Trane ReliaTel Diagnostic Manual page 102

ReliaTel Economizer Operation
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During unoccupied mode, the minimum position is 0%
The following inputs are used:
Mixed Air Sensor (MAS)
MAS measures the dry bulb temperature of the air leaving the evaporator coil while economizing.
Return air, outdoor air and cooling caused by any compressor cooling make up the Mixed Air input.
The MAS is plugged into the Economizer Actuator Module (ECA).
Outdoor Air Sensor (OAS)
The OAS measures the ambient air surrounding the unit. It is located in the compressor section on
the lower or upper left side for Precedent units depending on model, or the right side beneath the
control panel on Voyager 2, or the economizer end of unit for Voyager 3 units. Ventilation holes in
the access panel of the unit allow air movement across the sensor. The OAS connects to the RTRM
module.
Outdoor Air Sensor
Outdoor Humidity Sensor (OHS)
The OHS measures the relative humidity of the outside air. It is located inside the economizer hood.
The OHS is plugged into the ECA.
Return Air Temperature Sensor (RAT)
The RAT measures the return air temperature. It is located on the return air damper of the
economizer. The RAT is plugged into the ECA.
Return Humidity Sensor (RHS)
The RHS measures the relative humidity of the return air. It is located on the return air damper of
the economizer. The RHS is plugged into the ECA.
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Night Setback — During NSTS, the damper drives to full closed position. If there is a call for
cooling, the damper opens to satisfy the cooling requirement. The damper stays closed during
heating mode.
RT-SVD03G-EN