Aircon New Install Undercharged Gas

Case Details

What We Checked

• Low-side pressure well below the manufacturer spec for this model at the ambient conditions.
• High-side pressure correspondingly low, pointing to undercharge rather than a restriction or expansion device fault.
• Leak check on all pipe connections, flare joints, and service ports found no leak — the charge had been set too low at installation.
• Airflow, filter, and coil condition all normal — no obstruction or mechanical issue apart from the refrigerant deficit.

The Diagnosis

The unit had been undercharged at installation. Refrigerant was approximately 35 percent below the manufacturer specification for the installed pipe length. Either the installer did not connect gauges to verify the final charge, or the reading was taken but not compared against the manufacturer table for this specific pipe run distance. Both high-side and low-side pressures were proportionally low, which confirmed a simple refrigerant shortfall rather than a restriction, blockage, or expansion device fault. There was no leak at any connection point. The unit had been running with this deficit since the day it was installed, which is why cooling had never reached the expected level.

What Fixed It

We added refrigerant incrementally while monitoring both high-side and low-side pressures in real time. The charge was brought up to the correct specification for the installed pipe length as listed in the manufacturer table for this Daikin model. After reaching the target pressures, we re-measured under steady-state operation to confirm both readings fell within the acceptable range. Supply air temperature at the vent dropped significantly compared to before the correction. We documented the before and after pressure readings so the client could raise the issue with the original installer.

The bedroom reached set temperature for the first time since installation. The client was advised to raise the undercharge with the original installer.

Why This Happens

New units should cool properly from day one.

• There is no settling-in period for air conditioning. A correctly charged unit reaches its rated capacity from the first day. If it does not, the installation needs checking.
• Undercharge happens when the installer does not verify final pressure against the manufacturer spec for the installed pipe length. It is a process gap, not a product defect.
• An undercharged new unit behaves the same as an older unit that has lost gas over time. The compressor runs and airflow feels normal, but the air never gets as cold as it should.
• If a new unit underperforms, get an independent pressure check before accepting any explanation about settling in. The readings will confirm or rule out undercharge in minutes.