Page 62 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

The City & Guilds Textbook: Plumbing Book 1

In domestic properties, the type of electricity supply is 230 V, single phase.
The EAW Regulations require that LIVE WORK IS NOT ATTEMPTED unless it is
impracticable to work on the circuit when it is dead.
All electrical circuits must be properly switched off, isolated and, whenever
possible, locked in the off position.

You must then prove that the circuit is dead by the use of an approved voltage
indicator. Volt sticks and neon screwdrivers are NOT suitable for this purpose.

To safely isolate an electrical supply, you must do the following.
p Figure 1.30 Voltage proving
meter and unit 1 Identify the circuit or the equipment you wish to work on.
2 Make sure that it is convenient to isolate the supply.
3 Isolate the supply at the consumer unit by switching off the miniature circuit
breaker (MCB), residual current device (RCD) or removing the fuse.
4 Using an approved voltage indicator:
a First, check the indicator is working on a known live supply by testing live/
neutral, live/earth, neutral/earth.
b Then use the indicator to check that the circuit you wish to work on is
dead.
c Then re-check that the indicator is still working on the known live supply
once again.
5 Lock off the isolator (RCD, MCB) using an approved lock or keep the fuse you
have removed in a safe place. To be absolutely sure that no one can put the
fuse back in, the safest place is in your pocket!
p Figure 1.31 MCB safety lock 6 Place a notice or sign at the consumer unit advising that the circuit is off and
must not be turned back on.

Temporary continuity bonding
Temporary continuity bonding involves the use of two crocodile clips joined by
2
KEY TERM 10 mm earth cable. This is called a temporary continuity bonding clip.
Equipotential bonding: a All gas, water and central heating copper pipework should be bonded to the
system where all metal main electrical equipotential bonding system. In other words, copper pipework
fixtures in a domestic must be earthed. When we cut into a copper pipe to make a tee connection,
property, such as hot for instance, we in effect disconnect all pipework after the cut from the earth
and cold water pipes, system and, if a fault to earth already exists, then all the pipework after the cut
central heating pipes, gas could become live.
pipes, radiators, stainless
steel sinks, pressed steel The reason for temporary continuity bonding before removing or replacing
enamelled washbasins and metal pipework is to provide a continuous earth for the pipework, to prevent an
steel and cast iron baths, electric shock in the event of any electrical fault. Installing temporary continuity
are connected together
through earth bonding bonding clips before we make the cut will ensure that, once the pipe has been
so that they are at the severed, any bonding applied to the pipework will not be interrupted and the
same potential voltage pipework will not become live. Once the connection has been made, the clips
everywhere. can be removed safely.

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