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Mixed Air Temperature Mode
The Mixed Air Temperature mode varies the percentages of outside air and return air to
maintain a constant mixed air temperature. The AireLogic controller computes the mixed
air temperature using the outside air and return air temperatures and the ratio of their
respective airflows. Direct fired units that recirculate after the burner do not have mixed
air temperature control.
MRT Control
To place the damper operation in Mixed Air Temperature Mode on an MRT control
system be sure the appropriate terminals in the unit control panel are shorted. See the
Typical Wiring Schematic and Multiplexed Input sections of this manual for more
information. Rotate the damper control knob on the
remote control panel
to the desired
mixed air temperature. The allowable range is 55°F - 90°F. If the unit served by this
control is a direct-fired heater, that recirculates air before the burner, and is operating in
the heating mode, the unit will automatically keep the minimum outside air at 20%. If the
outside air drops below 20%, the burner will cycle off.
See Minimum Ventilation.
MRT-Expert Control
To place the damper operation in Mixed Air Temperature Mode on and MRT-Expert
control system scroll through the menu tree, locate the Damper Mode branch and select
MA Temp Ctrl. Next, scroll through the menu tree, locate the Setpoints branch, select
Mixed Air, and enter the desired temperature. The allowable range is 30°F - 90°F. If the
unit served by this control is a direct-fired heater, that recirculates air before the burner,
and is operating in the heating mode, the unit will automatically keep the minimum
outside air at 20%. If the outside air drops below 20%, the burner will cycle off.
See
Minimum Ventilation.
MDT and MDT-Expert Controls
The MDT and MDT-Expert control systems do not support mixed air temperature control
mode.
Building Pressure Mode
The Building Pressure mode varies the percentages of outside air and return air to
maintain a constant pressure within the space. A pressure transducer compares the
pressure outside the space to the pressure inside the space and transmits a corresponding
signal to the AireLogic controller. The controller compares this signal to the desired
building pressure setpoint and uses a
PID
loop to modulate the outside air and return air
dampers to maintain the specified building pressure.
MRT and MDT Controls
The MRT and MDT control systems do not support building pressure control mode.
MRT-Expert and MDT-Expert Controls
To place the damper operation in Building Pressure Mode on an MRT-Expert or MDT-
Expert control system scroll through the menu tree, locate the Damper Mode branch and
select Bldg Pres Ctrl. Next, scroll through the menu tree, locate the Setpoints branch,
select Bldg Pres, and enter the desired pressure. The allowable range is –0.05”wc to
+0.05”wc. If the unit served by this control is a direct-fired heater, that recirculates air
before the burner, and is operating in the heating mode, the unit will automatically keep
