|Here is one the HFC refrigerants being offered as a retrofit option for use in R-22 systems.|
While this can provide a guideline, The NEWS urges readers to contact refrigerant manufacturers directly to discuss the specific R-22 system being considered for retrofit and what HFC refrigerants might best work in such applications. This listing is in alphanumerical order according to ASHRAE designations.
Gus Rolotti, technical marketing director of Arkema’s North American fluorochemicals business, described R-407A as a refrigerant for low- and medium-temp refrigeration. “Both R-407A and R-407C are well proven in the industry and provide good performance coupled with a lower GWP. They require the use of a POE oil.” Because of that, there needs to be a changeout of the mineral oil in an existing R-22 system.
Noted Rolotti, “First, fix any leaks and identify components that may need to be replaced or fixed. Recover the R-22 completely, repair/replace any components as identified earlier and pull the system into a deep vacuum. Remove the required amount of mineral oil either by flushing with an external agent or using the R-22 from the system. Once most of the mineral oil is removed, replace it with POE oil and pull the system into a deep vacuum again. Refill with the appropriate amount of the retrofit refrigerant and run the system to set up controls and operating conditions. It is recommended that the filter drier is always replaced when the system is opened to ensure that there is fresh desiccant available to dry the system.”
Arkema’s Rolotti considers R-407C a choice for air conditioning. Retrofit procedures are similar to those with R-407A refrigerant.
In his comments regarding R-407C, Ron Vogl, technical marketing manager for Honeywell Refrigerants, described it as a choice for residential and light commercial a/c applications. The retrofit process for R-407C, he said, involves recovering R-22. Then, regarding oil, Vogl said, “POE is recommended. If existing MO is used, the addition of some POE to the system is required for proper oil return.” The use of the refrigerant requires a minimum of 20 percent POE for close-coupled a/c systems with no liquid receivers. No TXV change required, but minor adjustments may be needed. Replace any O-rings, seals, and other elastomers used in the system. In most air conditioning and heat pump systems this only applies to the Schrader valve seal and cap seal material. The next step is to evacuate and recharge. (Pounds of 407C = pounds of original refrigerant x 70.6 divided by 73.9.) Then adjust system safety and operating controls; label system indicating refrigerant and charged lubricant.
According to information supplied by Honeywell, R-407F is for retrofits involving medium- and low-temperature refrigeration applications (supermarkets, cold storage, and process refrigeration); direct expansion system design only.
The retrofit process involves the following: recovering R-22; one compressor oil change (POE required), use synthetic lubricant as specified by the compressor manufacturer; no TXV change or adjustments; elastomeric O-ring replacement; change liquid line filter driers, suction filters and oil system filters if present; evacuate and recharge (pounds of 407F = pounds of original refrigerant x 69.2 divided by 73.9); adjust system safety and operating controls; label system indicating refrigerant and charged lubricant.
Will Gresham, national sales manager of Dynatemp International, said R-421A “has only two components, requires no oil changes, and contains no hydrocarbons.” Its application range, he said, is “air conditioning split systems, heat pumps, supermarket pak systems, dairy chillers, reach-in storage, bakery applications, refrigerated transport, self-contained display cabinets, and walk-in coolers.”
To retrofit, he said, “In order to have a baseline comparison of the system after the retrofit, an initial evaluation of the system’s operational characteristics should be recorded. The next step is to completely evacuate R-22 from the system and change the liquid line filter driers. Noting that an oil change from MO to POE is not required, the final step is to charge and label the unit with R-421A, taking into account the manufacturer’s recommended R-22 charge and the desired operational characteristics, e.g., superheat/subcooling.”
R-422B, according to Gordon McKinney, vice president and COO of ICOR International, is for low-, medium- and high-temperature applications. It is being used, he said, “in direct expansion applications ranging from residential a/c and commercial a/c to industrial process cooling.” He added that because it is a zeotrope, it is not recommended for use in flooded applications. He said that R-422B’s “efficiency difference from R-22 will depend on the system. Testing has showed a 5 percent decrease in current, 10 percent lower discharge temperature, and a 1 percent increase in WB/DB evaporator temperature in air conditioning. In refrigeration, R-422B’s compressor run time will be longer, a 0˚F SET/110˚ SCT may have a 20 percent longer run time; a 25˚ SET/110˚ SCT may have 15 percent longer run time.”
The conversion process involves recording pre-conversion data; recovering 100 percent of the R-22 refrigerant in accordance with EPA guidelines; installing a new filter drier; leak checking the system; evacuating system to a minimum 500 microns; initially charging the system with 95 percent of the existing charge; removing liquid only from the R-422B cylinder; running the system to check subcooling and/or superheat; properly labeling system, and recording post conversion data. Critical seals (elastomers) may need to be replaced.
This refrigerant is for medium- and low-temperature applications, said ICOR’s McKinney. “We have seen kW-usage to be as much as 30 percent lower and system Btu capacity to be higher.”
The retrofit process is the same as for R-422B. McKinney did say regarding R-422C that the TXV power element will need to be changed to a 404A/507A element and critical seals (elastomers) may need to be replaced.
R-422D “has higher efficiency and capacity versus R-22 for low-temp applications, and is mineral oil compatible,” said Joyce Wallace, North America marketing manager, DuPont Refrigerants. “It can be used in low- and medium-temperature applications. The high mass flow rate makes it unsuitable for air conditioning applications due to the component changes that must be completed.”
Honeywell’s Vogl said R-422D is a “near drop-in for residential and light commercial a/c application.”
The retrofit process is as follows: recover R-22; no oil change or TXV change in most installations; replace filter drier; replace elastomeric seals and Schrader valve; evacuate and recharge (pounds of 422D = pounds of original refrigerant x 70.9 divided by 73.9); label system indicating refrigerant and charged lubricant.
R-424A, according to ComStar International’s Steve Mella, is said to work with MO, AB, and POE oils with air conditioning as well as medium-temp refrigeration temperature ranges of 20 to 50˚F. He said air conditioning applications include rooftops, splits, window, heat pumps, plate-type and tube-in-type heat exchangers, and non-flooded chillers. Refrigeration applications include walk-in coolers, beverage coolers, and display cases. It works with TXVs, cap tubes, and fixed orifice devices.
Retrofit procedures include collecting baseline data, recovery of R-22, evacuation to 500 microns, liquid charge to 90 percent then add as needed, adjust superheat on TXV, adjust pressure controls, and check SST and SCT. Following the retrofit, service techs should expect suction pressure to be 10 to 15 psig lower and discharge pressure to be 20 to 25 psig lower.
Arkema’s Rolotti said R-427A is “a hybrid blend for both air conditioning and refrigeration applications. R-427A mirrors R-22’s operating pressures, allowing it to be used in a wide range of systems and has a high tolerance to mineral oil. Its performance would be slightly below that of R-407A or R-407C in their particular applications, but would perform adequately in most cases while allowing for a retrofit that does not require all the mineral oil to be removed.”
ComStar’s Mella said R-434A applications include “water cooled and process chillers for air conditioning and MT and LT refrigeration such as with coolers, freezers, display cases, and ice machines in the -40 to +50 degree range.” It works with TXVs. It is also suitable for and is operating successfully in flooded systems, said Mella. The retrofit procedures, efficiency changes, and service aspects are similar to R-424A.
According to Wallace of DuPont, R-438A “combines R-22 pressure-enthalpy characteristics with mineral oil compatibility in an HFC refrigerant that can be used in R-22 replacement over a wide range of evaporator temperatures. It matches R-22 in terms of capacity and efficiency in most systems, but with a significantly lower discharge temperature, which may prolong the life of the compressor. It’s compatible with all lubricants. It is used in low-, medium-, and high-temperature applications but is seeing the most usage in air conditioning applications.”
To retrofit: Consult retrofit guidelines, check baseline R-22 performance, remove R-22 from the system, replace filter drier, replace Schrader valve core seals, pull vacuum on system, charge system with R-438A, and label system.
Publication date: 12/3/2012