The Water Paddle Flow Switch provides dependable mechanical flow status verification, dry-run pump safety interlocking, and process circulation monitoring across commercial HVAC hydronic loops, chiller evaporator barrels, cooling towers, and industrial pumping networks.

Dependable Flow Interlocking with the Water Paddle Flow Switch

Designed as an essential protective safety device, the Water Paddle Flow Switch detects liquid motion within pressurized piping systems without requiring auxiliary operating power. As fluid begins to move through the line, hydraulic velocity exerts dynamic force against an engineered stainless steel paddle vane immersed in the stream. This paddle deflection pivots an internal mechanical actuating lever across a sealed bellows seal to trigger an instantaneous snap-action microswitch.

The instrument incorporates an adjustable range screw that allows field commissioning engineers to fine-tune the exact cut-in (flow initiated) and cut-out (flow stopped) trip points to match specific system velocities. By integrating a flexible set of segmented, trimmed paddles, a single switch assembly can be adapted on-site to fit nominal pipe diameters ranging from 1 inch (DN 25) up to 8 inches (DN 200). Its isolated elastomeric or phosphor-bronze sealing bellows completely isolates the electrical microswitch housing from process fluid contact, eliminating line leakage risks and seal fouling.

Featuring a heavy-duty Single Pole Double Throw (SPDT) electrical contact configuration, the unit can be wired simultaneously to signal normal flow conditions to building automation systems (BMS) while providing an instant fail-safe circuit break to chiller compressors, electric duct heaters, or boiler burner circuits in the event of pump failure or line blockage.

Key Features and Engineering Advantages

• Fail-Safe Mechanical Actuation: Operates directly on hydrodynamic kinetic force, ensuring immediate contact changeover during circulation failures without software lag.
• Universal Segmented Paddle Set: Includes trimmed 304 stainless steel paddle vanes that easily stack or detach to accommodate pipe sizes from DN 25 to DN 200.
• Robust SPDT Electrical Switching: Heavy-duty contact block rated up to 15 A at 250 V AC enables direct pilot-duty control of motor starter contactors without slave relays.
• Hermetic Mechanical Separation: Flexible metallic bellows barrier prevents process fluid, line debris, and treated water chemicals from reaching the electrical switch head.
• Field-Adjustable Trip Calibration: Top-accessible sensitivity adjustment screw permits simple on-site calibration of actuation flow velocity thresholds.

Technical Specifications

Industrial Applications and Process Integration

The Water Paddle Flow Switch provides vital proof-of-flow interlocking across commercial, institutional, and manufacturing facilities, including:

• Chilled water air conditioning systems to prevent chiller evaporator freezing caused by loss of primary water flow.
• Hot water boiler systems and heat exchangers to prevent dry firing and thermal damage to heating tubes.
• Cooling tower water supply circuits and condenser water distribution headers.
• Water booster pump sets and irrigation skids providing run-dry protection against intake pipe air locks.

Frequently Asked Questions

How are the paddles trimmed for different pipe diameters?
The unit includes multiple nested stainless steel paddle blades. For smaller 1-inch lines, only the shortest paddle blade is installed. For larger lines (up to 8 inches), additional segmented paddle lengths are bolted together so the paddle tip extends approximately two-thirds into the core pipe cross-section without catching on the opposite pipe wall.

What is the proper pipe orientation for mounting the Water Paddle Flow Switch?
The switch is designed for installation in horizontal pipe runs or vertical pipes with upward liquid flow. When installed in horizontal piping, the switch must be mounted vertically on top of the pipe (within 120 degrees of upright) to ensure gravity and flow velocity act predictably on the paddle mechanism.

What straight run of pipe is required before and after the flow switch?
To maintain steady flow dynamics and prevent paddle flutter caused by turbulence, install the switch in a straight section of pipe with at least five pipe diameters (5 × DN) of undisturbed piping upstream and three pipe diameters (3 × DN) downstream from any elbow, valve, or strainer.