10. Discharge Air Control
Page 43
PRODIGYT M2 UNIT CONTROLLER
For outdoor air based DACC setpoint reset, the discharge air cooling setpoint starts to increase when the outdoor air temper-
ature (OAT) drops to the DACC_OAT_RS_SP (ECTO 8.05) (default 80°F). The reset setpoint will continue to increase at the
rate equal to the DACC_OAT_RS_Adjustment_Band (ECTO 8.07) divided by the DACC_OAT_RS_Proportional_Band
(ECTO 8.06). See the following example:
EXAMPLE: The application calls for the discharge air cooling occupied setpoint (DACC_OCP_SP) (ECTO 7.16) to be 55°F
when OAT is 80°F or higher. When the OAT drops below 80°F, the setpoint needs to increase proportionately with the OAT
decrease (maximum setpoint increase of 10°F). The 10°F OAT decrease is called the DACC_OAT_RS_ Proportional_Band
and the setpoint increase of 10°F is called the DACC_OAT_RS_ Adjustment_Band. See figure 21.
DACC_OAT_RS Adjustment Band
ECTO 8.07
Example 10°F
DACC_OAT_RS_Proportional_Band
ECTO 8.06
Example 10°F
Reset Setpoint (Approx. 60°F at 75°F OAT)
55°F
65°F
70°F Outdoor
Air Temp.
DACC_OAT_RS_SP ECTO 8.05
DACC or Free Cooling Setpoint
80°F
Figure 21. Outdoor Air Reset Example
To use example values, set the following parameters:
S ECTO 8.05 – DACC OAT RS SP – Set to 80°F
S ECTO 8.06 – DACC OAT RS Proportional Band – Set to 10°F
S ECTO 8.07 – DACC OAT RS Adjustment Band −− Set to 10°F (this setting enables DACC outdoor air reset.
10.3. Return Air Reset
IMPORTANT − Return air reset can be used to adjust the free cooling setpoint (ECTO 6.23) when DACC is not used. All
references to the DACC setpoint apply to the free cooling setpoint.
The DACC and free cooling setpoint can be automatically reset when return air temperature becomes cooler. Use ECTO
8.04 to enable Return Air Reset.
For return air based DACC setpoint reset, the discharge air cooling setpoint starts to increase when the return air tempera-
ture (RAT) drops to the DACC_RAT_RS_SP (ECTO 8.02) (default 70°F). The reset setpoint will continue to increase at the
rate equal to the DACC_RAT_RS_Adjustment_Band (ECTO 8.04) divided by the DACC_RAT_RS_Proportional_Band
(ECTO 8.03). See the following example:
EXAMPLE: The application calls for the discharge air occupied setpoint (DACC_OCP_SP) (ECTO 7.16) to be 55°F when
RAT is 70°F or higher. When the RAT drops below 70°F, the setpoint needs to increase proportionately with the OAT de-
crease (maximum setpoint increase of 10°F). The 10°F RAT difference is called the DACC_RAT_RS_ Proportional_Band
and the setpoint increase of 10°F is called the DACC_RAT_RS_ Adjustment_Band. See figure 22.
DACC_RAT_RS Adjustment Band
ECTO 8.04
Example 10°F
DACC_RAT_RS_Proportional_Band
ECTO 8.03
Example 10°F
Reset Setpoint Approx.60°F (at 65°F RAT)
55°F
65°F
60°F Return
Air Temp.
DACC_RAT_RS_SP ECTO 8.02
70°F
DACC or Free Cooling Setpoint
Figure 22. Return Air Reset Example
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