SAE standards automatically come up for review every five years, which forces the sponsors to review the documents to see if they require updating. In the easiest of cases, a standard can just be renewed, perhaps with minor revisions. But what if the standard has become seriously out of date, and even a major rewrite won’t work?
The Interior Climate Control Standards Committee (ICCC) has a number of standards that cover service of automotive air conditioning, one of which (J2788) is in the Clean Air Act and another (J2843) which is scheduled to be referenced in the law this year. J2843 is the one that’s problematic because the A/C in the certification vehicle, a 2005-09 Chevrolet Suburban, is nothing like the systems in current use, even on the latest Suburban.
The two standards cover certification of high-efficiency recovery/recycle/recharge equipment for R-134a (J2788), the refrigerant on a phaseout schedule, being replaced in OEM production by R-1234yf (J2843), a refrigerant with an ultra-low-global-warming impact number (4 vs. 1430 for R-134a). Recovery, then recycle and reuse, keeps the refrigerant out of the atmosphere so it doesn’t contribute to global warming. Because of R-1234yf’s low global warming impact, this issue is less of a concern, but EPA does not permit venting any chemical refrigerant, and the very high cost of R-1234yf (15-20 times that of R-134a) makes it highly uneconomical to waste.
Further, even when it degrades in ambient air, the refrigerant releases tri-fluoroacetic acid, a plant growth inhibitor.
Focus on refrigerant recovery
When J2843 was developed for R-1234yf, the same vehicle as in J2788 was used for certification, a 2005-09 Chevrolet Suburban with a rear A/C system, which had been tested some 15 years ago to assure that it was a challenge for R-134a equipment to meet. A primary requirement: recovery of a minimum of 95% of the system’s refrigerant charge –3.0 lb (1363 g), within a maximum of 30 minutes. This percentage would leave no more than 5% that would be vented to the atmosphere, a number recommended in U.S. EPA documents.
Equipment in earlier use was found to recover as little as 50% of the refrigerant, which meant that half the refrigerant was being vented and contributing to global warming.
The old Suburban’s vehicle system uses an orifice tube to meter refrigerant into the under-dash evaporator (heat exchanger) and a refrigerant accumulator at the evaporator outlet. Depending on the machine’s recovery strategy, this could lead to trapping refrigerant under an oil layer that chilled in the accumulator, so a careful approach had to be used to minimize this, as equipment manufacturers learned. That established one of the challenges.
Equipment manufacturers have long certified their machines to J2788 with the Suburban and with EPA under Federal restrictions regarding regulations, the 2005-09 model will not be replaced at this time.
With R-1234yf, the vehicle systems were significantly changed, with the widely used orifice tube/accumulator design replaced by an expansion valve, which also was long used on many R-134a systems and had some performance efficiency benefits. An internal heat exchanger (IHX), had been added to further improve system efficiency with both refrigerants.
New test-vehicle needed
The committee realized it had to validate a vehicle with an expansion valve and IHX, but which one? An added concern was that a conventional vehicle, as the Suburban, was being run for 15 minutes to circulate refrigerant and simulate driving a car into a service shop. The leading test lab performing certifications advised the committee that this engine operation cycle produced some variation in recovery efficiency. Although the laboratory itself maintained a precise interior temperature of 72-75 deg F. (21-24 deg C.), as required by the standard, the variation existed and led the committee to select the Chrysler Pacifica—a plug-in hybrid which had enough battery capacity to run a certification test, including A/C operation to circulate refrigerant, without engine operation.
Six leading U.S. suppliers of J2843 equipment agreed to participate in a certification test recovery/recharge simulation: CPS Products, Mahle Service Solutions, Mastercool, Ritchie Engineering, Robinair and Snap-On Tools. Testing was run over a period of one month by the ICCC Service Committee officers, at the training center of the Mobile Air Conditioning Society Worldwide, in Lansdale, Pennsylvania, with MACS training director Steve Schaeber assisting.
The center obtained laboratory-grade scales to accurately weigh the machines, and therefore the changes in the amounts of refrigerant recovered and recharged during each step in the certification process. Weight of the reservoir that collected any oil removed during the recovery process was measured at refrigerant pre-recovery and post-recovery and factored into the performance calculations.
A manufacturer participated in testing of his equipment, with no competitors present. Each set of performance measurements was logged by a code letter (known only to the service committee officers) for each company. So only the company and the service committee officers knew what each machine did, and no company knew any competitor’s equipment performance data.
The testing established that R-1234yf equipment generally produced Chrysler Pacifica performance that was reasonably comparable to the 2005-09 Suburban. The SAE J2843 revision was unanimously approved by the ICCC Service Committee in a recently concluded vote and became the new certification vehicle for tests as of July 1.Continue reading »