HVAC - Recovery and Evacuation

What is HVAC?

HVAC stands for Heating, ventilation, and air conditioning. The main goal is to provide thermal comfort and quality indoor air. The mechanical engineering, based on the principles of thermodynamics, fluid mechanics and heat transfer, is the mother of the HVAC system.

Recovery

Why do we recover refrigerant? 

Refrigerants are main players in the heat transfer process that paves the way to the possibility of air conditioning and heating system. The Environmental Protection Agency (EPA) has been cutting down these refrigerants. They are big contributors to ozone layer depletion and the increasing potential of global warming. Intentional or unintentional venting of refrigerants thus harming the environment is punishable by law. Mandated by law, technicians have to recover refrigerants instead of venting them. 

Recovery machines 

In the early 90’s the EPA (Environmental Protection Agency) passed some laws that requires us to recover refrigerant. Prior to that, refrigerants are just simply dumped into the atmosphere. In the past, people make their own machine but you can’t do that anymore. What most manufacturers did was take household refrigerator compressors and use them in recovery machines. Every one of which failed. Later, they used quote oil-less compressors. They are compressor design that did not require a lot of oil and last longer. Despite the effort, a lot of them failed too. Fortunately, they are getting better now. So, what does a recovery machine do? Basically, it is a condensing unit. It has a compressor, coil, and fan inside. It draws refrigerant in, condense it and pumps it out into storage. It removes the gas without dumping it into the air. It is also highly advertised that you can recover liquid with it however, it is not a really good idea. It could lead to a broken recovery machines because of too much liquid slugging in there. Recovery machines are not cheap to begin with. They run from 400 to 1000 dollars.

Refrigerant recovery has two phases

• The first phase focuses on reducing the need for use of environmentally harmful refrigerants and eventually eliminate them.
• Refrigerant reclamation is the focus of the second phase of refrigerant recovery. The basic concept of reclamation is the evacuation of refrigerants from HVAC/R equipment. Reclaimed refrigerant can be recycled. Recycling can be performed at the service site; however, it must be remembered that reclaimed refrigerants must reenter the equipment it was originally taken from. Otherwise, it must be sent offsite to a reclamation facility to go through an EPA-regulated purification process. An EPA-certified reclaimer will dispose of too contaminated refrigerants as they can’t be recycled in adherence with federal regulations.

Evacuation

Many types of HVAC systems rely on refrigerants to transfer heat. Thanks to refrigerants, refrigeration process works in equipment. Although the HVAC system leans toward bettering the world, our main character of this article has its own enemies as well. Any air, water or nitrogen in the unit is the weakness of refrigerants causing it to not work properly and damage the equipment itself. Only oil is welcome to enter the system as its side-kick. As the enemies try to sneak into the equipment, technicians are left with a solution: refrigerant evacuation. Here are the basics of refrigerant evacuation. 

What Is Refrigerant Evacuation?

Basically, moisture, air and non-condensable gases from the refrigeration system are what is being removed during refrigeration evacuation. During this process, the sealed HVAC system is being drawn into a vacuum by a vacuum pump. This removes air, nitrogen, and moisture from the unit.

The removal of these substances occurs in two stages:

Degassing Stage

• Air and vapor are sucked out of the HVAC system. This stage is typically quick and easy.

Dehydration Stage

• In order to decrease the pressure lower than the vapor pressure of water at room temperature, a vacuum pump is used. This will cause the boiling off of any liquid present in the system. The success of this process relies greatly on the use of deep vacuum and tightly sealed system.  

When Is Refrigerant Evacuation Necessary?

The following are some common situations that make and HVAC technicians decide to evacuate water, air, and other unwanted substances from the system. 

• Before charging a new system with refrigerant.
• When installing the liquid and suction lines where the ends of the tubing are open.
• After opening the system to make repairs.
• If the system has lost its refrigerant due to leaks or refrigerant recovery.

Why Is Refrigerant Evacuation Important?

Any contamination in an HVAC system can majorly prevent the equipment from working properly and in worst-case scenario results in premature failure. Following are some of the specific issues that can arise:

Non-Condensable Gases

• Refrigerants transfer heat when they change phases. They absorb heat while in the evaporator, transforming from a liquid to a vapor. Once the gaseous refrigerant enters the condenser, the heat would be released outside and cooling the refrigerant at the same time. Consequently, it flows into the expansion valve and returns to a lower pressure, cooler liquid. Taking up space, limiting the refrigerants’ ability to condense is one of the disadvantage non-condensable gases as this reduces the efficiency of the unit and forces the HVAC compressor to work harder.

Moisture

• Water in a heat pump or air conditioner can mix with the lubricating oil in the compressor, forming an acid sludge that can corrode the component, causing it to fail. Since the compressor is one of the most expensive parts of an HVAC system, this can be a serious problem. The conditioning of the air could be restricted if the moisture enters the circuit and freeze inside the control.

Conclusion

Recovery and Evacuation of refrigerants are necessary for environment care and is mandated by law. Refrigerants are recovered using a recovery machine and evacuated and recycled. Recycled refrigerants can only reenter the machine it came from otherwise it should go through an EPA-regulated purification process. If proven too contaminated, the refrigerants will be disposed of by an EPA-certified reclaimer.