Dwyer Series TDFS2 Thermal Dispersion Flow Switch
Dwyer Series TDFS2 Thermal Dispersion Flow Switch

Dwyer Series TDFS2 Thermal Dispersion Flow Switch

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Dwyer Series TDFS2 Thermal Dispersion Flow Switch is a thermal flow switch that indicates whether the flow rate is above or below a user set flow rate. The unit incorporates two LED status indicators providing visual switch indication. The set flow rate (setpoint) is field adjustable and the unit has both NO and NC NPN outputs. See Figure 1 on catalog page for output and LED actions on change of flow.

Thermal flow switches are sensors with an electrical contact output at a specific flow rate. Dwyer models provide a complete system for leak detection and feature a selectable NO or NC operation. Applications include chillers, hot water heaters, and liquid transfer systems.

Dwyer Series TDFS2 Features

  • Better reliability and life expectancy than mechanical flow switches with no paddles or vanes to wear or break, no jams in the paddle movement, and no seals on movement assembly to wear or leak
  • Not affected by empty pipe as it avoids overheating by actively heating above the process temperature and then cooling down to process temperature
  • Set point is easily field set by tapping the included magnet on the set point target three times at the desired flow rate
  • LED status indicators provide visual switch indication of flow rate in comparison to the set point
  • Low pressure drop; only needs to be inserted 10% into the flow (e.g. 1/8″ for 3/4″ schedule 40 pipe)


  • Boiler flow proving
  • Hot water heaters
  • Chillers
  • Liquid transfer systems
Another Article:


Service Compatible water-based fluids.
Wetted Materials 316SS.
Set Point Range 0.5 to 10 ft/s (0.15 to 3.0 m/s).
Repeatability 0.07 ft/s +3% of set point.
Typical Deadband 0.1 ft/s +15% of set point.
Temperature Limits Ambient: 5 to 140°F (-15 to 60°C); Process: 5 to 140°F (-15 to 60°C); Storage: -40 to 185°F (-40 to 85°C).
Pressure Limits 300 psig (20.67 bar).
Response Time Approx. 8 s.
Power Requirement 9 to 24 VDC.

Ref: dwyer-inst.com

Download Data Sheet: Series TDFS2 Thermal Dispersion Flow Switch

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