{"product_id":"mcdonnell-miller-114400-fs4-3-flow-switch-1-npt","title":"McDonnell \u0026 Miller 114400 FS4-3 General Purpose Liquid Flow Switch (1 Inch NPT, SPDT, 160 PSI)","description":"\u003ch2\u003eMcDonnell \u0026amp; Miller 114400 (Model FS4-3) General Purpose Liquid Flow Switch\u003c\/h2\u003e\n\u003cp\u003e\n  Engineered for universal flow monitoring in commercial and industrial HVAC, hydronic, and process liquid piping networks, the \n  \u003cstrong\u003eMcDonnell \u0026amp; Miller 114400 (Model FS4-3)\u003c\/strong\u003e is a heavy-duty paddle-style liquid flow switch. Featuring a standard 1\" NPT male process connection and a single pole, double throw (SPDT) snap switch rated for 120\/240VAC operation, this unit automatically signals pumps, burners, or alarms when liquid flow starts or stops.\n\u003c\/p\u003e\n\u003cp\u003e\n  The FS4-3 incorporates a sealed Monel bellows and hardened stainless steel bearings to eliminate internal friction and maximize service life in continuous-duty applications. It comes factory-equipped with four trimmed stainless steel paddles (1\", 2\", 3\", and 6\") to fit pipe sizes ranging from 1\" up to 6\" diameter, making it one of the most versatile flow switches on the market.\n\u003c\/p\u003e\n\n\u003ch4\u003eKey Performance \u0026amp; Construction Highlights:\u003c\/h4\u003e\n\u003cul\u003e\n  \u003cli\u003e\n    \u003cstrong\u003eUniversal Pipe Fitting:\u003c\/strong\u003e Supplied with 4 interchangeable stainless steel paddles to accommodate 1\", 2\", 3\", and 6\" nominal pipe sizes.\n  \u003c\/li\u003e\n  \u003cli\u003e\n    \u003cstrong\u003eAdjustable Switch Sensitivity:\u003c\/strong\u003e Features an accessible sensitivity adjusting screw for fine-tuning flow activation thresholds on-site.\n  \u003c\/li\u003e\n  \u003cli\u003e\n    \u003cstrong\u003eSealed Monel Bellows Assembly:\u003c\/strong\u003e Isolates electrical snap components from fluid streams to ensure leak-free, corrosion-resistant operation.\n  \u003c\/li\u003e\n  \u003cli\u003e\n    \u003cstrong\u003eDual Electrical Knockouts:\u003c\/strong\u003e Enclosure features electrical knockouts on both sides for quick wiring from either orientation.\n  \u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003e\n  ⚠️ \u003cstrong\u003eApplication Profile:\u003c\/strong\u003e Ideal for water chillers, commercial boiler safety cut-offs, liquid heat exchange loops, water treatment systems, and pump proving circuits handling up to 160 PSI and fluid temperatures from 32°F to 300°F.\n\u003c\/p\u003e","brand":"McDonnell \u0026 Miller","offers":[{"title":"Default Title","offer_id":43041399996510,"sku":"MM-114400","price":280.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0663\/7151\/8558\/files\/McDonnell_and_Miller_114400_FS4-3_General_Purpose_Liquid_Flow_Switch_1_Inch_NPT.jpg?v=1784748301","url":"https:\/\/nationalboilersupply.com\/products\/mcdonnell-miller-114400-fs4-3-flow-switch-1-npt","provider":"National Boiler Supply","version":"1.0","type":"link"}