The pumps for the atlantic feedwater systems are pre-selected to make it easy for you to select a system. For example, a model 100 FS is sized to supply one 100 HP boiler if it is chosen with one or two feed pumps. If the three pump unit is chosen, it includes two pumps sized for 50 HP each, with one 50 HP pump for standby. All catalog pump selections are based on "On-Off" pump control. Consult the factory if modulating feedwater control is used.

If you would like to size the pump yourself, here is how:

1. Convert the Boiler Horsepower
   • Convert the boiler horsepower to the amount of water the boiler needs to make the full capacity steam rating. For most firetube and commercial water tube boilers convert the horsepower to pounds (#) of steam per hour. Then divide the # per hour of steam by 500 to get the evaporation rate.
2. Calculate the Pump Flow Rate
   • The flow rate is determined by the amount of water the boiler needs to make steam at full capacity.
   • On-Off Pump Control: If the boiler level is controlled by turning the feed pump on and off, the pump is usually sized to pump twice the rate the boiler requires at full load. This provides enough capacity for the pump to catch up with the boiler when it is turned on.
   • Modulating Feedwater Control: If a modulating valve controls the boiler water level, the feed pump is sized to provide 25% more water than the full load evaporation rate. A second adjustment is required to provide for recirculation flow required to protect the pump.