General-Purpose, Liquid Flow Switches, the Series FS250 – FS251

(NEMA1 version), and FS254 (NEMA4 version). These flow switches incorporate key changes to address customer expressed needs of greater reliability and lower flow sensing capabilities in a general purpose flow switch.

• Universal design serves the widest variety of applications
• For starting or stopping electrically operated equipment such as signal lights, alarms, motors, automatic burners, metering devices and others.
• Replacement for common flow switches from Johnson/Penn, Potter/Taco, Watts,
• 1″ NPT Connection
• Two electrical knock-outs allows connection from either end
• Sensitivity adjusting screw makes flow adjustment easy
• Single pole, double throw snap switch
• EPDM O-ring sealed
• Four stainless steel paddles included -1″, 2″, 3″ & 6″ (25, 50, 80, & 150mm)
• Minimum temperature (fluid or ambient) 32°F (0°C)
• Maximum temperature 227°F (107°C)

Maximum pressure 160 psi (11.3 kg/cm2)

For starting or stopping electrically operated equipment such as signal lights, alarms, motors, automatic burners, metering devices and others. In-line configuration eliminates need for a pipe tee

• For starting or stopping electrically operated equipment such as signal lights, alarms, motors, automatic burners, metering devices and others
• In-line configuration eliminates need for a pipe tee

Sizes available

• 3⁄4″ NPT
• 1″ NPT

• Paddles available for low, medium or high flow
• Two electrical knock-outs allows connection from either end
• Sensitivity adjusting screw makes flow adjustment easy
• Single pole, double throw snap switch
• Hardened stainless steel bearings minimize friction
• Sealed Monel bellows
• Minimum temperature (fluid or ambient) 32°F (0°C)
• Maximum temperature 300°F (149°C)
• Maximum pressure 160 psi (11.3 kg/cm2)

For starting or stopping electrically operated equipment such as signal lights, alarms, motors, automatic burners, metering devices and others

• Universal design serves the widest variety of applications
• For starting or stopping electrically operated equipment such as signal lights, alarms, motors, automatic burners, metering devices and others
• Replacement for common flow switches from Johnson/Penn, Potter/Taco, Watts, Hydrolevel and other manufacturers
• 1″ NPT
• Two electrical knock-outs allows connection from either end
• Sensitivity adjusting screw makes flow adjustment easy
• Single pole, double throw snap switch
• Hardened stainless steel bearings minimize friction
• Sealed Monel bellows
• Four stainless steel paddles included -1″, 2″, 3″ & 6″ (25, 50, 80, & 150mm)

Optional Features

• Two SPDT switches to make or break two separate circuits
• Materials of construction suitable for corrosive liquids
• BSPT threads
• Minimum temperature (fluid or ambient) 32°F (0°C)
• Maximum temperature 300°F (149°C)
• Maximum pressure 160 psi (11.3 kg/cm2)

For heavy duty applications where high sensitivity is required, such as water treatment systems, cooling systems for electronic circuits, compressors, booster pumps, and bearings, and other applications that need instant switching

• In-line configuration eliminates need for a pipe tee
• Very high flow capacity
• Actuates at extremely low flow rate
• Single pole, double throw snap switch
• Switch compartment is completely sealed to protect it from the liquid
• Sensitivity adjusting screw makes flow adjustment easy
• Optional feature
• BSPT threads
• Minimum temperature (fluid or ambient) 32°F (0°C)
• Maximum temperature 225°F (107°C)
• Maximum operating pressure 100 psi (7 kg/cm2)

Sizes available

3⁄4″ NPT

 1″ NPT

For general purpose applications where high sensitivity is required and moderate or low flow rates are encountered such as air conditioning, heating and hydronic systems, water, fuel oil, some viscous liquids and oils in process work

• For general purpose applications where high sensitivity is required and moderate or low flow rates are encountered such as air conditioning, heating and hydronic systems, water, fuel oil, some viscous liquids and oils in process work
• In-line configuration eliminates need for a pipe tee
• High flow capacity
• 1⁄2″ NPT
• Single pole, double throw snap switch
• Switch compartment is completely sealed to protect it from the liquid
• Sensitivity adjusting screw makes flow adjustment easy
• Optional features
• BSPT threads
• Gold plated contacts
• Minimum temperature (fluid or ambient) 32°F (0°C)
• Maximum temperature 225°F (107°C)
• Maximum operating pressure 100 psi (7 kg/cm2)

For general purpose applications that require low flow rate sensitivity. In-line configuration eliminates need for a pipe tee.

• For general purpose applications requiring low flow rate sensitivity
• In-line configuration eliminates need for a pipe tee

Sizes available

• 3⁄4″ NPT
• 1″ NPT

• Single pole, double throw snap switch
• Sensitivity adjusting screw makes flow adjustment easy
• Optional feature
• BSPT threads
• Minimum temperature (fluid or ambient) 32°F (0°C)
• Maximum temperature
• 225°F (107°C) – Stainless Steel models
• 250°F (121°C) – Brass
• Maximum operating pressure 150 psi (10.5 kg/cm2)

Materials of construction

• Brass, carbon & EPDM elastomer (for water); Models FS5 & FS5-D
• Stainless steel, carbon & Buna N (for water or water and petroleum base compounds) Models FS5-S & FS5-DS

For heavy duty applications where high sensitivity is required, such as water treatment systems, cooling systems for electronic circuits, compressors, booster pumps, and bearings, and other applications that need instant switching

• In-line configuration eliminates need for a pipe tee
• Very high flow capacity
• Actuates at extremely low flow rate
• Single pole, double throw snap switch
• Switch compartment is completely sealed to protect it from the liquid
• Sensitivity adjusting screw makes flow adjustment easy
• Optional feature
• BSPT threads
• Minimum temperature (fluid or ambient) 32°F (0°C)
• Maximum temperature 225°F (107°C)
• Maximum operating pressure 100 psi (7 kg/cm2)

Sizes available

3⁄4″ NPT

 1″ NPT

For hazardous environment applications requiring a NEMA 7 (Class I, Group C or D) or NEMA 9 Class II, Group E, F, or G) rated flow switch

• 11⁄4″ NPT
• Brass with sealed tube construction
• Single pole, double throw snap switch
• Magnetic switching mechanism
• Sensitivity adjusting screw makes flow adjustment easy
• Paddles can be trimmed to suit application needs
• Minimum temperature (fluid or ambient) 32°F (0°C)
• Maximum temperature 300°F (149°C)

Optional features

• Extended paddle arm
• Stainless steel body and paddles
• BSPT threads

Maximum operating pressure

• 300 psi (21 kg/cm2)
• 1000 psi (70 kg/cm2) – Stainless Steel models

Universal design serves the widest variety of large pipe applications, including heating and hydronic systems, air conditioning, refrigeration and process work

• Brass with sealed tube construction
• Single pole, double throw snap switch
• Magnetic switching mechanism eliminates need for bellows
• Sensitivity adjusting screw makes flow adjustment easy
• Paddles can be trimmed to suit application needs
• Minimum temperature (fluid or ambient) 32°F (0°C)
• Maximum temperature 300°F (149°C)

Optional features

• Extended paddle arm – Model FS7-4L
• Two SPDT switches to make or break two separate circuits
• Stainless steel body and paddles
• BSPT threads

Maximum operating pressure

• 300 psi (21 kg/cm2)
• 1000 psi (70 kg/cm2) – Stainless Steel models

For applications requiring a water-tight, dust-tight or a NEMA 4X rated flow switch 11⁄4″ NPT

• Brass with sealed tube construction
• Single pole, double throw snap switch
• Magnetic switching mechanism eliminates need for bellows
• Sensitivity adjusting screw makes flow adjustment easy
• Paddles can be trimmed to suit application needs
• Minimum temperature (fluid or ambient) -65°F (-54°C)
• Maximum temperature 300°F (149°C)

Optional features

• Extended paddle arm
• Stainless steel body and paddles
• BSPT threads

Maximum operating pressure

• 300 psi (21 kg/cm2)
• 1000 psi (70 kg/cm2) – Stainless Steel models

For general purpose applications with environmental exposure or those requiring a water-tight, dust tight, or a NEMA 4 X rated flow switch 1″ NPT

• Sealed Monel bellows
• Single pole, double throw snap switch
• Four stainless steel paddles included -
• 1″, 2″, 3″ and 6″ (25, 50, 80 and 150mm)
• Sensitivity adjusting screw makes flow adjustment easy
• Minimum temperature (fluid or ambient) 32°F (0°C)
• Maximum temperature 225°F (107°C)
• Maximum operating pressure 160 psi (11.3 kg/cm2)
• Replacement for NEMA 4X-style flow switches from
• Potter/Taco, Watts, Penn and other manufacturers

Optional features

• BSPT threads
• Gold Plated Contacts