General Leak Testing and Tips
A persistent, methodic, and patient person will find a leak in a refrigeration system before anyone else. It may seem like it takes a long time, but it doesn’t hold a candle to the time involved with repeated evacuation and pressure testing, especially if the system is very large.
The following is an outline of how to approach leak testing to save time and effort.
1. Have a planned approach. Use a sketch of the system to mark the progress as you go. Start at one point and work along the system path, this prevents repetitive checking. Mark the sketch up as you go, for instance, note a section you can’t get at to test or got small hits, because once you eliminate the known area, the leak must be in the unknown area.
2. Know the tricks. Use tape to isolate flanged connections, wrap the connection and poke a small hole, this way you are testing one point rather than the entire flange. Another trick, test insulation at seams, the refrigerant will propagate under the insulation until it finds a way out. Look for oil, if there is oil stain there is a leak at some point. Put balloons over relief devices and plug the weep hole to find a slow leak valve. Put condenser or chilled water straight from the chiller in a closed container and let it sit, after a while use an electronic detector to sense if any residual refrigerant is in the container, could be a tube leak.
3. Use tags, chalk, or any removable marker to note leaks on the system as you go. Do not use paint or permanent markers because once the leak is repaired, the tag or mark needs removed.
4. Pick the right tool for the job and know how it works. There are many leak detection tools, and they all work, but there isn’t any one tool that will do it all.
I have listed the leak detection tools that I’m aware of below, they are not in any order, just as they occurred to me.
Ø Bubble solution: This can be homemade from dish-soap and water, or, commercially available, such as SNOOP®. It works by coating the area with a high surface tension fluid, when the gas seeps out of the pipe it is momentarily captured by the fluid and a bubble forms then pops. This is a tried and true method of testing for leaks. Couple draw-backs; it can freeze, and you do get liquid all over the place when you use it.
Ø Foaming shave cream: When applied to a leak, the gas will leave a little hole in the cream or blow it off completely. It also works well to find leaks on long seams or where a solution won’t hang long enough. Can find leaks on vacuum or pressure. Draw-backs; Is messy and short lived sometimes drying up or breaking before small leaks are found. Aerosol cans may not be permitted on premises and it isn’t good if its windy out.
Ø Ultra-sonic leak detectors: Several are available and all generally work to “listen” for the high frequency sound that occurs when gas leaks out. They are used by narrowing the search area based on the pitch, volume, or number of beeps increasing as you search. These can help isolate a leak in a wall. Draw-backs; they don’t work well in noisy or windy environments and lack the ability to “pin-point” a leak. If there are numerous leaks, you will hear them all.
Ø Sniffers: Or, electronic gas detectors, are designed to pick up trace amounts of gas in an air stream. They work by using a little air pump to pull samples across an LED light, a receiver, tuned to the specific frequency of the gas, compares the sample to its reference and alarms when it gets a match. These can be very accurate and are usually easy to use, hand held, and fairly rugged, but they have some draw-backs; get water or oil in the end and your done until you replace the filter. They will pick up false hits if you move too fast or get too close. They take a second or so to register a leak, so move slow.
Ø Halide and sniffers that use heated elements: they work, but do so by burning the sample. Draw-back; I avoid these since you don’t always know if there is a flammable atmosphere which could lead to an explosion.
Ø Helium leak detectors: These detectors work by identifying helium atoms in a sample stream, you can’t fool them, at least not ones that work on gas chromatograph basis. They will find the smallest leak possible. Draw-backs; the detectors are expensive, you need a supply of helium to add to the system, they are costly to maintain.
Ø Thermal imaging leak detectors: These are relatively new to the industry. Based, in part, on the fact that there will be a temperature drop associated with the leak. There is an image of the equipment you watch through a screen looking for the temperature zone that’s out of place, there’s the leak. Draw-backs; they are very expensive and costly to maintain/repair. If you have ever tried to take a picture of every aspect and all sides of a system, then you know how challenging these would be to maneuver in a congested mechanical room.
There are all kinds of ways to find leaks and new ones are invented every day. If you know of a clever way to spot a leak, please let me know!
I worked for over thirty years in the HVACR industry. I have designed, installed, serviced, and trouble shot units of various types throughout the years. The posts here are information based on that experience, I hope you find them useful. If you have a different experience, please comment.