WattMaster WM-WCC3-TGD-01B - Manual (Page 830)

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 HVAC unit is in the Unoccupied Supply Air Cooling mode be-
cause 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 position itself
to provide the Night/Reheat Minimum Position 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 HVAC unit 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 0.5 ºF above the Unoccupied Heating
Setpoint, the damper/airfl ow calculation causes the air valve to open
proportionally until the maximum setpoint is achieved at 1.5 ºF below
the setpoint. This is a 2 ºF proportional window starting 0.5 ºF above
the heating setpoint to 1.5 ºF 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 VAV/Zone Controller is in the Supply Air Heat-
ing mode, the damper will modulate open proportionally to the space
demand. The proportional window for the space temperature is 0.5 ºF
above to 1.5 ºF 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
Expansion Module has been connected and the correct number of heat-
ing 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 1.0 ºF below the heating setpoint. The third stage will activate if
the space temperature falls 2.0 ºF 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 1.0 ºF 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 1.0 ºF. See Table 4:
Fan & Reheat Relay Staging for a complete layout of the various fan
& heat relay staging points.
Modulating (Proportional) Heat
The VAV/Zone Controller Actuator Package expansion module 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 anytime 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 0.5 ºF above the
unoccupied heating 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 until the space temperature
falls to within 0.5 ºF 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 0.5 ºF above the unoccupied heating setpoint
and the damper will stay in the fully closed position.
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
If the VAV/Zone Controller has been confi gured as a Parallel Fan Pow-
ered terminal unit, the Parallel fan will run continuously when the VAV/
Zone Controller is in the Space Heating mode no matter whether check
for main fan status has been selected or not.
If check for main fan status is selected, the damper will remain in the
closed position until the HVAC unit controller is broadcasting that the
HVAC unit fan is operating, regardless of whether it is calling for heat
or not. The damper will be held at the closed position until the main fan
status broadcast is received. Once the broadcast is received, the damper
will then move to its Night/Reheat Minimum position until the space
temperature begins to fall below 0.5 ºF above the unoccupied heating
setpoint. If check for main fan status has not been selected, the damper
will stay in the closed position until the space temperature begins to fall
below 0.5 ºF above the unoccupied heating setpoint.. When in Supply
Air Heating mode the damper will modulate to maintain the Unoccupied
Heating setpoint.
NOTE: For the VAV/Zone controller to go into Supply Air Heat-
ing mode the HVAC unit fan must be operating and the
Supply Air temperature must be the deadband amount
above the Space temperature.
Unoccupied Mode Sequences
26 VAV/Zone Controller Actuator Package Technical Guide
Sequence of Operations