On a refrigerant line, the filler metal follows the parent metals rather than habit: the copper-phosphorus alloys of the CuP family under ISO 17672 melt between 645 and 890 °C depending on their silver content, are self-fluxing on copper and are strictly ruled out on ferrous metals. The nitrogen purge is not up for discussion either, since the oxides formed inside the tube end their journey in the expansion valve. And one regulatory consequence is almost always missed: an assembly brazed on site is not hermetically sealed equipment within the meaning of article 5 of Regulation (EU) 2024/573, which brings the entry threshold for periodic leak checks down from ten tonnes of CO₂ equivalent to five.
Choosing the filler metal before reaching for the torch
The alloys and the parent metals they suit
A filler metal is selected first on what it has to join, then on its melting range. The values below are the usual orders of magnitude for the ISO 17672 designations: the data sheet of the product in your hand governs, because the range varies within the permitted composition bands.
| ISO 17672 designation | Silver content | Indicative melting range | Parent metals | Flux |
|---|---|---|---|---|
| CuP 179 | 0 % | 710 to 890 °C | Copper, brass, bronze | None on copper |
| CuP 279 | 2 % | 645 to 825 °C | Copper, brass, bronze | Yes on brass and bronze |
| CuP 281 | 5 % | 645 to 815 °C | Copper, brass, bronze | Yes on brass and bronze |
| CuP 284 | 15 % | 645 to 800 °C | Copper, brass, bronze | Yes on brass and bronze |
| Ag 145 | 45 % | 640 to 680 °C | Copper, brass, steel, stainless | Yes, corrosive residues to remove |
Two absolute rules come out of that table. CuP alloys never go on a ferrous metal nor on an alloy above 10 % nickel, on pain of brittle intermetallics that will fail in fatigue. And a silver brazing alloy leaves corrosive flux residues that have to be removed once cool, where a CuP on copper leaves none: that is often what separates the two on a joint with difficult access.
Silver, which buys tolerance rather than strength
Going from 0 to 15 % silver lowers the solidus and narrows the melting range. The gain is not mechanical, it is operational: the alloy wets faster, flows better into an uneven gap, and forgives less even heating. On an accessible, well-prepared joint, a CuP 179 is enough. On a congested connection, at height, close to a heat-sensitive component, an alloy at 5 or 15 % silver cuts the heating time, and with it the risk of burning the copper or damaging a nearby seal.
Brazer and procedure qualification
EN 14276-2, which covers piping for refrigerating systems, refers to two distinct referentials: qualification of brazers and brazing operators under EN ISO 13585, and brazing procedure approval under EN 13134. These are a person qualification and a process qualification, not to be confused with the certificate for handling refrigerants. On a public contract or a commercial site, it is the first family you will be asked to produce, and it cannot be improvised the day before.
The work on the line, and what makes it checkable
The nitrogen purge, and the physical reason it is needed
Under heat, copper oxidises inside the tube in the presence of oxygen, and the oxides later break loose into circulation. They migrate towards the narrowest point of the circuit, which is the expansion valve, where they build a progressive blockage that the customer will read as a loss of performance rather than as a fault. The purge starts before the heat, is kept up throughout cooling, and requires an open outlet at the other end of the run. The flow is set to the minimum useful: too much nitrogen chills the heated zone and spoils the wetting.
Preparation, which decides the capillary action
A brazed joint does not hold through the metal added but through capillary action in the gap between the two tubes. That calls for a square cut, full deburring outwards so that no swarf is left in the circuit, mechanical cleaning to bare metal and an even fit checked dry before any heat. Heat the fitting rather than the rod, moving the flame around the full circumference: it is the part that must melt the filler, not the flame.
What you record during the intervention
Four records are enough to make an intervention defensible, and they are taken at the moment they happen, not from memory in the evening.
- Exact designation of the filler metal and the flux used, read off the packaging.
- Pressure and duration of the tightness test, with the ambient temperature at the start and at the end.
- Vacuum level reached on an electronic vacuum gauge and the result of the rise test after isolating the pump.
- Final charge weighed on scales, with the factory charge and the addition due to the line length.
The checks after brazing, and what they prove
The tightness test and the evacuation
The test is carried out with dry nitrogen, at the pressure stated by the manufacturer for the appliance concerned, and never at a pressure picked out of habit: test pressures differ by refrigerant and by section of the circuit. Record the starting and finishing pressures with the ambient temperature, because a temperature swing alone moves the pressure and a report without a temperature proves nothing. The evacuation that follows is measured on an electronic vacuum gauge and validated by a rise test after isolating the pump, a method set out in evacuating the refrigerant circuit.
The charge, which is a datum rather than a setting
The final charge is weighed and recorded. It is made of the factory charge plus the addition tied to the actual line length, following the manufacturer's rule, and it then governs the whole regulatory regime of the equipment. An approximate charge cannot be recovered: it falsifies the tonnes of CO₂ equivalent, therefore the check interval, therefore the log. The calculation method and its traps are covered in refrigerant charge.
The threshold that brazing moves
Article 5 of Regulation (EU) 2024/573 indexes the periodic leak check on the charge expressed in tonnes of CO₂ equivalent, that is the charge in kilograms multiplied by the global warming potential of the refrigerant. The first threshold is five tonnes, and it rises to ten tonnes for equipment sealed and labelled as hermetically sealed. Pipework brazed on site does not benefit from that exemption.
| Refrigerant | GWP, annex I of Regulation 2024/573 | Entry charge if hermetically sealed | Entry charge if brazed on site |
|---|---|---|---|
| R32 | 675 | 14.8 kg | 7.4 kg |
| R410A | 2,088 | 4.8 kg | 2.4 kg |
| R407C | 1,774 | 5.6 kg | 2.8 kg |
| R454B | 466 | 21.5 kg | 10.7 kg |
| R290 | 0.02 | Outside the scope of article 5 | Outside the scope of article 5 |
Above the first threshold the interval is twelve months from five to fifty tonnes and six months from fifty to five hundred. Above five hundred tonnes the base interval is three months, but article 6 requires a permanent detection system there, which doubles the interval: the top band is therefore checked every six months, never every three. R290 is not a fluorinated gas and falls entirely outside article 5, which exempts it from nothing else. The comparison of refrigerants and their constraints is covered in refrigerants for heat pumps in 2026.
The certificates, and what changes on 1 January 2027
The company certificate and the operator certificate
Two distinct titles govern the intervention in France. The company certificate, issued under article R. 543-99 of the environmental code for a maximum of five years. The individual competence certificate, issued to each person who handles refrigerant, under article R. 543-106. One does not replace the other, and a company loses its certificate if it no longer employs the competences matching the activities it carries out.
The overhaul of the categories by the orders of 21 November 2025
Two French orders dated 21 November 2025 replace the regime that came from the order of 30 June 2008. The historic categories numbered I to V give way to seven categories, A1, A2, B, C, D, E and V, indexed on the refrigerant and on the charge: A1 for work on equipment containing fluorinated gases or hydrocarbons, A2 for the same activities limited to small charges, B and C for CO₂ and ammonia, D for recovery alone on small equipment, E for leak checks without opening the circuit, V for vehicle air conditioning. The new regime becomes mandatory on 1 January 2027, the order of 30 June 2008 being repealed on 31 December 2026. The extension to hydrocarbons is the change to anticipate, since it covers the R290 monobloc units now spreading through detached housing: the detail of categories A1 to E and of the timetable says which endorsement to apply for given what you fit.
What goes into the log after the intervention
Every intervention feeds the equipment log: nature of the operation, quantity of refrigerant added or recovered, result of the leak check, identity of the operator and reference of their competence certificate. That log is kept per item of equipment and follows the appliance, it is not a company journal. Its keeping rules and the documents to retain are set out in the refrigerant log, and the output chosen upstream has to come from a sizing note compliant with EN 12831-1, failing which the charge and the check regime will be argued on a false basis.
