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How does a paddle flow switch work?

Flow switches are used in a variety of ways; to monitor flow rates, to trigger a warning if the flow rate falls outside of the pre-set parameters, or to protect a pump. Paddle flow switches are generally used for the detection of flow and the measurement of fan or pump speeds. But how does a paddle flow switch work? We take a look here in our latest article and look at where they can be found.

What is a paddle flow switch used for?

A paddle flow switch is used where fluid flow is present and required to be monitored. An example of where a paddle flow switch might be used is to protect a central heating system’s electric heating element from being energized before the water flow from the pump is established. Flow switches might also be used to trigger an alarm if a fire prevention sprinkler system is activated.

Some of the other applications where paddle flow switches are used include:

  • Boiler protection
  • Pump protection
  • Heat pumps
  • Cooling water or heat exchangers
  • Oil well system testing
  • Drain line flow
  • Relief valve monitoring

How does it work?

This type of flow switch comprises of a paddle system which is designed to be located within the flow. There are two basic designs of paddle flow switch:

Magnetic paddle flow switch design: this solution contains a reed switch above a magnet on the paddle that is located outside the flow of fluid. A second magnet with opposing poles creates the force necessary to reset the switch back into the ‘no flow’ position. When the monitored flow pushes the paddle and changes the position of the magnet in relation to the reed contact it activates the contact. As soon as the flow is interrupted, the paddle moves back to its starting position, which returns the reed contact to the initial position. The force necessary to push the magnet back is provided by the two magnets repelling each other. 

Leaf spring paddle flow switch design: this solution consists of a design whereby as the paddle is displaced by the liquid flow it compresses the leaf spring, touching the contact points and triggering the switch. The resistive force of the leaf spring moves the paddle back to the no flow position.

What are the advantages of a paddle flow switch?

A paddle flow switch is a relatively simple design and as such, has some distinct advantages over other flow switch options:

  • Cost-effective
  • Reliable performance
  • Reduced maintenance costs
  • Easier to install than most other flow meters

Best Pneumatic Systems offers a range of SMC flow switches, including the paddle flow switch. However, if you want further information about how a paddle switch works or are unsure whether a paddle flow switch is the right solution for your application, call our team on 01254 395000 or email us at [email protected].uk.  

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