The Greystone Model GLFS-1 Mechanical Paddle-Type Liquid Flow Switch, engineered and manufactured by Greystone Energy Systems, is a rugged, cost-effective, and highly dependable flow-sensing instrument widely specified for commercial building automation (BMS/HVAC), central chiller plants, hydronic loop control, and general industrial pumping installations.

Operating Principle & Mechanical Action of the GLFS-1:
The switch operates via dynamic fluid impingement on a flexible stainless steel paddle assembly suspended inside the fluid stream. When fluid flows through the pipe at or above the designated flow velocity, the kinetic drag deflects the paddle arm against a balance spring. This mechanical motion transfers through an isolated sealing bellows mechanism to actuate an internal high-capacity snap-action SPDT microswitch. Conversely, when fluid velocity falls below the calibrated setpoint or flow ceases entirely, the internal return spring pulls the lever mechanism back to its de-actuated position, reversing the electrical contacts to trip alarms or safety interlocks.

Key Engineering Features & Operational Advantages:
- Rugged Weatherproof IP65 / NEMA 4X Enclosure: Housed in a heavy-duty, UV-stabilized engineering plastic enclosure sealed with a continuous silicone perimeter gasket. The housing protects internal microswitch contacts from torrential rain, splashing water, high humidity, washdown detergents, and corrosive mechanical plant atmospheres.
- High-Rating SPDT Snap-Action Microswitch: Equipped with a premium Single Pole Double Throw (SPDT) electrical switch rated up to 15(8)A @ 24/250 VAC. This configuration provides high wiring flexibility: it can simultaneously command chiller compressor run interlocks (opening contacts to shut down refrigeration compressors upon flow loss) while closing auxiliary contacts to trigger remote BMS alarm annunciation.
- Segmented Stainless Steel Paddles for Multiple Pipe Sizes: Supplied with a set of modular stainless steel (SUS301/304) paddles that can be stacked or trimmed to accommodate standard pipe diameters ranging from 1" (DN25) up to 8" (DN200), drastically reducing spare parts inventory requirements across facility piping retrofits.
- Field-Adjustable Sensitivity Setpoint: Features an internal sensitivity adjustment screw that regulates the return spring tension. Maintenance technicians can easily calibrate the precise cut-in and cut-out flow thresholds to match the specific operating dynamics of low-flow or high-velocity fluid loops.
- Hermetically Isolated Phosphor Bronze Sealing Bellows: Isolates all internal electrical mechanisms from the pressurized pipeline fluid, completely preventing moisture intrusion or fluid migration into the electrical termination chamber and ensuring long mechanical life exceeding 100,000 switching cycles.
- Universal 1" NPT Male Connection: Constructed with a precision-machined heavy-duty forged brass fitting rated for continuous working pressures up to 10 bar (150 psi), threading seamlessly into standard pipe tees or thread-o-lets.

Typical Industrial Applications:
- Water-cooled chiller evaporator barrel freeze protection (interlocking compressor shutdown on water flow loss).
- Cooling tower and condenser hydronic loop flow verification.
- Pump dry-run protection on industrial booster pumps, heating hot water circulators, and municipal water treatment skids.
- Direct digital input signaling for Building Management Systems (BMS) and automated pump control panels.
- Liquid coolant flow monitoring in industrial air compressors, induction furnaces, and high-power generator sets.

• Manufacturer: Greystone (Greystone Energy Systems)
• Country of Origin: 100% China (Made in China)
• Product Line: GLFS Series Mechanical Liquid Flow Switches
• Model Designation: GLFS-1
• Switch Configuration: Single Pole Double Throw (SPDT) snap-acting microswitch
• Contact Electrical Rating: 15(8) A @ 24/250 VAC, 50/60 Hz
• Process Pipe Connection: 1" NPT Male thread (High-grade Forged Brass)
• Maximum Static Operating Pressure: 10 bar (150 psi)
• Burst Pressure Rating: 17.5 bar (250 psi)
• Process Liquid Temperature Range: 0°C to +100°C (32°F to +212°F)
• Ambient Operating Temperature Range: -20°C to +60°C (-4°F to +140°F)
• Ambient Operating Humidity Range: 10% to 90% RH (non-condensing)
• Included Paddle Set: Multi-segment Stainless Steel paddles (SUS301/304)
• Applicable Pipe Diameters: Suitable for pipe sizes from 1" (DN25) up to 8" (DN200)
• Sealing Mechanism: Flexible Phosphor Bronze sealing bellows isolating electrical chamber
• Enclosure Rating: IP65 / NEMA 4X (dust-tight and water-resistant against direct spray)
• Enclosure Material: Impact-resistant ABS / Polycarbonate with flame-retardant rating
• Fitting Metallurgy: Heavy-duty Forged Brass wetted fitting
• Electrical Wiring Interface: Conduit knockout with waterproof cable gland
• Sensitivity Adjustment: Internal range adjustment screw for setting cut-in / cut-out thresholds
• Mechanical Service Life: Exceeds 100,000 switching operations
• Unit Net Weight: Approximately 0.65 kg (1.43 lbs).