WattMaster WCC III part 5 - Manual (Page 13)

4. SCUSCR.EXE SCREENS
WCC III Technical Guide 4-11
Series Flow Fan Terminals
If the VAV/Zone 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
On parallel fan powered terminal units, the fan will run whenever
Space Heating mode is active. At all other times, the 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 fan will
be deactivated if there are no heating stages active and no space
demand exists.
The check for main fan status setting has no effect on the Parallel
Fan box when in the occupied mode.
Unoccupied Mode Sequences
NOTE: For the Unoccupied Mode Sequences to work
correctly the VAV/Zone controller must be able to read the
Main Fan Status.
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 (not
displayed).
Off Mode (Not Displayed)
During unoccupied mode, the mode is considered ‘OFF’ if the
space temperature does not generate a heating mode or cooling
mode based on the unoccupied heating & cooling setpoints.
When using non-fan powered terminal units, the VAVBOX TUC-
2R controller damper will position itself in the Night/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. If check main fan status has not been selected
the damper will be in the fully closed position.
Space Cooling Mode
During Unoccupied Mode, the HVAC unit is normally off.
Unoccupied Space Cooling mode is initiated by the temperature in
the space rising to the Unoccupied Cooling Setpoint.
If the VAVBOX TUC-2R controller is in the Unoccupied Supply
Air Heating mode because one or more of the VAVBOX controllers
has a heating demand, and another VAVBOX controller has a
cooling demand, the damper/airfl ow for the VAVBOX 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 Unoccupied
Supply Air Cooling mode, the damper will be held at the Night/
Reheat minimum position until the space temperature begins to
rise above the cooling setpoint. As the space temperature rises to
within 0.5 ºF of the Unoccupied 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 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 and check for main status has
been selected, the series fan relay will activate and run the series
box fan continuously anytime the HVAC unit fan is running. The
series fan relay will activate and run the series box fan when the
space temperature rises to 0.5 ºF below the unoccupied cooling
setpoint anytime the HVAC unit fan is not running. The damper
will be held closed if the HVAC unit fan is not running and will be
held at the Nite/Reheat minimum until the space temperature rises
to 0.5 ºF below the unoccupied cooling setpoint if the HVAC unit
fan is running. If check for main fan status has not been selected,
the series fan relay will activate and run the series box fan when
the space temperature rises to 0.5 ºF below the unoccupied cooling
setpoint. The damper will be in the fully closed position until the
space temperature rises to 0.5 ºF below the unoccupied cooling
setpoint.
WCC III VAV BOX III Operation Modes