{"product_id":"mcdonnell-miller-114550-fs4-3d-1-flow-switch-with-dual-spdt-switches","title":"McDonnell \u0026 Miller 114550 FS4-3D 1\" Flow Switch with Dual SPDT Switches","description":"\u003cp\u003eProtect your hydronic equipment from flow-related damage using the \u003cstrong\u003eMcDonnell \u0026amp; Miller 114550\u003c\/strong\u003e FS4-3D 1-inch flow switch. This versatile safety device provides reliable monitoring for liquid lines in commercial and industrial HVAC applications, utilizing the \u003cstrong\u003eFS4-3D\u003c\/strong\u003e model to actuate electrical circuits when flow reaches or drops below a specific set point.\u003c\/p\u003e\u003cp\u003eThe unit functions through a precision-engineered paddle mechanism that extends into the pipe. When liquid flows through the line, the force against the paddle moves an internal linkage that triggers the two integrated Single Pole Double Throw (SPDT) switches. This dual-switch design allows for simultaneous signaling of two separate devices, such as a burner cutoff and an alarm system, ensuring comprehensive system oversight.\u003c\/p\u003e\u003ch4\u003eKey System Performance Baselines:\u003c\/h4\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eDual switching capability:\u003c\/strong\u003e Includes two independent SPDT switches for versatile circuit control.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRugged flow sensing:\u003c\/strong\u003e Features a sensitive, heavy-duty paddle designed for consistent reaction to flow velocity.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eVersatile mounting:\u003c\/strong\u003e Engineered for easy installation into standard 1-inch NPT pipe configurations.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSystem protection:\u003c\/strong\u003e Provides a vital safety interlock to prevent equipment operation during low-flow conditions.\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003e⚠️ \u003cstrong\u003eApplication Profile:\u003c\/strong\u003e Ideal for monitoring flow in chilled water systems, hot water boilers, and industrial process piping where equipment protection against dry-fire or low-flow conditions is critical.\u003c\/p\u003e","brand":"McDonnell \u0026 Miller","offers":[{"title":"Default Title","offer_id":43123964837982,"sku":"114550","price":374.95,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0663\/7151\/8558\/files\/114550_image_7ab07d77-5cb5-4cd2-8705-7053f12532aa.png?v=1786027173","url":"https:\/\/nationalboilersupply.com\/products\/mcdonnell-miller-114550-fs4-3d-1-flow-switch-with-dual-spdt-switches","provider":"National Boiler Supply","version":"1.0","type":"link"}