New Aircon Never Cooled: Line Never Vacuumed Before Charging

A new system does not cool and a warranty claim is the natural route. Some new systems underperform for reasons the equipment did not cause.

By Team Snowflake | Updated 24 Aug 2026

Teaching case based on recurring Snowflake service patterns; identifying details are combined.

How this presents

A new installation underperforming from the day it was switched on, showing no fault code and leaving no trace of a loss anywhere. Pressures read high for the conditions. The system has never delivered what its label promises.

Setup: Daikin Wall-mountedNew installHDBTampines
Misread as: A defective new system, on equipment that has been installed for only a short time.
Check first: How long the vacuum was held, rather than whether one was pulled at all

What else produces this

High pressures for the conditions on a system with a plausible charge point at something in the circuit that should not be there. Moisture and air both do that, and both are what evacuation removes. The reading at the end of a pull tells you the pump reached its target; only holding that reading tells you whether the line was actually sealed and dry. A vacuum pulled and immediately broken can leave a great deal behind.

Underperformance from the very first day makes this a commissioning question, not a developing fault.
No trace of any loss removes a leak on new pipework from the explanation.
Pressures high for the conditions fit moisture or air occupying part of the circuit.
A vacuum drawn but never held explains how either could still be in the line.

Why it happens

A vacuum pump lowers the pressure in a line, and moisture boils off into vapour as it does. That takes time at low pressure, and it is not finished the moment the reading looks correct. Breaking the vacuum then leaves both moisture and residual air in the circuit, which raise pressures and cut capacity permanently. The number was true and it was not the whole story.

What resolution involves

Recovering the charge, evacuating properly with the vacuum held and proven, then filling by weight is what puts it right. Asking how long the vacuum was held, rather than whether one was pulled at all, is the question that separates a finished job from a started one. It costs nothing to ask and it decides between rated performance and a permanent shortfall.

How to tell it worked

The vacuum held and watched over a period before any refrigerant goes in. A line that holds its reading is sealed and dry; one that creeps back up has told you something no later test will.

Before you approve a quote

Pulling a vacuum is half of evacuating a line

Moisture boils off at low pressure, and that takes time. The reading is correct before it is done.
Holding the vacuum proves the line is sealed and dry. Reaching the number proves neither of those.
Ask how long it was held, not whether it was pulled. That is the whole of the difference.

Questions this case answers

New aircon not cooling properly: does it need time to settle in?

It does not need time: a system that underperforms from the first day was never finished commissioning; here the line was evacuated but the vacuum was never held, so moisture and air stayed in the circuit and pressures read high.

What does vacuuming the pipes before charging actually do?

It shows that the line is sealed and that the moisture has finished coming off. A reading that creeps back up means air is leaking in, and a reading that holds means the job is genuinely done.

Aircon cools weakly from day one: is more gas the answer?

More gas is not the answer. This system shows no trace of a loss; the weakness comes from moisture and air left in the line after a vacuum that was drawn but never held. Those occupy volume the refrigerant needs and raise the pressure the machine works against, so a top-up cannot correct it.

What should I ask for in writing after an installation?

How long the vacuum was held, not just whether one was pulled. The reading reaches its target before the line is dry, so the held period is what proves the line is sealed and the moisture has finished coming off.

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Tell us what’s going on. Symptoms, setup, photos, anything we should know. We’ll assess and come back with the right next step.

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