switch. The entire assembly can be mounted at any
switch casting is dry. The switch is mounted in the
magazine flooding system, and a sprinkling control
predetermined level, and the switch can be made
valve is installed between the switch and the firemain.
normally open or closed by reversal of the core. Level
When the sprinkling control valve is opened, water
conditions are indicated as normal, above normal, or
floods the switch casting and shorts out the 5-watt
resistor. With the supervisory resistor shorted, a
current of sufficient value to operate the alarm will
MAINTENANCE OF SWITCHES
flow in the circuit.
Switches should be checked periodically to ensure
A water switch is used principally in sprinkling
alarm systems (circuit FH).
that all electrical connections and mechanical
fastenings are tight. Lockwashers must be in place.
Liquid-Level Float Switch
Avoid overtightening the packing and nut on
watertight rotary switches, as excessive pressure on
A relatively new development in indicating alarm
the switch shaft will cause improper positioning of the
and control functions, the liquid-level float switch
(fig. 2-19), is replacing the float-and-switch
Remove dirt and grease from switch and relay
combination found in tank- and bilge-level alarms.
contacts with a cloth moistened with an approved
This float switch has a doughnut-shaped, floatable
solvent. No lubricants of any kind should be applied
magnetic core operating over an encapsulated reed
Figure 2-19.--Liquid-level float switch.