{"product_id":"mcdonnell-miller-311200-21-30-replacement-float","title":"McDonnell \u0026 Miller 311200 21-30 Replacement Float","description":"\u003cp\u003eMaintaining precise water level regulation is essential for boiler safety, and the \u003cstrong\u003e311200\u003c\/strong\u003e replacement float is engineered to restore optimal performance to your \u003cstrong\u003eMcDonnell \u0026amp; Miller 21 series\u003c\/strong\u003e controls. This component acts as the primary sensing element, ensuring that your system maintains the correct water line to prevent dry-firing and maintain thermal efficiency.\u003c\/p\u003e\u003cp\u003eThe float mechanism operates on a buoyancy principle, rising and falling with the water level inside the control chamber. As the water level fluctuates, the float triggers the switch assembly to either initiate makeup water or activate a low-water cutoff, providing critical protection for your hydronic or steam boiler system.\u003c\/p\u003e\u003ch4\u003eKey System Performance Baselines:\u003c\/h4\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePrecision Buoyancy:\u003c\/strong\u003e Calibrated to provide consistent, reliable activation of the switch assembly.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCorrosion Resistance:\u003c\/strong\u003e Manufactured from durable materials designed to withstand harsh boiler water environments.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOEM Compatibility:\u003c\/strong\u003e Precision-engineered for exact fitment within the model 21 series control housing.\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003e⚠️ \u003cstrong\u003eApplication Profile:\u003c\/strong\u003e Used exclusively for the maintenance and repair of McDonnell \u0026amp; Miller Model 21 series boiler water feeders and low-water cutoffs. Ideal for commercial and industrial steam heating systems.\u003c\/p\u003e","brand":"McDonnell \u0026 Miller","offers":[{"title":"Default Title","offer_id":43128506515550,"sku":"311200","price":538.95,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0663\/7151\/8558\/files\/311200_image_ede206d1-59e9-4b72-ac70-d198217aa327.jpg?v=1786066280","url":"https:\/\/nationalboilersupply.com\/products\/mcdonnell-miller-311200-21-30-replacement-float","provider":"National Boiler Supply","version":"1.0","type":"link"}