Armstrong In-Line Circulators are apart of the Series H line. The 116499-743 Armstrong H-66-1 Bronze Pump 3/4 HP 1PH ECM MotorĀ 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.