WattMaster WM-WCC3-TGD-01B - Manual (Page 826)

Scheduling
Occupied/Unoccupied Mode
The VAV/Zone Controller monitors the communications loop for its Oc-
cupied and Unoccupied mode of operation command. A week schedule
or a special Optimal Start Schedule can transmit the Occupied command
to the VAV/Zone Controller. This requires the VAV/Zone Controller
Actuator Packages to all be connected to the system communication
loop through their RS-485 connector and to be properly addressed for
the command to be received.
Push-button Override Operation
During unoccupied hours, the user can force the VAV/Zone Control-
ler back to occupied operation by pressing the override button on the
Modular Room Sensor or Digital Room Sensor. The operation for the
push-button override sequence is different depending on which sensor
you are using.
Modular Room Sensor
Pushing the override button for less than 3 seconds initiates the override
which will continue for a user-programmed duration. If during the over-
ride period the button is pressed a second time for less than 3 seconds,
the override timer is reset back to zero and the duration of the override
starts over again. If the button is then depressed for more than 3 seconds
anytime during the override duration, it cancels the override and places
the unit back into normal unoccupied operation.
Digital Room Sensor
Pushing the override button momentarily initiates the override which will
continue for a user-programmed duration. If during the override period
the button is pressed a second time, it will cancel the override. If it is
pressed again, the override will be initiated again for a user-programmed
duration. Every other time the button is pushed, it cancels the override
and places the unit back into normal unoccupied operation.
Grouping Controllers For Overrides
On larger installations with several terminal units, the VAV/Zone Con-
trollers can be confi gured into groups so that an override generated by
one VAV/Zone Controller can cause several other controllers to follow
along and return to occupied mode for the programmed duration. Other
VAV/Zone Controllers not in the same group will simply maintain an
unoccupied damper or airfl ow setting as set by the user.
Push-button overrides are broadcast continuously by the initiating VAV/
Zone Controller until the controller itself times out or the override is
cancelled by the user. This broadcast forces the air handler to start its
main fan and provide cooling or heating, if so confi gured. It will remain
on until the override broadcast has not been detected.
Modes of Operation
There are 7 possible modes of operation for the HVAC Unit and the
VAV/Zone Controller. These modes are determined by the supply air
and/or space demand conditions. They are:
  Supply Air Neutral Mode – (Based on HVAC Unit SAT)
  Space Vent Mode – (Based on VAV/Zone Controller Space
Temp.)
  Supply Air Cooling Mode – (Based on HVAC Unit SAT)
  Space Cooling Mode – (Based on VAV/Zone Controller
Space Temp.)
  Supply Air Heating Mode – (Based on HVAC Unit SAT)
  Space Heating Mode – (Based on VAV/Zone Controller
Space Temp.)
  Off Mode (Not displayed. See “Defi nitions of Modes”)
The process of determining each mode is in the following paragraph,
but the actual operation of each mode is explained in the sections that
follows.
Defi nitions of Modes
VAV & Zone Control Schemes
On all fan-powered and non-fan-powered terminal units, ‘VAV’ or ‘Zon-
ing’ supply air modes are calculated from supply air temperature and
space demands are calculated from setpoints. If the supply air tempera-
ture raises the deadband amount above the space temperature, the supply
air mode is heating. To cancel the supply air heating mode, the supply
air temperature must fall to within 2 °F of the space temperature. If the
supply air falls the deadband amount below the space temperature, the
supply air mode is cooling. To cancel the supply air cooling mode, the
supply air temperature must rise to within 2 °F of the space temperature.
If the supply air is between the heating and cooling deadband amounts,
it is considered neutral mode.
Supply Air Neutral Mode
This mode occurs when the Supply Air Temperature is within the dead-
band amount of the Space Temperature and stays in this mode until the
Supply Air Temperature is above or below the Space Temperature plus
or minus the Supply Air HVAC Mode Deadband.
Space Vent Mode
This mode occurs when the Space Temperature is between the Cooling
and Heating Setpoints.
Supply Air Cooling Mode
This mode occurs when the Supply Air Temperature falls the deadband
amount below the space temperature. To cancel the supply air cooling
mode, the supply air temperature must rise to within 2 °F of the space
temperature.
Space Cooling Mode
This mode occurs when the Space Temperature rises above the Space
Cooling Setpoint.
Supply Air Heating Mode
This mode occurs when the Supply Air Temperature rises the deadband
amount above the space temperature. To Cancel the supply air heating
mode, the supply air temperature must fall to within 2 °F of the space
temperature.
Scheduling and Operation Modes
22 VAV/Zone Controller Actuator Package Technical Guide
Sequence of Operations