19
Heating/Ventilating/Cooling Operating
Modes
The AireLogic DDC controller automatically switches between the heating, ventilating
and cooling modes of operation. The previous sections described the Heating and
Cooling Setback operation. This section concentrates primarily on the Occupied
operating modes. Figures 1 and 2 provide a pictorial representation of the slight
differences between the occupied and unoccupied periods.
Heating Mode
Depending on the control type, the Occupied Heating Mode allows the burner to operate
as needed and is activated whenever the room or outside air temperature is 2°F below the
heating setpoint. During the Unoccupied Heating Mode, the burner is activated whenever
the room or outside air temperature is at the heating setpoint and is deactivated 2°F above
the heating setpoint.
MDT and MDT-Expert control systems do not require a room sensor. As such, one
is not provided for units that ship from the factory configured for either of these
control systems.
General Burner Control
In the Heating Mode the burner will modulate to maintain a constant temperature.
To change the desired heating discharge or room temperature of an MDT or MRT control
system, rotate the temperature setpoint knob on the
remote control panel
clockwise to the
desired temperature. The allowable temperature range is 55°F - 90°F.
AireLogic units configured for MRT or MRT-Expert controls will have a fixed
discharge temperature of 70°F if the room temperature sensor is disconnected or
otherwise fails to communicate with the unit control module.
To change the desired heating room temperature of an MRT-Expert control system, scroll
through the SETPOINTS menu tree using the
BACview
, locate the Occupied Heating
Setpoint, and enter a new temperature. The allowable temperature range is 40°F - 130°F.
The burner will modulate using a
PID
loop to maintain this temperature.
To change the desired heating discharge temperature of a MDT-Expert control system,
scroll through the SETPOINTS menu tree using the
BACview
, locate the OA for Htg/Clg
Changeover Setpoint, and enter the desired temperature. The allowable temperature range
is 40°F - 130°F. Next scroll through the SETPOINTS menu tree using the
BACview
,
locate the Discharge Heating Setpoint, and enter a new temperature. The allowable
temperature range is 40°F - 130°F. The burner will modulate using a
PID
loop to
maintain this temperature.
Additionally, on all controls systems except the MDT and MDT-EXPERT the control
system modulates the burner to maintain the supply air temperature within a defined
operating window. This window defines the maximum and minimum discharge
temperatures.
