HVAC Leak Detection

by Dave on April 27, 2012

Hvac leak detection can be one of the hardest parts of being an Hvac Technician. Some refrigerant leaks will stand out at you, sometimes you can see traces of oil around the compressor, indicating a refrigerant leak, or sometimes you can smell the gas and pin point it from there.  But what about those tiny leaks that only seem to grow over the years.

You could have purchased a new system 2 years ago, and it may have only lost a pound of refrigerant. That refrigerant leak could be getting bigger and bigger as the years go by, but you just keep paying to have refrigerant added to the system. 5 years go by and the refrigerant leak gets bigger, to the point that it will only hang on a couple days and freeze the system up, or damage the compressor, or whatever. Let’s say the freon leak was in the evaporator coil, over 5 years from installation, that coil is out of warranty. Now the customer, or YOU if you are the customer, have to fork over a heck of a lot more money to get it replaced.

 

HVAC Leak Detection

 

Infrared Leak Detector SRL2 FieldpieceI’m going to cover some of the methods that I use for refrigerant leak detection. I won’t be covering gas leaks as I don’t deal with that type of HVAC and don’t want to lead anyone in the wrong direction.  These methods should only be performed by those that work in the HVAC field.

Heating and air conditioning is a very technical field and every situation is different, thus this article should be used as information purposes only per our sites disclaimer.

System is Out of Refrigerant, or Close to It

For this situation I wouldn’t even pull out my refrigerant leak detector. I would first look at the most obvious spot, because if a system is completely flat on Freon, then 9 times out of 10 it’s going to be outside at the condensing unit. I would first look around the compressor for any signs of oil. Then fill the system up with about 200lbs of dry nitrogen. You should be able to hear the leak hissing when examining all of the HVAC components.

Refrigerant Leak Detectors

When HVAC leak detection gets difficult, this is when it’s time to pull out your refrigerant leak detector. There are two types that I like to use and they are the heated diode type and the infrared type leak detector. Both work good, but remember if you are an air conditioning technician in training, don’t go cheap when buying a leak detector, you get what you pay for.

Infrared Leak Detectors

I like the Fieldpiece SRL2K7 Infrared Leak Detector. It gets great reviews from some of the professionals over at Hvac-Talk.com – Though this type of refrigerant leak detector is not for everyone, and can be a little tricky to use if you are used to using the heated diode type.  The advantage of this type of technology is that the sensors will last about 10 years. They trigger on refrigerant concentration, so a sweeping motion must be used with this type of leak detector. The only disadvantages I have with infrared leak detectors is that they are more expensive. But then again you get what you pay for.

Heated Diode HVAC Leak Detectors

The most famous one and talked about the most is the H10. Works great on sniffing out R-22 and 134A refrigerant leaks. 410A not so much, especially is they are very, very small leaks. I have heard good things about the D-Tek leak detector though, which has been upgraded to detect 410A accurately. If I were to buy another refrigerant detector it would be the D-Tek just because most the guys I work with use it and love it.

HVAC Dye Test

There are leaks that can occur in evaporator and condensing coils that just will not trigger on some leak detectors. Either that or they just take too long to find. One option that will save you time, and will 100% pinpoint your leak (unless line set is underground) is the dye leak detection test.

Dye kits will consist of dye cartridges, a UV flashlight and glasses. You basically inject the dye into the system while it is running, and let the dye cycle for a couple of days. Return with your UV flashlight and glasses and the dye will light up where the refrigerant leak is present.

One of the most efficient ways to pinpoint small refrigeration leaks. The drawbacks to this is it can be pretty messy. Wear gloves, and make sure you have the proper stuff to clean up the mess you will make, which is usually included in the dye kits.

3 Component Isolation Test with Nitrogen

Last but not least, is the 3 component nitrogen test. In commercial applications this could be more than 3 components but this article is focused on residential Hvac leak detection. This is performed by recovering the remaining refrigerant in the system. Braze the suction line and liquid line together at the air handler, the condensing unit, and then the line set.

You will also need 3, ¼” shraeder valve stems brazed into these connections, as you will be filling them up with nitrogen at about 150 psi (some go higher but I wouldn’t recommend going over 150psi). Use soap bubbles to ensure that you brazes are good, once confirmed, wait a couple days then come back and check all of your gauges to see which one lost pressure.

As I have said this will be a situational decision you will have to make, as a technician or as a customer. Hands on is the best Hvac Training you can get and will have to learn how to make the best decisions on how you are going to apply HVAC leak detection through experience.

 

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