WattMaster WM-WCC3-TGD-01B - Manual (Page 790)

VAV/Zone Controller Technical Guide
Operator Interface 22
Sequence of Operations
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 0.5ºF 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 0.5ºF 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 0.5ºF below the unoccupied cooling setpoint. The
damper will be in the fully closed position until the space temperature
rises to 0.5ºF 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 Nite/Reheat
minimum until the space temperature begins to rise to 0.5ºF 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 0.5ºF below the unoccupied cooling
setpoint.
Unoccupied Space Heating Mode
During unoccupied mode, the HVAC unit is normally off. Unoccupied
Space Heating mode is initiated by the temperature in the space falling
below the Unoccupied Space Heating Setpoint.
If the VAV/Zone Controller is in the Unoccupied Supply Air Cooling
mode because one or more of the VAV/Zone Controllers has a cooling
demand and another VAV/Zone Controller has a heating demand, the
damper/airfl ow for the VAV/Zone Controller requiring heating will po-
sition itself to provide the Night/Reheat setpoint 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.
When the VAV/Zone Controller is in the Unoccupied Supply Air Heating
mode, the damper will be held at the Night/Reheat minimum position
until the space temperature begins to fall below the Unoccupied Heating
Setpoint. As the space temperature falls to 0.5ºF above the Unoccupied
Heating Setpoint, the damper/airfl ow calculation causes the air valve
to open proportionally until the maximum setpoint is achieved at 1.5ºF
below the setpoint. This is a 2ºF proportional window starting 0.5ºF
above the heating setpoint to 1.5ºF below the heating setpoint.
As with the Occupied Mode of operation, two different confi gurations
are available for the Unoccupied Space Heating mode. If the box is
confi gured to allow reheat during HVAC Heat mode, the reheat relays
can be activated even when the VAV/Zone Controller is in the Supply
Air Heating mode. If the box is confi gured not to allow reheat when the
HVAC unit is in Heat mode, the box heat relays will be de-energized
when the VAV/Zone Controller is in Supply Air Heating mode. In either
confi guration, when the HVAC unit is in the Supply Air Heating mode,
the damper will modulate open proportionally to the space demand. The
proportional window for the space temperature is 0.5ºF above to 1.5ºF
below the heating setpoint. This allows the space to take advantage of
the warm supply air in the duct.
If Check for Main Fan Status is not selected and the VAV/Zone terminal
unit has auxiliary heat (baseboard heat etc.) that does not require the
HVAC unit fan to operate, reheat can be used without the HVAC unit
fan operating. If Check for Main Fan Status is selected, the reheat will
only operate when the HVAC unit fan is operating.
The VAV/Zone Controller can activate auxiliary heating relays if the relay
Expansion Board has been connected and the correct number of heating
stages (1,2, or 3) has been confi gured. During demands for heat, the
fi rst stage will activate whenever the space temperature drops below the
heating setpoint. The second stage will activate if the space temperature
falls 1.0ºF below the heating setpoint. The third stage will activate if
the space temperature falls 2.0ºF below the heating setpoint. There is a
two-minute delay between staging. This prevents stages from activating
at the same time. Once a heating stage has been activated, it must remain
on for at least one minute. Once it has been deactivated, it must remain
off for at least two minutes. The third stage relay will deactivate when
the space temperature rises to within 1.0ºF of the heating setpoint. The
second stage relay will deactivate when the space temperature rises to
the heating setpoint. The fi rst stage relay will deactivate when the space
temperature rises above the heating setpoint by 1.0ºF. See Table 4: Relay
Staging - Unoccupied Mode for a complete layout of the various fan
& heat relay staging points.
Modulating (Proportional) Heat
The VAV/Zone Controller expansion board also provides an analog
output for control of a modulating hot water valve or SCR electric
heater. It provides a 0-10 VDC signal to control the heating device.
When the space temperature drops to 0.5 ºF above the Heating Setpoint,
the output starts at 0 VDC and ramps up to 10 VDC at 1.5 ºF below the
Heating Setpoint.
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 any time the
HVAC unit fan is running. The series fan relay will activate and run the
series box fan when the space temperature falls to within 0.5ºF above the
unoccupied heating setpoint any time 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 falls
to within 0.5ºF above the unoccupied heating 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 falls to within 0.5ºF above the unoccupied heating setpoint
and the damper will stay in the fully closed position.