CEMP-E
TI 810-11
30 November 1998
relationship between these two extremes.
Table 3-1. Setpoint reset schedule
Outside air temperature
HC discharge air temperature setpoint
-18 C (0 F)
49 C (120 F )
16 C (60 F)
32 C (90 F)
Figure 3-4. Outside air temperature controller input / output schedule.
d. To achieve the schedule defined in Figure 3-4 and Table 3-1, the controller parameters shown in
Table 3-2 must be selected.
Table 3-2. Controller configuration parameters
Outside air temperature controller
Discharge air temperature controller
(TC REV)
(TC DIR)
Scaled low range of the PV input
Scaled low range of the PV input
Scaled high range of the PV input
Scaled high range of the PV input
Setpoint
Scaled low range of the CPA input
Proportional band
Scaled high range of the CPA input
Manual reset
Minimum setpoint (optional)
Minimum output
Maximum setpoint (optional)
Maximum output
e. The PV input configuration parameters of both controllers must be selected so that the controllers
scale their inputs to the ranges of their respective temperature transmitters. The outside air controller PV
input low range and high range is -35 C (-30 F) and 55 C (130 F), at 4 and 20 mA, respectively.
Similarly, the discharge air controller PV input low range and high range is 5 C (40 F) and 60 C (140 F),
respectively. With these configuration parameters defined, the controllers scale, in a linear fashion, their
PV input signals between 4 and 20 mA to the range of their corresponding temperature transmitters.
f. The discharge air temperature controller CPA input signal must be scaled independently of its PV
input to recognize that a 4 mA signal at its CPA input from the outside air controller corresponds to a
32 C (90 F) discharge air setpoint. Likewise the discharge air controller must recognize that a 20 mA
3-3
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