- 15500 - Heat Generation
- 15510 - Heating Boilers and Accessories
- 15540 - Fuel-Fired Heaters
- 15620 - Packaged Water Chillers
- 15640 - Packaged Cooling Towers
- 15660 - Liquid Coolers and Evaporative Condensers
- 15670 - Refrigerant Condensing Units
- 15700 - Heating, Ventilating, Air Conditioning Equipment
- 15710 - Heat Exchangers
- 15720 - Air Handling Units
- 15760 - Terminal Heating and Cooling Units
- 23 50 00 - CENTRAL HEATING EQUIPMENT
- 23 52 00 - Heating Boilers
- 23 52 16 - Condensing Boilers
- 23 52 19 - Pulse Combustion Boilers
- 23 52 23 - Cast-Iron Boilers
- 23 52 33 - Water-Tube Boilers
- 23 52 39 - Fire-Tube Boilers
- 23 55 00 - Fuel-Fired Heaters
- 23 55 13 - Fuel-Fired Duct Heaters
- 23 55 23 - Gas-Fired Radiant Heaters
- 23 55 33 - Fuel-Fired Unit Heaters
- 23 57 00 - Heat Exchangers for HVAC
- 23 57 16 - Steam-to-Water Heat Exchangers
- 23 57 19 - Liquid-to-Liquid Heat Exchangers
- 23 60 00 - CENTRAL COOLING EQUIPMENT
- 23 63 00 - Refrigerant Condensers
- 23 64 00 - Packaged Water Chillers
- 23 64 13 - Absorption Water Chillers
- 23 64 16 - Centrifugal Water Chillers
- 23 64 19 - Reciprocating Water Chillers
- 23 64 26 - Rotary-Screw Water Chillers
- 23 65 00 - Cooling Towers
- 23 65 13 - Forced-Draft Cooling Towers
- 23 65 16 - Natural-Draft Cooling Towers
- 23 65 33 - Liquid Coolers
- 23 70 00 - CENTRAL HVAC EQUIPMENT
- 23 73 13 - Modular Indoor Central-Station Air-Handling Units
- 23 73 23 - Custom Indoor Central-Station Air-Handling Units
- 23 74 00 - Packaged Outdoor HVAC Equipment
- 23 75 00 - Custom-Packaged Outdoor HVAC Equipment
- 23 76 00 - Evaporative Air-Cooling Equipment
- 23 80 00 - DECENTRALIZED HVAC EQUIPMENT
- 23 82 00 - Convection Heating and Cooling Units
- 23 82 16 - Air Coils
- 23 82 19 - Fan Coil Units
- 23 82 23 - Unit Ventilators
- 23 82 26 - Induction Units
- 23 82 33 - Convectors
- 23 82 36 - Finned-Tube Radiation Heaters
- 23 82 39 - Unit Heaters