Occupied Heating Operation - Trane Voyager CV Installation And Maintenance Manual

will be made based on the previous sections, however, the
economizer control point will now be variable based on
the zone cooling demand.
Economizer Enabled at Cooling Start.
has a request for economizer cooling and the unit has met
all Cool mode transition requirements, the Economizer
will open beyond minimum position in order to meet the
calculated discharge air setpoint value. If the economizer
at 100% alone cannot meet the active discharge air
setpoint, the Supply Fan Speed will remain at 58% for 3
minutes. Once the 3 minute compressor inhibit delay has
expired, compressors will be allowed to energize to meet
the space demand. The supply fan speed output will
continue to modulate in order to meet the zone cooling
requirements.
Once compressors are being utilized for additional cooling
capacity, the economizer will be forced to 100% if enabled.
As the cooling capacity begins to stage back (less cooling
load) the economizer will remain at 100%, if enabled, until
all compressors have de-energized.
Economizer Enabled to Disabled.
enabled and the unit is actively cooling with the
economizer, if the economizer becomes disabled the
economizer will be closed to the active minimum position
and compressors will be allowed to stage without delay if
the minimum off timers have expired and there is a
Cooling demand requesting compressor operation.
During this transition, the fan will continue to modulate in
order to meet the space demand.
Economizer Disabled to Enabled.
energized for Cooling and the economizer was disabled,
but becomes enabled due to desirable ambient
conditions, the economizer will be forced to 100% as on
traditional VAV units.
Compressor Cooling
Compressor output control and protection schemes will
function much like on non-SZ VAV units. Normal
compressor HPC and LPC control will remain in effect as
well as normal 3-minute minimum on, off, and inter-stage
timers. Also, the condenser fans will be controlled as on
non-SZ VAV units and compressor staging sequences will
be as described in Table 21 above based on unit tonnage
configuration and lead/lag status.
Cooling Sequence.
If the control determines that there
is a need for compressor stages in order to meet the
discharge air requirements, once supply fan proving has
been made, the unit will begin to stage compressors
accordingly. Note that a 5 second delay will be enforced
between the command for supply fan output operation
and the command for compressor output operation. This
delay is enforced to ensure that the supply fan is energized
and ramping up to operating speed prior to energizing
compressors.
RT-SVX34F-EN
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. Note that the supply fan speed will
Once the unit
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.
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
If the economizer is
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 58% of the unit's full airflow capacity. At
Stage 1 of DX Cooling the Fan Speed will be at a minimum
of 58% and at Stage 2 of DX Cooling the Fan Speed will be
at a minimum of 67%.
If compressors are
3-Stage Cooling Units (40-50T Units)
The minimum fan speed for units with 3 stages of DX
Cooling will be 58% of the unit's full airflow capacity. At
Stage 1 of DX Cooling the Fan Speed will be at a minimum
of 58% and at Stages 2 and 3 of DX Cooling the Fan Speed
will be at a minimum of 67%.

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 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
Sequence of Operation
As the unit
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