Armstrong S-55-1 BF Cast Iron In-Line Circulating Pump

Armstrong S-55-1 BF Cast Iron In-Line Circulating Pump is a 1/2 HP, single‑phase inline circulator built for HVAC and general hydronic loops. It features a cast‑iron housing with bronze‑fitted (BF) construction and 3" NPT flanges for straightforward integration into existing piping. The inline three‑piece design runs at 1800 RPM and delivers up to 121 GPM with a maximum head of 24 ft, making it suitable for radiant floor heating, baseboard systems, and other hydronic distribution tasks. Powered by 115/230 V, 60 Hz, and 1 phase, this Series S pump is designed for reliable, maintenance‑free operation in residential and light commercial installations. Maximum operating pressure is 148 psi at 225°F, with a maximum fluid temperature around 107°F in typical service, ensuring compatibility with common heating and cooling water preparations. The combination of cast‑iron body, bronze fittings, and 3" flange compatibility supports durable service in standard 3" piping configurations, while its compact inline form factor facilitates retrofits and retrofit‑friendly installations.