Variable Air Volume Applications (Single Zone Vav); Supply Fan Output Control; Minimum Supply Fan Output; Supply Fan Mode Operation - Trane Voyager CV Installation And Maintenance Manual

CV Units with Modulating Heat
On units with Modulating Gas Heat, Supply Air Tempering
is inherent to the Modulating Heat design and does not
require any additional configuration/enabling. Modulating
Heat Tempering is accomplished by allowing the unit to
return to heating if the Zone is marginally satisfied and the
Supply Air temperature begins to fall. The following
conditions must be true to enable the unit to perform
"Tempering":
1. The supply fan is ON.
2. The unit is in Occupied mode.
3. Zone Temp. is less than the active Cooling setpoint.
4. The unit is in Heat mode but is not actively heating OR
5. The unit is in AUTO-COOL mode but not actively
cooling and cooling capacity has been OFF for 5
minutes.
Once the above conditions are met, and the supply air
temperature drops below the ZHSP - 10°F , the unit will
transition back into active heating operation and will begin
to control the modulating heat output to maintain the
supply air temperature.
Once the unit has entered into Tempering mode, the unit
will leave active heating either by normal heat termination
as determined by the heating control algorithm or when
the Zone Temperature reaches the active ZCSP .
SZ VAV Units with Staged Heat
For SZ VAV units configured with a Staged Heating type,
the Supply Air Tempering function will operate as on a CV
unit with Staged Heat.
SZ VAV Units with Modulating Heat
For units configured with a Modulating Heat type,
"Tempering" is an extension of normal Heating control
which allows a transition from inactive "Auto-Cool" mode
to Heating based on supply air temperature if the Zone
Temperature is in control. The following conditions must
be true to allow the unit to enter Supply Air Tempering:
1. Supply Fan is ON.
2. The unit is in Occupied mode.
3. The unit is operating in Auto-Cool Mode.
4. Cooling has been inactive for 5 minutes.
When the above conditions are true, Tempering will be
allowed when the Supply Air Temperature falls below the
user selectable Minimum Supply Air Cooling Setpoint
(minus deadband) as long as the Zone Temperature is <
ZCSP - 1°F . Once the unit transitions into "Tempering" the
unit will transition to normal heating control and will
control the supply air temperature between the minimum
and maximum supply air setpoints.
If the Zone Temperature rises above the ZCSP during
"Tempering" the unit will de-energize Heating and
"Tempering" will be disabled until conditions allow for it
RT-SVX34F-EN
again. Normal Auto-Changeover requirements will be in
control to allow the unit to transition into Active Cool
mode.
Variable Air Volume Applications
(Single Zone VAV)

Supply Fan Output Control

Units configured for Single Zone VAV will include a VFD
controlled supply fan motor which will be controlled via
the 0-10Vdc Indoor Fan Speed output located on the RTOM
and the RTRM Supply Fan output. With the RTRM Supply
Fan output energized and the RTOM Indoor Fan Speed
output at 0Vdc the fan speed output is 58% (35Hz) from the
VFD motor and at 10Vdc the fan speed output is 100%
(60Hz). The control will scale the 0-10Vdc output from the
RTOM linearly to control between the 58%-100%
controllable range based on the space heating or cooling
demand.

Minimum Supply Fan Output

Refer to the table below for details on minimum supply fan
output signals associated with each unit function. Note
that each value represents the actual Fan Output %.
Function
Ventilation Only
Economizer Cooling
Cool 1 (C1 Energized)
Cool 2 (C1 or C2)
Cool 3 (C1 + C2 Energized)
SZVAV Modulating Heat
CV Staged Heat
SZVAV Modulating Heat Tempering
CV Staged Heat Tempering
Modulating Reheat

Supply Fan Mode Operation

Units configured for Single Zone VAV control will utilize
Supply Fan Mode selection as is currently implemented
into Reliatel controls for normal Zone Control and will be
selectable between AUTO and ON via a connected Zone
Sensor module or through BAS/Network controllers.
Supply Fan Mode Auto Operation
For active Cooling, Heating, and Dehumidification
operation the Supply Fan will be commanded ON and will
ramp up to the appropriate minimum speed once the unit
determines that there is a request for capacity control.
Once the active request is cleared and all capacity is de-
energized normal supply fan off delays as implemented on
constant volume units will be in effect. During the Supply
Fan Off-Delay, the supply fan will remain energized for the
Startup
Minimum Fan
Output %
58%
58%
58%
67%
67%
58%
100%
58%
100%
80%
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