Leak detection is more important today than in any other era of air-condition- ing and refrigeration because of R-4lOA's emergence as a preferred HFC refrigerant and replacement to R-22. Finding and eliminating leaks in R-41OA systems is important because of its near-azeotropic characteristics. R-41OA consists of R-32 and R-125, the former of which has the potential to escape
more freely from a leak hole because its molecules are smaller.
Whethes its due to copper sources, R- 41OA's higher pressures, rOE oil's affinity for moisture, the proliferation of household volatile organic compounds that attack copper coils, or brazing craftsmanship at the manufacturing and service-technician level, leaks are more prevalent and intermittent than before.
Leak- Check Methods:
1. Visual Checks
2. Soap-bubble test
3. Nitrogen pressurization hold test;
4. Electronic leak test;
5. Ultrasonic detection; and
6. U'V-dye injection.
These techniques are not new, but because of the increasing occurrence and difficulty of finding leaks, all six methods have a place and a time in the leak-detection process.
Visual checks-The adage, "look before you leap," applies to the first leak-detection technique. The first inspection should investigate unusual colored markings or dirt buildups around joints or on piping. Too many technicians disregard this potentially quick diagnosis in favor of resorting to the industry's higher technology leak-detection tools.
Soap-bubble test-Super soap solutions are still tried and-true leak tests since refrigeration evolved in the early half of the 20th century. Soap is fast, and it is very visual in that the exact leak point can be seen.
Nitrogen pressurization hold test-Recovering a system's refrigerant and then pressurizing it with nitrogen at 150 psi is a good method of leak detection. The holding process should be observed for at least 10 minutes. If the system loses any pressure over the course of 30 minutes or more, then it is a sure indication the system is leaking. itrogen pressure hold tests can also indicate a small leak or if the system has a large or multiple leaks.
Some leaks are not detectable until the system operates, and so nitrogen has some disadvantages. Never leave an unattended nitrogen tank pressurized on the regulator, which can leak and infiltrate the system with too high a pressure.
Electronic leak test-While the system is nitrogen charged, a small 10 charge of refrigerant can be used so that electronic leak instruments-such as infrared absorption, heated diode and corona discharge-will have refrigerant to detect. Many service technicians incorrectly assume refrigerant is projected at a 90-degree angle from the piping run, thus, they hold their sniffer at that angle. However, laboratory research leak-mapping reveals all leaks have a unique shape that causes refrigeration projection in any possible direction. Therefore, electronic sniffer paths should be in a circular motion along the pipe.