This is part two of the Discover HVAC EPA section 608 certification core course.
Image by Free-Photos from Pixabay
Text Stephen Peters August 2016, updated December 2019
Refrigerant recovery is now a legal requirement to protect the environment. You should know how to safely and fully recover refrigerants to comply with the law and pass the section 608 core test.
As the environmental protection requirements for refrigerant recovery have become more strict the cost of HVAC service to consumers has increased. This has naturally resulted in some pushback from HVAC end users. You will need to know enough about the legal requirements are and why they have been put into place by the government to explain to customers why costs have increased. You will also need to know what the practical effects are for the service technician as well as the increased equipment costs to fully recover refrigerants.
One of the cost increases when purchasing equipment is that it is now a legal requirement for all systems containing Class I or Class II refrigerants to have a service port. This is to make it easier to recover refrigerant which makes recovery more likely to happen.
Before attempting to recover refrigerant from a system you must find out which refrigerant type you are recovering. If you mix refrigerants in a cylinder reclamation facilities may not be able to process and recycle your refrigerant. This can mean that you do not get paid for the recovered refrigerant but instead have to pay a disposal fee. These fees can be substantial. Check the nameplate on the system to find out which refrigerant it contains first. Only recover one type of refrigerant into a recovery cylinder and make sure you know which refrigerant is already in a partially full cylinder before adding more refrigerant to it.
When working on a system it is possible that the compressor may have burnt out. A burnt out compressor may have contaminated the compressor oil, which often results in a strong smell. Once all of the refrigerant has been recovered you can use nitrogen to flush any remaining contamination from the system. This nitrogen can be vented to the atmosphere. Always install a new filter drier on the suction line to collect any remaining contaminants that could damage the new compressor.
When you are recovering refrigerant use the shortest hose you can. Hose length effects how efficient the recovery process is with longer hoses being less efficient. Using longer hoses causes pressure drop, and increased recovery times. Which means you will be standing there waiting for refrigerant to transfer to the recovery cylinder longer rather than finishing the job faster. Additionally refrigerants have a relationship between pressure and temperature, as you can see from a pressure temperature chart. This means that on a cold winter day recovery will take longer than on a hot summer day.
When you have finished a recovery operation and are disconnecting the hoses from the tank and system the hose will still contain a small amount of refrigerant. You cannot avoid releasing this refrigerant from the hoses, which is known as a "De minimis" release. Using a longer hose means that more refrigerant is released when you disconnect the hoses. Shorter hoses release less refrigerant and cause less environmental damage, which is why it is good practice to use shorter hoses.
Finally make sure you do not trap any liquid refrigerant between the service valves.
Before you recover refrigerant from a system to a recovery cylinder you will need to learn what types of recovery method should be used. In this video both system dependent and self contained recovery methods are demonstrated when fully purging a system.
HVAC systems must not have any fluids circulating within them other than refrigerant and oil. Any other fluids if they are present are a contaminant and may cause harm to the system. Water and water vapour can be extremely harmful to the system and may cause hydrochloric acid or hydrofluoric acid to form. The conventional method of dehydration of a system is evacuation. A system cannot be over evacuated.
Refrigerant recovery must be performed first before evacuating the system to the ambient air to remove any remaining moisture.
The time spent evacuating the system down to the specified level is dependant on several factors; the size of the system undergoing evacuation, the ambient temperature, and the capacity of the pump and suction line you are using. Make sure you are using the correct size of vacuum line for the pump, as the line must be equal in size to the pump intake or larger. Make sure you use the shortest length of hose possible as linger hoses negatively affect pump efficiency.
Your set of gauges should be fitted as far away from the pump as possible. Any measurements taken should be performed when the pump is not running and the system is isolated. If the system cannot hold the vacuum when it is evacuated there is a leak you will need to resolve before proceeding.
Heating the system when you are evacuating it will shorten the time it takes to dehydrate it. Once the vacuum gauge shows you have reached the required vacuum dehydration is finished. Do make sure the vacuum holds though.
When recovering refrigerant from small appliances falling under the type 1 rules you may need to fit a piercing valve. This video explains how to fit some of the different types of valve available and also has tips for when the valve leaks.
When you are recovering refrigerant from a system you will need a container to store and transport the used refrigerant before it is recycled. To comply with the EPA section 608 as well as the Department Of Transportation (DOT) laws for transportation of refrigerant the cylinder must be DOT approved. Disposable refrigerant cylinders must never be used for refrigerant recovery.
Recovery cylinders are designed for both reuse and transport. Approved recovery cylinders can be easily identified by color as they have a yellow top and a gray body. All refillable cylinders must be hydrostatically tested every 5 years and stamped with the test date. Do not use a cylinder date stamped more than 5 years ago. Cylinders that are rusty should also not be used. On the collar of the cylinder are the identification and specification stamps. These tell you all of the information you need when recovering refrigerant:
Recovery cylinders must not be filled above 80% of its capacity by weight. You must ensure this safe fill level is not exceeded by measuring the weight of the cylinder or using a mechanical float or an electronic shut off.
In this video learn about refrigerant recovery cylinders. Find out how cylinders are labeled and how to identify a recovery cylinder. Also discover tank safe handling and use with safe filling capacity explained. Find out how to use the tank valves and what they are used for.
Filling a recovery cylinder with refrigerant is quite simple. You simply need to keep the tank on a scale and make sure that you do not exceed the safe total weight of the tank plus the safe fill weight of the refrigerant type you are recovering. The weight of the tank itself is stamped on its collar. This is marked as the tare weight or simply TW. The maximum amount of the refrigerant type you are recovering that will fill the cylinder to 80% full is calculated from the liquid capacity of the tank. This capacity is stamped on the collar as Water Capacity or simply WC.
Water capacity is used to show the liquid volume of the cylinder. Water has a different volume to weight ratio than refrigerants and even amongst refrigerants the volume to weight ratios are different. So you cannot just multiply the water capacity by .80 and use the result as your capacity limit. Instead you need to compensate for the weight volume difference and then calculate the safe maximum fill weight for the cylinder. This maximum weight can be calculated with a simple formula:
To use the formula you will need to know the amount of space in the tank. This is commonly measured in cubic feet or ft3. The tank is stamped with the weight of water it takes to fill the tank so we can simply work out the tank internal volume with this formula:
For example a 30lb tank has a water capacity of 26.2lbs. Water has a volume of 62.42 pounds per cubic foot. To find out the number of cubic feet in the tank we simply divide the water capacity by the water volume per ft3 to get our capacity of 0.419:
If we are going to be filling our tank with R410a then we next need to find out how many pounds of refrigerant fit in a cubic foot at 130°. Refrigerant data sheets have this figure and for R410a it is 54.70. So to get the amount of R410a that will fill the tank we use this formula:
As we already calculated the ft3 of the tank we simply divide this by weight of refrigerant per ft3 to get the maximum amount of R410a that will fit in the tank:
This gives us the amount of refrigerant to completely fill the tank, however you MUST NOT fill the tank more than 80% full so we need to adjust our refrigerant quantity to allow for this. This is done with the following simple formula:
As we have calculated the amount of refrigerant required to completely fill the tank we simply divide this figure by 0.80 to get out 80% full weight:
Finally to find the total maximum weight of the tank and refrigerant we simply add the tank tare weight to the 80% refrigerant weight. Remember the tare weight is simply the weight of the empty tank and valves. To calculate this we use this formula:
Finally to find the total maximum weight of the tank and refrigerant we simply add the tank tare weight to the 80% refrigerant weight. Remember the tare weight is simply the weight of the empty tank and valves. It is customary to round down the 80% refrigerant weight to the nearest lb so we will round our 18.32lbs to 18 lbs. To calculate the maximum weight we use this formula:
If you do not know what type of refrigerant is in a cylinder you can find out by checking the weight and temperature on a pressure/temperature (P/T) chart. Using this method you can even find out if the tank contains a mixture of different refrigerants or other gases.
When you are adding more refrigerant to an partially full cylinder it is good practice to check before adding more refrigerant what is in the tank. Using the P/T chart you can tell what refrigerant is in a cylinder, and if it has a mixture of refrigerants or air. To use a P/T chart properly you need as the name suggests both the pressure and temperature of the refrigerant you are using. Finding the temperature is simple, just use a thermometer. Then attach the high pressure red hose to the high pressure red gauge of your manifold gauges. Make sure that the gauge is closed and the hose is tight before opening the tank valve.
Then simply find the row on the P/T chart for the temperature your refrigerant is at and go to the pressure number that matches your pressure reading. This should correspond to the refrigerant column you are using. If the pressure is not what you are expecting then your tank contains either mixed refrigerants or air.
Refrigerants mixed with air can be a dangerous explosion hazard as some refrigerants are highly flammable. Air in a system also significantly degrades the performance of the equipment. It raises the pressure in the compressor and as it is a not a good heat transfer medium reduces the efficiency of the condenser. This results in higher wear on the motor and can rupture seals due to the higher pressure in the system. While refrigerant recycling companies can accept cylinders where refrigerant has been mixed with air doing this costs you money. Using a recovery machine it is simple to separate the air from the refrigerant for reuse (if you use a filter drier in the recovery line) or for resale to an authorized recovery company.
When recovering refrigerant you may end up with air in the tank. This may have entered the system from leaks, previous maintenance or impurities in the existing refrigerant. Following recovery you have a refrigerant cylinder containing a mixture of air and refrigerant. In fact air is the most prevalent contaminant in recycled refrigerant. It is however possible reclaim pure refrigerant from the cylinder. In this video you can watch a demonstration of this recovery being carried out.
Make sure you check the system you are working on as well as your service equipment for damage and corrosion before using it. Check for leaks, bends, and broken parts. There must be no corrosion in the body of a relief valve, if there is any corrosion the valve MUST be replaced. Relief valves MUST NOT be installed in series and should be installed downstream from the pressure regulator. Corroded or damaged recovery cylinders should be replaced, refrigerant cylinders should never be heated with an open flame.
Should a large refrigerant leak occur in a confined area IMMEDIATELY leave the area. The area should be ventilated and no one should return to the area unless they are wearing a Self Contained Breathing Apparatus (SCBA). Refrigerants are heavier than air and displace oxygen when this occurs they can cause heart irregularities, unconsciousness, suffocation, and death. Refrigerants have a very faint odour so when working in a confined space have a refrigerant monitor with you as you work. Do not enter an area where a large release has occurred until the area has been properly tested and is safe.
Both R-12 and R-22 present a significant hazard when exposed to high temperatures. Never expose R-12 or R-22 to hot surfaces or open flames. Both refrigerants decompose at high temperatures and form Hydrochloric acid, Hydrofluoric acid, and Phosgene gas. These substances are a significant health hazard, cleanup methods are expensive and require special precautions.
Each refrigerant type is required to have a Material Safety Data Sheet (MSDS) to be available from the chemical manufacturer, distributor or importer. These MSDS will contain the following information about the refrigerant:
MSDS are a valuable source of information when you are training as a reference when you are learning the characteristics of each refrigerant. They are also extremely useful when you have passed your test as they have sections about the type of safety equipment you should be using when handling them. They are also useful in the event of an accident as you can easily find out how to deal with accidental releases and can hand the sheet to emergency services to let them know the type of hazard present in an emergency.