Lennox ZGB Series - Economizer Operation Modes; Economizer Control Logic and Setpoints; Economizer Data and Calculations


-20
-29
-10
-23
0
-18
10
-12
20
-7
30
-1
40
4
50
10
60
16
70
21
80
27
90
32
100
38
0
10
30
40
50
60
70
80
90
100
20
0
10
30
40
50
60
70
80
90
100
20
MIXED AND RETURN AIR TEMPERATURE
CHART 1
CALCULATE MINIMUM FRESH AIR PERCENTAGE
A
BC
F
C
F
C
-20
-29
-10
-23
0
-18
10
-12
20
-7
30
-1
40
4
50
10
60
16
70
21
80
27
90
32
100
38
F
C
F
C
TABLE 14


THERMOSTAT DEMAND
DAMPER POSITION
MECHANICAL COOLING
UNOCCUPIED OCCUPIED
OFF   NO
G  MINIMUM NO
   NO
   STAGE 1

Economizer Operation
The occupied time period is determined by the thermostat
or energy management system.
Outdoor Air Not Suitable:
During the unoccupied time period dampers are closed.
During the occupied time period a cooling demand will
open dampers to minimum position and mechanical cool-
ing functions normally.
During the occupied time period dampers will open to
        -

Outdoor Air Suitable:
        
twostage thermostat.
        

    


MAX may override damper free cooling position when
occupancy is high and outdoor air temperatures are low.

dampers will move to minimum position until discharge air
