PAT Testing
Multiway adapters and GFCI Adapters
Multiway adapters are used to increase the number of connection points
at any location within a property. The use of these adapters should be
avoided wherever possible, and a suitable judgement made during the visual
examination as to how appropriate their use is in any specific application.
Extension Cords and GFCI-protected Extension Cords
An extension cord is used where an item of equipment needs to be supplied
but a convenient socket/outlet is not nearby. Preferably, the use of extension
cords should also be avoided whenever possible. They can present physical
hazards such as tripping that could be avoided if an installation has sockets
in the appropriate place. A GFCI extension cord is one that includes GFCI
protection either at the plug or near the sockets, for powering equipment
used outdoors.
Hand-held Equipment
These appliances require the operator to hold them in their hand(s) during
normal operation (i.e. steam irons, hair dryers, soldering irons and drills).
Portable Appliances
These appliances are ones that can be easily moved while they are energized
and have a mass of less than 40 lbs. Equipment included in this category are
items such as coffee makers and electric space heaters.
Information Technology (IT) Equipment
This category covers IT business equipment that is found in most commercial
offices (i.e. mains-powered computers, telephones, printers, photocopiers,
fax machines, laminators, shredders etc.).
Portable Equipment
This category covers equipment that is:
n Not fixed to the location and weighs less than 40 lbs, (i.e. a small
television).
n Furnished with wheels or casters which is intended to be moved on an
occasional basis. (i.e. commercial kitchen or laundry equipment).
www.megger.com A Guide to PAT Testing 7
Static Equipment
This equipment weighs over 40 lbs and is not provided with a carrying
handle (i.e. large televisions, washing machines, refrigerators).
Fixed Appliances
This equipment is securely installed in one location. Typical appliances in this
category are hot water boilers and hand dryers.
Built-in Equipment
This equipment is intended to be built into a cupboard or similar where
some electrical protection is provided by the location. Typically this
equipment does not have an enclosure on all sides because that side is
inaccessible when the equipment is in use (i.e. a built-in oven).
Construction of Electrical Equipment
The type of asset can be classified depending on the way it is designed
and made, these being Class I, Class II or Class III. The class of construction
determines what electrical tests need to be carried out.
There are also Class 0 and Class 01 assets, which are not within the scope of
this guide.
Class I Equipment
Class I equipment does not rely solely on insulating materials to protect
against electric shock, but includes the connection of exposed metal parts to
the supply earth/ground via the earth/ground conductor in the supply cable,
(sometimes referred to as CPC) in the fixed wiring of the installation. Class I
items can be identified by the presence of an earth/ground conductor in the
supply cable. Some exposed metalwork may be bonded to earth/ground, and
some may be only in casual contact with earth/ground. This casual contact
may give an unexpectedly high bond resistance when tested, and should not
be confused with a poor connection/fail.
Class II Equipment
Class II equipment has extra layers of insulation to provide additional
barriers between the operator and any hazardous voltages, and does not
rely on just one layer of insulating material to protect against electric shock.
There is no provision for connecting any exposed or internal conductive
parts to the system earth.
8 A Guide to PAT Testing
Loading...