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Table of Contents
ii
customer.honeywell.com
70-6925
Introduction ....................................................................... 125
Definitions ......................................................................... 125
Abbreviations .................................................................... 126
Symbols ............................................................................ 126
Basic Pneumatic Control System ..................................... 126
General ........................................................................ 126
Air Supply and Operation ............................................ 127
Restrictor ..................................................................... 127
Nozzle-Flapper Assembly ............................................ 127
Pilot Bleed System ...................................................... 127
Signal Amplifier ............................................................ 128
Feed and Bleed System .............................................. 128
Sensing Elements ........................................................ 128
Throttling Range Adjustment ....................................... 129
Relays and Switches ................................................... 130
Air Supply Equipment ....................................................... 130
General ........................................................................ 130
Air Compressor ............................................................ 130
Air Drying Techniques ................................................. 131
Pressure Reducing Valve Station ................................ 132
Thermostats ..................................................................... 133
Controllers ........................................................................ 134
General ........................................................................ 134
Temperature Controllers .............................................. 134
Humidity Controllers .................................................... 134
Pressure Controllers .................................................... 135
Sensor-Controller Systems ............................................... 135
Pneumatic Controllers ................................................. 135
Pneumatic Sensors ..................................................... 136
Velocity Sensor-Controller ........................................... 136
Actuators and Final Control Elements .............................. 137
Actuators ..................................................................... 138
Control Valves ............................................................. 138
Dampers ...................................................................... 140
Relays and Switches ........................................................ 140
Switching Relay ........................................................... 141
Snap Acting Relay ...................................................... 141
Lockout Relay ............................................................. 141
High-Pressure Selector Relay ..................................... 142
Low-Pressure Selector Relay ..................................... 142
Load Analyzer Relay ................................................... 142
Capacity Relay ............................................................ 143
Reversing Relay .......................................................... 143
Positive-Positioning Relay .......................................... 143
Averaging Relay .......................................................... 143
Ratio Relay ................................................................. 144
Pneumatic Potentiometer ............................................ 144
Hesitation Relay .......................................................... 145
Electrical Interlocking Relays ...................................... 145
Electronic-Pneumatic Transducer ............................... 146
Pneumatic Switch ....................................................... 146
Manual Positioning Switch .......................................... 146
Pneumatic Control Combinations .................................... 147
General ....................................................................... 147
Sequence Control ....................................................... 148
Limit Control ................................................................ 148
Manual Switch Control ................................................ 149
Changeover Control For Two-Pressure
Supply System ....................................................... 149
Compensated Control System .................................... 150
Electric-Pneumatic Relay Control ............................... 150
Pneumatic-Electric Relay Control ............................... 150
Pneumatic Recycling Control ...................................... 151
Pneumatic Centralization ................................................. 152
Pneumatic Control System Example ............................... 153
Start-Stop Control Sequence ...................................... 153
Supply Fan Control Sequence .................................... 155
Return Fan Control Sequence .................................... 155
Warm-Up/Heating Coil Control Sequence .................. 156
Mixing Damper Control Sequence .............................. 157
Discharge Air Temperature Control Sequence ........... 157
Off/Failure Mode Control Sequence ........................... 157
Summary of Contents for VP525C
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