Refrigerant Use in Mass Transit Sonora CA

That certain refrigerants have been or are being phased out due to damage to the ozone layer should be old news. The Montreal Protocol was signed in 1987 — 20 years ago.

Refrigerant-22 is one of the most popular refrigerants, used in everything including passenger transportation. It will no longer be used in new equipment starting in 2010.

Many transit agencies have already switched to R-407C, the first satisfactory zero-ozone-depletion replacement for R-22. While it is an acceptable substitute for R-22, most systems require more energy with R-407C, over the same system using R-22. Therefore, this isn't a particularly good direction to go long term due to energy cost and consumption concerns.

Another concern with R-407C is the compressor lubricant, which, if exposed to moisture in the air, creates acid. Acid has the potential to create all types of havoc inside an air conditioning system. This should never happen since refrigerant systems are supposed to be sealed, but various seals can leak, cracks can develop and copper thieves can slice into copper pipe.

Other new systems are using R-410A. This refrigerant allows for smaller and more energy-efficient air conditioning systems than R-22. It is popular in stationary air conditioning but there are potential problems. Each fluid requires removing energy to turn it from a gas to a liquid, and as temperature increases the amount of energy required to do this decreases. At the "critical point" this energy becomes zero. Air conditioning capacity depends on this energy removal, as that is what happens in the condenser (the outdoor fan and coil). As R-410A has a fairly low temperature critical point (161 F or 72 C), the capacity may become very limited at temperatures seen in transit air conditioning. It is probably acceptable in many cities, but it would probably not work well in, say, Phoenix or a few other places. It is primarily aimed at building air conditioning markets, and those systems don't generally see the high condenser temperatures seen in our industry.

Also, R-410A requires the same type of compressor oil as R-407C, which can turn to acid if exposed to moisture.

Three recently approved R-22 alternatives for use in transit equipment are R-417A, R-422B and R-422D. Two of these do not appear on the reference list of approved refrigerants for railroad passenger car and bus applications, but reading through the various month-by-month EPA decisions shows they have been approved. All three of them are attempts at producing a refrigerant that closely matches R-22 in performance yet does not require the moisture-sensitive lubricants of R-410A and R-407C.

R-417A has been used to replace R-22 in a number of industries and while the capacity of the air conditioning goes down, the total energy used by the system sometimes goes down more, which means using it may wind up decreasing overall operating costs. My understanding is that this is being used on the Rio de Janeiro metro, but I don't think any transit agency in North America is using it.

R-422B and R-422D are the newest of the refrigerants approved for transit use. They have the same components but the blend is slightly different. Their use appears to be very limited so far but it seems to have a lot of potential for use in transit. If any transit agencies have used these refrigerants it would be interesting to know what the results have been.

Why does all this matter to Mass Transit readers?

Vehicle and railway car specifications tend to state what refrigerant is required for use in the air conditioning systems. If each transit agency decides to specify a different refrigerant, it will mean that each will require its own custom air conditioning equipment. This will increase the capital cost of buying air conditioning equipment because of a lack of standardization.

Also, energy consumption and operating costs are becoming more and more important. When transit agencies first started specifying and using R-407C, the primary goal was to eliminate the use of ozone-depleting refrigerants. As time has gone on, more satisfactory substitute refrigerants for R-22 may have been developed (certainly alternatives have been developed, but are they really satisfactory in transit use?).

With experimentation and research, the passenger transportation industry should be able to determine the best refrigerant for use in our industry. There isn't a huge difference in the various operating environments and, with the possible exception of R-410A, it should be possible to standardize on one refrigerant that is best for use in pretty much any transit vehicle or railroad air conditioning system in use anywhere.

However, for that to happen transit agencies need to be able to consider alternatives, rather than write in stone in their specifications, what refrigerant gets used in their air conditioning systems.

Glenn Laubaugh is an engineer for Northwest Rail Electric.