WattMaster WCC III part 5 - Manual (Page 11)

4. SCUSCR.EXE SCREENS
WCC III Technical Guide 4-9
Occupied Mode
If the VAVBOX TUC-2R controller is used on a non-fan-powered
terminal unit that has reheat, the VAVBOX damper will move
to the Nite/Reheat position whenever a Space Heating demand
occurs and the HVAC unit is in Supply Air Cooling or Neutral
mode. When the HVAC unit is in Supply Air Heating mode, the
VAVBOX damper will modulate as required to maintain the Space
Heating setpoint.
Unoccupied Mode
When using non-fan powered terminal units, the VAVBOX damper
will position itself in the Nite/Reheat minimum position. In order
for fan powered terminal units to position the damper to the Nite/
Reheat minimum position, the check for main fan status must be
selected and the HVAC unit fan must be operating.
Occupied Mode Sequences
Space Vent Mode
This mode only applies to the Occupied Mode of operation. If the
equipment is in the Unoccupied Mode, then a lack of heating or
cooling demand would generate the Off Mode.
If the HVAC unit is in Supply Air Neutral Mode, you can adjust
the damper position on pressure dependent terminal units and
the airfl ow on pressure independent terminal units to provide a
fi xed amount of ventilation air into the space when there are no
heating or cooling demands. During this time, the damper does
not modulate on pressure dependent terminal units. On pressure
independent terminal units, it only modulates to the extent required
to maintain the vent minimum airfl ow setting.
If the VAVBOX
Controller detects that the HVAC unit is in Supply Air Heating
mode, indicating that the air handler has activated its heat, the
heating airfl ow minimum will be substituted for the vent minimum
position. If the VAVBOX Controller detects that the HVAC unit
is in Supply Air Cooling mode, indicating that the air handler
has activated its cooling, the cooling airfl ow minimum will be
substituted for the vent minimum position.
Space Cooling Mode
Occupied Space Cooling mode is initiated by the temperature in
the space rising above the Occupied Cooling Setpoint.
If the VAVBOX TUC-2R controller is in the Supply Air Heating
mode and another VAVBOX TUC-2R controller has a cooling
demand, the damper/airfl ow for the VAVBOX TUC-2R controller
requiring cooling will position itself to provide the heating
minimum setpoint amount of air into the space. No modulation
open will occur because the space does not want the warm air
currently being supplied by the air handler.
When the VAVBOX TUC-2R controller is in the Supply Air
Cooling mode, the damper is normally held at the minimum
cooling position until the space temperature begins to rise above
the cooling setpoint. As the space temperature rises to within 0.5 ºF
of the Occupied Cooling Setpoint, the damper/airfl ow calculation
causes the air valve to open proportionally until the maximum
setpoint is achieved at 1.5 ºF above the setpoint. This is a 2 ºF
proportional window starting 0.5 ºF below the cooling setpoint to
1.5 ºF above the cooling setpoint.
The damper/airfl ow is never allowed to modulate outside the
user adjusted minimum setpoint and the maximum setpoint. The
maximum damper/airfl ow setpoint applies to heating and cooling
modes of operation only. All of the modes have their own individual
minimum setting.
Series Flow Fan Terminals
If the VAVBOX TUC-2R controller has been confi gured as a Series
Fan Powered terminal unit, the series fan relay will activate and
run the series box fan continuously anytime the VAVBOX TUC-
2R controller is in occupied mode.
In all cases, before the series box fan can be activated, the air
damper is driven fully closed and held that way for 30 seconds to
make sure the series box fan hasn’t inadvertently started to spin
backwards. Once the series box fan starts, it waits an additional
10 seconds to allow the fan to spin up before it starts to open the
damper and introduce airfl ow from the HVAC unit fan.
Parallel Flow Fan Terminals
During normal cooling or vent mode and adequate air supply,
the parallel fan will be off. During the occupied cooling or
vent mode, the Parallel fan will only activate if the damper/
airfl ow is below a user defi ned low limit setting. This causes it
to be used as a make-up air source. When the damper/airfl ow
rises 15% above the low limit setpoint, the Parallel fan will be
deactivated.
The check for main fan status setting has no effect on the
Parallel Fan box when in the occupied mode.
Space Heating Mode
Occupied Space Heating mode is initiated by the temperature in
the space falling below the Occupied Heating Setpoint.
If the VAVBOX TUC-2R controller is in the Supply Air Cooling
mode and another VAVBOX TUC-2R controller has a heating
demand, the damper/airfl ow for the VAVBOX TUC-2R controller
requiring heating will position itself to provide the Cooling
Minimum amount of air into the space. No modulation open will
occur because the space does not want the cold air currently being
supplied by the air handler.
WCC III VAV BOX III Operation Modes