Air Conditioning & Heat Pump Refrigerant Leak Repair Procedures

Accurate Diagnosis of a Refrigeration System Leak

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.

1. Confirm that the problem is a refrigerant leak:
   
   First, see LOST COOLING CAPACITY to diagnose just why the system is not working.
2. Find the refrigerant leak:
   
   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 or best repair is to find and fix the refrigerant leak.
3. 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.
4. 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.
   
   See REFRIGERANT PIPING DAMAGE & LEAKS for a list of common causes of damage and leaks in refrigerant piping.
   
   Details about refrigerant piping installation or replacement are
   
   at REFRIGERANT PIPING INSTALLATION.
5. 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.
6. 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.

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).

Sketch: showing the use of a sight glass on refrigrant piping is provided courtesy of Carson Dunlop Associates, a Toronto home inspection and education firm.

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.

Gas bubbles in the liquid refrigerant line can result in complaints of running water, gurgling, burbling, or similar sounds coming from the refrigerant piping system.

See REFRIGERANT PIPING GURGLING.

Watch out: 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.

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.

While in the short run it may seem cheaper to just "add refrigerant" when the system refrigerant level is low, that ignores the fact that the system is illegally releasing refrigerant to the atmosphere, contaminating the environment. In fact, 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.

OPINION: 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.

A step by step example of adding refrigerant to an air conditioning system using a rather minimalist approach is illustrated

at SPLIT SYSTEM AC / HEAT PUMP REPAIRS.

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

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 refrigerant that has been recovered and/or recycled can be returned to the same system or other systems owned by the same person without being reclaimed. But the refrigerant charging procedure using a gauge set and charging cylinder or scale.

Refrigerant Charging or "Topping Off Low Refrigerant" is Not a Homeowner Task

Watch out: Charging a home air conditioner is not a step I recommend to homeowners or a handyman; special equipment including refrigerant gauge set and possibly temperature measuring equipment, training, even knowing how to purge and then hook up the gauge and charging equipment, matching the right refrigerant, knowing the right charge amount are all stuff learned in HVAC school.

The risks are an over-charge, under-charge, or introducing air or dirt into the refrigeration system, leading to a still more-expensive repair than if you'd had a trained person do the job in the first place.

Laws Governing Refrigerant Release / Recapture / Re-Use

• US EPA STATIONARY REFRIGERATION REFRIGERANT RECLAMATION REQUIREMENTS [PDF]
  Excerpt:
  
  EPA regulations (40 CFR Part 82, Subpart FEXITEXIT EPA WEBSITE) under Section 608 of the Clean Air Act restrict the resale of used ozone-depleting and substitute (e.g., HFC) refrigerant to a new owner unless it has been reclaimed by an EPA-certified refrigerant reclaimer.
  
  To be properly reclaimed, used refrigerant must be reprocessed to at least the purity level specified in Appendix A to 40 CFR Part 82, Subpart FEXITEXIT EPA WEBSITE [based on Air Conditioning, Heating, and Refrigeration Institute (AHRI) Standard 700-2016EXITEXIT EPA WEBSITE].
  
  This purity level must be verified using the laboratory protocol set forth in this same standard.
• RELEASE of REFRIGERANT to the ENVIRONMENT is PROHIBITED - 42 U.S. Code § 7671g - National recycling and emission reduction program [PDF]
  
  Excerpt: Effective July 1, 1992, it shall be unlawful for any person, in the course of maintaining, servicing, repairing, or disposing of an appliance or industrial process refrigeration, to knowingly vent or otherwise knowingly release or dispose of any class I or class II substance used as a refrigerant in such appliance (or industrial process refrigeration) in a manner which permits such substance to enter the environment.
  
  De minimis releases associated with good faith attempts to recapture and recycle or safely dispose of any such substance shall not be subject to the prohibition set forth in the preceding sentence.

Refrigerant Leak Research

• Brownell, K. A., Klein, S. A., & Reindl, D. T. (1999). REFRIGERATION SYSTEM MALFUNCTIONS [PDF] ASHRAE Journal, 41, 40-48. Retrieved 2019/02/03, original source: citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.618.5464&rep=rep1&type=pdf
• Ishii, Noriaki, Kenichi Bird, Kiyoshi Sano, Mamoru Oono, Shinji Iwamura, and Takayuki Otokura. REFRIGERANT LEAKAGE FLOW EVALUATION FOR SCROLL COMPRESSORS [PDF] (1996).
  
  Purdue University, International Compressor Engineering Conference, School of Mechanical Engineering. Retrieved 2019/01/03, original source: docs.lib.purdue.edu/cgi/viewcontent.cgi?article=2174&context=icec
• Tang, Weier, Guogeng He, Dehua Cai, Yihao Zhu, Aoni Zhang, and Qiqi Tian. "The experimental investigation of refrigerant distribution and leaking characteristics of R290 in split type household air conditioner." Applied Thermal Engineering 115 (2017): 72-80.
• Taylor, Dan W., and David W. Corne. "Refrigerant leak prediction in supermarkets using evolved neural networks." In Recent Advances In Simulated Evolution And Learning, pp. 643-661. 2004.
• US DOE, COMMON AIR CONDITIONER PROBLEMS [PDF] retrieved 2019/02/03, original source: energy.gov/energysaver/common-air-conditioner-problems
  Excerpt:
  
  If your air conditioner is low on refrigerant, either it was undercharged at installation or it leaks. If it leaks, simply adding refrigerant is not a solution.
  
  A trained technician should fix any leak, test the repair, and then charge the system with the correct amount of refrigerant.
  
  Remember that the performance and efficiency of your air conditioner is greatest when the refrigerant charge exactly matches the manufacturer's specification, and is neither undercharged nor overcharged. Refrigerant leaks can also be harmful to the environment.
• Maclaine-Cross, I. L., and E. Leonardi. PERFORMANCE AND SAFETY OF LPG REFRIGERANTS [PDF] In Proceedings of the Fuel for Change Conference—Australia, Surfers’ Paradise Queensland, Australian Liquefied Petroleum Gas Association Ltd, ISBN 0, vol. 646, no. 24884, p. 7. 1995.