T916_O / T961_O: Discharge Temperature
On the VSODC, this fault would be displayed on the seven-segment LED as a number 15. A 15 displayed is one of several inverter faults. You will need to validate this fault at the EcoNet Thermostat or by looking at the red or yellow flashing LED's in the upper right quadrant of the drive itself
The Drive LED's will be flashing the Yellow LED 6 times.
High compressor discharge temperature is generally caused when there is not enough refrigerant vapor coming back to cool the compressor (high suction superheat). High Superheat can be a result of low refrigerant charge, restricted refrigerant flow, or excessive heat load on the evaporator coil.
When the discharge temperature reaches 225 degrees F, the system will fold back if slower speeds are available in order to reduce the discharge temperature.
The compressor will continue to fold back until the discharge temperature gets below 200 degrees F. Once it stabilizes, the compressor may again try to ramp up as long as the discharge temperature stays below 225 degrees F.
Check the discharge line thermistor against the thermistor chart to ensure it is calibrated. Physically inspect the sensor and sensor wires to make sure the insulation is in tact and not damaged. If it is damaged or the sensor does not read proper resistance against a known temperature, replace the discharge sensor.
Also, check the suction line temperature going into and coming out of the reversing valve to make sure there is no hot gas leaking into the cooler suction line leading to the compressor.
When checking for high heat load on the evaporator, take a measurement of the return air going into the coil to eliminate any infiltration into the return duct work that may be putting excessive load on the coil.
Check for restrictions in the refrigerant circuit such as kinks, plugged filter drier or strainers or an otherwise improperly operating EEV.
