Sterling boiler feed pumps, model 4100, store the returning condensate in their large receiver tanks. Once the boiler control “calls” for water, the pumps kick-on until the boiler control tells the pump to “stop.” These Sterling brand boiler feed pumps are pre-packaged and sold based on the horsepower of your boiler. 20 psi pumping pressure. Select from Simplex (1 pump) or Duplex (2 pump) models. 1-phase motors wired 115V, field convertible to 230V; 3-phase motors @ 208-230/460V. Mechanical water make-up valves and gauge glass standard on all models. The receiver is sized to handle the condensate from the maximum Boiler HP shown. Call State Supply City Desk for professional product application information: 877-775-7705.