Xenta 104-A defaults to HVAC_HEAT mode on every control transition

[Product_Support]

Issue

• When the Xenta 104-A goes from occupied to unoccupied mode, it switches from HVAC_COOL to HVAC_HEAT.
• This shows up on the graphic by the nvoEffectiveStpt showing the UNOCCUPIED_HEAT setpoint when the UNOCCUPIED_COOL was expected.

Environment

Xenta 104-A

Cause

Switching from occupancy mode, or override mode, causes the 104-A to go into HVAC_HEAT mode unexpectedly.

Resolution

1. The above graphic shows the room temperature over time as a red/blue line.
   • When the line is shown in red, the 104-A would be in HVAC_HEAT mode.
   • When the line is shown in blue, the 104-A would be in HVAC_COOL mode.
2. Make note that on the first program cycle, if the box is occupied, but the temperature is below the OCCUPIED_COOL setpoint, it will default to HVAC_HEAT mode.
3. During the occupied time, the box performs as expected.
   • If the temperature rises above the OCCUPIED_COOL setpoint, the box goes into HVAC_COOL mode.
   • If the temperature falls below the OCCUPIED_HEAT setpoint, the box goes into HVAC_HEAT mode.
4. Make note of the circled portion of the chart. When the RTU transitions from occupied to unoccupied mode, if the temperature is below the UNOCCUPIED_COOL setpoint, it will default to HVAC_HEAT mode, even if it was in HVAC_COOL prior to the transition. The unit will not be calling for heat, but will display the heating setpoint on the effective setpoint output.