Armstrong H-52 BF In-Line Circulators are apart of the Series H. The 1/3 HP bronze fitted circulator pump is suitable for hydronic heating and cooling, domestic water systems, multi-stage zoning and general industrial service applications. Built using a standard three-piece design that features a radially-split body, oversized shaft, centrifugal impeller, positive mechanical seal and modular construction, Armstrong Pumps Series H Circulators are a trusted, durable product that have been used by HVAC professionals for decades.