If your LG Multi V system is showing error 150, the system has calculated that liquid refrigerant is at risk of flooding back to the compressor.
This code is unusual, and worth understanding properly: it warns you before the damage, not after it.
What this means for your building
Refrigerant should reach the compressor as vapour. The system measures superheat — how far above its boiling point the returning refrigerant is — to confirm that.
When superheat falls too low, refrigerant may still be partly liquid on its way back. Error 150 is the system reporting that calculation and flagging the risk.
Compressors compress vapour. They cannot compress liquid. When liquid arrives, it causes mechanical stress inside the compressor, and it washes lubricating oil away from surfaces that need it. The combination is how compressors are destroyed.
Why this code is worth more than most
Nearly every fault code reports something that has already happened. A compressor has failed, a sensor has died, a fan has stopped.
Error 150 reports something about to happen.
That makes it one of the few genuine early warnings a VRF system gives you, and it means the economics are unusually favourable. The correction is typically a valve, a charge adjustment or a sensor. What it prevents is the largest repair on the system.
Buildings that act on a 150 rarely see a compressor failure from flood-back. Buildings that reset it often do.
How urgent is it?
Urgent. The condition is causing wear right now, while the system runs.
There is no safety hazard and no refrigerant escaping. The risk is entirely to the compressor, and it accumulates for as long as the condition persists.
What it typically costs
Moderate, and usually well short of the outcomes it warns about.
Most causes resolve to an expansion valve, a refrigerant charge correction, or a sensor giving inaccurate readings. Those are contained repairs.
Set against a compressor replacement — component, refrigerant recovery, system cleanup, and substantial labour — the case for acting immediately is not close.
What causes it
- Expansion valve not metering correctly — allowing more refrigerant through than the evaporator can boil off
- Refrigerant overcharge — often from a previous top-up rather than a proper repair
- Low load conditions — little heat available to boil the refrigerant, particularly in mild weather or lightly occupied space
- Sensor faults giving the system inaccurate superheat readings
- Distribution problems across a heat recovery system where refrigerant is not routed as expected
That third cause catches people out. A system can be fine at full load and flood back in mild conditions, which makes the code look intermittent when the underlying fault is constant.
What happens if you leave it
The compressor absorbs it.
Liquid flood-back damage is cumulative and mechanical. It does not announce itself day to day — the system keeps running and tenants stay comfortable. Then the compressor fails, and nobody connects it to a code that was appearing months earlier.
This is precisely the failure pattern that makes fault history worth reviewing. A 150 in the log a year before a compressor failure is not a coincidence.
What we check
- Verify superheat measurements and confirm the reading is genuine rather than a sensor fault.
- Test expansion valve operation across the affected circuit.
- Assess refrigerant charge — overcharge is a common driver.
- Check the operating conditions when the code appears, particularly whether it correlates with low load.
- Inspect temperature sensors feeding the superheat calculation.
- Review distribution on heat recovery systems, where routing affects where refrigerant ends up.
- Assess compressor condition, since flood-back may have been occurring for some time before the code was noticed.
What you can tell us before we arrive
- When does it appear? Mild weather or low occupancy points toward low-load flood-back.
- Has refrigerant been added recently? Overcharge is a frequent cause.
- How long has this been showing? It tells us how much exposure the compressor has had.
- Any change in compressor noise? Liquid return is sometimes audible.
Related codes
- 42 — Low pressure sensor error. A faulty sensor can distort the superheat calculation this code depends on.
- 204 — Heat recovery unit communication. Distribution problems can contribute to flood-back conditions.
Act on the warning while it is still a warning
We are certified on LG, Daikin and Mitsubishi VRF platforms, and we service systems we did not install.
Next business day service for commercial VRF.
Related codes
Error 35 means low side pressure dropped far enough to shut the system down. Usually a refrigerant leak — but a failed expansion valve reads the same.
Error 42 is a low pressure sensor fault — the sensor itself, disconnected or shorted, rather than an actual pressure problem in the system.
Error 204 means the outdoor unit is receiving no signal from the heat recovery unit — the box that lets one zone heat while another cools.
Frequently asked questions
What does error code 150 mean on an LG Multi V system?
The system calculated superheat and determined there is a high possibility of liquid refrigerant flooding back toward the compressor. It is a predictive warning based on measurement, raised before damage occurs rather than after the compressor has already been harmed.
Why is liquid refrigerant returning to the compressor a problem?
Compressors are designed to compress vapour, not liquid. Liquid does not compress, so it causes mechanical stress and damage inside the compressor. It also washes lubricating oil away from the surfaces that need it, which compounds the wear considerably.
Is error 150 an early warning or an actual failure?
It is a warning, which makes it unusually valuable. Most VRF codes report something that has already gone wrong. This one reports a condition that will cause damage if it continues, so acting on it is genuinely preventive rather than reactive.
What causes liquid flood-back on a VRF system?
Commonly an expansion valve not metering correctly, refrigerant overcharge, low load conditions where little heat is being absorbed, or sensor faults giving the system inaccurate superheat readings. Each requires a different correction, so diagnosis matters. Adding or removing refrigerant without establishing the cause rarely resolves it.
How much does error 150 cost to resolve?
Moderate in most cases, because the fault is usually a valve, a charge correction or a sensor rather than a major component. The value is in what it prevents: acting on this code is substantially cheaper than the compressor damage it warns about.
Can I keep running the system with error 150?
You should not. The condition the code describes actively damages the compressor while it persists. Every hour of continued operation with liquid returning is accumulating wear on the most expensive component in the system. The damage is mechanical and cannot be reversed later.