R-Pro › Field cases › Heat pumps
Heating COP Drop at Low Outdoor Temp (Below -10°C)
Likely causes
Evaporation pressure drops excessively below -10°C
Check: reduced compressor suction density
What to do: Measure suction/discharge pressure and superheat simultaneously → compare to design specs at low-temperature rating
Suction superheat too high (over 15°C)
Check: insufficient refrigerant circulation
What to do: Check EEV opening log → if superheat control response is delayed at low temp, update firmware or apply manual offset
EEV control logic not adapted for low-temperature operation
Check: Inspect with instruments or visually
What to do: Check refrigerant charge: observe sight glass for bubbles during -10°C operation → replenish if insufficient
Refrigerant charge near lower limit
Check: more sensitive at low temperatures
What to do: Measure outdoor fan current and RPM → inspect fan motor or inverter if deviation exceeds 10% from rated value
Outdoor fan speed control fault
Check: reduced heat recovery from air
What to do: Check low-temp output limit parameter in inverter drive → reset to manufacturer-recommended value
If suction pressure drops below 1.5 bar during sub -10°C operation, manually increase EEV opening by 5–10% and check for immediate COP improvement
All 565 cases work offline in R-Pro, with error codes for 62 brands and P-T data for 108 refrigerants.
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