Handbook of air conditioning and refrigeration / Shan K

System Characteristics
AC SYSTEMS: CENTRAL SYSTEMS AND CLEAN-ROOM SYSTEMS 30.13
Cost and Electric Demands. The actual bidding price of the HVAC&R system for this project was
approximately $9 million, or $8.57 per ft 2 ($92.2 per m 2 ) gross area. Compared with the originally
proposed conventional air conditioning system using centrifugal chillers, the air system power input
was reduced from 1679 to 1136 kW, and the electricity demand dropped from 5960 to 4330 kW. The
estimated total annual energy consumption per ft 2 gross area was 33,190 Btu/ft 2 �yr (105
kWh/m 2 �yr).
System charateristics of fan-powered VAV central systems are listed in Table 30.2.
TABLE 30.2 System Characteristics for Fan-Powered VAV Central Systems (FPVAVCS) and Clean-Room Systems
FPVAVCS CRS
Zone thermal and sound control
Control zone Multizone Single or multizone
Control methods DDC DDC, or electric
Control modes PI or PID PI or PID
Heating-cooling mode changeover Automatic Cooling mode year-round,
summer-winter mode
changeover, automatic
Sound control
Indoor air quality (IAQ)
35–45 dBA NC 50–65
Minimum ventilation control DCV or MPC Constant-volume
Filters Medium to high efficiency HEPA or ULPA with prefilters
Humidity control Optional Dew point control
Humidifiers
Air system
Steam, or heating element
Types VAV air mixing MAU and RAU conditioning and mixing
Supply fan Forward, or airfoil centrifugal Centrifugal or vane-axial
Supply fan total pressure 4.5–5.5 in. WC MAU 4–4.5 in. WC, RAU 2–2.5 in. WC
Combined fan-motor-drive efficiency 55% MAU 55%, RAU 55%
Relief/return fan Centrifugal or axial Centrifugal or axial
Relief/return fan total pressure Relief 0.6 in. WC, return 0.5–1 in. WC Return 0.5–1 in. WC
Combined fan-motor-drive efficiency 35–40% 35–40%
Fan-powered VAV box fan Centrifugal, forward N/A
Box fan total pressure 0.5 in. WC
Combined fan-motor-drive efficiency 25%
Air economizer
Cooling systems
Fixed or differential dry-bulb or
enthalpy
N/A
Refrigeration compressor Centrifugal or screw Centrifugal or screw
Refrigerants HCFC-123, HCFC-22, HFC-134a HCFC-123, HCFC-22, HFC-134a
Evaporator Flooded liquid cooler Flooded liquid cooler
Condenser Water cooled or evaporatively cooled Water cooled or evaporatively cooled
Energy performance (compressor) 0.5–0.7 kW/ton 0.5–0.7 kW/ton
Heating system Hot water coil, or electric heater Space, year-round cooling,
preheating—outdoor air,
reheating—part load; hot water,
electric heating
Boiler AFUE
Maintenance
Conventional 78%, condensing 93% Conventional 78%, condensing 93%
Fault detection and diagnostics AHU, chiller AHU, chiller, filters