An ‘automatic’ water system must have certain basic control equipment. Special system problems may require additional controls for automatic, safe operation.
Basic controls required include:
Pressure Switch to start and stop the pump at fixed on and off pressures. Without this control, the system would not be automatic. A manual switch is recommended for pumps on farm installations where the pump may be required to run continuously. These switches should be in accordance with Water Systems Council Standards.
Thermal Overload Switch – a device that will automatically shut off the motor if it becomes overheated.
Air Volume Control – to maintain the required volume of air in the storage tank. Various types of controls are available such as those which add air, those which exhaust air, and those that physically separate air from the water in the tank. The type to be used depends upon the particular installation and type of pump used. All automatic water systems that include a hydropneumatic storage tank must have an air cushion above the water in the tank. Without an air volume control of some sort, the system is not fully automatic, since the tank would become waterlogged. Tanks are available with permanent air bags installed for a maintenance-free system.
Optional controls or safety devices include:
A Pressure Relief Valve having a discharge rate which will limit the pressure build-up equal to the tanks maximum working pressure rating should be furnished with water systems that can develop pressures greater than the working pressure rating of the tank.
Lightening Protectors are common and recommended in many pump installations. The protectors are used to protect motor windings against high voltage line surges.
A Low Water Level Cut-Off Switch is recommended where pumps may overpump the source of water supply. This switch stops the pump when water is drawn to a predetermined level, and keeps the pump from running dry.
Loss of Prime Switches are available to protect pumps from running dry after losing prime.