Page 288 - 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

Float switches, transducers and

temperature sensors

Float switches, transducers and temperature sensors play a vital part in modern
boosted large-scale cold water systems. The problems encountered are not
just those of how to install them but also where to install them. Installations
of large cisterns are often undertaken in tight and restricted spaces. Difficulties
arise in positioning these components while providing access for maintenance
and inspection.

Here, we will look at these important components.

Float switches
Float switches, often called level switches, provide detection of water levels
within the cistern to activate various other pieces of remote equipment, such
as start/stop functions on boosting pumps, open/close functions on solenoid
valves, water level alarms and water level indicators.
There are many different types of float switch available, and these can vary
in sophistication from simple magnetic toggle switches to ultrasonic and
electronic types. Popular types include:
● magnetic toggle – a simple float switch that uses the opposing forces of
magnets to activate a micro-switch
● sealed float
● pressure-activated diaphragm
p Figure 5.39 Magnetic toggle ● electronic
float switch
● ultrasonic.

Micro-switch de-activated Raised water level Float raised

Magnets with opposing poles repel each other
Micro-switch activated opening and closing the micro-switch to operate
either a booster pump set or solenoid valve

Float lowered

Lowered water level

p Figure 5.40 A magnetic toggle float switch and how it works
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