CNT-SVX05A-EN
43
Sequence of operation
The effective discharge air temperature setpoint is determined from:
• communicated or configured discharge air setpoint value
• minimum and maximum heat/cool setpoint limits
• the effective heat/cool mode
Example:
Table 24 — Configuration parameters
Note 1:
When the controller is applied to an air handling unit with a draw-through supply fan, the maximum discharge
air heating setpoint should be set to 104
°
F (default setpoint). This prevents the discharge air temperature from
exceeding the high temperature limit of the supply fan motor. Exceeding the motor's temperature limit can cause
premature failures.
Table 25 — Communicated values
Since the effective heat cool mode is
Cool
and the communicated value has
precedence over the local configuration value, the discharge air cooling
setpoint is
50
°
F
. The maximum and minimum discharge air cooling setpoint
limits are then applied to determine an effective discharge air temperature
setpoint of
53
°
F
, from Table 23.
In this example, if the effective heat cool mode is
Heat
, the effective discharge
air temperature setpoint would be 100
°
F.
The discharge air temperature control loop uses the effective discharge air
temperature setpoint, discharge air temperature (from the wired sensor), and
the configured control gains to calculate an output capacity for the end devices.
Discharge air cooling setpoint
55
°
F
Maximum discharge air cooling setpoint
68
°
F
Minimum discharge air cooling setpoint
53
°
F
Discharge air heating setpoint
100
°
F
Maximum discharge air heating setpoint
(Note 1)
104
°
F
Minimum discharge air heating setpoint
86
°
F
Discharge air cooling setpoint input
50
°
F
Discharge air heating setpoint input
none
Effective heat cool mode
Cool
