Install Instructions

Temperature is above the SAT Changeover Temp plus 2° Fahrenheit, the SAT Changeover
Mode is set to HEAT. The default changeover temperature is 74° Fahrenheit.
See the topic Discharge Air Temperature (DAT) limiting on page 56 and Input sources on
page 52.
Discharge Air Temperature (DAT) limiting
A Discharge Air Temperature senor and DAT limiting is required to control VAV units with
reheat. If a Discharge Air Temperature (DAT) sensor is detected and DAT Limiting is
enabled, the VAV terminal will be controlled by the DAT loop. The unit will also limit the
Discharge Air Temperature to within 15° F of the Space Temp Reference.
When there is a call for heat and the primary air is cool air, the reheat outputs are directly
controlled by the DAT Loop and the DAT Setpoint reset based on the output of the Heating
loop. As the Heating loop increases from 0% to 50%, DAT Setpoint is proportionally
calculated between Space Temp Reference and Space Temp Reference + 15° F up to
maximum 90° F. This allows the reheat to be controlled by the DAT loop over the first 50% of
a call for heating.
Illustration 7–1 DAT limiting operation
HTG SP
HTG SPAN
50%
100%
0%
ROOM TMP
DAT loop
ROOM TMP+
15°
(Max 90°F)
If DAT Limiting is enabled, and a DAT sensor is not connected, the controller will lockout
reheat control only in the cooling mode. The unit will operate this way until a DAT sensor is
detected or until the unit is commanded to control to the Active Heating Setpoint by a
supervisory BMS.
If the unit has detected a DAT sensor and DAT Limiting is not enabled, the unit’s reheat is
controlled by the Heating loop instead of the DAT loop.
See also the topics Changeover on page 55 and Input sources on page 52.
Section 7: Sequences of operation KMC Controls, Inc.
56 Revision G