Variable Air Volume (Vav) Units - Trane IntelliPak Installation, Operation And Maintenance Manual

General Information
Unoccupied Mode
In Unoccupied mode the unit will utilize setback setpoints,
0% Minimum OA Damper position, and Auto Fan Mode
operation as on normal CV units.The Supply Fan speed,
and cooling and modulating types of heat, will be
controlled to the discharge air target setpoint as is done
during occupied periods.The Supply fan speed during
staged heat control will be forced to 100% as on normal CV
units.
Occupied Heating Operation
If the unit has 2 Stage Gas or Electric Heat, the unit will
drive the supply fan to maximum flow and stage heating
to control to the Zone Heating Setpoint. If the unit has
Modulating Gas or Hydronic heat, the supply fan VFD will
modulate as needed. On an initial call for heating, the
supply fan will drive to the minimum heating airflow. On
an additional call for heating, the heat will control in order
to meet the calculated discharge air target setpoint. As the
load in the zone continues to request heat operation, the
supply fan will ramp-up while the control maintains the
heating discharge air temperature. If the unit has
Modulating Gas or Hydronic heat, heating can be
configured for either the energy saving SZVAV Heating
solution as described above, or with the supply fan
required to ramp to 100% during heating.
Compressor (DX) Cooling
Compressor control and protection schemes will function
identical to that of a traditional unit. Normal compressor
proving and disable input monitoring will remain in effect
as well as normal 3-minute minimum on, off, and inter-
stage timers. Also, all existing head pressure control
schemes will be in effect.
Cooling Sequence
If the control determines that there is a need for active
cooling capacity in order to meet the calculated discharge
air target setpoint, the unit will begin to stage or modulate
compressors accordingly. Once the discharge air target
setpoint calculation has reached the Minimum Setpoint
and compressors are being utilized to meet the demand,
the control will begin to ramp the supply fan speed up
toward 100% to meet any additional cooling demand.
As the cooling load in the zone decreases the zone cooling
algorithm will reduce the speed of the fan down to
minimum per compressor stage and control the
compressors accordingly. As the compressors begin to
stage or modulate back, the supply fan speed will fall back
to the Cooling Stage's associated minimum fan speed, but
not below. As the load in the zone continues to drop,
cooling capacity will be reduced in order to maintain the
discharge air within the ± ½ discharge air target deadband.
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Variable Air Volume (VAV) Units

Occupied Heating - Supply Air Temperature
When a DischargeTemperature Control unit 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 status until the
changeover relay contacts are opened.
Occupied Cooling - Supply Air Temperature
When a DischargeTemperature Control 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 required.The
changeover relay contacts must be open on units with
"Modulating Heat" for the cooling to operate.
Daytime Warm-up (VAV Only)
On DischargeTemperature Control units equipped with
heat, if the zone temperature falls below the daytime
warm-up initiate temperature during the occupied mode,
the system will switch to full airflow. 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 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 relay will be de-energized, releasing the
VAV boxes, the VFD output will go back to duct static
pressure control 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 DischargeTemperature Control unit is equipped
with gas, electric, or hydronic heat and is in the
unoccupied mode, the zone temperature will be controlled
to the default or customer provided setpoint. During an
unoccupied mode for a VAV unit, the VAV box/unocc relay
will be in the unoccupied position and the VFD 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.
Unoccupied Cooling - Zone Temperature
When the unit is in the unoccupied mode, the zone
temperature will be controlled to the default or customer
provided unoccupied cooling setpoint. During an
unoccupied mode for a VAV unit, the VAV box/unocc relay
will be in the unoccupied position and the VFD will be at
RT-SVX36K-EN