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Operation
RT-SVX20A-E448
Operation with a
conventional thermostat
The ReliaTel module has
conventional thermostat
connections as well as Zone Sensor
Module connections. When a
conventional thermostat is
controlling the unit, operation
differs as follows:
• Supply Air Tempering feature is
not available. If outdoor air is
being introduced through the
equipment, discharge air
temperature may be cold when
not actively heating.
• Proportional Integral (PI) control
is not available.
• Zone Sensor Diagnostics are
only available on the RTRM
module on the J6 terminals,
instead of at the Zone Sensor in
the space.
• Intelligent Fall-Back is not
available. If a failure occurs in
the device controlling the
equipment, operation will cease.
• Heat Pump Smart Recovery and
Smart Staging is not available.
Heat Pump operation becomes
more costly unless the generic
control being applied can
accomplish this.
• Remote Sensing Capabilities are
not available on most
mechanical thermostats.
• Space Temperature Averaging
capabilities are not available on
most mechanical thermostats.
• 27½ to 50 VAV - Conventional
thermostat input terminals are
inactive.
• Built in Night Set Back and
Unoccupied Functions function
differently with a conventional
mechanical thermostat.
• A built-in algorithm which allows
for automatic reset of the
discharge air temperature while
economizing is not available.
The terminal strip for attaching the
thermostat wires is located on the
RTRM module in the control
compartment.
When the unit is operating from a
conventional thermostat or other
binary input, the economizer
setpoint feature, relative to the
cooling and heating setpoints, is
lost. The economizer control is
based strictly on a signal from the
thermostat, but still maintains
mixed air temperature control of
53°±3°F when in the economizer
mode. The economizer enable and
disable function is still determined
by the outside air sensor through
the RTRM.
If a single-stage thermostat is used,
only the economizer (if enabled) or
the compressor (if economizer is
disabled) will operate on a call for
cooling. A twostage thermostat is
required to achieve economizer
operation and compressor
operation at the same time.
With economizer enabled, a Y1 call
for 1st stage cooling will be the
economizer. The damper will
modulate between minimum
position and 100% to maintain
mixed air temperature at 53°±3°. At
50°F the damper will be at
minimum position. If the
economizer is enabled, a Y2 call for
2nd stage cooling will start the first
compressor if required. If the
economizer is disabled, 1st stage
(Y1) will be the first compressor. If
the unit has two compressors, a call
for 2nd stage cooling (Y2) will start
the second compressor. When using
a conventional thermostat, or other
binary input, the ReliaTel controls
will only allow two stages of
cooling.
Figure 30 - Terminal strip
Customers occasionally require
operation with a conventional
thermostat rather than a zone
sensor. In some cases there is a
preference for a specific thermostat
model, and in others there is
reluctance to adopt newer
technology that may not be as well
understood as conventional
thermostats. In addition, non-Trane
Building Controllers typically
provide an interface to HVAC
equipment based on a conventional
thermostat interface. Units applied
with this type of controller need to
accept conventional thermostat
inputs.
COM
T
R
Y1
W1/0
G
W2
X2
Y2