To properly leak check a refrigeration system you will need to become proficient at using a few different methods. As a refrigeration technician, you should know that not one refrigeration leak detection method can locate all the leaks in a refrigeration system. This is why you should know which method is ideal for a particular AC or refrigeration system.
The method used will depend on whether the system currently has refrigerant still in the system or is being pressure tested with nitrogen, this is up to the technician to decide on the best method/s to use.
An electronic leak detector can be very precise as long as it's in good working order, sensors are clean and there aren't any outside factors that may influence the sensors ability to detect such as wind smoke or moisture. This can be an issue, especially on outdoor units. This is why this method should always be used in conjunction with the bubble solution method.
Today, there are two main types of electronic leak detectors; heated diode and corona suppression.
The heated-diode electronic leak detectors come with a ceramic-based element that heats up the refrigerant and breaks the molecules apart. This leaves behind the positively charged fluorine and chlorine ions which get attached to a negatively charged centre collection wire. As the fluorine and chlorine ions flow towards the centre collection wire, a small electric current is generated. When the refrigerant level between these two points increase, the current hikes up to a point that it sets off an individual alarm. This makes heated-diode electronic leak detectors to be less prone to false triggers and more precise than corona suspension detectors.
On the other hand, corona-suspension detectors measure the change in conductivity between the unit’s two electrodes. During operation, a high voltage DC spark will be created in the sensor. This spark jumps from one point to the next. A baseline current between the two points is therefore established. If the current between these two points drops, you should be certain that there’s an insulating gas in the system. Higher amounts of insulating gas result in a bigger current drop.
Electronic leak detectors are designed to detect a specific type or a number of refrigerants; HFCF, HFC, CFC and more.
It’s important to note that:
Bubble Solutions – It’s the oldest refrigeration leak detection method. This method is usually applied at a suspected leak point. Any refrigerant that escapes will produce bubbles at leak points. Best to be used in conjunction with an electronic leak detector.
Halide Torches – Here, the torch’s flame turns green the presence of when exposed to refrigerants containing CFCs or HCFCs. Another great method which works well on older refrigerants. Capable of finding very small leaks, again bubbles solutions are used to pinpoint the leak.
Fluorescent leak detection – Here, you will be required to add a fluorescent-based dye to the AC or refrigeration unit. Any leak points will be coloured by the dye. The only downside with this method is it can take days, if not weeks for a leak to appear so should be used in conjunction with other methods.
Detecting leaks on a refrigeration unit is not that complicated while using the right tools. It is, however, time-consuming. The biggest mistake made is finding a leak, repairing that leak and leaving the job. You should check the entire system before leaving as there can be multiple leaks on a system and you don't want to be getting called back to a job for something that should have been fixed first time around.