How Do Float Switches Work (Diagram & Working Principle)

Float Switch Diagram - How Do Float Switches Work

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In the past, old float switches worked by opening and closing dry contacts to send electrical signals that set off a low water level alarm.

How Do Float Switches Work Diagram

They used magnetic reed switches that would complete the circuit once the float reaches its lowest point in the water (or when the storage tank is empty). The magnet would disconnect once the water reaches the adequate level again, opening the circuit back up. These old float switches didn’t have many operations and needed to be replaced about every 3 years or so, making them expensive to keep up with. However, new float switch manufacturers are producing water level control technology that is getting rid of old float switches for good.

How New Float Switches Work

Float switches of the 21st century have come much further in the amount of operations your float switch can perform.

For example, Water Level Controls is a float switch manufacturer that is revolutionizing the way float switches are used for water level sensing.

Water Level Control’s NEW Float switches work by using probes (instead of floats) to detect or (sense) water levels in a storage tank (water, oil, gas, etc).

How Float Switches & Water Levels Controls Work

The sensor probes actually act as their own sensors and do not pass electricity through the probes which keeps them from fouling, degrading and deteriorating. Also, all of the electronics are built into the head so you can connect directly to your control panel. Once the water level is detected by one of the sensors, this causes one of six alarms to be triggered (High Alarm, Low Alarm, Fill Start, Fill Stop, etc). Depending on the type of float switch you have, there can be single point alarm or a multi point alarm that is triggered.

Different alarms control different start and stop mechanisms. For example, if a low alarm was triggered in a water storage tank, that alarm could do one of 2 things (or both in some setups).

How Single Point & Multi Point Switches Work

In a single point float switch, a low alarm sensor will trigger an LED light on your control board

How Single Point Float Switches Work

In a multi point float switch, a low alarm could trigger the LED light to turn on and send a signal to turn on an automatic water pump to refill the water back to the preprogrammed water level.

How Multi Point Float Switches Work

Also, in a multi-point float switch, the process could go even further by programming your automatic pump to stop after the water level has reached the Fill Stop probe.

In the most basic way to say it, float switches detect water levels and provide a signal to a computer to tell it what to do once the water reaches different probe levels. If the water level is too low, it will signal a low alarm and fill up the water, if the water level is too high, it will send a signal high alarm signal and automatically drain the water etc. This helps cooling tower operators keep their water levels at the adequate height “automatically” without manually performing these operations manually themselves.

Almost any storage tank that uses float switches can use this technology and should. These water levels controls last 5 times as long for only double the price of a typical float switch.

New Float Switch Working Principle

Float switches and water level controls usually start out closed, meaning there are no alarms that need to be triggered because the water level is at the predetermined height.

Once the cooling tower starts using the water for its industrial processes, the water level starts dropping. No alarms have been triggered at this point.

Float Switch Working Diagram - No Alarms Triggered

No Alarms Triggered

Once the water level drops below the probes, an conductive signal is passed between the probes telling the low alarm to trigger.

Float Switch Working Diagram - Low Alarm Triggered

Low Alarm Triggered

Once the low alarm is triggered it can be programmed to tell the fill start to begin filling up the water.

Float Switch Working Diagram - Fill Start Triggered

Fill Start Triggered

Finally, once the water reached the predetermined height, the fill stop kicks in and the process starts all over again.

Float Switch Working Diagram - Fill Stop Triggered

Fill Stop Triggered

With proper maintenance, your cooling tower float switches can last for years of operation. Most float switch failures usually happen due to fouling, degrading, or deteriorating. Cooling tower coatings can protect your storage tank, but what’s protecting your float switches? Our water level controls can replace your float switches for good and will never foul, deteriorate or degrade do to any water quality. View our float switches for sale

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