Steam and Hot Water Heating Systems
Steam and Hot Water Heating Systems
This domain covers steam traps, condensate return, air venting, piping arrangement, hot-water circulation, expansion tanks, air elimination, and balancing. The exam tests how systems remove air and condensate and how they control temperature and pressure.
Core rules
- Steam traps pass condensate and non-condensable gases while holding steam.
- Air vents at high points and at traps remove air that otherwise blocks steam.
- Condensate must drain by gravity to a receiver or be lifted by a pump; trapping before a lift is common.
- Hot-water systems need an expansion tank and air elimination; pressure relief protects the system.
- Balancing valves distribute flow so terminal units receive design flow.
Worked example
A 100 gal hot-water system is heated from 40°F to 180°F. Water expands roughly 4% over that range, so expansion volume is about 4 gal. The expansion tank must accept that volume while maintaining minimum and maximum system pressures. Reason: water is nearly incompressible; without an expansion space, pressure rises rapidly and may open the relief valve.
Traps
Do not trap at the end of a main without considering dirt and air; do not install a steam trap upside down or without strainer; do not omit air vents at high points; and do not size an expansion tank only by system volume without checking pressure limits.