Trane Voyager TS 150-300 Series Installation, Operation And Maintenance Manual page 43

actuator (ECA) to open the economizer damper. The RTRM
tries to cool the zone utilizing the economizer to slightly
below the zone temperature setpoint. If the mixed air
sensor (MAS) senses that the mixed air temperature is
below 53°F, the damper modulates toward the closed
position. If the zone temperature continues to rise above
the zone temperature setpoint controlband and the
economizer damper is fully open, the RTRM energizes the
first stage compressor contactor (CC1). If the zone
temperature continues to rise above the zone temperature
setpoint controlband and the economizer damper is fully
open, the RTRM energizes the second stage compressor
contactor (CC2). The ECA continues to modulate the
economizer damper open/closed to keep the mixed air
temperature that is calculated by the RTRM. If
economizing is not possible, the ECA drives the damper to
the minimum position setpoint when the indoor fan relay
(F) is energized and allows mechanical cooling operation.
When the unit is equipped with the optional fan failure
switch (FFS), wired to the RTOM, the RTRM will stop all
cooling functions and produce an analog output if the fan
failure switch (FFS) does not open within 40 seconds after
a request for fan operation. When the system is connected
to a remote panel, the "SERVICE" LED will flash when this
failure occurs.
Economizer Set-Up
Adjusting the minimum position potentiometer located on
the unit economizer actuator (ECA) sets the required
amount of ventilation air.
Two of the three methods for determining the suitability of
the outside air can be selected utilizing the enthalpy
potentiometer on the ECA, as described below:
1. Ambient Temperature-Controlling the economizing
cycle by sensing the outside air dry bulb temperature.
Table 13 lists the selectable dry bulb values by
potentiometer setting.
2. Reference Enthalpy-Controlling the economizer cycle
by sensing the outdoor air humidity. Table 10 lists the
selectable enthalpy values by potentiometer setting. If
the outside air enthalpy value is less than the selected
value, the economizer is allowed to operate.
3. Comparative Enthalpy-By utilizing a humidity sensor
and a temperature sensor in both the return air stream
and the outdoor air stream, the unit control processor
(RTRM) will be able to establish which conditions are
best suited for maintaining the zone temperature, i.e.
indoor conditions or outdoor conditions.
The potentiometer located on the ECA is non-functional
when both the temperature and humidity sensors are
installed.
Table 13. Potentiometer settings
Potentiometer
Setting Dry Bulb
A 27 Btu/lb (63 kJ/kg)
B 25 Btu/lb (58 kJ/kg)
RT-SVX25Q-EN
Table 13. Potentiometer settings
(a) Factory setting
ReliaTel Control Heating Operation for
Cooling Only Units
When the system switch is set to the "Heat" position and
the zone temperature falls below the heating setpoint
controlband, the RTRM energizes the first stage of electric
heat. If the first stage of electric heat cannot satisfy the
heating requirement, the RTRM energizes the second
stage electric heat if applicable. The RTRM cycles both the
first and second stages of heat "On" and "Off" as required
to maintain the zone temperature setpoint.
Dehumidification
The dehumidification cycle is only permitted above 40 ºF
and is not permitted during a heating cycle or during a
demand for 2
installed zone humidity sensor indicates a relative
humidity equal to or greater than the RH set point as
adjusted on the ReliaTel Options Module (RTOM), a
dehumidification cycle is initiated.
Notes:
• Dehumidification takes priority over a call for one
stage cooling.
• Heating or 2 stage cooling takes priority over
dehumidification, and a relative humidity sensor takes
priority over a humidistat.
Dehumidification Coil Purge Cycle (for units
with the Dehumidification option)
On multiple circuit units with Dehumidification/Reheat
configured, a purge cycle will be active for compressor
reliability. The purpose of this function is to properly
distribute refrigerant and lubricant throughout the system
by temporarily switching to the unused section of the coil
for 3 minutes (purge cycle). The function operates as
follows:
1. A purge cycle will be initiated after 90 minutes of
accumulated compressor run time in only one mode:
cooling or dehumidification, without transitioning to
the other mode.
2. A purge cycle will consist of transitioning to the mode
that hasn't run in 90 minutes of total compressor
operation. The cycle will last for a period of 3 minutes.
3. The 90-minute cycle count will be reset anytime there
is a normal transition between cooling and
dehumidification. Transitioning from one of these
modes to any other mode (off or heat) will not reset the
Enthalpy
counter.
73°F(22.8°C)
4. If the purge cycle is a cooling cycle, only the first circuit
70°F (21.1°C)
will be activated. If it is a dehumidification cycle then
Sequence of Operation
(a)
C 23 Btu/lb (53 kJ/kg)
D 22 Btu/lb (51 kJ/kg)
E 19 Btu/lb (44 kJ/kg)
nd
stage cooling. Otherwise, when an
67°F (19.4°C)
63°F (17.2°C)
55°F (12.8°C)
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