WattMaster WM-WCC3-TGD-01B - Manual (Page 789)

Operator Interface
VAV/Zone Controller Technical Guide
21
Box Fan Relay & Reheat Relay Staging Occupied Mode
Relays
Stage On
At
Series
Fan
Parallel
Fan
Heat
Stage
1
Heat
Stage
2
Heat
Stage
3
+0.5 F
Above
Box Heat
Setpoint
See
Note 1
See
Note 2
At Box
Heat
Setpoint
X
-1.0 F
Below
Box Heat
Setpoint
X
-2.0 F
Below
Box Heat
Setpoint
X
Relays
Stage Off
At
Series
Fan
Parallel
Fan
Heat
Stage
1
Heat
Stage
2
Heat
Stage
3
+1.0 F
Above
Box Heat
Setpoint
See
Note 1
See
Note 2
+1.0 F
Above
Box Heat
Setpoint
X
At Box
Heat
Setpoint
X
-1.0 F
Below
Box Heat
Setpoint
X
Notes: 1) The Series Fan will run continuously any time the VAV/
Zone Controller is in Occupied Mode.
2) On parallel fan powered terminal units, the fan will run whenever
Space Heating mode is active. At all other times, the fan will only ac-
tivate if the damper/airfl ow is below a user defi ned low limit setting.
Table 3: Relay Staging - 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 and 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.
Unoccupied 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 VAV/Zone Controller 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 posi-
tion 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 VAV/Zone Controller 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 0.5ºF of the Unoccupied Cooling
Setpoint, the damper/airfl ow calculation causes the air valve to open
proportionally until the maximum setpoint is achieved at 1.5ºF above
the setpoint. This is a 2ºF proportional window starting 0.5ºF below the
cooling setpoint to 1.5ºF above the cooling setpoint.
The damper/airfl ow is never allowed to modulate outside the user adjust-
ed minimum setpoint and the maximum setpoint. 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.
Sequence of Operations