A new evaporator coil

Fixing a Refrigerant Leak – You had the new air conditioner or heat pump system installed some years ago and suddenly it stopped heating or cooling properly so you call the HVAC contractor to check it out. The HVAC technician arrives and spends about thirty minutes HVAC troubleshooting and then he comes to you with the news.

The unit needs a charge of refrigerant. It is low on refrigerant (R-22) or R-410A. You ask the HVAC technician if it is normal for this to occur and he informs that, no, it is not normal for the HVAC system to lose refrigerant that you have a refrigerant leak. Is it the evaporator coil? Is it the air conditioner condenser? Something else with the air conditioning system? Or heat pump?

Fixing a Refrigerant Leak

So you advance to the next question and ask, “can you find and fix the refrigerant leak with the air conditioner”. The HVAC technician says yes he can. Here are the options for you and depending on which option you choose will depend on the cost. Prices vary widely from AC contractor to AC contractor and from region to region. Always get at least 3 quotes for any major work for HVAC.

He can do a cursory look and check the basics such as shraeder ports, flare connections, and other basics. If no refrigerant leak is found then a more thorough refrigerant leak check can be scheduled and depending on where the leak is found will depend on the cost of the repair for fixing the refrigerant leaks.

Most air conditioning contractors will do a cursory check for refrigerant leaks for no charge if the air conditioner unit was installed within a year because it goes back to workmanship and the quality of HVAC equipment.

After the year is up it all depends on the air conditioner manufacturer’s warranty as to what will be covered so make sure you discuss this with the HVAC contractor first before agreeing to the thorough refrigerant leak check because a thorough refrigerant leak check can be expensive and not necessarily be covered under any air conditioner manufacturer’s warranty.

The following list is not comprehensive but it is a list of possible places where your air conditioner or heat pump can possibly have a refrigerant leak and the actual cause of the refrigerant leaks.

Refrigerant Leak Locations

• Leak in the line-set (Suction line). The customer had a new roof installed and the roofer shot a nail through the suction line which ran through a chase to the attic. The customer had the system filled three times before deciding on fixing the refrigerant leak. It took over 8 hours to find and fix the refrigerant leak. Add up the cost to find and fix the leak and compare it to the original three times the customer had the system charged.

It would have been cheaper to find and fix the refrigerant leaks the first time than to wait as this customer did. Fixing a refrigerant leak can be frustrating at times because finding this leak was difficult, to say the least. An easy repair to fix though.

• Refrigerant leak in the evaporator coil. A long screw had rubbed up against the coil and caused a hole in the u-bend at the end of the evaporator coil. The air conditioning technician did find and fix the refrigerant leak on the first service call so the cost was minimized.
• The old evaporator coil was vibrating against the tube sheet at the end of the coil. The customer had the system filled multiple times before deciding to find and fix the refrigerant leak. The refrigerant leak fix turned out to be to replace the old air handler which was over 20 years old. Sometimes fixing a refrigerant leak is not the best option.
• Condenser coils were leaking refrigerant. The air conditioning condenser coils had rubbed up against a screw and the vibration caused the screw to puncture the condenser coils. This was a catastrophic refrigerant loss which causes the system not to work at all. The system was repaired and recharged in about 2 hours and worked fine with no further problems until the system was replaced 5 years later. Fixing a refrigerant leak required brazing skills and charging a refrigeration system.
• Leak in the accumulator on a heat pump. The accumulator was replaced and the system recharged in about 3 hours of work. This is a common occurrence for heat pumps as the accumulator is made of steel and is prone to rusting out. The rest of the refrigeration system is copper or copper/aluminum depending on the manufacturer. Fixing a Refrigerant Leak with heat pump accumulators is a common repair. How to Tell if a heat pump has a refrigerant leak?
• Capillary tubes rubbed together coming out of the distributor going to the evaporator coil. The vibration of the air handler operation wreaks havoc on any copper that can rub against something. The leak caused a catastrophic refrigerant leak and caused the unit to cease operating. It was the first leak the HVAC equipment had experienced in the seven years since it was installed. The air conditioning unit was repaired in a little over three hours. Fixing a refrigerant leak required ingenuity in piping because cap tubes are difficult to repair simply because they are very small.

Fixing a Refrigerant Leak

There are other cases of  HVAC refrigerant leaks and causes but fixing a refrigerant leak takes anywhere from a few hours all the way up to a full day depending on how fast the leak can be found, where the leak is, and if the parts are available and can be replaced in a reasonable amount of time.

There are cases where the air conditioning equipment should be replaced especially when the equipment is very old e.g. it is insane to spend a lot of money replacing an evaporator coil on a unit that is more than 10 to 12 years old since the equipment is close to reaching its replacement date.

(Money magazine says the replacement of residential HVAC systems is an average of 13 years). It does not make common sense since the cost of repair can go to a very good down payment on a new unit that can and will save you money in efficiency (typically 20% plus depending on the efficiency rating you purchase).

Methods of Finding the Refrigerant Leak

There are various techniques used by HVAC technicians to find and fix a refrigerant leak. Some ways a more reliable than others but can be more intensive resulting in a higher cost to be performed. The following lists methods used to find air conditioning refrigerant leaks:

• An electronic refrigerant leak detector can be used to find a leak
• An ultraviolet dye can be injected into the system and allowed to circulate through the refrigeration system. Ultra-violet light can then be used to spot the leaks.
• Looking for oil on or near refrigerant lines
• Hearing the leak if the environment is quiet and the leak can be heard
• Leaving a trace amount of refrigerant in the system and then pressurizing the refrigeration system with nitrogen. Using either soap bubbles, listening for the leak, or using an electronic leak detector the refrigerant leak can often be found and repaired.

Fixing the leak is often done using oxyacetylene and silver soldering (brazing) the place where the system is leaking. Sometimes the part of the system leaking needs to be replaced other times it can simply be soldered. Once the leak is repaired the refrigeration system is evacuated completely and repressurized with nitrogen. Both when the system is evacuated and when the system is pressurized with nitrogen the gauges are checked to make sure there is not another leak.

The system should be evacuated and purged with nitrogen no less than three times Triple Evacuation) to ensure there are other leaks and to ensure there is no moisture or non-condensable gasses left in the system. After this is completed then refrigerant is introduced into the refrigeration system and the unit is charged properly using either the manufacturer’s PT chart and the superheat/subcooling methods for properly charging the system.

Conclusion - Freon Leak Repair

Fixing refrigerant leaks is never cut and dry and decisions have to be made that can save money for the future. Hopefully, the leak is repaired quickly and efficiently by the HVAC technician and there are no further worries.

Fixing a Refrigerant Leak

Technical Resource: Refrigeration and Air Conditioning Technology