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Damper Control Modes
There are four different modes that control the unit damper operation: Manual, Mixed Air
Temperature, Building Pressure, and 100% Outside Air. Except for the 100% Outside Air
mode, these operating modes are selected through the menu tree of the BACview or PC.
Not all damper modes are available on all units.
The sequence described in the following paragraph overrides manual, mixed air
temperature, and building pressure control modes during the Unoccupied period of
Auto mode. It does not override the 100% outside air function.
Outside air dampers will remain in the fully closed position during the Unoccupied
period of Auto mode unless a minimum percentage of outside air (20% or 25%) is
required for ventilation as described in the following paragraphs of this section of the
manual.
Manual Mode
Manual Mode is the default damper operational mode. This will set the outside air
damper to a fixed position.
MRT and MDT Controls
To place the damper operation in Manual Mode on an MDT or MRT control system be
sure the appropriate terminals in the unit control panel are not 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 percentage of
outside air.
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.
If the unit served by this control is a direct-fired heater, that recirculates air after the
burner, it is designed to provide a minimum of 25% outside air. Therefore the damper
control knob on the remote control panel has no effect below 25%. See Minimum
Ventilation.
MRT-Expert and MDT-Expert Controls
To place the damper operation in Manual Mode on an MRT-Expert or MDT-Expert
control system scroll through the menu tree, locate the Damper Mode branch and select
Manual Pos. Next, scroll through the menu tree, locate the Setpoints branch, select Man
Vent SP, and enter the desired damper position. The allowable range is 0% to 100%. If
the unit served by this control is a direct-fired heater that recirculates air after the burner,
the unit is designed to provide a minimum of 25% outside air. 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.
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