Fan Control - Greenheck DOAS v8.1 Reference Manual

Control Variables

Fan Control

Supply Fan Control
Menu
e r w
nergy ecovery heel
This screen displays the energy recovery wheel jog combine to setpoints. This
screen only appears if the unit is equipped with an energy recovery wheel.
When the wheel has been disabled for the delay time, the wheel jog function
enables the wheel for the duration.
e r w
nergy ecovery heel
This heat wheel minimum speed screen will appear when the energy recovery
device is a modulating wheel. The minimum speed set point determines the
minimum speed a modulating wheel can rotate.
The Supply Fan Control menu allows the user to adjust supply control
setpoints.
s F d
upply an elay
The supply fan delay will begin once the damper sequence is complete. This delay
can be used to offset starting times between the supply fan and exhaust fan.
s F s
upply an peed
This screen displays min and max supply fan speed percentages. The speed
setpoint is the proportional percentage of the analog output from the controller to
the VFD.
50% Speed = Min speed
100% Speed = Max speed
Setpoint Selections:
Constant Volume – The fan speed will be constant; set from screen (e.g. 100%).
BMS – The BMS can directly control the fan speed (requires BMS communication
option).
Duct Pressure – Fan speed is determined by duct pressure control loop.
Space Pressure – Fan speed is determined by building pressure control loop.
CO – Fan speed is determined by CO
2
Single Zone VAV - The supply fan is modulated in addition to the supply air
temperature to satisfy the space temperature setpoint.
2-Speed - Supply fan control utilizes a contact closure to determine which
speed the supply fan speed 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 Hardwired – The 0-10V signal hardwired at the controller determines the
speed of the fan after the controller sends an enable command to the vfd. When
the signal is below the minimum fan speed setpoint, the fan will operate at
minimum. When the signal is above the maximum fan speed setpoint, the fan will
operate at maximum.
s s e
oFT huTdown nable
During a soft shutdown the following will occur:
• Tempering outputs immediately revert back to their off value; while
• Dampers remain open and fans continue to run; until
- The supply air temperature falls below the soft shutdown enable setpoint
(85.0°F) minus 5ºF; or
- The soft shutdown delay timer has expired.
j F
og uncTion
m s
inimum peed
control loop.
2
Microprocessor Controller for DOAS 25