Pressure Testing a Newly Installed Circuit
You are commissioning a new split system charged with R-32 (A2L, GWP 675). The installation is in a first-floor office above a busy café. Before charging, you need to pressure-test the pipework. You have nitrogen, a regulator, and the manufacturer's instructions, which specify a test pressure. A colleague suggests using the R-32 cylinder itself to pressurise the line 'to save time' and then just venting the test gas. The office has a low ceiling and the indoor unit is mounted close to a ceiling void with electrical equipment.
1. Evaluate the colleague's suggestion to pressure-test with R-32 and vent afterwards, and state the correct method.
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Reject the suggestion. Using refrigerant to pressure-test and then venting it:
- Releases a controlled F-gas to atmosphere - prohibited. Even a small quantity of R-32 at GWP 675 is an avoidable emission.
- Is not a valid strength/pressure test - refrigerant pressure varies with temperature and is not a controlled test medium.
- Wastes product and risks over-pressurising the line.
Correct method: pressure-test with oxygen-free nitrogen using a regulator set to the manufacturer's specified test pressure, with the system isolated and gauges connected. Hold for the specified period and check for decay. Nitrogen is inert, leaves no residue, and does not contribute to emissions. Only after a successful pressure test and evacuation should the system be charged with R-32.
Also note: never use oxygen or air for pressure testing a refrigeration circuit - oil/refrigerant mixtures can ignite.
2. Given R-32 is A2L and the room has a low ceiling with nearby electrical equipment, what charge-related safety checks must you make before charging?
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A2L flammability checks:
- Confirm the maximum charge permitted for the room against the manufacturer's data and the applicable standard for A2L refrigerants in occupied spaces. The room volume (low ceiling) limits the allowable charge; if the charge exceeds the limit, additional measures (e.g. ventilation, leak detection, or a different location) are needed.
- Check the lower flammability limit context: ensure no ignition sources are within the required clearance - the nearby electrical equipment in the ceiling void is a concern. Verify it is suitable for A2L service or relocate/isolate.
- Ensure the indoor unit's location and any ceiling void do not allow leaking refrigerant to accumulate in an enclosed space with ignition sources.
Practical steps: charge by weight, label the system as A2L, ensure ventilation during charging, and follow the manufacturer's installation instructions. Record the charge quantity in the logbook. The judgement point is that the low ceiling and electrical proximity turn a routine charge into a charge-limit and ignition-source assessment.