Heat pump: brazing rules for refrigerant connections in 2026

Understanding the stakes of brazing on a heat pump (safety, performance, compliance)

What's at play on the refrigerant circuit: tightness, moisture, cleanliness

On a heat pump, brazing isn't just "joining two tubes." It's what guarantees lasting tightness of the circuit. Under heat, the inside of the copper can oxidise. Without a nitrogen purge, these particles end up in the expansion valve. Moisture, meanwhile, reacts with the refrigerant and the oil. The result: acids, corrosion, and performance losses.

The risks of poorly executed brazing: leaks, compressor failures, oil return issues

A microleak is enough to reduce the charge, degrade the COP, and overheat the compressor. A poorly controlled hot spot can also damage a seal, a sensor, or a valve. And if the circuit is dirty or damp, you'll see blockages, frost at the expansion valve, and then a compressor failure. Oil return goes off track. Lubrication follows poorly, and the machine wears out fast.

Traceability and liability: what you need to be able to prove on site

In 2026, you'll mainly be asked for simple evidence. Vacuum procedure, tightness test, quantity of refrigerant recovered or added, and a commissioning sheet. In the event of an inspection or a claim, this is your best protection — and the client's.

Preparing the site and equipment before any refrigerant brazing

Choosing the right filler metal and fittings for the tubing (copper, phosphor-copper, etc.)

On a heat pump, the choice of filler metal depends first on the materials. For copper on copper, a phosphor-copper braze alloy can work, without flux. As soon as there's brass or steel involved (valves, fittings), switch to a silver braze alloy with suitable flux. Keep fittings clean and well fitted, with a consistent gap so capillary action does its job.

Essential tooling: torch, regulators, tube cutter, deburring tool, brushes

Prepare a torch sized to the diameter, regulators in good condition, and checked hoses. Cut straight with the tube cutter, then deburr and brush down to bare metal. A lint-free cloth and a degreaser help avoid inclusions. Remember fire protection and safety glasses.

Setting up the nitrogen purge: settings, flow rate, best practices

Set up a dry nitrogen purge running through the tube, with an open outlet. Set a low pressure and a continuous flow, just enough to expel air without cooling the heated area. Start the purge before heating and maintain it during cooling to limit internal oxides.

Step-by-step brazing rules for refrigerant connections on a heat pump

Cleaning, deburring, fitting: achieving a clean, consistent joint

On a heat pump, start with clean, dry tubes. Cut straight, then deburr to avoid shavings in the circuit. Clean the copper with an abrasive pad. Do a dry fit. The joint must be consistent, without forcing, with an even gap. Prepare the rod and the suitable filler metal. Perfect cleanliness.

Managing the heat: areas to heat, protecting sensitive components, controlling the flame

Sweep with nitrogen during brazing to limit internal oxidation. Heat the fitting first, not the rod. Move the flame in a circular motion to bring the temperature up without burning the copper. Protect valves, insulation, cables and plastics with a heat shield or a damp cloth. Controlled heating.

Immediate checks: bead appearance, residue cleaning, cooling without shock

The bead should be continuous, smooth, well wetted, with no blobs or gaps. Let it cool naturally, without water or cold air. Clean off flux residue if used, then visually inspect the whole perimeter. Before commissioning, plan for a pressure test and tightness check. Gentle cooling.

Tightness checks and commissioning after brazing on a heat pump

Nitrogen pressure test and leak detection: method, pressures, points to watch

After brazing, put the circuit under dry nitrogen with a regulator. Raise the pressure gradually, then stabilise at the test pressure specified by the manufacturer, often 25 to 35 bar on small heat pumps. Hold the pressure and monitor it, accounting for ambient temperature. Then check each joint with foam solution and an electronic detector.

• Brazed joints, service valves, Schrader cores
• Gauge and pressure-switch fittings
• Heat exchanger, heated zones, capillaries

Vacuum: duration, vacuum level, preventing residual moisture

Carry out a vacuum with a vacuum gauge. Target a deep vacuum (often below 1 mbar, roughly 500 microns). Hold for 30 to 60 minutes, then run a rise test over 10 to 15 minutes. A rapid pressure rise signals a leak or moisture. Clean pump oil and short hoses save time.

Commissioning: charge, readings, settings and operational checks

Charge by weight with a scale, based on the factory charge and the length of the connecting lines. Open the valves, start the unit, then log pressures, temperatures, current draw, and air or water temperatures. Adjust the settings per the manual (flow rate, heating curve, defrost). Confirm stable operation and record the measurements for the site file.

Points of vigilance for 2026: on-site best practices and client expectations

Adapting your practices to site constraints: accessibility, weather, fire safety

Before installing a heat pump, lock down access. Handling route, supports, condensate drainage. Anticipate the weather — rain and frost complicate tightness and sealing work. For brazing, apply a "hot work" logic. Cleared area, fire screen, extinguisher ready, and monitoring after the work.

Limiting rework: common mistakes and tips to save time without cutting corners

Rework often comes from poor sizing, forgetting to insulate the connecting lines, or a poorly flushed network. Save time with a checklist. Readings, photos, cable identification. Do a real vacuum, then a tightness test. These are your minutes saved on callbacks.

Reassuring the client: simple explanations about refrigerant brazing and the heat pump's durability

Explain that brazing is a clean, durable joint. If you purge with nitrogen, you avoid internal oxidation and leaks. A heat pump holds up mainly on three points: good installation, settings and maintenance. A reassured client means a lighter relationship. To frame the obligations and best practices, build on settings and maintenance.