Supply Air Tempering - Trane SYMBIO 700 Troubleshooting Manual

Supply Air Tempering

Supply Air Tempering Operation
If the Supply Air Tempering function is configured and the Discharge Air Temperature local sensor is
valid, the Space Temperature Control algorithm manages the Supply Air Tempering function to prevent
excessively cold discharge air from being supplied from the unit. The sequence for VVZT systems are
consistent with CVZT systems, utilizing single-speed, and full airflow operation.
Supply Air Tempering is not applicable when a Conventional TStat is configured as the Space
Controller.
The following requirements must be met to allow Supply Air Tempering on a Staged Heat unit:
• The supply fan is ON.
• The unit is in Occupied mode.
• The unit is in any heating mode, including Heat, Emergency Heat, Morning Warmup, Max
Heat but is not actively heating OR
• The unit is in any cooling mode except night purge, but not actively cooling and cooling
capacity has been OFF for 5 minutes.
If the discharge air temperature drops to the Discharge Air Temperature Minimum Cool Limit -
Active and the Space Temperature is less than the Active Space Temp Cooling Setpoint Status –
0.5°F and if there are no stages of heat on, the Supply Air Tempering function will bring ON one
stage of available staged auxiliary heat.
Note: Heat Pump units will energize 1 stage of auxiliary Heat in order to meet the Supply Air
Tempering request; compressor-based heating will not be used to satisfy Supply Air Tempering.
Once Supply Air Tempering is active, the stage of heat will be turned OFF if the Discharge Air
Temperature rises to 10°F ABOVE the Discharge Air Temperature Minimum Cool Limit - Active,
or the Space Temperature rises to the Space Temp Cooling Setpoint Status. Additionally, if the
Space Heat Control function determines that 1 or more stages of Heat are required to meet the
Space Temp Heating Setpoint Status, Tempering will be discontinued, and the unit will stage
heating to meet the current space demand.
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