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Handbook of air conditioning and refrigeration / Shan K

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CHAPTER 23<br />

AIR SYSTEMS: MINIMUM<br />

VENTILATION AND VAV<br />

SYSTEM CONTROLS<br />

23.1 MINIMUM VENTILATION<br />

CONTROL 23.2<br />

Basic Approach 23.2<br />

Specific Controls in VAV Systems 23.2<br />

Types <strong>of</strong> Ventilation Control 23.2<br />

ASHRAE St<strong>and</strong>ard 62-1999 23.3<br />

Recirculation <strong>of</strong> Unused Outdoor Air in<br />

Multizone Systems 23.4<br />

Ventilation Controls for High-Occupancy<br />

Areas 23.5<br />

23.2 CO 2-BASED DEMAND-CONTROLLED<br />

VENTILATION 23.5<br />

CO 2-Based Dem<strong>and</strong>-Controlled<br />

Ventilation or Time-Based<br />

Constant-Volume Control 23.5<br />

CO 2 Sensor or Mixed-Gases Sensor 23.7<br />

Location <strong>of</strong> CO 2 Sensor 23.7<br />

Substantial Lag Time in Space CO 2<br />

Concentration Dilution Process 23.8<br />

Base Ventilation <strong>and</strong> Purge Mode 23.9<br />

A CO 2-Based Dem<strong>and</strong>-Controlled<br />

Ventilation System 23.10<br />

Application <strong>of</strong> CO 2-Based Dem<strong>and</strong>-<br />

Controlled Ventilation System 23.11<br />

23.3 MIXED PLENUM PRESSURE<br />

CONTROLS 23.12<br />

Basics 23.12<br />

Case Study: Mixed Plenum Pressure<br />

Control Monitoring Plenum<br />

Pressure 23.12<br />

Monitoring Pressure Drop <strong>of</strong> Louver<br />

<strong>and</strong> Damper Controlling Mixed Plenum<br />

Pressure 23.13<br />

Applications 23.14<br />

23.4 OUTDOOR AIR INJECTION FAN,<br />

DIRECT MEASUREMENT, AND FAN<br />

TRACKING SYSTEMS 23.14<br />

Outdoor Air Injection Fan 23.14<br />

Direct Measurement <strong>of</strong> Minimum<br />

Outdoor Air Intake 23.15<br />

Fan Tracking Systems 23.15<br />

23.5 CONFERENCE ROOMS 23.16<br />

23.6 SPACE PRESSURIZATION AND<br />

RETURN VOLUME FLOW<br />

CONTROLS 23.16<br />

Characteristics <strong>of</strong> Space Pressure<br />

Control 23.16<br />

VAV Systems Return/Relief Fan<br />

Volume Flow Control 23.17<br />

23.7 DISCHARGE AIR TEMPERATURE<br />

CONTROLS 23.18<br />

Basics 23.18<br />

System Description 23.19<br />

Operation <strong>of</strong> Air Economizer<br />

<strong>and</strong> Outdoor Air Intake—Case<br />

Study 23.21<br />

Discharge Air Temperature<br />

Reset 23.22<br />

23.8 DUCT STATIC PRESSURE AND<br />

FAN CONTROLS 23.23<br />

Duct Static Pressure Control 23.23<br />

Set Point <strong>of</strong> Duct Static<br />

Pressure <strong>and</strong> Sensor’s<br />

Location 23.24<br />

Comparison between<br />

Adjustable-Frequency Drives<br />

<strong>and</strong> Inlet Vanes 23.24<br />

23.9 FUNCTIONAL CONTROLS FOR<br />

VAV SYSTEMS 23.26<br />

Nighttime Setback, Warm-Up, <strong>and</strong><br />

Cool-Down Control 23.26<br />

Steam Humidifier Control 23.27<br />

Dew Point Control 23.27<br />

Diagnostics 23.28<br />

23.10 RECOMMENDATIONS AND<br />

INTERACTION BETWEEN<br />

CONTROLS 23.28<br />

Recommendations for VAV<br />

Controls 23.28<br />

Interaction between<br />

Controls 23.29<br />

Stability Problems 23.30<br />

23.11 SEQUENCE OF OPERATIONS<br />

OF A VAV REHEAT SYSTEM<br />

WITH MINIMUM VENTILATION,<br />

DISCHARGE AIR TEMPERATURE,<br />

AND DUCT STATIC PRESSURE<br />

CONTROLS—CASE STUDY 23.30<br />

HVAC&R System 23.30<br />

Sequence <strong>of</strong> Operations 23.30<br />

Primary Considerations 23.34<br />

REFERENCES 23.35<br />

23.1

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