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Handbook of air conditioning and refrigeration / Shan K

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29.6 CHAPTER TWENTY-NINE<br />

TABLE 29.1 System Characteristics <strong>of</strong> Packaged Systems<br />

SZCVPS SZVAVPS VAVCPS, VAVRPS, PHVAVPS<br />

Zone thermal <strong>and</strong> sound control<br />

Control zone Single-zone Single-zone Multizone<br />

Control methods Electric, two-stage<br />

thermostat<br />

DDC, electric DDC<br />

Control modes On/<strong>of</strong>f PI, PID, on/<strong>of</strong>f PI, PID, on/<strong>of</strong>f<br />

Heating-cooling mode changeover Manual, automatic Automatic Automatic<br />

Sound control<br />

Indoor <strong>air</strong> quality (IAQ)<br />

35–45 dBA NC 30–45 NC 30–45<br />

Minimum ventilation control Constant-volume DCV, MPC DCV, MPC<br />

Filters Low- or medium- Low-, medium-, high- Low-, medium-,<br />

efficiency efficiency high-efficiency<br />

Humidity control Optional Optional Optional<br />

Types <strong>of</strong> humidity control Heating element, Heating element, Heating element,<br />

Air systems<br />

wetted element wetted element wetted element<br />

Types Constant-volume<br />

<strong>air</strong> mixing<br />

VAV, <strong>air</strong> mixing VAV, <strong>air</strong> mixing<br />

Supply fan Forward-curved Centrifugal, forward, Centrifugal, forward,<br />

centrifugal <strong>air</strong>foil <strong>air</strong>foil<br />

Fan total pressure 2.5 in. WC 4.0 in. WC 4.5 in. WC<br />

Combined fan, motor, <strong>and</strong> drive<br />

efficiency<br />

40% 40% 45%<br />

Volume flow control Constant-volume Inlet vanes, variablespeed<br />

drive (VSD)<br />

Inlet vanes, (VSD)<br />

Relief/return fan total pressure N/A 0.4–1.0 in. WC 0.4–1.0 in. WC<br />

Combined fan, motor, drive<br />

efficiency<br />

35% 45%<br />

Economizer<br />

Cooling system<br />

Air, water Air, water Air, water<br />

Refrigeration compressor Scroll, reciprocating Scroll, reciprocating Scroll, reciprocating<br />

Capacity control On/<strong>of</strong>f cycling On/<strong>of</strong>f cycling, hot- Cycling, hotgas<br />

bypass gas bypass<br />

Refrigerants HCFC-22, HCFC-22, HCFC-22,<br />

HFC-407C, HFC-407C, HFC-407C,<br />

HFC-410A HFC-410A HFC 410A<br />

Evaporator DX coil DX coil DX coil<br />

Condenser Air-cooled Air-cooled, Air-cooled,<br />

evaporatively cooled evaporatively cooled<br />

Refrigerant flow control Expansion TXV, restrictor TXV, electric<br />

valve (TXV), capillary tube expansion valve<br />

Energy performance<br />

Heating system<br />

� 5 tons, 9.3 EER 10–12 EER<br />

Types <strong>of</strong> heating system Gas furnace, Gas furnace, VAVCPS N/A;<br />

heat pump heat pump, VAVRPS <strong>and</strong> PHVAVPS:<br />

electric heating hot water, electric heating<br />

AFUE Gas furnace, Gas furnace, Boiler,<br />

conventional, 78%, conventional 78%, conventional 80%,<br />

Maintenance<br />

condensing 93% condensing 93% condensing 93%<br />

Fault detection <strong>and</strong> diagnostics Packaged unit Packaged unit Packaged unit<br />

N/A means not available.

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