When you think of applications for float switches and other liquid level sensors, HVAC (heating, ventilation, and air conditioning) applications probably aren’t the first ones that come to mind. Nevertheless, float switches are important components in many heating and air conditioning systems, primarily by preventing dangerous overflows. How exactly does this work? Keep reading to find out.

The Function of Float Switches in Air Conditioner Systems

An FS20 Vertical Float Switch from SMD Fluid ControlsTo explain the role of float switches in many air conditioning systems, we first have to go into how air conditioners themselves work. Air conditioners remove heat and moisture from the air by a process called phase conversion. The air conditioner uses refrigerant chemicals and converts them from liquid to gas and back again.

The refrigerant gas vapor moves into a device called a compressor, where it is heated and compressed before being sent to the condenser to be pressurized further into a liquid state. The liquid then moves to an expansion valve, where it suddenly expands back into gas form, lowering its temperature in a process called flash evaporation. It is then sent through the evaporator, where warm air passes over it, being cooled. The process thus repeats.

This cycle results in the slow buildup of liquid condensate which accumulates in a drain pan before emptying outside. However, particles, algae, and other contaminants can build up and impede the draining process. This causes an overflow of liquid that both damages the A/C unit and likely any building in which it’s installed.

Vertical float switches can prevent this harmful overflow by activating when the drain pain reaches dangerous levels, sending a signal to deactivate the compressor.

Float Switches for BoilersA large boiler system such as one which might utilize float switches.

By comparison, boilers are relatively simple in their function. Some fuel like natural gas or oil is used in controlled combustion to heat water past the boiling point. The super-heated water is then circulated throughout the building through radiators, which transfer the heat into the air.

Boilers can also be used for steam power, steam cleaning, sterilization equipment, and more.

If water levels in the boiler circuit drop beyond the point of safe operation, a properly installed float switch can trigger either an emergency shut-off or an automatic water feeder to prevent damage to the system and the surrounding building. Liquid level sensors can also aid in proper pump functioning by accurately keeping track of water volume.

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