Honeywell AUTOMATIC CONTROL Engineering Manual page 220

AIR HANDLING SYSTEM CONTROL APPLICATIONS
FEATURES
1. Smoke, low temperature, and high static pressure safety
shutdown (hard-wired).
2. Optimized start-stop control of supply, return, and exhaust
fans.
3. Proof of operation interlocking and alarming on supply
and return fans.
4. Software on-off-auto system command.
5. Zero ventilation/exhaust during preoccupancy operational
periods.
6. May be modified for night purge and prepurge operation.
7. After-hours operation function; duration is operator
adjustable.
8. Positions valves and dampers properly during off modes.
9. Night low temperature operation.
10. See Smoke Management Fundamentals section for smoke
control considerations.
CONDITIONS FOR SUCCESSFUL OPERATION
1. See REQUIREMENTS FOR EFFECTIVE CONTROL.
2. Proper hardware and software interlocks with heating,
cooling and terminal equipment.
3. To protect the AHU housing and ductwork, the high
pressure cutout must be hard-wired and located with a
minimum of tubing to prevent delays of operation.
Modulating limit control is not recommended since the
problem causing the high pressure is rarely a control loop
malfunction, but a physical one (smoke damper slamming
shut, sensor tubing cut or failed, vane actuator linkage
failure, etc.).
ENGINEERING CMANUAL OF AUTOMATION CONTROL
LIMITATIONS
1. Heating and cooling equipment must be available to
operate.
2. On large 100% OA systems and systems where OA and
RA dampers both close upon fan shutdown, dampers
should be enabled prior to fan start, and the fan should
start only after damper end switches prove dampers are
in safe positions.
SPECIFICATIONS
Air handling system shall be under program control, subject
to SA and RA smoke detectors, SA high pressure cutout, and
heating coil leaving air low-temperature limit control; and shall
be subject to system software on-off-auto function.
Supply fan shall be started and stopped by an optimum start-
stop seven day time schedule program, an unoccupied low space
temperature limit program, or by an occupant via push button
request. The push button shall be integral with the space
temperature sensor. Any push button request shall provide sixty
minutes (operator adjustable) of full system operation.
Return fan shall operate anytime the supply fan proves flow
(via a current sensing relay).
The exhaust fan shall operate during scheduled occupancy
periods and during occupant requested after-hour periods
anytime the return fan proves flow.
Heating/cooling plant (based upon fan system demands),
temperature, humidity, pressure, and ventilation controls shall
be enabled to operate anytime the fan system operates. Unless
otherwise specified, during fan off periods, N.O. heating and
cooling valves shall position closed, N.C. steam valves shall
position closed, N.C. humidifier valves shall position closed,
N.C. outdoor and relief dampers shall position closed, and N.O.
RA dampers shall position open.
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