Replacing R-12 Is Not a ‘Drop-In’ Task
In the early days, alternatives to R-12 were called ‘drop-ins’ or ‘near drop-ins.’ Today, such terms raise red flags. Manufacturers of such gasses have specific retrofit procedures and expect such work to be done by trained, qualified technicians.
This article will look at the procedures of a specific R-12 alternative currently on the market: R-416A. It is produced by InterCool Distribution and distributed by CFC Refimax, both of Marietta, GA. While many alternatives for R-12 use R-22 as part of the blend, R-416A uses R-134a rather than 22 in its mix. CFC Refimax says the use of 134a rather than 22 “lowers the blend operating pressure to more closely duplicate R-12 operating pressures.”
The description that follows is specifically for R-416A, but can provide some idea of what is involved in many retrofits of R-12 systems.
In all cases, technicians should check with the manufacturer of any refrigerant as well as the compressor manufacturer to make sure of proper procedures.
THE BASICSFor R-416A, here are the basics:
PREPARATIONVerify that the refrigeration system is in a normal operating condition with the existing R-12. Make repairs as indicated in the service manual. If the system is not operating satisfactorily with R-12, its performance with R-416A will not improve.
Attach refrigeration manifold gauges and record the suction and discharge pressures, ambient temperature, and box or evaporator temperature(s) when the system is stable (after 10 to 15 min of operation). These will be the baseline performance and operating parameters.
Leak check all service caps and joints. Make all necessary repairs. If any component (such as the receiver/filter-drier, condenser, etc.) needs to be replaced, drain the mineral oil and replace it with the same amount of polyolester (POE) synthetic oil. The POE should be of the same viscosity as that recommended for the mineral oil in the service manual.
Once all repairs are made, the system is ready for adaptation to R-416A refrigerant.
Assemble all the refrigerant, POE oil, and equipment needed for the R-416A installation. EPA-approved recovery or recycling equipment should be used, as well as an accurate charging scale.
1. Remove all R-12 from the system using an approved recovery-recycling machine.
Restart the machine several times to make sure all of the R-12 is removed. Note the amount of refrigerant recovered. If a system refrigerant charge amount is not found on the refrigeration unit or in the service manual, use the recovered amount as a recommended charge level, assuming that the system is operating properly.
2. Note the type of thermal expansion valve in the system.
If it must be moved for adjustment, do so after the R-12 is recovered and the valve superheat adjustment is turned clockwise approximately one turn. This usually results in the correct superheat (a setting similar to R-12).
3. Know that under normal operating conditions, no oil change is necessary when converting to R-416A.
Be sure to identify system-operating conditions during service. If the system has a history of oil return problems or exhibits unfavorable oil return characteristics due to long line sets (greater than 20 ft) or low evaporator temperature (less than 20Â°F), it is recommended changing from mineral oil to alkylbenzene (AB) or POE.
Since residual mineral oil in the system will not have negative effects on performance, the system does not need to be flushed. The viscosity of the AB or POE oil should be the same as the mineral oil recommended by the manufacturer.
If the oil removed from the system is dirty or contaminated, a second oil change is strongly advised. InterCool Distribution recommends an oil change after one year of use for large nonhermetic systems, unless an oil analysis indicates otherwise.
4. Evacuate the system for at least 1 hr with a vacuum pump to a pressure below 500 microns (29.9 in. Hg).
Charge the system to 50 psig with the refrigerant through the high-side port. Check for leaks with an electronic leak detector (or soap bubbles, dyes, etc.); repair as needed. R-12 or -134a electronic leak detectors will work with R-416A. Recover the R-416A, repair any leaks found, and re-evacuate the system, then repeat the 10-minute vacuum hold test. If the system is tight, proceed with the installation.
5. Charge the system with R-416A.
Note: R-416A must be charged as a liquid. Turn the cylinder upside down for a liquid charge.
Note: A liquid line sight glass should not be used exclusively to determine the correct refrigerant charge level. Some systems that are optimally charged may have some bubbles in the sight glass.
6. After charging, check the system’s performance after the pressures have stabilized (about 15 min of operation). Operate the equipment and check against target or baseline temperature settings as recorded with R-12.
The unit’s performance with R-416A installed should be comparable to that when R-12 was used. Generally, the suction pressure will be about 2 to 10 psig below R-12 at the same ambient temperatures. The discharge pressure should be within a few pounds of that measured for R-12. Performance readings should only be taken after operating for at least 15 min. This allows a period for the box or space to cool down and the system to stabilize.
If the suction pressure is too high and discharge pressure too low compared to the original R-12 readings, and the box or evaporator temperatures are too high, check the conditions at the compressor. If the compressor is running with a cold suction line, with heavy sweat or frosting, and the discharge line is warm (not hot to the touch), this may be due to some liquid refrigerant carryover to the compressor. This calls for an adjustment to the superheat setting on the thermal expansion valve.
The most accurate approach is to measure the superheat. Ideally, the superheat should be the same or slightly higher with R-416A than is specified for R-12.
If the system has a thermal expansion valve, superheat can be adjusted by turning an adjustment screw. The methods and adjustments of superheat settings vary by valve manufacturer. Many valves can be adjusted externally with a wrench or screwdriver.
Before adjusting, mark and record the starting point. To increase superheat, turn the valve adjustment screw clockwise to increase spring tension. The suction pressure should drop.
Superheat screw adjustments may vary from one to several turns depending on many factors; therefore, you need to make superheat calculations. R-416A may operate at the same or a slightly higher superheat (2Â° to 3Â°) than R-12.
Valve adjustments should only be attempted after the system is properly charged; that is, between 80% and 90% of the original R-12 charge level.
Since R-416A operates at lower pressures than R-12, some system control setpoints (i.e., pressure unloaders, low-pressure cut-outs, switches, back-pressure regulators, evaporation pressure regulator, or any control set to operate on suction or low-side pressure) may require adjustment. Always check the system’s or compressor’s service manual when setting these safeties or controls.
R-416A will also work in a reverse or heat pump cycle for heating and defrosting, but will work at lower pressures than the R-12 in the system.
If the system is equipped with a capillary tube, some of the refrigerant can be removed from the system to optimize performance.
7. Check the system for leaks after removing the refrigeration manifold gauge set. Replace the seal caps on service ports.
8. Apply a label showing the system adaptation date, quantity of R-416A installed, and quantity of lubricant added.
Finally, remember that EPA recovery and recycling rules apply to all refrigerants. Therefore, if any service work needs to be performed on a system that contains R-416A, it must be recovered or recycled, not vented into the atmosphere, with an appropriate recovery unit.
Information in this article came from published materials available through InterCool Distribution, 1935-G Delk Industrial Blvd. S.E., Marietta, GA 30067; 800-555-1442.
Sidebar: Ingersoll-Rand Acquires NRSWOODCLIFF LAKE, NJ — Ingersoll-Rand Co. (IR), a diversified industrial firm headquartered here, recently announced the acquisition of National Refrigeration Services, Inc. (NRS), headquartered in Atlanta, GA. Terms of the deal have not been disclosed.
According to Herbert L. Henkel, chairman, president, and chief executive officer of Ingersoll-Rand, “The acquisition of National Refrigeration Services is consistent with our overall strategy to increase participation in downstream distribution and service activities.
“NRS represents a perfect fit within our Climate Control Sector. In particular, NRS expands our existing Hussmann refrigerated equipment capabilities in 20 states to provide IR the industry’s most comprehensive coast-to-coast product and service network for commercial food and beverage refrigeration.”
NRS is a provider of commercial refrigeration products and services for food storage, distribution, and display throughout the United States. The company also serves customers in a variety of commercial refrigeration applications, including supermarkets, convenience stores, food processors, food service facilities, and much more. NRS was also formed in 1998 through a combination of 12 refrigeration services companies and has headquarters in Atlanta, GA.