Energy Recovery - Greenheck DOAS v8.1 Reference Manual

Control Variables

Energy Recovery

24 Microprocessor Controller for DOAS
Menu
0% = Full recirculation air
100% = Full outside air
*
Note: If the unit is equipped with a modulating OA damper but intended to be 100%
outside air, the minimum and maximum should both remain at 100%.
Minimum Position – When in the occupied mode, the active setpoint will be
equal to a local minimum OA setpoint, which may be constant or reset by fan
speed if equipped with a modulating supply fan.
Maximum Position – Each sequence that can adjust the OA damper setpoint
contains a max position to prevent excess OA. The active setpoint will be
determined based on the greatest demand of the configured sequences.
The OA damper setpoint can then be further adjusted between the minimum
and maximum OA settings with sequences such as CO
Economizer.
Setpoint Selections:
Constant Position – The min OA percentage is constant; set by the controller.
SF Reset – The min and max positions are reset by the supply fan speed.
BMS – The BMS can directly control the OA damper position between the min ad
max percentages.
Building Pressure – Damper position is reset by a building pressure control loop.
CO – Damper position is reset by a demand-controlled ventilation control loop
2
based on space CO levels. The CO
2
damper can modulate when solely based on CO
2 Position – Damper sequence that utilizes a contact closure to determine which
position the OA damper is commanded; minimum or maximum. The "Max Vent"
contact closure maybe be field configured to temporarily force the unit into
occupied mode. Reference Ctrl Variables/Advanced/Advanced Setpoints/Max
Vent to enable this option.
0-10 By Others – The 0-10V signal directly correlates to the damper position
of 0-100%. When the signal is below the minimum damper position setpoint,
the damper will modulate to minimum position. When the signal is above the
maximum damper position setpoint, the damper will modulate to max position.
o d p
uTside amper osiTion
Occupied and unoccupied damper control have minimum and maximum set
points for the specific mode of operation. Unoccupied OA Damper control
typically will only show the minimum set point. The maximum will also appear if
the OA Damper is controlling to building pressure.
The Energy Recovery menu allows the user to adjust energy recovery device
sequence setpoints.
d r
eFrosT amp
This screen displays the temperature at which the unit will enable frost control
mode if necessary. The factory default is dependent on the energy recovery
device installed. This screen only appears if the unit has energy recovery and a
frost control method was selected.
Max active time and min off time will be available if the frost control method
selected was timed exhaust.
max is the highest percentage that the OA
2
.
2
- u
noccupied
, Building Pressure and
2