Economizer Cycle Decision-Outdoor Air/Return Air Enthalpy Comparison - Honeywell AUTOMATIC CONTROL Engineering Manual

AIR HANDLING SYSTEM CONTROL APPLICATIONS
ECONOMIZER CYCLE DECISION—OUTDOOR AIR/RETURN AIR
ENTHALPY COMPARISON
Functional Description
OA
1
49
16.8
ENTHALPY
BTU PER POUND
Item
No. Function
1 Sensor senses OA temperature.
2 Sensor senses OA humidity.
3 OA 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.
ENGINEERING CMANUAL OF AUTOMATION CONTROL
EA
83
10
2
9
83
52
3
ECONOMIZER MODE SELECTOR
1
1 = AUTO BASED UPON OA/RA
ENTHALPY COMPARISON.
2 = AUTO BASED UPON OA DB
7
72.0
BELOW
3 = MANUAL, ECONOMIZER ON.
4 = MANUAL, ECONOMIZER OFF.
NOTE: THE SYSTEM IS LOCKED OUT OF THE ECONOMIZER
MODE ANYTIME THE OA DRY BULB IS
81.0
ABOVE
ENTHALPY
BTU PER POUND
29.0
6
78
45
4 5
RA
MA
OTHER INPUTS
AND OUTPUTS
CONTROL
22
PROGRAM
11
DEGREES
DEGREES.
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.
218
8
OA MINIMUM SETPOINT
(NOTE: THE TEST AND
BALANCE INITIAL
VALUE FOR PROPER
VENTILATION IS 22)
M10456