Dwyer FS‑2 Vane Flow Switch – Reliable Pump and HVAC/BMS Protection

Explore the Dwyer FS‑2 Vane Flow Switch, a mechanical paddle-type water flow sensor, ensuring pump and HVAC/BMS protection. Genuine product from DLK with detailed specifications and model selection guidance.

Overview of the Dwyer FS‑2 Vane Flow Switch

The Dwyer FS‑2 Vane Flow Switch is a mechanical paddle-type flow switch designed to detect the presence or absence of water flow in piping systems. This product belongs to the FS Series from Dwyer Instruments – USA and is widely used in industrial water systems, HVAC applications, and BMS for pump protection, circulation verification, and safe system operation.

Unlike continuous flow meters, the FS‑2 does not provide analog flow measurement. Instead, it delivers a reliable ON/OFF signal via an electrical contact, enabling control systems to confirm flow conditions. DLK – DLK TRADING SERVICE COMPANY LIMITED is the official distributor of Dwyer Instruments in Vietnam, supplying genuine products with full certification and professional technical support for engineering projects.

Detailed product information can be found on the DLK website at FS‑2 Water Flow Sensor.

Operating Principle of the Dwyer FS‑2 Vane Flow Switch

The Dwyer FS‑2 Vane Flow Switch operates on a mechanical paddle vane principle. Inside the switch body, a paddle is positioned directly in the flow path. When water flows through the pipe, the force of the fluid deflects the paddle, which actuates an internal SPDT snap-action switch.

When flow reaches the preset threshold, the electrical contact changes state and sends a signal to a PLC, HVAC controller, or BMS. If flow stops or drops below the threshold, the switch returns to its original state. This design enables simple and reliable detection of flow or no-flow conditions without requiring an auxiliary power supply.

The actuation point is field-adjustable by trimming the paddle length and adjusting the set screw, making the FS‑2 suitable for various pipe sizes and flow rates.

Real-World Applications Across Industries

In commercial HVAC systems, the Dwyer FS‑2 Vane Flow Switch is commonly installed on chilled water or hot water piping to verify pump operation and ensure proper circulation. Integrated with a BMS, the sensor prevents chillers or AHUs from operating without adequate water flow, reducing the risk of equipment damage.

In pump stations and water supply systems, the FS‑2 serves as a water flow switch for pump protection, detecting low or absent flow due to empty tanks, blocked pipes, or pump failure. The sensor’s signal can shut down pumps or trigger alarms, minimizing the risk of dry-running.

In industrial boiler and heating systems, maintaining water circulation before energizing heating elements is a critical safety requirement. The FS‑2 confirms the presence of water flow, allowing controllers to enable heating only under safe conditions.

In manufacturing plants and equipment cooling systems, water flow sensors monitor cooling water supplied to machinery. If flow is interrupted, the FS‑2 sends a signal to stop equipment, preventing overheating and component damage.

For engineers comparing flow switch solutions, additional guidance is available in the article which flow switch is suitable for water and HVAC systems, providing selection criteria for different applications.

Benefits of Using the Dwyer FS‑2 Vane Flow Switch

Using the Dwyer FS‑2 Vane Flow Switch offers practical advantages. Its mechanical design ensures stable operation, minimal maintenance, and no dependency on auxiliary power. Wetted materials such as forged brass, stainless steel, and tin bronze provide durability and compatibility with both hot and cold water systems.

The aluminum enclosure meets NEMA 4 / IP64 protection standards, allowing installation in mechanical rooms or humid environments. The internal SPDT snap-action switch, rated up to 10 A at 250 VAC, allows direct connection to control panels, relays, or automation systems used in HVAC and industrial applications.

Key Technical Specifications

Selecting the Right Model

When choosing the Dwyer FS‑2 Vane Flow Switch, pipe size and operating conditions must be evaluated first. The adjustable paddle design allows FS‑2 to accommodate a wide range of pipe diameters and flow rates. For HVAC or BMS systems requiring only flow verification, the FS‑2 is an efficient and cost-effective solution.

If continuous flow measurement or analog output is needed, other flow sensors may be more suitable. However, for flow confirmation and equipment protection, the FS‑2 remains highly reliable and easy to integrate.

Why Buy the Dwyer FS‑2 from DLK

DLK – DLK TRADING SERVICE COMPANY LIMITED is the official distributor of Dwyer Instruments in Vietnam. Purchasing the Dwyer FS‑2 Vane Flow Switch from DLK ensures genuine products, full documentation, and expert technical consultation tailored to HVAC, water, and BMS projects.

Updated product information and quotation requests are available on the DLK website at FS‑2 Water Flow Sensor.