Honeywell AUTOMATIC CONTROL User Manual

PNEUMATIC CONTROL FUNDAMENTALS
ENGINEERING MANUAL OF AUTOMATIC CONTROL
90
PNEUMATIC CONTROL SYSTEM EXAMPLE
The following is an example of a typical air handling system
(Fig. 74) with a pneumatic control system. The control system
is presented in the following seven control sequences (Fig. 75
through 79):
—Start-Stop Control Sequence.
— Supply Fan Control Sequence.
— Return Fan Control Sequence.
—Warm-Up/Heating Coil Control Sequence.
—Mixing Damper Control Sequence.
—Discharge Air Temperature Control Sequence.
—Off/Failure Mode Control Sequence.
Controls are based upon the following system information
and control requirements:
System Information:
—VAV air handling system.
— Return fan.
— 35,000 cfm.
—4,000 cfm outside air.
—3,000 cfm exhaust air.
—Variable speed drives.
—Hot water coil for morning warm-up and to prevent
discharge air from getting too cold in winter .
— Chilled water coil.
—Fan powered perimeter VAV boxes with hot water reheat.
—Interior VAV boxes.
—Water-side economizer.
—8:00 A.M to 5:00 P.M. normal occupancy.
— Some after-hour operation.
GRAVITY
RELIEF
RETURN
AIR
RETURN FAN
SUPPLY FAN
EAST
ZONE
DISCHARGE
AIR
WEST
ZONE
MIXED
AIR
OUTSIDE
AIR
EXHAUST
M10298
Control Requirements:
— Maintain design outside air airflow during all levels of
supply fan loading during occupied periods.
— Use normally open two-way valves so system can heat
or cool upon compressed air failure by manually running
pumps and adjusting water temperatures.
—Provide exhaust/ventilation during after-hour occupied
periods.
— Return fan sized for 35,000 cfm.
START-STOP CONTROL SEQUENCE
Fans 1M through 3M (Fig. 75) operate automatically
subject to starter-mounted Hand-Off-Automatic Switches.
The Supply Fan 1M is started and controls are energized
by Electric-Pneumatic Relay 2EP at 0645 by one of the
following:
— An Early Start Time Clock 1TC
—A drop in perimeter space temperature to 65F at Night
Thermostat TN
— An after-hour occupant setting the Spring-Wound
Interval Timer for 0 to 60 minutes.
The Supply Fan 1M operation is subject to manually reset
safety devices including Supply and Return Air Smoke
Detectors; a heating coil, leaving air, Low Temperature
Thermostat; and a supply fan discharge, duct High Static
Pressure Cut-Out.
Fig. 74. Typical Air Handling System.

Honeywell AUTOMATIC CONTROL Specifications

General

Brand	Honeywell
Model	AUTOMATIC CONTROL
Category	Controller
Language	English