Using refrigerants

Refrigeration and air conditioning equipment, in the past, has relied on chlorofluorocarbon (CFC) refrigerants to operate. After evidence began mounting that CFCs were harming the earth's ozone layer, their production in the U.S. was banned under the Montreal Protocol, effective December 31, 1995.

Refrigerants released many months or years ago are suspected of affecting the ozone layer today. Over time, these refrigerants slowly rise to the earth's stratosphere where they react with the ozone layer. When this happens, new chemical compounds form and ozone no longer exists in its original form.

Many refrigerants contain chlorine atoms that are thought to combine with ozone atoms to cause ozone depletion. Most refrigerants in use today are classified as CFCs, hydrochlorofluorocarbons (HCFC), and hydrofluorocarbons (HFC).

CFCs contain chlorine, fluorine, and carbon and are considered the most damaging because they reach the stratosphere intact.

A second group of refrigerants in common use is HCFCs. They contain hydrogen, chlorine, fluorine, and carbon. The hydrogen makes them less stable in the atmosphere. These refrigerants have much less potential for ozone depletion because they tend to break down in the atmosphere. The small amount of chlorine in these compounds is released before it reaches and reacts with ozone. This group is due for phaseout in 2020 and 2030 (depending on the compound) because of the chlorine content.

The third group of refrigerants is HFCs. They contain no chlorine and do not harm the ozone layer.

Other refrigerants are mixtures of some existing refrigerants and are called azeotropes and blends.

Azeotrope refrigerants are blends that are combined in such a manner that they will not separate into their individual components. They are considered a unique refrigerant even when they leak into the atmosphere.

Some blended refrigerants are not azeotropes, they are sometimes referred to as "near azeotropes" or simply as blends. They also are considered a unique refrigerant when they leak into the atmosphere.

As existing supplies of refrigerants become depleted, substitutions must be made. The following tables illustrate which refrigerants and blends will work and what must be done to implement their use.

Plant Engineering magazine extends its appreciation to E.I. DuPont Co., Suva Refrigerants Div. and York International Corp. for their assistance in the preparation of this article.

With the phaseout of CFCs, some decisions have to be made.

Convert to service refrigerants

Service refrigerants, such as R-401A and R-402A, make good sense because they offer proven performance, are easy to use, result in a low-cost retrofit, and will be available longer than the expected service life of most equipment.

They are economical because only 75% to 90% of the CFC charge is required, minimal changes are needed, and retrofitting is simple and easy.

Convert to HFC

Retrofitting to an HFC refrigerant such as R-134a or R-404A is more expensive and involved than retrofitting to a service refrigerant. An HFC retrofit requires conversion to a polyol-ester lubricant and three or more lubricant flushes may be needed. However, HFC refrigerants are not scheduled for phaseout, which could make their use cost-effective in equipment expected to last 20 yr or longer.

Replace the unit

If the future performance of a system is deemed unreliable, total replacement is probably the most cost-effective solution. The difficulty of retrofitting old or malfunctioning equipment might not be worth the cost or effort. An additional bonus of replacing aging units with new equipment designed to use HFC refrigerants is that the new units can achieve improved energy performance.

Keep CFCs until supply runs out

This might be the best option for older units that are running properly and have no significant leakage. Before selecting this option for equipment with a long expected service life, remember the price of CFCs will continue to increase and availability will decline.

Convert to R-22

R-22 is frequently considered as a retrofit choice because it has been in use for years and people are familiar and comfortable with it. Although R-22 is currently inexpensive, total conversion costs are usually higher than converting to a service refrigerant because compressor modification or replacement as well as other equipment changes are often required.