Trane RT-SVX10C-EN Variable Air Volume VAV Units, Unit Component Layout and Shipwith Locations

Variable Air Volume (VAV) Units

Occupied Heating - Supply Air Temperature

When a VAV units is equipped with "Modulating Heat", and the system is in an occupied mode, and the field supplied changeover relay contacts (5K87) have closed, the supply air temperature will be controlled to the customer specified supply air heating setpoint. It will remain in the heating sta- tus until the changeover relay contacts are opened.

Occupied Cooling - Supply Air Temperature

When a VAV unit is in the occupied mode, the supply air temperature will be controlled to the customers specified supply air cooling setpoint by modulating the economizer and/or staging the mechanical cooling "On and Off" as re- quired. The changeover relay contacts must be open on units with "Modulating Heat" for the cooling to operate.

Daytime Warm-up

On VAV units equipped with heat, if the zone temperature falls below the daytime warm-up initiate temperature dur- ing the occupied mode, the system will switch to full air- flow. During this mode, the VAV box/unocc relay, RTM K3, will be energized (this is to signal the VAV boxes to go to 100%). After the VAV box max stroke time has elapsed (factory set at 6 minutes), the VFD/IGV output will be set to 100%. The airflow will be at 100% and the heat will be turned on to control to the occupied heating setpoint. When the zone temperature reaches the daytime warm-up termination setpoint, the heat will be turned off, the K3 re- lay will be de-energized, releasing the VAV boxes, the VFD/IGV output will go back to duct static pressure control

General Information (Continued)

and the unit will return to discharge air control. If the occ zone heating setpoint is less than the DWU terminate setpoint, the heat will turn off when the occ zone heat setpoint is reached, but it will stay in DWU mode and cycle the heat to maintain setpoint.

Unoccupied Heating - Zone Temperature

When a VAV unit is equipped with gas, electric, or hydronic heat and is in the unoccupied mode, the zone temperature will be controlled to within the customers specified setpoint deadband. During an unoccupied mode for a VAV unit, the VAV box/unocc relay will be in the unoccupied position and the VFD/IGV output will be at 100%. This means that if there is a call for heat (or cool) and the supply fan comes on, it will be at full airflow and the VAV boxes in the space will need to be 100% open as signaled by the VAV box/ unocc relay.

Supply Air Tempering

On VAV units equipped with "Modulating Heat", if the sup- ply air temperature falls 10 F below the supply air tempera- ture setpoint, the hydronic heat valve will modulate to maintain the supply air temperature to within the low end of the setpoint deadband.

Supply Duct Static Pressure Control (Occupied)

The RTM relies on input from the duct pressure transducer when a unit is equipped with Inlet Guide Vanes or a Vari- able Frequency Drive to position the Inlet Guide Vanes or set the supply fan speed to maintain the supply duct static pressure to within the static pressure setpoint deadband. Refer to the Transducer Voltage Output vs Pressure Input values listed in the Space Pressure Transducer (3U62) section.

Unit Component Layout and "Shipwith" Locations

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