Air Conditioning & Heat Pump Refrigerant Leak Repair Procedures
REFRIGERANT LEAK REPAIR - CONTENTS: 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?
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Air conditioning, heat pump or refrigerator / freezer refrigerant gas or liquid leaks:
How do we repair refrigerant leaks in air conditioning, heat pump, or other refrigeration systems?
This article series 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.
As we explain in our articles on lost cooling capacity or air conditioning systems or heat pumps that are not working, 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.
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.
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.
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.
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. 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.
"Stop leak" products have been in use for decades, particularly in the automotive industry where they were used to address leaks in automotive cooling systems. Those products traditionally used a carrier and fibers (originally asbestos) - an approach not suitable for refrigeration systems whose refrigerant metering devices may not tolerate particulates, even small ones.
Since the 1980's several inventors (e.g. Packo & Bailey 1980, 1982, 1984) have patented other approaches (and chemistry) for sealing small leaks in refrigeration systems. Some of these refrigerant leak sealant products use triethoxyl (vinyl) silane that forms a seal when exposed to air and can seal small openings in refrigeration systems without clogging up the capillary tube or thermostatic expansion valve.
Evaluating Evaporator Coil or Condensing Coil Refrigerant Leaks and Deciding to Repair or Replace a Coil
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.
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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
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Thanks to reader Don Jackson for HVAC refrigerant leak soldering repair tips (Aug-Sept 2008).
 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
"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]
Fiberglass: Indoor Air Quality Investigations: Fiberglass in Indoor Air, HVAC ducts, and Building Insulation
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