Facilities Management and Design Chapter 7 HVAC Systems

Thermal Comfort Balancing heat produced by one’s body with surrounding environment. Body heat lost by convection, radiation, and evaporation

Factors that influence comfort indoor temperature humidity air movement room surface temperatures overall air quality

Comfort zone Insert comfort zone chart

Heat sources Electricity– Used in all electric heaters. Requires no flue. Usually most expensive. Natural gas – Clean burning. Flue required. Very efficient. Delivered via underground pipe Liquefied petroleum – relatively clean burning. Requires on-site storage tank. Delivered via truck. Fuel oil – tendency to create dirt/smoke. Requires on- site storage tank. Delivered via truck. Various grades available. Steam – more common in urban areas where available from local utility or in large complexes with central steam plant. Supply and return lines required.

Heating equipment Furnaces and Boilers Combustion efficiency Furnace Heat Exchanger Flue

Cooling Systems Boyles Ideal Gas Law – Pressure – Temperature – Volume Certain gases react more actively – Refrigerants – CFC’s – HCFC’s

The Refrigeration Cycle Compressor Condenser Coil Expansion Valve/ Metering Device Evaporator Coil

Cooling system operating and maintenance concerns Types of compressors – Reciprocating – Centrifugal – Rotary Energy efficiency ratio (EER) Integrated part load values (IPLV) Environmental Protection Agency – supervises aspects of refrigeration equipment maintenance – importance of eliminating or reducing refrigerant leaks

Cooling system operating and maintenance concerns Types of compressors – Reciprocating – Centrifugal – Rotary Energy efficiency ratio (EER) Integrated part load values (IPLV) Environmental Protection Agency – supervises aspects of refrigeration equipment maintenance – importance of eliminating or reducing refrigerant leaks

HVAC system types Centralized systems; quiet – two-pipe – three-pipe – four-pipe Decentralized systems; not as quiet – heating and cooling sources in guestroom itself or along outside wall Hybrid systems – characteristics of centralized and decentralized systems

System types and maintenance needs of HVAC systems for other building areas Air handling units – Isolation of zones (housekeeping, kitchen, maintenance…) Packaged air conditioning units – usually mounted on roof Maintenance issues – Filter replacement – belt checking and replacement – cleaning of fans and heat transfer surfaces

HVAC controls Today’s controls are often electronic Thermostat – enthalpy or economizer control – Older control sensors—mechanical sensing Digital control systems – variable air volume (VAV) systems – load sensing equipment – EMS sensors

Cooling towers Startup and shutdown concerns Inspection and lubrication of pumps and fans Removal of dirt and other debris Treatments to reduce bacteria, scale, and corrosion Inspection of metal surfaces