Page 671 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

Chapter 11 Electrical principles and processes for building services engineering

to carry out this procedure. As with the electrician’s screwdriver, these tools
have been manufactured to prevent the user getting an electric shock if the
system accidentally goes live during the work.

3 ELECTRICAL TESTS AND

PROCEDURES FOR SAFELY

ISOLATING SUPPLIES p Figure 11.26 All-in-one stripper,

crimper and cutter
Being able to safely isolate a supply will not only allow you to do your work but
could also save your life and that of others. Your day-to-day duties may involve
fault diagnostics and rectification, but you shouldn’t leave it at controlling the
immediate risk to yourself – it should be your focus to ensure that others’ safety
is not compromised while you are working or after you leave. Any work that
involves electricity should include the formal process of ‘safe isolation’. This set
procedure (discussed later) lays down a set of rules to be followed to ensure
the part of electrical circuit you need to work on cannot become live under any
circumstances. p Figure 11.27 Electrician’s knife

Testing
You must understand the following electrical tests:

● continuity of conductors: protective conductors, including protective bonding
conductors, and in the case of ring final circuits, live conductors
● insulation resistance
● polarity.

It is essential to use the correct equipment when carrying out these tests.
Testing should be carried out in such a manner that no danger arises to person,
livestock or property.

Multifunction meters

There are many different meters available commercially for testing electrical
circuits, so great care has to be taken to ensure an approved and appropriate
meter is used. Individual meters can be used for continuity, polarity and
insulation resistance but good multifunction meters also do the job by changing
between the required test functions on the dial.
p Figure 11.28 Multimeter/
Before you test, the test meter and probes must be GS38-compliant to protect ohmmeter – the left dial is set
the user from electric shock. Before doing any tests the meter and leads must to the Ω scale and the right
be checked to make sure they are sound with no cracks or damage. The test dial is set at 20 Ω
probes must be protected and ideally no more than 2 mm of metal showing.
The correct meter and settings need to be chosen and understood. Remember, if
you are unfamiliar with the meter, consult the manufacturer’s instructions and
seek advice from a qualified person. The prime concern with testing is safety
and this means ensuring the circuit is completely isolated and secure.

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