Siemens QVE1900 Paddle Flow Switch for Liquids
The Siemens QVE1900 is an industrial-grade, paddle-type flow switch engineered to monitor the flow of liquid media within piping systems. Functioning as a critical safety and control interlock, this robust device detects the presence or absence of fluid velocity, triggering a potential-free microswitch to protect downstream systems—such as chillers, pumps, and heat exchangers—from dry running or structural thermal damage. Suitable for pipe diameters ranging from DN20 to DN200, the QVE1900 provides exceptional operational reliability across commercial HVAC loops and industrial fluid networks.
Key Features
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Universal Pipe Size Adaptability: Outfitted with a segmented stainless steel paddle assembly that can be easily trimmed or adjusted to fit a wide range of nominal pipe diameters from DN20 up to DN200.
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Dependable Single-Pole Double-Throw (SPDT) Switch: Employs a high-quality, inductive microswitch that can be wired as a normally open (NO) or normally closed (NC) contact to seamlessly trigger alarms, control loops, or system shutdowns.
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Rugged and Weather-Resistant Enclosure: Features a durable, impact-resistant housing rated to IP65 protection standards, making it highly resilient against dust, moisture, and demanding plant room conditions.
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High Operational Range Limits: Built to withstand demanding fluid environments with an upper operational media temperature ceiling of up to 120°C and a maximum working pressure rating of 11 bar ($1.1\text{ MPa}$).
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Corrosion-Resistant Material Composition: Designed with a high-grade brass threaded connection body and a stainless steel paddle mechanism to prevent scaling and fluid degradation over long service intervals.
Technical Specifications
| Feature | Specification |
| Model / Reference | QVE1900 |
| Brand | Siemens |
| Product Type | Paddle-Type Flow Switch for Liquids |
| Compatible Pipe Diameters | DN20 to DN200 (Adjustable paddle segments) |
| Switching Output | Potential-free changeover contact (SPDT microswitch) |
| Contact Rating | AC 250 V, 15 A / DC 230 V, 0.25 A |
| Process Connection | R 1″ Threaded Brass Connection (Male) |
| Max. Medium Temperature | 120°C |
| Max. Operating Pressure | 11 bar (1.1 MPa) |
| Ingress Protection Rating | IP65 |
| Standards Compliance | CE Certified, RoHS Compliant |
Applications
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Chiller and Boiler Protection: Monitoring water flow loops in commercial central HVAC plants to prevent evaporator freezing or boiler dry-boiling if a pump fails.
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Industrial Cooling Systems: Safeguarding high-power machinery, welding lines, and induction furnaces by ensuring continuous coolant delivery.
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Pump Control Networks: Serving as a minimum-flow safety interlock to shut down circulation pumps and prevent catastrophic pump-head cavitation.
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Water Treatment Filtration: Activating chemical dosing loops or backwash systems only when active fluid movement is securely verified.
