Servicing in HVAC Industry
Updated: Apr 5
EPA 608 Core Chapter 9
The Three Rs
In this module, we will discuss three important processes within the HVAC industry.
The Three Rs
The three Rs of refrigeration are:
These three Rs describe three important processes within the HVAC industry.
Recovering is when the technician removes refrigerant from a system and stores it in an external container. When we recover refrigerants, we’re not testing or processing the refrigerant in any way. All we’re doing is storing it in a separate container.
We recover refrigerants for a number of reasons. Recall that CFCs and HCFCs have been phased out, meaning they can no longer be produced or imported. We recover refrigerants so that we can have supplies of CFCs and HCFCs to service equipment with.
You can think about recovering refrigerants like filling up a water bottle for the road. You store the water in a container so that you can drink it later.
Recall that venting, or releasing CFC and HCFC refrigerants into the atmosphere, is harmful to the ozone layer. This is another reason we recover refrigerants — to prevent damage to the ozone layer.
Recycling is the process of cleaning refrigerants for immediate reuse. We recycle refrigerants by separating the oil from the refrigerant and using filter driers to remove moisture and acidity from the refrigerant.
You can think of recycling as washing your plate and using it again. With recycling refrigerants, you’re just cleaning out the contaminants so you can use the same refrigerant again.
Reclaiming is when the refrigerant is processed to new product specifications. After the refrigerant is processed, we need to verify its properties through chemical analysis.
If a refrigerant is reclaimed, it has basically the same properties as a newly manufactured refrigerant.
Recall that since CFCs and HCFCs have been phased out, we can no longer produce or import these refrigerants. So the closest we can get to new supplies of these refrigerants is reclaimed refrigerants.
Reclaimed refrigerant has to meet the standard AHRI 700 - 2016 before it can be resold. You can think of reclaiming like refurbishing, good as new. But the properties are chemically verified, so it would be better than refurbishing.
In this module, we discussed the three Rs and how are the refrigerants recovered, dehydrated, and evacuated.
In this module, we will discuss the various recovery equipment and techniques used in the industry.
Types of Equipment
All technicians need to be able to operate equipment used in their normal services. Technicians must also follow manufacturer instructions on how to properly operate the equipment.
Under Section 608, all new recovery equipment is required to have an EPA approved certification label. This lets the technician know that the equipment is up to EPA standards and can operate on refrigerant chemicals.
There are two main types of recovery equipment:
System Dependent Recovery Equipment, and
Self Contained Recovery Equipment
As we discussed in Equipment Requirements, system dependent equipment depends on the pressure of the compressor to recover refrigerant. System dependent equipment can only be used with appliances that contain 15 pounds of refrigerant or less.
This also means that for all appliances with more than 15 pounds of refrigerant, the technician must use self-contained equipment.
Self contained equipment can operate without relying on the pressure of the compressor. As we said, we use self contained equipment for larger appliances, with more than 15 pounds of refrigerant.
When recovering refrigerants, technicians must use recovery cylinders. These are the containers specifically designed to hold refrigerants. They will have gray bodies and yellow tops.
Only one type of refrigerant can be recovered in each cylinder. This is to avoid mixing refrigerants.
As we discussed in Refrigerant Blends, blending your own refrigerants gives the refrigerant unpredictable temperatures and properties. It is also illegal to blend your own refrigerants.
If multiple refrigerants are recovered in a cylinder, this mixture cannot be used. In addition, the mixture may be impossible to reclaim.
If a technician discovers that Refrigerant B was added to a system that operates on Refrigerant A, you must recover the mixture in a separate recovery tank.
For example, let’s say a technician is working on an R-22 system. If you discover that R-410a was added to this system, you need to recover the mixture in a separate recovery tank.
This is why technicians can only recover one type of refrigerant per recovery cylinder. If it is necessary to recover more than one type of refrigerant (for multiple devices), you must use a separate recovery cylinder for the other refrigerant.
At the end of recovery service, technicians need to make sure that there is no liquid refrigerant trapped in the service hose. Any refrigerant trapped in the hose will be vented and this is not allowed under the Venting Prohibition.
Ozone Depleting Substances
Recall that for all ozone depleting refrigerants and their substitutes, there are special requirements for this refrigerant when they are recovered. Recall that this includes CFC, HCFC, and HFC refrigerants.
For CFC, HCFC, and HFC refrigerants, technicians must be reclaimed to AHRI standards before being resold. We discussed this in Section 608 Regulations.
This means that if you recover these refrigerants, you can only use the recovered refrigerant in
The same appliance, or
Another appliance owned by the same person.
For example, if you recover R-22 from an appliance, that recovered R-22 can only be used in the same appliance you recovered it from. You can also use it in another appliance owned by the same person.
In order to use the R-22 refrigerant in an appliance owned by a different person, you must send it to be reclaimed per AHRI standards for the virgin refrigerant.
In this module, we saw different types of recovery equipment. We also discussed various recovery practices while using these devices.
Factors Affecting Recovery Time
In this module, we will define the term 'recovery time' and, we will also discuss various factors affecting recovery time.
Minimizing Recovery Time
Recovery time is the time it takes to recover a refrigerant.
Generally, we want to recover refrigerant in the least possible amount of time. This is because the longer it takes for the technician to recover the refrigerant, the higher the chances of venting.
The time it takes to recover refrigerant changes depending on:
Ambient Temperature, and
Ambient temperature just refers to the temperature of the system.
Recall from our Essential Chemistry module that temperature is a measure of how fast molecules are moving. If the temperature is low, that means the molecules inside the system are moving slowly.
The lower the temperature of the system, the longer the recovery time will be. This is because the refrigerant molecules inside the system are moving slower, so it will take more time to move them out of the system.
The second main factor that affects your recovery time is how long your hose is between the system and recovery machine. The longer the hose, the longer the time it will take to recover the refrigerant.
This is because the refrigerant has to travel through the entire length of the hose before reaching the recovery device. So we want to keep the hose length to a minimum to minimize recovery time.
Long hoses also cause excessive pressure drops between the system and recovery device. Recall that recovery depends on pressure difference, so an excessive pressure drop with interfere with proper recovery.
In this module, we defined recovery time and saw the various factors affecting the recovery time.
In this module, we will take a look at the term dehydration and its affects the HVAC systems.
Recall from our module on Refrigerant Oils that oils can react with water to create toxic and corrosive acids. This will cause major system failures. So we do not want water or water vapor in the system.
Dehydration is the process of removing water and water vapor from the system. We dehydrate the system by evacuating it.
The recommended method to dehydrate a system is to evacuate it. Evacuation is when we remove all water vapor and air from the system.
A system is considered dehydrated when you have reached and held a vacuum of 500 microns or less.
If the system contains a hermetic compressor, you need to make sure it is not operating when you pull a dehydration vacuum. If the hermetic compressor is operating, it will prevent you from pulling a deep vacuum.
So basically, in addition to removing all the water vapor from a system, evacuation includes removing all the air from the system as well.
So to reiterate, evacuation is the best method for dehydrating a system. We also need to evacuate a system before any major system repairs.
To remove all the air and water vapor from the system, we need to use a vacuum pump to pull a vacuum on our system.
To pull a vacuum, we need to make sure that the vacuum pump is capable of pulling a deep vacuum. We define a deep vacuum to be 500 microns.
Vacuum lines or hoses need to be equal to or larger than the pump intake connection. If the mouth of the hose is smaller, you would not be able to pull a vacuum.
The piping connection to the vacuum pump should be:
As short in length as possible, and
As large in diameter as possible
To measure the final system vacuum,
Isolate the system,
Turn off the vacuum pump, then
Measure the final system vacuum
To measure correctly, we need to attach the
Vacuum Gauge to the high side, and
Vacuum Pump to the low side
Over-evacuation of a system does not occur. Recall that the purpose of evacuation is to remove all air and water from the system.
You cannot remove too much air and water from the system because you want all of it to be gone. If you evacuate past the point that is necessary, this will not damage refrigeration line sets. This is because they are made of metal such as copper, aluminum, or steel.
You have reached dehydration when the vacuum indicator shows you have reached and held a vacuum of 500 microns or less.
Factors Affecting Dehydration Time
Dehydrating time is the time it takes to remove all water and water vapor from a system. Recall that dehydrating is done by evacuating a system, which involves removing air and water from the system.
We generally want to minimize the amount of time spend dehydrating a system. The longer we spend dehydrating, the larger the risk of any component failing in the system. Your time as a technician is also valuable.
That being said, we need to make sure we are taking safe measures to decrease our dehydration time. Safety is always number one.
The following factors contribute to a system’s dehydration time:
Amount of Moisture
Vacuum Capacity, and
Suction Line Size
The larger the equipment, the longer it will take to dehydrate it. This is simply because there is more work to do. Imagine mowing a lawn. The bigger the lawn, the more time it takes to get the job done.
The ambient temperature is the temperature of the system. The colder it is or the lower the ambient temperature, the more time it’s going to take to dehydrate.
That’s why we want to heat up the system to decrease the dehydration time. The higher the temperature, the less time it will take to dehydrate. We can use a heat blanket to heat the system safely.
Recall that we never use a flame to heat up the system. We are working with possibly flammable materials that operate on high pressure. Using an open flame can lead to explosions.
The more moisture there is in the system, the longer it will take the dehydrate the system. Going back to the lawn mowing scenario, the mount of moisture would be like the amount of overgrown grass in your lawn. The more grass you have, the longer it will take to mow.
And lastly, the vacuum capacity is the rate at which your vacuum can pull out moisture and air. The smaller your vacuum capacity, the longer it will take to dehydrate the system. The smaller your lawn mower, the longer it takes to mow the lawn.
The longer the suction line, the longer it will take a dehydrate a system. That’s why we want to keep the suction line as short as possible.
In this module, we defined the term dehydration and discussed the factors affecting dehydration time.
In this module, we will go over the details of recharging the refrigerant and, we will also discuss the precautions to take while servicing the equipment.
When working with flammable refrigerants, we need to take a few additional precautions before recharging the system. This is because flammable refrigerants can cause explosions and injuries if not handled properly.
Recall that flammable refrigerants include hydrocarbons and HFOs. Hydrocarbons are generally highly flammable, or Class 3 according to ASHRAE classification. HFO-1234yf is mildly flammable, at Class 2L.
For all hydrocarbons, we need to complete the following before recharging:
Electrically ground the system
Install a fresh filter-drier
Complete a standing-pressure leak check at the maximum system pressure
Evacuate to 500 microns or lower
We need to ground the system before recharging flammable refrigerants. This is to reduce the chance of electrical fires while working with flammable refrigerants.
We have to install a fresh filter drier with flammable refrigerants. Filter driers absorb contaminants and installing a fresh one reduces the chances of flammable refrigerants reacting with contaminants.
We also need to perform a standing pressure leak check at the maximum system pressure. Leaks with flammable refrigerants can cause fires or explosions. So we need to make sure the system is not leaking, even at its highest pressure.
And lastly, before recharging with flammable refrigerants, we need to evacuate to 500 microns or less. This ensures that there are basically no contaminants in the system that the flammable refrigerant can react with.
All of these steps need to be taken in order to make sure the flammable refrigerant does not cause an explosion.
During servicing, liquid refrigerant can get trapped in the service hose between closed service valves. This happens when you transfer refrigerant between the system and a recovery unit.
It’s like using a straw. Imagine sipping soda through a straw. When you are done with your sip, there is still soda in the straw. What happens to the soda in the straw? Well when you let go of the straw, the soda falls back into the can. This is backwash.
The same thing happens with refrigerant. You can think of the service hose as a straw.
We want to make sure we don’t trap any liquid refrigerant in the service hose. Any refrigerant trapped in the service hose will be vented when you disconnect it. And recall, it is illegal under Section 608 to vent refrigerants that deplete ozone (CFCs, HCFCs, and their substitutes).
In this module, we discussed the recharging techniques and procedures used while servicing the equipment.