Safe handling, charging, commissioning and decommissioning
Handling and pressure testing
Work to a written procedure, wear gloves and eye protection, work in ventilated space, and never use a naked flame to search for leaks - use an electronic detector or soap solution suitable for the refrigerant. Pressure testing is done with oxygen-free nitrogen (OFN) and a regulator; never use oxygen or compressed air, which can ignite with oil and cause an explosion. Never braze or solder on a system that is pressurised or still holds refrigerant. Respect design pressures: R-410A and R-32 systems run at roughly 1.6 times the pressures of R-22, so use only rated hoses, gauges and recovery equipment.
Charging and commissioning
Evacuate with a vacuum pump and micron gauge - a vacuum is not a leak test. Charge by weight, not by gauge pressure, and record the exact mass, gas type and GWP. Blends (R-410A, R-407C, R-404A) must be charged as liquid, because the components have different boiling points; vapour charging causes fractionation and a refrigerant of the wrong composition. Charge from the liquid valve into the liquid line, throttling as required.
Decommissioning
Pump down or recover the full charge, isolate and lock off, label the equipment with the gas recovered, remove and dispose of the refrigerant through an authorised route, and complete the record. Do not cut pipework until pressure is confirmed at atmospheric.
Traps
- Using nitrogen with a cylinder regulator absent or an unregulated high-pressure hose.
- Vapour-charging a blend.
- Treating a standing vacuum as proof of tightness.
Worked rule of thumb
Cylinder weight loss gives the charge: a cylinder reading 24.6 kg before and 21.8 kg after charging has delivered 2.8 kg. Compare with the nameplate charge and investigate any discrepancy greater than a few percent before signing off.