Occupied Heating Operation; Staged Heating Operation; Modulating Heat Operation With; Szvav Heating - Trane Voyager Commercial Installation, Operation And Maintenance Manual

As the zone cooling demand continues to increase, if
additional capacity is required, the supply fan output
will be modulated above minimum speed in order to
meet the zone requirements.
N N o o t t e e : : The supply fan speed will remain at the
compressor stage's associated minimum value
until the control requires additional capacity to
meet the zone demand.
As the cooling load in the zone decreases the control
will reduce the speed of the fan down to minimum per
compressor stage and control the compressor outputs
accordingly. As the compressors begin to de-energize,
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
calculated discharge air setpoint.
Cooling Stages Minimum Fan Speed
As the unit begins to stage compressors to meet the
cooling demand, the following minimum Supply Fan
Speeds will be utilized for each corresponding Cooling
Stage. Note that the Supply Fan Speed will be allowed
to ramp up beyond the minimum speed in order to
meet the zone cooling demand.
2-Stage Cooling Units (27.5-35T Units)
The minimum fan speed for units with 2 stages of DX
Cooling will be 45% of the unit's full airflow capacity. At
Stage 1 of DX Cooling the Fan Speed will be at a
minimum of 45% and at Stage 2 of DX Cooling the Fan
Speed will be at a minimum of 67%.
3-Stage Cooling Units (40-50T Standard
Efficiency VAV Units)
The minimum fan speed for units with 3 stages of DX
Cooling will be 45% of the unit's full airflow capacity. At
Stage 1 of DX Cooling the Fan Speed will be at a
minimum of 45% and at Stages 2 and 3 of DX Cooling
the Fan Speed will be at a minimum of 67%.
5-Stage High Efficiency Cooling Units and 40-50T
Standard Efficiency CV Units
The minimum fan speed for units with 5 stages of DX
Cooling will be 33% of the unit's full airflow capacity. At
Stage 1 of DX Cooling the Fan Speed will be at a
minimum of 33%.
Add % for other stages 2-5.

Occupied Heating Operation

Occupied Heating operation on units configured with
Single Zone VAV control will utilize two separate
control methodologies based on heating
configurations. For all "Staged" Heating types (Electric
and Gas), the unit will utilize 100% full airflow during all
active heating periods like traditional Constant Volume
units. For Modulating Gas heat units, the unit will have
the ability to control the discharge air temperature to
RT-SVX34R-EN
the calculated discharge air heating setpoint in order to
maintain the Zone Temperature to the Zone Heating
setpoint.

Staged Heating Operation

For units configured with Staged Heat once the control
determines that there is an active heating capacity
request, the unit will energize the Supply Fan and ramp
up to full speed. The control methodology during
Active Heating on units configured with Staged Heat
types will be identical to traditional Constant Volume
units; heating stages will be energized/de-energized to
meet the Zone Heating demand. Note that all Electric
and Gas Heat staging sequences will be identical to as
on Constant Volume units.
Modulating Heat Operation with SZVAV
Heating
Units configured with Modulating Gas Heat will utilize
true Single Zone VAV control in the same manner as
during Active Cooling.
Heating Sequence
Once the unit has met all Auto-Changeover
requirements and the control determines that there is a
space heating demand, the unit will transition into zone
heating. Once the Discharge Air Temperature falls
below the calculated discharge air temperature
setpoint, the unit will initiate the Modulating Heat
output request and control the supply fan at minimum
speed. At this point, the Modulating Heat output will be
controlled to maintain the discharge air temperature
requirements and the supply fan speed will be
controlled between 58%-100% to meet the zone heating
requirements.
As the heating load in the zone decreases the fan speed
will decrease down to minimum (58%) and control the
modulating heat output as necessary to meet the
discharge air heating requirements. As the load in the
zone continues to drop the fan speed will be
maintained at this minimum airflow and the
modulating heat output will be controlled accordingly.
N N o o t t e e : : The gas heat staging sequences will be the same
on SZ VAV units as on traditional CV units.

Unoccupied Cooling and Heating

Operation

For SZ VAV units, the unit will control Heating, Cool,
and Hot Gas Reheat as during Occupied periods using
the normal heating and cooling Single Zone VAV
algorithms. In Unoccupied periods the unit will utilize
setback setpoints, a 0% Minimum OA Damper position,
and Auto fan mode operation as on normal Constant
Volume units.
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