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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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LG LSU180HEV - heat pump /heat ductless unit. Outdoor

Customer Question

LG LSU180HEV - heat pump for ac/heat ductless unit. Outdoor fan will not run, unit hums though. Indoor unit runs but will not cool enough.
Submitted: 2 years ago.
Category: HVAC
Expert:  MattR757 replied 2 years ago.
LG mini split systems control the outdoor fan according to discharge pressure, and the compressor speed according to suction pressure. If the outdoor fan isn't running, the compressor is running at a very low speed (the hum you mention - I describe it as kind of a fast putt putt sound rather than the normal louder motor sound) and the copper pipes are not cold then you almost certainly have a low refrigerant charge. Charging can be tricky because the system will vary the motor speeds to keep pressures near target - We either recover all of the charge and recharge by weight or connect LGMV diagnostic computer to monitor compressor speed, valve positions and coil temperatures. It's possible you have a failure of the fan control but the init is controlled by one big board and we usually see an error code indicating some type of failure if a problem occurs.