*LCU Troubleshooting Mix Air Temperature Sensor (MAT) and Return Air Temperature Sensor (RAT)
Economizer Actuator Module - Prior to 8/01/2005
Read the DC voltage with the sensor attached. If the voltage does not appear to be correct, read the resistance of the circuit, then the sensor itself, to see if a problem exists in the sensor or the wiring. With the sensor not
attached there should be approximately 2.50 VDC at the terminals listed above.
Refer to table 109. Page 153 of RT-SVD03N-EN - Click the link below
Economizer Actuator Module - 8/01/2005 and later
Read the DC voltage with the sensor attached. If the voltage does not appear to be correct, read the resistance of
the circuit, then the sensor itself, to see if a problem exists in the sensor or the wiring. With the sensor not
attached, there should be approximately 5.0 VDC at the terminals listed above.
Refer to table 110. Starting on pages 153 - 154 of RT-SVD03N-EN - Click the link below
Sensor Faults
A sensor fault will occur if a sensor fails during normal operation. When power is freshly applied to the unit, the ECA, and RTEM recognize which sensors are installed.
Note: If only the MAT is hooked up, the economizer control action will be dry bulb. If the OAH/OAS and MAT are hooked up, the economizer control action will be in reference enthalpy. If after power up one of the connected sensors is disconnected, the economizer should indicate a fault.
Note: The mixed air temperature sensor (MAT) and outdoor air sensor (OAS) input from the RTEM are the minimum required sensors.
Error Code for MAT - RAT 1/2 second on, 1/4 second off
4 Flash - RA temp sensor
8 Flash - MA temp sensor
Mixed Air Temperature Low Limit Diagnostic
In all conditions on all ReliaTel™ controlled units, if the mixed air temperature falls below 45°F, the mixed air temperature low limit is active and the economizer actuator will close to the active minimum position. On Title 24 compliant units, ReliaTel™ will set an auto-reset diagnostic to be used by BAS and TD-5 when the mixed air temperature low limit is active. The RTEM will revert to normal operation when the mixed air temperature rises above 48°F. The diagnostic will be reset when the mixed air temperature low limit is inactive.
*Please refer to the latest available literature when available.* - Click the link below:
WARNING:
Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.