WattMaster WM-WCC3-TGD-01B - Manual (Page 829)

Unoccupied Mode Sequences
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 VAV/Zone 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 HVAC unit is in the Unoccupied Supply Air Heating mode because
one or more of the VAV/Zone Controllers has a heating demand and
another VAV/Zone Controller has a cooling demand, the damper/airfl ow
for the VAV/Zone 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 HVAC unit 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 and the maximum setpoints. 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 VAV/Zone 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 unoc-
cupied 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 Night/Reheat Minimum Position 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.
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.
NOTE: If check for main fan status is selected, the series fan will
activate any time the HVAC unit fan is operating.
Parallel Flow Fan Terminals
In the Unoccupied Cooling mode, the parallel fan will be off whether
check for main fan status has been selected or not. If check for main fan
status has been selected, the damper will be held at the Night/Reheat
Minimum Position until the space temperature begins to rise to 0.5 ºF
below the unoccupied cooling setpoint. If check for main fan status has
not been selected, the damper will be held in the fully closed position
until the space temperature begins to rise to 0.5 ºF below the unoccupied
cooling setpoint.
25 VAV/Zone Controller Actuator Package Technical Guide
Sequence of Operations