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The refrigerant left in a system after recovery

By Richard Hawkins, MACS contributor

What about the refrigerant left in a system after recovery? This is the third in a series of MACS blogs about refrigerant recovery. You can read the preceding blogs here.   Don’t overlook a diagnostic clue  RRR Machine Test

Last week’s article ended with the following:  “Check back in next week and we will explore issues related to large amounts of refrigerant being left in a system after recovery.” So, it is time to explore those issues. They break down into three categories.

1. Ecological 

2. Economical

3. Technical

First, here is a brief review of the results of the R/R/R machine test covered in last week’s article.   A J2210 R/R/R machine left 9 ounces of refrigerant in a system which had contained 27 ounces, after doing a “complete” recovery. 

This of course is 1/3 (or 33%) of the charge.  This a bit more than what I had expected.  Based on information that I had read and a conversation I’d had with someone who conducted a similar test, the amount was expected to be about 20% to 25% (about 5 1/2 to 6 3/4 ounces).  It seems that 25% seems to be a reasonable amount of refrigerant for a J2210 machine to leave in a system after a “complete” recovery and that is the percentage we will use in the following examples.

To illustrate the issues, we will use a 20-ounce system as an average size system. With a 20-ounce system,  25% of the charge remaining in the system after a recovery would equal 5 ounces.   Now, back to the issues.

The refrigerant left in a- system after recovery

Ecological
The purpose of recovery and recycling is to prevent refrigerant from being released into the atmosphere and reduce the amount of refrigerant which has to be manufactured.  If a R/R/R machine leaves 25% of the refrigerant in a system, then that refrigerant is going to be released into the atmosphere.

This will occur when the system is opened for service and the remainder of the refrigerant boils off or if a deep vacuum is pulled on the system before the refrigerant has a chance to boil off.  One exception to that would be if a system were charged almost immediately after the recovery was completed (more on that next week).

Economical
The price of R-134a, is constantly changing and will likely continue to change, so it is impossible to use a consistent number.  However, over the past year or so the cost to shops for a 30lb. cylinder of R-134a seems to have ranged from about $300.00 to $350.00. $325.00 seems like a good average price to use. $325.00 equals $10.83 per pound or about .67 an ounce.

Using the example of a 20-ounce system and a J2210 machine leaving 25% of the refrigerant in a system after a recovery yields the following results:  A J2210 machine is leaving about $3.35 worth of refrigerant in a system after each recovery.

The number of recoveries a machine might do in a year can vary from shop to shop. As a result, it will be necessary to select a number to represent an average. If a machine did just three recoveries a week, that would be 156 recoveries annually.  Using the average of $3.35 worth of refrigerant left in a system for each recovery, which would be $522.60 worth of refrigerant lost in a year. That is over $500.00, that could go to a shop’s bottom line or used to purchase a newer more efficient machine. The figure of course could be more or less depending on the variables.

R-134a, A valuable commodity

Technical
A shop could end up with a overcharge of refrigerant in a system and a resulting performance problem and waste a lot of time trying to diagnose what the problem is.

Check back in next week for a recap of a tech call conversation with a technician who encountered that very problem.

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2 responses to “The refrigerant left in a system after recovery”

  1. Thomas Lech says:

    I come across this problem constantly from vehicles that have been back to a previous shop on more than one occasion trying to figure out the problem. And if it’s a cold day the system will work perfectly but as soon as the customer drives away on a hot weekend that refrigerant has nowhere to expand and that’s where the poor performance or in severe cases slipping clutch come in to play.

    Don’t forget about the vehicles that have a shut off solenoid in the liquid line trapping refrigerant in the rear AC system line. Technician thinks they recovered all the refrigerant but there still some trapped behind that closed solenoid.
    Same situation then the technician does a full recharge let’s say 1000 g is what the factory spec calls for but there’s still a few hundred grams extra trapped behind that closed electric solenoid.

    When you start working on more of these electric cars and Teslas and heat pump systems you will find this out the hard way and possibly extremely extremely expensive result of a comeback,

    It’s too bad education in the trade in which somebody is going to practice is not mandatory. Instead of throwing the parts cannon at it and charging customers for broken components that’s a Technician Burnt up a compressor or good components get replaced that were never needed in the first place. Sound familiar ?

  2. Tim Dooley says:

    This is why the j2788 standard was created, to recover a minimum of 95% in a single recovery.

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