Hierarchy classification:

1. top of the aat hierarchies
2. Objects Facet
3. Object Groupings and Systems (hierarchy name)
4. systems (equipment)
5. [systems by function]
6. HVAC
7. heating systems
8. steam heating

Anotations

Scope note:

Steam heating systems that include vacuum pumps that separate air from condensation in the return main of the system, maintaining the pressure at a constant level and accelerating the circulation of steam.