Error Codes: System Malfunctions
ESIE13-02
Part 4 – Troubleshooting
146
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5.5
“UF”
Malfunction of Transmission between Hydro-box and Outdoor Unit or Gas
Shortage
Remote controller
display
UF
Method of
malfunction
detection
Check the transmission between the indoor and outdoor units with a microcomputer when the power
turned ON.
Detect by checking the following temperature differences during compressor operation.
A: Difference in temperature detected by the indoor liquid thermistor (R3T) and the indoor suction
air thermistor (R1T)
B: Difference in evaporation temperature (Te) (or condensation temperature (Tc) during heating
operation) detected by the indoor heat exchanger thermistor (R2T) and the compressor sensor
Malfunction
decision conditions
When the inter-unit wiring between the indoor and outdoor units is incorrect
When the following conditions continue for 20 minutes during compressor operation
A: R2T – R1T < 4ºC, and
B: R2T – Te (or Tc during heating operation) > 14ºC (24ºC during heating operation)
Supposed causes
Faulty inter-unit wiring between the indoor and outdoor units
Refrigerant shortage (out of gas)
Clogged refrigerant piping system
