Honeywell AUTOMATIC CONTROL - Economizer Cycle Decision-Outdoor AirReturn Air Enthalpy Comparison

ENGINEERING CMANUAL OF AUTOMATION CONTROL
AIR HANDLING SYSTEM CONTROL APPLICATIONS
218
ECONOMIZER CYCLE DECISION—OUTDOOR AIR/RETURN AIR
ENTHALPY COMPARISON
Functional Description
16.8
OA
MA
RA
EA
1
22
ECONOMIZER MODE SELECTOR
OA MINIMUM SETPOINT
(NOTE: THE TEST AND
BALANCE INITIAL
VALUE FOR PROPER
VENTILATION IS 22)
OTHER INPUTS
AND OUTPUTS
ENTHALPY
BTU PER POUND
ENTHALPY
BTU PER POUND
M10456
7
9
11
3
8
6
83
10
1 2
83
CONTROL
PROGRAM
1 = AUTO BASED UPON OA/RA
ENTHALPY COMPARISON.
72.0
81.0
2 = AUTO BASED UPON OA DB
BELOW DEGREES
3 = MANUAL, ECONOMIZER ON.
4 = MANUAL, ECONOMIZER OFF.
NOTE: THE SYSTEM IS LOCKED OUT OF THE ECONOMIZER
MODE ANYTIME THE OA DRY BULB IS
ABOVE DEGREES.
49
52
29.0
4 5
78
45
Item
No. Function
1 Sensor senses OA temperature.
2 Sensor senses OA humidity.
3OA enthalpy calculated from OA temperature
and humidity.
4 Sensor senses RA temperature.
5 Sensor senses RA humidity.
6 RA enthalpy calculated from OA temperature
and humidity.
7 Economizer mode selector and command
schedule.
8 Setpoint for minimum OA damper position.
9 Actuator positions OA and RA dampers.
10 Actuator positions EA dampers.
11 Control program coordinates occupancy,
temperature, smoke control, and ventilation
controls.