Common Operations - Honeywell CVL4022ASVAV1 Engineering Manual

APPENDIX

Common Operations

This Appendix describes some of the common control
sequences supported by the AscVAV controller.
Room Temperature Sensor (RmTemp)
This is the room space temperature sensor. This sensor is the
T7770/TR2x or theTR71/75(Zio) Wall Module. When it is
configured, it provides the temperature input for the
temperature control loop. If it is not configured, it is required
that a room temperature sensor value be transmitted from
another device via the Lon network by binding nviSpaceTemp.
Another option is to Share a Wall Module using nviShare. If no
valid room temperature value is available to the controller, the
temperature control algorithm in the controller is disabled,
causing the heating and cooling control outputs to be turned
off and the airflow or damper position is set to the minimum
setpoint.
The room temperature sensor can be calibrated via the Zio
interface or using the custom calibration view available in the
Niagara tool.
Center Setpoint
This is the Setpoint Potentiometer contained in the T7770/
TR2X Wall Module. Zio also allows center setpoint to be
modified in the tenant mode under the 'View More' section via
a selected Home Screen or View More. The parameter
nciWallModCom.UseWmStPt must be set to 1 to indicate that
the controller can use the center setpoint value from the
wallmodule. The values configured for
nciWallModCom.LowSetPt and HighSetPt determine the
method used to calculate the effective setpoint: (Offset) and
(AbsoluteMiddle).
These values limit the range of the center setpoint. Absolute
versus relative center setpoint is determined by the model of
T7770/TR2X selected and the configuration of the UI type:
2: TR2x SetPt Absolute (UI_TR2xSetPtAbs)
3: TR2x SetPt Relative (UI_TR2xSetPtRel)
Offset: When the Wall Module setpoint limits are between -10°
to +10°F , the center setpoint value is added to the configured
occupied setpoints for the heat and the cool.
Absolute: When the Center Point value limit is greater than 10
°F then the setpoint knob becomes the center of the Zero
Energy Band (ZEB) between the cooling and heating
occupied setpoints. The size of the ZEB is calculate by taking
the difference between the heating and cooling occupied
setpoints;
Effective setpoint (in cooling mode) = Center setpoint +
(CoolOccSpt - HeatOccSpt) / 2.
Effective setpoint (in reheat mode) = Center Setpoint -
(CoolOccSpt - HeatOccSpt) / 2
The Wall Module center setpoint is active only when the
effective occupancy is Occupied or Bypass.
31-00083—02
Bypass Mode
During Unoccupied periods, the facility occupant can
request that Occupied temperature control setpoints be
observed by depressing the Bypass pushbutton on the
wallmodule. When activated, the controller remains in Bypass
mode until:
1. Bypass Duration Setting has timed out (BypassTime), or
2. User again presses the Wall Module pushbutton to switch
off Bypass mode, or
3. Occupancy schedule switches the mode to Occupied.
The LED on the Wall Module indicates the current bypass
mode status.
BypassTime
BypassTime is the time between the pressing of the override
button at the wall module (or initiating OC_BYPASS via
nviManOcc) and the return to the original occupancy state.
When the bypass state has been activated, the bypass timer
is set to BypassTime (defaultof 180 minutes).
OverrideType (conventional wall modules)
OverrideType specifies the behavior of the override button on
the wall module. There are three possible states that have the
following meanings:
NONE-Disables the override button.
NORMAL-Causes the override button to set the Override state
to OC_BYPASS for BypassTime (default 180 minutes), when
the override button has been pressed for approximately 1 to 4
seconds, or to set the override state to UNOCC when the
button has been pressed for approximately 4 to 7 seconds.
When the button is pressed longer than approximately 7
seconds, then the override state is set to OC_NUL (no manual
override is active).
BYPASS_ONLY causes the override button to set the override
state to OC_BYPASS for BypassTime (default180 minutes),
on the first press (1 to 7 seconds). On the next press, the
override state is set to OC_NUL (no manual over ride is
active).
Zio Override
Occupant override is not a configurable option. The Zio has a
fixed override feature set:
Occupied with fixed interval configured by:
nciWallModCom.BypassTime
0 = range = 65535 min
UnOccupied with a Zio user selectable UnOccupied override
interval:
1 = interval = 99 days
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