McDonnell Miller FS4-3 1inch Liquid Flow Switch with Nema 4×2 Housing

Original price was: $217.93.Current price is: $170.63.

43 in stock

SKU: 38332 Category:


The McDonnell Miller FS4-3 1″ Liquid Flow Switch is a versatile and widely used device for monitoring and controlling liquid flow in various applications. Here’s a breakdown of its key features and benefits:


  • 1-inch NPT connection: Fits seamlessly into standard 1-inch pipe systems.
  • Single Pole, Double Throw (SPDT) switching: Provides two electrical circuits that switch depending on the flow status (on/off).
  • Adjustable sensitivity: Allows you to fine-tune the switch activation point based on your specific flow requirements.
  • Sealed Monel bellow: Ensures reliable operation and leak prevention even under harsh conditions.
  • Universal design: Suitable for various liquids like water, oil, and glycol solutions.
  • Multiple electrical knockouts: Offers flexibility for convenient wiring connections from either end.
  • Durable construction: Stainless steel and Monel materials provide long-lasting performance and resistance to corrosion.
  • Compact size: Fits easily in tight spaces near piping.


  • Controls equipment: Triggers alarms, pumps, or other equipment based on flow changes, optimizing system operation and preventing damage.
  • Protects against dry running: Ensures pumps and other equipment operate only when sufficient flow is present, preventing overheating and malfunctions.
  • Improves efficiency: Automates equipment control based on flow conditions, reducing energy consumption and operational costs.
  • Versatile applications: Suitable for various industries and applications, including boilers, HVAC systems, irrigation systems, and industrial processes.
  • Easy installation and maintenance: Simple wiring and readily available replacement parts make it user-friendly.
  • Reliable and durable: Robust construction and high-quality materials ensure long-lasting performance and minimal maintenance.

Things to consider:

  • Flow rate compatibility: Choose the appropriate model based on the expected flow rate range of your system.
  • Liquid type: Ensure the switch is compatible with the specific liquid you’ll be using.
  • Electrical requirements: Match the switch’s electrical specifications (voltage, amperage) with your equipment.
  • Installation location: Select a location with easy access for wiring and maintenance.
  • Professional assistance: Consider seeking professional help for installation and setup if needed, especially for complex systems or high-pressure applications.

Overall, the McDonnell Miller FS4-3 1″ Liquid Flow Switch is a reliable and versatile option for monitoring and controlling liquid flow in various applications. Its adjustable sensitivity, durable construction, and ease of use make it a popular choice for both industrial and residential use.

Additional information

Weight 2.25 lbs


There are no reviews yet.

Only logged in customers who have purchased this product may leave a review.