How to Locate Refrigerant Leaks in Your Air Conditioning System
In the past I have written articles that helped the homeowner repair one of the most complicated systems know to man, the heating, ventilation, air conditioning; HVAC for short. Sometimes after all of your best efforts, the system still does not cool the air in your home. You call a qualified HVAC technician to look at the system. Even though you have checked everything you know the technician still goes through his routine of inspection steps until he gets to the refrigeration system itself. Chances are that the system is low on refrigerant, commonly referred to as Freon®, much like Xerox is used to refer to photocopies.
Air conditioners, refrigerators, and heat pump do not consume refrigerant. The system is sealed system the compressor does not burn or use up refrigerant to make your house cool, or warm if you have a heat pump for heating in the winter. The refrigerant in your air conditioner or heat pump is a hermetic system and sealed tight. From time to time a leak occurs in the refrigeration system and the unit needs to be charged so that it can continue cooling the home. As the refrigerant leaks out, the system still cools, but it cools too much. The indoor evaporator coil begins to freeze up because the temperature of the coil drops below the dew point. The air conditioning system experiences a reduced amount of air flow because of the coil icing up. You may notice ice on the lines which run to the outside condenser. If you see this it is important to shut the system off immediately and call your HVAC service company. If the system is left running the indoor evaporator coil could turn into a block of ice and no air flow will come out of the vents.
Here are some common reasons that your air conditioner has a refrigerant leak:
1. A Schrader valve is leaking refrigerant and needs to be replaced. There is a tool which can be used to change this Schrader valve without having to recover the entire amount of refrigerant from the system. These Schrader valves look like the air valves in your tire on your car or bicycle and they allow the technician to access the system with his test gauges to check the system pressures. These Schrader valves are important components but over time the rubber seals deteriorate or the Schrader valve gets stuck and allows refrigerant to leak out of the air conditioner system. This is a fairly simple problem to repair.
Schrader Valve - Core Removed
2. On heat pump systems there are accumulators which are necessary for the heat pump system to provide heat in the winter and protect the compressor from liquid slugging. Accumulators are usually made from steel and after a few years they can rust. These rust holes allow the Freon or refrigerant to leak out of the system. The heat pump accumulator can be replaced but the entire system needs to be recovered and a new accumulator installed. Newer accumulators sold today are also made of steel and will eventually leak after rusting occurs in the future. The life expectancy of an accumulator depends on quality of steel used to make them so it is difficult to say when an accumulator will leak. You can spray the accumulator with a rust-proof paint to slow the process.
3. A capillary tube can begin to leak on the inside evaporator coil or if you have a heat pump on the outside heat pump condensing unit. These capillary tubes are very small copper tubes, about the size of a coffee stirrer, and with vibration in the system they rub together or rub against another piece of metal and a hole forms causing refrigerant to leak out. These leaks can be difficult to find because disassembly of the system is necessary in order to find the leaking capillary tube. When the leak is found the capillary tube can be cut and another larger piece of copper tubing soldered over the capillary tube. Thermostatic expansion valve (TXV) bulbs are not connected to the refrigerant system and do not contribute to refrigerant leaks.
4. If the air conditioning or heat pump system has any flare connections leaks generally occur at these connection. Sometimes these flare connections can be repaired while other times the flare fitting and connection has to be replaced completely to prevent future leaks.
5. The indoor or outdoor air conditioning or heat pump coil is leaking and needs repair or replacement. Most of the time the leaks in the coils (whether they be outside or inside coils for an air conditioning or heat pump system) occur at the u-tubes at the end of the coil. There is a tube sheet made of sheet metal which holds the coils together and over time and through vibration the tubing of the coil rubs against the tube sheet and a refrigerant leak occurs. Sometimes this can be repaired but other times it the coil needs to be replaced. Depending on the age of the unit indoor and outdoor coils are available for replacement. The problem with leaks near the tube sheet is when the technician uses heat to repair the leak in the coil the heat loosens other parts of the coils and another leak could occur.
6. Filter dryers are installed in all refrigeration systems and are necessary for absorbing minute amounts of moisture in the system and for filtering debris before it enters the compressor. These dryers have screens and desiccant inside them and the outer shell is made if steel. The same problem that occurs with a heat pump accumulator will eventually occur with a filter dryer and a refrigerant leak occurs. These filter dryers can be replaced after recovering the charge of refrigerant or by pumping the refrigerant contained in the air conditioner or heat pump system into the condenser coil.
7. The line set which carries refrigerant back forth from the condenser to the evaporator coil has been pierced or damaged. Damage can occur from a lawn mower or stepping on the line set. Occasionally lines can be punctured by nails or screws during construction or home renovation projects.
The age of the system and the type of refrigerant leak found will help you decide whether to repair or replace the air conditioning system. Many air conditioning and heating service and repair companies will not provide a warranty for refrigerant leak repairs simply because it is possible to repair one refrigerant leak and have another refrigerant leak occur in a different location. Weigh the cost of repeated repairs to the installation of a new system. Consider the energy efficiency of a new system and possible rebates from utilities, state, or federal sources.