R-410A Charging Practices

April 5, 2004

Last month we discussed the importance of using the proper filter-drier in an air conditioning system that uses R-410A. This month we will take a look at other service practices that can affect the operation of an air conditioning system that uses R-410A.

In order to install and service the increasing number of 410A unitary air conditioners and heat pumps continuing to enter the market, large numbers of contractors have sought training. Some of it is specific to 410A systems, but much of it is just good service practice that should be applied to any unitary system.

Safety Issues

Safety, of course, is an essential part of working with any refrigerant. R-410A's higher operating pressures (60-70 percent higher than R-22) mean that contractors and techs are now using gauges designed for 410A. Refrigerant recovery equipment also must be designed for this refrigerant's pressures.

R-410A will also produce refrigerant burns more quickly than R-22. Protective equipment is a vital part of safe work practices.

In general:

When working, use gloves and safety glasses with a visor.

Use proper storage in the service vehicle (standing up, strapped down).

Don't let the cylinders get too hot in the service vehicle.

Avoid fumes and inhaling vapors in an enclosed space; like any other refrigerant, 410A displaces oxygen.

Similarities To R-22

There are plenty of similarities between the R-22 and -410A, both in operating characteristics and equipment. For example, R-410A unitary systems have the same superheat/subcooling levels as R-22. Many top trainers recognize that 410A's glide is minimal.

R-410A refrigerant must be removed from the drum in a liquid state. The two refrigerants that comprise it boil at close to the same temperature. Therefore, for slight leaks, R-410A can be topped off. Just make sure it's removed from the drum while it is in a liquid state.

If you are charging it into the low side of the system, remember that the liquid must be vaporized before it enters the suction line. Then check the system's performance.

When in doubt, recover all the refrigerant and recharge the system.

Oil Differences

As we pointed out in last month's Tech Tips article, keeping the system clean and dry is essential with 410A systems. It's also important with R-22 systems, but it is critical for the polyolester oils (POEs) used with 410A.

POE oils have a much greater affinity for water; if a system is left open and air gets in, the moisture in the air condenses and the moisture gets into the oil. POEs plus moisture creates acids and sludge that damage the system.

In addition to not leaving the system open unnecessarily, contractors and technicians should take the following new installation precautions so that condensation cannot get into the oil:

Use a sling psychrometer or other measuring device to get indoor wetbulb readings, in order to perform proper charging.

Run a load calculation in order to have a proper refrigerant line size.

Use proper brazing techniques so that condensation cannot get into the oil.

Because of problems with condensation, sloppy installation techniques on 410A systems can lead to many callbacks, and the use of several driers to clean and dry the system. In short, the callbacks can eat up the profits from the job.

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