Air Conditioning & Heat Pump Refrigerant Leak Repair Procedures

How to diagnose & repair refrigerant leaks in the air conditioning or heat pump system
Leak repair tips for the HVAC cooling coil or evaporator coil; Causes of leaks in air conditioning or refrigeration equipment; How to find air conditioning leaks; How to fix air conditioning or refrigerator refrigerant gas leaks; Where do leaks occur in refrigeration equipment? Why do leaks occur in refrigeration equipment?
REFRIGERANTS & PIPING - separate article
- GAUGE, REFRIGERATION PRESSURE TEST - separate article
- REFRIGERANT CHARGING PROCEDURE - separate article
- REFRIGERANT DRIERS & FILTERS - separate article
- REFRIGERANT LEAK DETECTION - separate article
- REFRIGERANT LEAK REPAIR
- REFRIGERANT METERING DEVICES TEVs - separate article
- REFRIGERANT METERING CAPILLARY TUBES - separate article
- REFRIGERANT PIPING & DISTANCES - separate article
- REFRIGERANT PIPING INSULATION - separate article
- REFRIGERANT PRESSURE READINGS - separate article
- REFRIGERANT SIGHT GLASS - separate article
Questions & Answers about how to find and fix leaks in air conditioner or heat pump refrigeration piping systems
References

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Refrigerant gas or liquid leaks: this article discusses how to repair refrigerant leaks in air conditioning and cooling systems, using as an example, repairing a leaky or damaged air conditioning the cooling coil (evaporator coil) in the air conditioning air handler unit. Our photo at page top shows the cooling coil in the attic air handler component of a central air conditioning system.

How To Repair HVAC Air Conditioner Refrigerant Leaks

If your air conditioning or heat pump system has lost its cooling capacity or won't start see REPAIR GUIDE for AIR CONDITIONERS. See How to determine the cooling capacity of air conditioning equipment if the system seems to be working but is inadequate to cool your building. Also see REFRIGERANTS & PIPING, see PRESSURE READINGS, COMPRESSOR, and A/C REFRIGERANT LEAK DETECTION for more details.and see REFRIGERANT PIPING & DISTANCES. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

As we explain in our articles on lost cooling capacity or air conditioning systems or heat pumps that are not working (see AIR CONDITIONING & HEAT PUMP SYSTEMS), a refrigerant leak in your air conditioner or heat pump means that eventually it will just not produce cool air (during air conditioning) nor warm air (during heating if it's also a heat pump).

First we need an accurate diagnosis of the air conditioning problem. If your air conditioning or heat pump system has lost cooling (or heating) capacity, there can be various causes besides loss of the refrigerant in the system.

First, see LOST COOLING CAPACITY to diagnose just why the system is not working.
If you know that the refrigerant level is low or zero, don't just re-charge the system. Find and fix the refrigerant leak. See REFRIGERANT LEAK DETECTION. While it's quick (and cheap) to just add refrigerant to a system, we were taught at HVAC school to scorn earning a living by developing a refrigerant gas delivery route.

An air conditioning or heat pump system is normally completely sealed and should never "use" refrigerant. Refrigerant gases are not a substance which is "consumed" in an HVAC system.

In an emergency, such as at a commercial establishment needing time to move frozen food, one might just add refrigerant, but the proper repair is to find and fix the refrigerant leak.
If the refrigerant gas leak is in a valve or access port, such as the service ports to which the HVAC technician connects her gauge set, the valves there may be able to be cleaned and salvaged, or the valves may need to be replaced.

Replacing a refrigerant gas service port valve is a soldering job similar to what we describe just below. In our AC repair career we never had to replace one of these valves but we did have to install them on some systems where they were not already in place.

Our photo at left shows refrigerant gauge access ports on a compressor/condenser unit.
If the refrigerant gas leak is in the air conditioning or heat pump copper tubing a repair should be easy - the damaged line is re-soldered using high silver content solder and a high temperature torch. (We used MAPP gas for silver soldering of copper fittings, some technicians use Acetylene or other gases).

A damaged section of refrigerant line may need to be cut out and replaced. The repair is about the same regardless of whether the leak was in the larger diameter suction line or the smaller diameter high pressure line.
If the refrigerant gas leak is in the condensing coil or in the evaporator coil, repair might be possible, but we're less optimistic that repair is possible, but it might be, as we explain just below.
Use a halogen gas leak detector to pinpoint refrigerant gas leaks and for thorough inspection & testing of the entire refrigerant piping system, including the condensing and evaporating coils. Details are at Using the TIF 5000 Gas Detector.

Should We Just Add Refrigerant Rather Than Finding and Fixing the Leak in our Air Conditioner or Heat Pump?

At HVAC school we were taught that some HVAC technicians, in the opinion of the instructor (and our own as well), like the idea of a "delivery route" business, coming around periodically to replace lost refrigerant. In our view in many circumstances this can be a questionable practice.

Air conditioners and heat pumps are designed as a closed, hermetically sealed system - they are not supposed to leak refrigerant, and refrigerant leaks are an abnormal condition. The refrigerant leak can be found and repaired.

If the technician was in a hurry, perhaps given many service call assignments, or if s/he didn't want to be hassled by a customer complaining over an "attempt convert a simple recharge to a costly service call", or if the company just likes to deliver refrigerant (lots of repeat business), or finally, if the system with the refrigerant leak is large, commercial, complex, and old - at end of life, s/he may not have mentioned that refrigerant leak repair is even possible.

If you are faced with a costly service call or repair on an old air conditioning system (such as the need to replace a corroded, leaky evaporator coil) on a system that is at or near end of life, it is understandable that you might just prefer to wait and replace the whole system.

But it is not air conditioner or heat pump system age that makes a refrigerant leak able to be found or not, it is system complexity. Sometimes, especially with large complex commercial systems, because tracing all of the piping and tubing and looking for leaks is time consuming, some people opt to just add refrigerant.

Just adding refrigerant is not the best practice. And with old freon-based cooling or heat pump systems such leaks might be illegal as you are damaging the environment and making a prohibited release of Freon gases to the air.

The refrigerant gauge set photo above is discussed in detail at GAUGE, REFRIGERATION PRESSURE TEST.

Guide to Repairs of an Air Conditioning or Heat Pump Evaporator Coil or Condensing Coil

Review the coil inspection, diagnosis, and repair tips at COOLING COIL or EVAPORATOR COIL. We find that the terms "cooling coil" and "evaporator coil" are used as synonyms in most cases. Sketch at left courtesy of Carson Dunlop Associates.

Even if the cooling or condensing coil has a repairable leak, if the coil is badly damaged such as having all crushed fins, it may be best to replace it.

Damaged cooling / evaporator coil fins over more than 10% of the coil surface, blocking air flow may be a reason to replace the coil.
If the cooling coil or condensing coil is in good physical condition but it's dirty, it needs to be cleaned before it can be repaired. Spray-on coil cleaners are used by lots of HVAC technicians.

If the coil is dirty with moldy dust and debris and especially if the building is occupied by people at extra health risk, we don't like to see an indoor coil cleaned by blowing it off with compressed air, as you're simply sending all of this moldy junk into the building. See DIRTY COOLING COIL and see Mold Growth in Air Handlers. You may also want to check out Leaks, Rodents In Air Handlers.
Next check the cooling coil or evaporator coil for visual evidence of refrigerant leaks. Visual evidence of a refrigerant leak on a coil may include stains from refrigerant oil left at the point of leakage. See REFRIGERANT LEAK DETECTION.
When the one or more places where the cooling coil or evaporator coil is leaking refrigerant gas have been found, it's time to decide if we can perform a solder repair of if the coil has to be replaced. We offer some suggestions just below at Guide to Evaluating Evaporator Coil or Condensing Coil Refrigerant Leaks

Guide to Evaluating Evaporator Coil or Condensing Coil Refrigerant Leaks and Deciding to Repair or Replace a Coil

Evaporator coil or cooling leaks or holes: if an evaporator coil is leaking (or also if the condensing coil is leaking) you'll find out pretty quickly as refrigerant will be lost and the cooling system will stop providing cool air.

You'll need expert diagnosis by an HVAC service technician. Sketch at left courtesy of Carson Dunlop Associates.

How easily a cooling system refrigerant leak repair will be depends on where the refrigerant leak has occurred and what caused the leak.

If the cooling coil has a single point leak caused by some mechanical damage (one of our readers accidentally drilled a hole in his coil while trying to drill a drain hole in his air handler), it may be possible to find the hole and repair it using silver solder.

If the refrigerant leak is in copper tubing anywhere in the cooling or heat pump system that is not too close to an evaporator coil or condensing coil, it should be possible to solder a repair, then evacuate and recharge the cooling system.
If the refrigerant leak is in thin copper tubing that just melts when you try to solder it, as suggested by one of our readers, your technician may fabricate a copper sleeve that slips over the damaged tubing and is then soldered in place.
If the refrigerant leak is in copper tubing in or close to the cooling coil (or in a condensing coil) a solder repair is hard to complete because the heat of the soldering process tends to de-solder other nearby connections. It might be possible if the technician is very expert and if s/he knows how to keep nearby surfaces cooled (we've used a wet rag).
If the refrigerant leak is in an aluminum part, soldering aluminum is more tricky and may not be feasible. Ordinary procedures using a torch, for example, just melt the aluminum. Expert welders use inert gas welding methods.
If the refrigerant leak is due to severe corrosion anywhere in an HVAC system we're not optimistic that a solder repair is possible. The conditions that caused a corrosion-related leak are likely to have thinned and weakened other parts. The cost of an attempted repair may be wasted.

Replacement of the cooling coil (or condensing coil) is more often going to be recommended by your HVAC technician because of these difficulties.

Bubbles seen or heard in the liquid refrigerant line?

Clean Dust & Dirt Off of the Condensing Coil - Air conditioning and refrigeration performance &maintenance tip

As we also introduce at CONDENSING COIL REPAIR REPLACE, there is a big payoff in cleaning dust, debris, grass clippings off of a dirty refrigeration condensing coil (this includes outdoor condenser/compressor units for air conditioners and heat pumps and also the condensing coil on a home refrigerator or freezer).

Because a refrigeration system works by transferring heat from hot refrigeration gas/liquid to ambient air around the condensing coil, if the condenser coil is blocked by dirt and debris, this can prevent complete cooling of the high temperature refrigerant gas back to a liquid state.

The result is you'll get refrigerant gas bubbles passing through the refrigerant metering valve. On refrigeration systems that include a sight glass you can actually see these gas bubbles passing through the system.

More details are at REFRIGERANT SIGHT GLASS.

Incidentally a second source of bubbling sounds heard in the refrigerant piping suction line near the compressor could be refrigerant oil pooling in that location.

This oil pooling is not usually a consequential problem provided the collection of oil does not block passage of refrigerant in the system. In good HVACR design the refrigerant piping slopes back from the evaporator unit (cooling unit or air handler) towards the compressor/condenser unit so that refrigerant oil in the line finds its way back to the compressor motor.

Recharging the HVAC System after Refrigerant Leak Repair

In case you didn't realize it, in order to solder a repair in an air conditioner or heat pump piping, tubing, evaporator coil/cooling coil, or condensing coil, it will first be necessary to remove all of the refrigerant from the system.

The HVAC technician will connect a pump to pull a vacuum on the system to remove as much air, gas, debris, and moisture as possible. An evacuator pump is needed for this step. [We made our own vacuum pump using a particularly good performing Frigidaire rotary compressor retrieved from an abandoned antique refrigerator.]

The HVAC technician will probably want to install a refrigerant filter/drier (see our photo below) to remove any moisture that leaked into the system while it was open to the atmosphere, and perhaps she will install other filtration equipment on the system at this time. It's a good idea.

See GAUGE, REFRIGERATION PRESSURE TEST for details about the refrigerant charging procedure using a gauge set and charging cylinder or scale.

Installing a Refrigerant Dryer / Filter Unit on the Air Conditioning or Heat Pump Refrigerant Line

Once a system refrigerant leak has been repaired, it will be necessary to flush the refrigerant piping system (usually using nitrogen), pull a new vacuum on the system, and then re-charge the system with the proper type and quantity of refrigerant.

Our photo at left shows that a Catch-All™ C-163_S refrigerant dryer and filter has been installed on the high pressure refrigerant line leaving the outdoor compressor/condenser unit. This is where we usually see this device installed. Notice that the refrigerant dryer, which removes un-wanted moisture from the refrigeration system, is labeled with the types of refrigerant with which it is designed to be used.

Most driers are designed to be soldered in place, as is the unit shown at left. Some driers may permit connection using flare fittings - a connection we consider less secure and more leak prone.

When a refrigeration system is or has been "open" - has been emptied of refrigerant for re-charging, for example, the last repair step before re-charging the repaired air conditioning or heat pump system with refrigerant is to install a filter/drier such as shown in our photo at left.

The purpose of a refrigerant drier is to absorb (and thus remove) moisture in the refrigeration system. The effects of moisture on refrigeration systems are detailed at REFRIGERANT LEAK DETECTION but in sum we can say that moisture in the system can prevent proper operation and can even completely stop the system from working at all, even causing costly damage.

We also find a drier installed on refrigeration systems that have been serviced for a refrigeration leak, especially a low-side piping leak, because of the increased chance that the system has been contaminated by moisture and perhaps dirt. In fact if the system was open and badly contaminated the HVAC technician may install a drier right after the repair and may install a new or second drier on the same system a few months later.

While some technicians always install a filter/drier on the refrigerant system, even at original installation, more often when we see a refrigerant drier canister on a system (usually at the compressor/condenser unit) we assume that the system has undergone some service or repair as that's most often when the device is added.

Refrigerant Debris Filtering and Installation Position

Refrigerant Driers not only remove moisture, they also are intended to filter debris from the refrigerant piping system. Filtering the refrigerant liquid leaving the compressor/condenser protects the Thermal Expansion Valve or capillary tube from clogging. In at least some refrigerant drier/filter models, the presence of the strainer means that the drier/strainer device has to be installed in a particular direction such that particles of the desiccant do not break free and travel through the refrigerant piping system.

Why is a filter-dryer critical on an air conditioner or refrigeration system that has been worked-on?

Water anywhere inside the refrigerant handling system (tubing, compressor, condenser, or refrigerant metering cap tube or thermostatic expansion valve) freezes, making the system inoperative. The inside of any refrigeration system must be pure refrigerant: no air, no dirt, no water, and no mix of various refrigerant gases other than a single gas for which the system is designed.

Watch out: above we mentioned that on a badly contaminated refrigeration system the technician may install a new or a second drier a few months after the original repair/service. If a drier has become saturated in the course of doing its job (of removing moisture from the refrigerant system), it begins to restrict the flow of refrigerant through the system. This refrigerant flow restriction will cause pressure changes indicated by a temperature difference on either side of the drier - that's one way you could quickly test for a clogged refrigerant drier.

Watch out: if you change the size of the drier that you have installed on a refrigeration system that does not use a refrigerant receiver (as is the case with most residential appliances and air conditioners/heat pumps, you will have to compensate in the charge used in the system (if it is a "critically-charged" or precise charge system as we've discussed here). For example if you install a larger drier than was previously in place you'd need more refrigerant charge in order to assure that the frost line will still extend to the end of the evaporator.

Special Filters Used after a Compressor Motor Replacement

A "burnout drier" is a special drier installed on refrigeration systems when a compressor motor has burned out and the compressor is changed out. In this case we have to clean the acid and lacquer out of the refrigeration system. (Using Karene-R11). The system is washed out and then the burnout drier is put in temporarily in the low side or return refrigerant line, replaced one or more times as needed, until the system is cleaned. Therefore you might not normally see a drier in this position on a system except during that repair process.

More details about what moisture and contaminants do to a refrigeration system are discussed at REFRIGERANT LEAK DETECTION

What is the Life Expectancy of a Refrigerant Drier Installed on an Air Conditioner or Heat Pump or Refrigerator/Freezer?

Ordinarily a drier should last the life of the equipment, given no leaks or problems with the system that require that the refrigerant piping be cut. (The piping will be cut and the system opened, for example, if a cooling coil or condensing coil has to be replaced.)

Where is the Drier Usually Located on an Air Conditioning, Heat Pump, or other Refrigeration System?

The drier is installed at the coolest location on the system, on the liquid line, outside of the refrigerated space, and ahead of any refrigerant metering devices like thermostatic expansion valves or capillary tubes.

In our photo (left) you can see that the drier has been installed outdoors, at the point where the high side liquid refrigerant line is exiting the compressor/condenser unit.

Replacing an HVAC Cooling Coil or Evaporator Coil

If the decision is to replace the cooling coil or the evaporator coil, be sure that the new coil is the proper size and shape to match the condenser or evaporator unit itself. See ADDING A/C: RETROFIT SIZING for an example of a mismatch that means poor heating or heat pump system operation.

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

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Thanks to Ato Guy Benfante, Chesapeake, VA 8/26/07 for the photograph of an ice-blocked air conditioning system evaporator coil and for his suggestion that we provide an air conditioning system troubleshooting FAQ.
Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
John Cranor is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-747-7747 or by Email: johncranor@verizon.net
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides:
- Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
- Home Inspection Education Courses including home study & live classes at eleven colleges & universities.
- Home Inspection Education Home Study Courses - ASHI@Home Training 10-course program.
  Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference Book, a reference & inspection report product for building owners & inspectors.
  Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones.
  Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter inspectaehrb in the order payment page "Promo/Redemption" space.
- The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors.
  Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
- The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones.
Carson Dunlop, Associates, Toronto, have provided us with (and we recommend) Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
Thanks to reader Don Jackson for HVAC refrigerant leak soldering repair tips (Aug-Sept 2008).
[6] Refrigerant Piping Design Guide, Application Guide AG-31-011, McQuay Air Conditioning, Daikin McQuay International Equipment, 13600 Industrial Park Blvd. Minneapolis, Minnesota 55441 800-432-1342 (Toll Free), Website: http://www.daikinmcquay.com/, [Copy on file as http://www.inspectapedia.com/aircond/AC_Guide_McQuay.pdf ]
Wikipedia provided background information about the definition of HEPA and airborne particle interception.

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.

The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.

Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.

Building inspection education & report writing systems from Carson, Dunlop & Associates Ltd

Carson Dunlop, Associates, Toronto, have provided us with (and we recommend) Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
Complete List of Air Conditioning & Heat Pump Design, Inspection, Repair Books at the InspectAPedia Bookstore.
Modern Refrigeration and Air Conditioning, A. D. Althouse, C.H. Turnquist, A. Bracciano, Goodheart-Willcox Co., 1982
Principles of Refrigeration, R. Warren Marsh, C. Thomas Olivo, Delmar Publishers, 1979
"Air Conditioning & Refrigeration I & II", BOCES Education, Warren Hilliard (instructor), Poughkeepsie, New York, May - July 1982, [classroom notes from air conditioning and refrigeration maintenance and repair course attended by the website author]
Refrigeration and Air Conditioning Technology, 5th Ed., William C. Whitman, William M. Johnson, John Tomczyk, Cengage Learning, 2005, ISBN 1401837654, 9781401837655 1324 pages
Air Conditioning SEER - New DOE Air Conditioner and Heat Pump Efficiency Standard
Asbestos HVAC Ducts and Flues field identification photos and guide
Fiberglass: Indoor Air Quality Investigations: Fiberglass in Indoor Air, HVAC ducts, and Building Insulation

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