How to Leak Test an AC With Nitrogen Pressure

Leak testing an air conditioning (AC) system using nitrogen pressure is a crucial step to ensure that there are no leaks before the system is put into operation. This process helps to identify any potential leaks in the system, especially after brazing or making mechanical connections. Here are the steps to perform a nitrogen pressure test for leak detection:

Step 1: Check Schrader Cores and Seals

Before conducting the pressure test, it is important to ensure that there are no leaks at the Schrader cores. If you notice any signs of oil around the Schraders, it is recommended to replace them. Additionally, make sure that the caps on the Schrader ports have seals, and any hoses used for the pressure test should have new seals as well.

Step 2: Bubble Testing

When performing a bubble test, it is best practice to place a cap without a seal over the port and spray bubbles on the cap instead of directly into the Schrader port. This prevents soap from entering the system and allows for easier detection of leaks using electronic leak detection methods.

Step 3: Pressure Testing

1. Release any existing nitrogen in the system.
2. Proceed with the pressure test by attaching pressure probes to each side of the system. This can be done using CRTS core remover tools with pressure probes or a manifold.
3. Pressurize the system with nitrogen to the recommended pressure range, typically between 250 to 600 psig. Follow the manufacturer’s recommendations for the specific system you are working on.
4. Valve off the nitrogen from the system and ensure there are no leaks at the valve connections.
5. Let the system stand for the recommended time frame, usually 30 to 60 minutes for residential systems. For larger systems like VRF or VRV, longer test periods may be required as per manufacturer specifications.
6. Monitor for any pressure drop during the test. If there is a drop, start over and retest the system.

Step 4: Leak Detection

1. Use soap bubbles to check for leaks on any field-fabricated joints, especially brazed joints or flares.
2. If performing electronic leak detection, add a small amount of trace refrigerant to the system before the pressure test. The amount of trace refrigerant needed may vary, but generally, it will be well under a pound for residential systems.
3. Use electronic leak detection equipment to identify any leaks by tracing the refrigerant.

Remember to follow best practices and manufacturer guidelines when performing a nitrogen pressure test for leak detection. This process ensures that the AC system is clean, dry, and tight, which is essential for its longevity and efficient operation.