Page 676 - 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

defects later they will then know to come to you instead of going directly to
the consumer unit and trying to operate something they shouldn’t. This is why
it is important to ‘lock off’ and label the circuit breaker/s you have isolated.
Remember, if you are in any doubt at all, consult a qualified electrician.

Safe isolation of valves, etc from a fused
connection unit

Some works you carry out will involve a simple change of valve, such as a pump,
zone valve or immersion heater. These are usually connected via a flex to the
fused connection unit. Some fused connection units will have a red neon light
indicating when the supply is on; if the switch is flicked off the light will go out,
but this cannot be entirely trusted as the load may have been disconnected, or
the neon could be broken.
It is always safest to carry out a full isolation of the system following the
p Figure 11.36 Switched fused procedures described, but if this cannot be done the following procedure should
connection unit with neon be adhered to.
1 Locate the source of supply (this will be direct, at the valve’s electrical
connection box).
2 Isolate the source of supply by turning off the switch on the fused
connection unit and removing the fuse. (It is your responsibility to have
control of the fuse and not leave it where somebody can put it back in the
unit – a way to avoid this is by locking the fuse housing, as shown.)
3 Test your voltage indicator on a known good source.
4 Test that the supply is isolated at the valve/appliance electrical point. (Line
to neutral, earth to line, earth to neutral.)
5 Re-test using the voltage indicator using a known good source to ensure your
meter/voltage indicator is still functioning.
6 Once confirmed, you may remove the connections at the valve/ appliance
terminal and change it as required.

Other voltage indicators, such as voltage sticks, are available. These must not
be used to confirm full isolation of any component/circuit – only an approved
voltage indicator may be used.

4 IDENTIFY CRITICAL SAFETY

FAULTS ON ELECTRICAL
p Figure 11.37 Locked fuse
COMPONENTS

All faults – incorrectly fitted cables and components – must be reported to
your boss or the customer. If you have not created the fault but you find a fault
with the existing circuits, an 18th edition electrician must be brought in to
remedy it.

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