Sequence of operation
Remote Occupancy Override
– The controller monitors its
Remote
input that is typically connected to the isolated,
dry contact of an occupancy sensor located in the zone. (To use the occupancy override as described here, the
Standby Offset
value must be set to zero.) The controller can override the occupancy state based on whether or
not the space is actually occupied. If the occupancy sensor contact is in the same state as
Occ Override Normal
Logic State
setting, the zone follows its normal occupancy schedule. If the contact is in the opposite state, it
overrides the zone into the unoccupied mode. The input can be configured for normally closed or normally opened
contact types and is set to Open by default so that it does not affect the controller occupancy operation if left
unused.
The
Remote
input can also be used to expand the setpoints during occupied periods without affecting the
occupancy status of the zone. Whenever the zone is occupied and the
Remote
input senses the occupant has left
the zone, if a value greater than zero has been entered for the
Standby Offset
, then the occupied setpoints will be
expanded by that number of degrees. This provides the ability to save energy but recover more rapidly rather than
having the zone go unoccupied.
Learning Adaptive Optimal Start
– This function gradually adjusts the unoccupied setpoints over a specified
period of time to achieve the occupied setpoint by the time scheduled occupancy begins. This learning adaptive
algorithm uses the
learned heating capacity
and
learned cooling capacity
values to calculate the effective
setpoints prior to the occupied start time. The algorithm calculates a learned cooling and heating capacity during
the previous unoccupied time. Set the
Learning Adaptive Optimal Start
recovery period from 1 to 4 hours in
Optimal Start
. When the
Learning Adaptive Optimal Start
routine runs, adjustments are based on the color that is
achieved when occupancy begins. Adjustment amounts are defined in the thermographic color fields located
directly above the
Effective Setpoints
graph under
Setpoints
.
BAS On/Off
– This function allows third party control of the controller occupancy.
Occupancy Schedules
must be
set to
Disable
to use this function. When set to
Occupied
or
Unoccupied
,
Optimal Start
is automatically disabled.
Alarms
Space Temp Sensor Alarm
– The VAV Zone Controller monitors each space temperature sensor and the network
input for space temperature. If no valid space temperature value is available, the controller generates an alarm
and disables all local heating or cooling. The controller modulates the damper to the minimum heat, minimum
cool, or ventilation position based on the air source mode. Normal operation resumes when the controller detects
a valid sensor value.
Space Temperature Alarm
– The controller generates an alarm if the space temperature exceeds the alarm
setpoint. The occupied alarm setpoints are determined from the configurable
Occupied Alarm Hysteresis
(5∆°F
[2∆°C) default) which is subtracted from the configured occupied heat and added to the configured occupied cool
setpoints. If the space temperature rises above or falls below this value and the condition lasts for more than 15
minutes, an alarm is generated. The configurable unoccupied high and low alarm setpoints have a fixed 10
minute alarm delay. When a transition from unoccupied to occupied occurs or the occupied temperature setpoints
are changed causing an immediate alarm condition, the controller automatically calculates an additional alarm
delay equal to 10 minutes for each degree of change. This additional delay is added to the 15 minute fixed delay
and allows the space temperature to recover and achieve the new setpoints, preventing unnecessary alarms. The
space temperature alarm returns to normal when the space temperature again falls between the current mode’s
alarm setpoints.
Supply Air Temperature Alarm
– The controller generates an alarm if the SAT exceeds the configured
High SAT
Alarm Limit
(120°F [48.9°C] default) or falls below the
Low SAT Alarm Limit
(45°F [7°C] default) for more than
5 minutes. The hysteresis for return to normal is 3∆°F (1.6∆°C). The
High SAT Alarm Limit
should be set to a
value at least 15∆°F (8.3∆°C) ( abov
e the
Maximum Heating SAT
or the maximum discharge temperature from
the air source, whichever is greater.
42
VAV Zone Controllers