Facilities Management and Design

Chapter 7HVAC 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