Issue
Confusion over behavior of the Xenta 121 when using a occupancy sensor.
Environment
Xenta 121-FC
Xenta 121-HP
Cause
When an occupancy sensor is not defined in the configuration of a Xenta 121 controller the effective occupancy will follow the command given by nviOccManCmd. However, when an occupancy sensor is defined, either as a network bound point or a hardwired sensor, the effective occupancy of a Xenta 121 will behave differently.
Resolution
The Xenta 121 operates as follows when using an occupancy sensor:
The most notable difference in how the Xenta operates are:
- When nviOccManCmd is in either the OC_UNOCCUPIED or the OC_STANDBY modes then the Xenta 121 will ignore the state of the occupancy sensor.
- When nviOccManCmd is in the OC_OCCUPIED mode the Xenta 121 will follow the state of the occupancy sensor. Note that this means that the controller could actually enter the unoccupied mode even though nviOccManCmd is set to be occupied.
- When nviOccManCmd is in the Oc_Nul mode the effective occupancy of the Xenta 121 will Oc_Standby until a signal is received from the occupancy sensor at which time it will change to be Oc_Occupied.
This behavior should be taken into consideration when deciding on how to implement an occupancy sensor. It may be desirable to set the nviOccManCmd to Oc_Nul whenever the occupancy sensor should be considered and to set it to Oc_Unoccupied when the occupancy sensor should be ignored. This effectively utilizes the occupied, unoccupied and standby modes as three distinct modes of operation to maximize comfort and efficiency.
