Our chillers need refrigerant ... but what?

Air conditioners, refrigerators and freezers rely on the circulation of a refrigerant – a chemical that can efficiently remove heat from the surroundings as it repeatedly cycles between the liquid and gaseous states.

It seems that our chillers are filled with R22 refrigerant. This is being phased out because of ozone-depleting effects.

R134a refrigerant is a possible alternative that contains no chlorine and hence no ozone depletion potential. It's a greenhouse gas, though, and it doesn't work as well as R22.

Like R12, which is the original ozone-depleting refrigerant, R22 is marketed under the brand name Freon, and it's one of the earliest CFC alternatives. Its chemical name is chlorodifluoromethane, and while it isn't technically one of the CFCs banned by the Montreal Protocol, it belongs to a closely related class known as hydrochloroflurocarbons (HCFCs). These refrigerants also contain chlorine that can potentially find its way into the upper atmosphere. HCFCs like R22 are being phased out of production and will be all but illegal in 2021.

R134a belongs to another class of CFC alternatives, called hydrofluorocarbons (HFCs), that don't contain chlorine. Its chemical name is tetrafluoroethane. It isn't the only CFC alternative on the market, and it isn't the best. HFCs may not be ozone depleting gases, but they contribute to global warming, and R134a has more global warming potential than some other HFCs. This fact has led the European Union to ban R134a from use in new vehicles. The ban became effective in 2011.

Can you use R134a in Systems Designed for R22?
If the system is designed to work with R22 refrigerant, and it needs a recharge, a number of issues prevent the direct substitution of R134a. For one, the cooling capacity of R134a is only 60% that of R22, so the system condenser has to work overtime to produce the same amount of cooling. Some other issues are :

R134a has a lower thermal conductivity than R22, so an R134a system needs a larger heat exchanger.
A system circulating R134a needs a drier, because of the propensity of the refrigerant to absorb water.
R134a swells the rubber components in the refrigeration system and causes leaks.
R134a corrodes copper, so the system must include an additive to prevent it.
R134a systems require special lubricating oils that are inferior to those used in an R22 system.
R134a costs more than R22, and the costs of maintaining an R134a system are also higher.

The best replacement for R22 Freon is R407c. It has a very low loss in capacity (0 – 5%) relative to R22 and is less expensive than many other R22 replacement refrigerants.

If a system has R22 in it already, you cannot use a replacement refrigerant to simply add to the R22. For one, R22 is its own refrigerant whereas the replacement refrigerants are made up of several different kinds of refrigerants designed to mimic operating pressures/temperatures of R22. The system must first be purged so that there is little to no refrigerant in it.