Understanding a heat pump's refrigerant charge and the 2026 regulations
What the refrigerant charge is for: performance, consumption and reliability
The refrigerant charge is your heat pump's "fuel". Too little, and heat exchange collapses. Too much, and pressure climbs. Either way, the machine consumes more, loses comfort, and wears out the compressor. A correct charge also protects oil return and limits nuisance shutdowns.
Which refrigerants you encounter on site: R32, R410A and points of vigilance
On site, you mostly work with R32 and R410A. R32 is classed A2L (mildly flammable). It requires strict ventilation, no sparks, and respect for the maximum charge set by the manufacturer. R410A, older, is increasingly constrained by the HFC phase-down. Never mix refrigerants, and always recover the charge before working on the circuit.
Key obligations in 2026: F-Gas, traceability, certificate of competence and leak checks
In 2026, the F-Gas regulation tightens the reduction of HFCs. On the ground, remember four reflexes. Competence of the company and certification of the technician. Traceability of quantities (added, recovered). A ban on venting refrigerant to atmosphere. Leak checks and a register kept according to the CO2e thresholds, with automatic detection allowed to space out the checks. To anticipate upcoming changes on the refrigerant side, see also refrigerants for heat pumps in 2026.
Calculating a heat pump's refrigerant charge: a practical method for the field
Starting from the nameplate and the manufacturer's manual (nominal charge)
On a heat pump, start with the nameplate. There you find the refrigerant type and the nominal charge (often the factory charge). Then open the manual. Many units are pre-charged for a maximum line length. The manual also states the additional charge beyond that length, and the conditions for applying it.
Adjusting for the refrigerant lines: diameter, length and elevation
Measure the actual line lengths, out and back, then check the diameters installed. The manufacturer usually supplies a table in g per metre by diameter. Elevation difference is not compensated "by feel". It is managed through installation limits and, sometimes, a dedicated procedure. Make the adjustment using manufacturer values only.
Checking with the right tools: scale, recovery unit, manifolds and superheat/subcooling readings
Charge by weight with a scale. Pull a vacuum with a suitable recovery unit, then open the valves per the procedure. At commissioning, stabilise the machine and take reliable readings of superheat and subcooling with probes and manifolds. Compare against the manufacturer's expected values before correcting.
When and how to top up the refrigerant charge without falling foul of the rules
Identifying the right moment: commissioning, line replacement, intervention after a leak
On a heat pump, a top-up charge is decided on facts, not "by feel". It is done at commissioning if the line length differs from the manufacturer's pre-charge, after replacing refrigerant lines, or after repairing a leak. In the latter case, there is no top-up until the leak is fixed, tightness verified, and the circuit clean again.
Choosing the charging method: by weight, in liquid phase, and special cases by refrigerant
The safest rule remains charging by weight, with a scale and the manufacturer's value. For blends (e.g. R410A), you charge in liquid phase to avoid fractionation, limiting the flow rate on the suction side. For A2L or A3 refrigerants, also apply the site's and manufacturer's safety instructions.
Avoiding common mistakes: mixing, moisture, insufficient vacuum pull-down and overcharging
Avoid mixing refrigerants and never "top up" a wet circuit. An insufficient vacuum pull-down leaves air and water behind, then acids and failures. Finally, overcharging drives up pressures and currents. Check operating conditions, superheat and subcooling, then log the intervention.
Safety and quality precautions: the essential reflexes on a heat pump
Site safety: gas risks, burns, pressure, ventilation and PPE
On a heat pump, you cut the power, secure access and maintain sufficient ventilation throughout the intervention. Watch for refrigerant leak risks, especially on certain flammable-refrigerant models. Avoid any ignition source, check hose pressure, and protect yourself from burns on the heat exchanger and pipework. Minimum PPE. Gloves, goggles, boots, hearing protection if needed.
Circuit tightness and cleanliness: nitrogen, brazing, dehydration and vacuum pull-down
Quality is in the details. Pressure test and leak search with nitrogen. Nitrogen purge during brazing to limit internal oxidation. Then a careful vacuum pull-down, with a hold check, to remove air and moisture. A clean circuit means fewer failures and a COP that holds up over time.
Mandatory traceability: intervention reports, register, labelling and refrigerant recovery
Recover the refrigerant before opening the circuit and use suitable equipment. Note the quantities recovered, added, and the refrigerant reference. Keep the intervention report, update the register, and check the labelling. This traceability protects the client, the company and the environment.
Troubleshooting: signs of an incorrect charge and corrective actions on air/water and air/air heat pumps
Client-facing symptoms: lack of heating, short cycles, abnormal frost and compressor noise
On a heat pump, a refrigerant charge that is too low or too high shows up quickly. The client describes a lack of heating or cooling, a temperature that plateaus, repeated short cycles, or defrost cycles that are too frequent. You may also observe abnormal frost on the exchanger, oil return issues, and a compressor noise that is drier or irregular.
Quick diagnosis: pressures, temperatures, currents and comparison against manufacturer charts
Before touching the refrigerant, secure the operating conditions. Compliant air or water flow, clean filters, open valves. Record low and high side pressures, pipe temperatures, superheat and subcooling. Check compressor and fan current, then compare against the manufacturer's chart. Reliable measurements require the system to stabilise and well-placed probes.
Fixing it for good: leak search, repair, pressure test, recharge and final check
The right answer is rarely a simple top-up. Run a leak search, repair it, then nitrogen pressure test and vacuum pull-down. Recharge using the manufacturer's method, ideally by recharging by weight. Finish with a full test, before/after readings, a check of the defrost cycle and delta T, and traceability on the intervention report.
Key figures
mandatory
Certificate of competence
for 5 to 7 m of line
Factory charge
15 to 30 g/m extra
Top-up
Frequently asked questions
You reason in tonnes of CO2 equivalent (tCO2e) tied to the refrigerant and its charge: above the F-Gas thresholds, periodic leak checks and keeping a register become mandatory. The frequency depends on the tCO2e and can be relaxed if automatic leak detection is installed. In practice, rely on the manufacturer's data sheet and your refrigerant register to calculate the CO2e and schedule the checks.
Louis Airy
COO of Argile
