513. If a boiler generates saturated steam at 125.3 psig, how much heat is required to change the water into steam if the feed water temperature is 240°F

The heat required to convert feedwater to saturated steam is determined by subtracting the feedwater enthalpy from the saturated steam enthalpy at the boiler pressure. Converting the gauge pressure to absolute pressure (140 psia) and consulting steam tables yields an enthalpy difference of 984.7 Btu/lb.