WattMaster WM-WCC3-TGD-01B - Manual (Page 786)

VAV/Zone Controller Technical Guide
Operator Interface 18
Sequence of Operations
During Override operations, the user can cancel the override by press-
ing the override button for a period of time between 3 seconds and 10
seconds. This restores the normal unoccupied operation.
On larger installations with several terminal units, the VAV/Zone
Controllers can be confi gured into groups so that an override 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 set-
ting 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 can force 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.
NOTE: The VAV/Zone Controller will go into an override condi-
tion for the user-programmed amount of time when this
button is pushed even if the unit is already in an occupied
condition.
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 nition below)
The process of determining each mode is discussed below, but the actual
operation of each mode is explained in the section 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 rises 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 2ºF 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 within 2ºF 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 between the
heating and cooling deadband amounts.
Space Vent Mode
This mode occurs when the Space Temperature is between the heating
and cooling 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 2.0°F of the space
temperature.
Space Cooling Mode
This mode occurs when the Space Temperature rises above the Space
Temperature.
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 2.0 °F of the Space
Cooling Setpoint.
Space Heating Mode
This mode occurs when the Space Temperature falls below the Space
Heating Setpoint.
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.