HPAC Engineering, Jan. 2017, by Eric Chrencik.
http://hpac.com/heating/design-high-temperature-hot-water-plant-expansion

"There are four main components of HTHW-plant design:
  • HTHW-generator selection.
  • Pump selection.
  • Consideration of system expansion and makeup.
  • Stress analysis and piping layout.
This article discusses all four for a recently completed HTHW-plant expansion at George Mason University in Fairfax, VA."