MACS Service Reports - 2015 - MAY2

an accumulator, it has been one of the more difficult systems
to evacuate to high efficiency. So it was deemed to qualify as a
suitably tough vehicle for the recovery phase of the certification test. Like a J2788 machine, the J2843 machine must have a
scale calibration check feature to ensure accuracy of the charge
to within a half-ounce. This level of recovery and charge accuracy is important, because newer car systems have charges in
the range of 12-16 ounces with a margin of perhaps 10% (less
than two ounces). Although there are cars with larger charges,
the high price of R-1234yf is a strong incentive for the car makers to engineer systems for the smallest possible charge. At the
service industry end, there's a similar importance to do the job
right on an R-1234yf system.
R-1234yf is a mildly-flammable refrigerant, and because of
this J2843 requires the equipment to meet the latest version of
UL (Underwriters Laboratories) 1963 and ANSI/ISA 12.12.01
(American National Standards Institute/International Standards for Automation). These are safety standards that are intended to effectively require such engineering features as antiincendiary design (such as anti-arcing switches and solenoids)
and a venting system that prevents any refrigerant and/or oil
vapors from accumulating. The machine is tested to be sure it
goes through six air changes an hour when in use, and in fact
must go through one air change before it begins operation. And
there is a sensing system that locks the machine out of operation
if the airflow is not detected. About the only time the internal
fan may be shut off is momentarily while the machine is taking a reading on the scale. The reason: airflow could jostle the
machine, although ever so slightly, enough to upset the reading.
For refrigerant conservation with a non-refillable cylinder, the

machine must ensure that the refrigerant remaining in an empty
tank (i.e. the heel) is no more than 2% of the tank's rated capacity.
This also was a requirement for J2788 (R-134a) machines, but it
becomes more important with the higher cost of R-1234yf.
The latest version of J2843, which is currently the only standard to which a machine you are considering should be certified, also requires that it operate only with a valid identification signal for a system containing R-1234yf. There are two
possible ways this is done: 1) a built-in refrigerant identifier;
2) a USB port on the machine to accept an R-1234yf signal
from a hand-held identifier. The identifier should meet the
SAE J2912 standard, and will look for a 98% pure R-1234yf
sample from the vehicle system (tolerance of plus 2%, minus
1%, so the refrigerant should be 97-100% R-1234yf). You can
save a fair bit of money by buying a machine with the builtin identifier, but if you buy a separate, hand-held identifier,
you'll be able to use it on more than one machine (if you ever
need more than one), take it with you to test a possible refrigerant tank purchase for purity, etc. The J2788 standard for
R-134a mentions the value of a refrigerant identifier to cover
the possibility of contaminated refrigerant, but there was no
requirement for identification and recovery machine lockout
as there is with J2843 for R-1234yf.

Leak Detecton

Paul Weissler

With the price of R-1234yf so high (and unlikely to ever
be really cheap because it's somewhat expensive to produce), the J2843 certified machines have been designed to
incorporate leak detection before recharging. The J2788
machines for R-134a merely had to ensure that after vacuuming, the system was 98% free of refrigerant and air,
although a deep vacuum leak test (no more than a 2"Hg
drop in five minutes) has been a standard recommendation to detect a large leak.
With R-1234yf, there is a complex automatic test built
into the machine to check for a gross leak. At a point in
this test, if a leak is detected by the vacuum decay method
incorporated into the equipment, the charge operation is
aborted and the vacuum decay test can be repeated or
the system can be charged with 15% of the programmed
charge for leak detection with a J2913 electronic detector.
This is the unit that basically meets the testing sequence
that has been in effect for J2791, the SAE standard for the
R-134a detector. And as noted later in this report (see SAE
"BUYERS GUIDE"), your J2791 detector actually may
also meet the J2913 standard because of the similarity in
performance testing, although you probably won't find
that out until you try the detector on an R-1234yf system.
If the system fails the gross leak test, the machine display calls for a leak detector test, and if the technician
presses the YES button on the display to answer the "Was
a leak found?" question, the charging operation also is
automatically aborted. The machine then repeats the sequence with a display asking if there's a rear evaporator.
Yes, a technician could lie and deny a leak was found.
But then, he'd end up wasting an awful lot of expensive
R-1234yf refrigerant. ■

Figure 3: USB port on an R-1234yf machine (or J3030 dual refrigerant
equipment) saves the cost of a built-in refrigerant identifier. Either machine
will require a compatible identifier to provide the refrigerant signal needed to
power the machine into operation.

May 2015

MACS Service Reports

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