The Annual Top-Up Is a Business Model
A household that pays to have refrigerant added every spring is not maintaining an air conditioner, it is subsidising a leak. The cost compounds badly — refrigerant prices have climbed sharply through the phase-down — and none of that money improves the equipment.
It also does mechanical harm. An undercharged system runs with poor oil return and can slug liquid back to the compressor, so the slow leak nobody investigated eventually presents as a compressor failure that costs many times the original repair. Anyone at AC Repair Wellington will explain that before adding a pound of anything.
Testing Under Pressure
Where a leak cannot be found with a detector and bubble solution, the honest method is a standing pressure test. The system is recovered, isolated and charged with dry nitrogen to a test pressure, then left and watched. Nitrogen is inert, dry and cheap, and unlike refrigerant it can be vented without consequence.
A gauge that has not moved after a couple of hours says something very different from one that has drifted downward, and it will tell you which section of the system is at fault when the components are isolated and tested in turn. It takes longer than a sniff around the fittings and it produces an answer rather than an opinion.
- Evaporator coils perforated from the inside by formicary corrosion
- Schrader valve cores, cheap to replace and very frequently the culprit
- Brazed joints where the line set meets the service valves
- Line sets worn through where copper has vibrated against a strap or stud
- Condenser return bends, particularly on units exposed to weather
- Factory joints inside the outdoor cabinet fatigued by years of vibration
Charging It Correctly
Once the system is sealed again it is evacuated to a deep vacuum with a micron gauge fitted, and held there long enough to prove it. That step removes air and, more importantly in this humidity, moisture — which combines with refrigerant and oil to form acids that corrode the system from the inside.
Then the charge goes in by weight, to the manufacturer figure, adjusted for line set length. Not by gauge pressure, not to a target that looked about right. Afterwards superheat and subcooling are checked once the system has settled, because a charge that is nearly correct behaves like a fault.
Older Systems and Phased-Out Refrigerant
R-22 has not been produced or imported since 2020, so what circulates now is reclaimed stock priced accordingly. On an R-22 system, funding a significant leak repair almost never makes sense, and that money is better held toward replacement.
R-410A is following the same path more slowly under the current phase-down. It is not an emergency, and a healthy R-410A system should be kept and looked after — but on a system with a real leak and some age on it, the refrigerant question belongs in the repair-or-replace conversation rather than being discovered later.
Questions We Get Asked
- Can you just top it up for now?
- Once, on a system where you understand what that means and want breathing room to plan. What we will not do is book you in every spring for the same thing, because that is charging you repeatedly for a problem nobody is fixing.
- How much refrigerant should a system lose in a year?
- None. That is the entire point of a sealed circuit. A slow annual loss is not normal wear, it is a small leak being tolerated, and small leaks reliably become larger ones.
- Is the dye method any good?
- It is useful for slow leaks that a detector cannot pin down, since the dye circulates and marks the spot. The drawback is time — the system needs to run for a week or two before the return visit — so it is a second resort rather than a first.