We have standardized on HFC-404A on the high side of the cascade. On the low side we use HFC-23 for -100° F (-73° C) applications and HFC-508B (SUVAâ 95) for -120° F (-84° C) applications. You may see other refrigerants used for the same purposes by other reputable chamber manufacturers. Some of these are:
To Replace HFC-404A:
HFC-404A (SUVAâ HP-62) Composed of:
- 44% HFC-125
- 52% HFC-143a
- 4% HFC-134a
HFC-507 (AZ-50) Composed of:
To Replace HFC-508B:
HFC-508B (SUVAâ 95) Composed of:
HFC-508 (Kleaâ 5R3) Composed of:
As you can see, these blends are similar to each other in composition, and in a closed system, you will not be able to discern a difference in performance between the substitutes. However, their characteristics may be different when a leak occurs, concentrating one component in the system, more than the other. In these cases, some performance differences may arise. If a small amount of refrigerant has leaked from the system, "topping-off" is an acceptable approach to regaining the proper charge after the leak has been corrected. If a large amount of refrigerant has leaked, it is best to recover the remaining refrigerant, fix the leak, completely evacuate the system, and recharge with new refrigerant.
Knowledge of proper lubricant selection and handling can substantially influence the reliability of your refrigeration system. One of the complications of changing refrigerants is the need to decide whether a lubricant change is necessary at the same time, which lubricant is recommended for the system, and what precautions must be exercised to safeguard the purity of the lubricant. Enough has been written about lubricants that we summarize only a few points.
Use of any HFC requires a non-mineral based oil to be used as the lubricant. Many different lubes are available for use with HFCs, but we recommend that you follow the compressor manufacturer’s specifications. All CSZ chambers use a 22 centistoke polyol ester (POE) lubricant.
All POE lubricants are highly hygroscopic. Keep the can closed tightly at all times and keep systems open for as short a time as possible when servicing. Always change the filter/drier after opening a POE system. POEs out of the can have a water content of less than 50 ppm. After being open for an hour or less, the POE will absorb moisture from the air and can reach a water content of 1,000 ppm or greater. After two weeks of running through the filter/drier, levels can again be down to less than 100 ppm. The effects of high moisture content in the oil may be: formation of acids, poor lubricity washing out bearings, low oil pressure, or high discharge temperatures. Moisture is very difficult to remove from the oil. The best advice is to keep it from ever entering the system.
When changing refrigerants (retrofitting) in older systems, be certain that residual mineral oil is less than 1% of the oil charge. Depending on the source of the information, you may see figures quoting up to 5% of mineral oil content as acceptable. Remember, there are two criteria for the lube. They are the ability of the lubricant to keep the compressor operating properly without causing system related problems. Mineral oil depositing in valves or capillary tubes at low temperature is the result of its inability to disperse in the HFC refrigerant. The less mineral oil, the lower the chance for a system problem. We can supply you with an effective flushing procedure. Contact your Technical Sales Manager at firstname.lastname@example.org
or (513) 326-5252.
The ability of a chemical to create a greenhouse effect in the atmosphere, reflecting back to earth some of the energy that would have been re-radiated to deep space, is the principal measuring parameter of refrigerants and other chemicals in their Greenhouse Warming Potential (GWP). Now that the refrigeration industry has switched over to "ozone-friendly" refrigerants, our choices of these chemicals will be restricted based on their global warming impact.
Although CFCs (all refrigerants) represent only 15% of the contributed greenhouse effect, CO2 from power generation and other sources represents 50%. For this reason, the measure of Greenhouse Warming Potential (GWP) of a chemical includes both direct and indirect effects of the chemical as defined below:
The effect of releasing the refrigerant into the atmosphere relative to the GWP of an equivalent amount of CO2.
The added affect of CO2 released during production of power to run the refrigerant device. Includes the efficiency of the refrigerant device.
The sum of these two factors is often referred to as Total Equivalent Warming Impact (TEWI). Because of GWP, manufacturers are scrutinizing the HFCs used in refrigerant systems. Recovery, recycle, and reclaim are current issues for HFCs also, not just CFCs and HCFCs. Whenever an HFC has a particularly high GWP or a very long atmospheric lifetime, it will get careful attention. Of particular note is SUVA® 95 (R-508B). This refrigerant is an excellent replacement for CFC-503, however, one of it’s components is PFC-116 which has a very long atmospheric lifetime. Therefore, in cooperation with the manufacturer, We have notified our customers of the need to recover, recycle, and reclaim. In order to minimize emissions of SUVA® 95 (R-508B) and as a prerequisite to purchasing the refrigerant, we are obligated to treat it as we would any CFC or HCFC. In short, we must:
- Implement practices to recover, reclaim, recycle, or destroy the PFC refrigerants during equipment servicing and upon the retirement of equipment.
- Reduce or contain to a minimum the emission of PFC refrigerants during normal operation, maintenance, manufacture or installation of systems; and ensure that the annual leakage from systems containing PFC refrigerants will not exceed 25% of the system charge in the previous year. On July 1, 1997, the maximum allowable annual leakage will be reduced to 20%.
We are notifying our service contractors and customers (in new product manuals) of the need to have any CSZ equipment serviced by certified personnel in a responsible manner. This equipment will have a label on the SUVA® 95 (R-508B) compressor that instructions for servicing can be found in the equipment manual. CSZ chambers with -120°F capability currently use SUVA® 95 (R-508B), such as Thermal Shock Baths, VTSs, Ts, Vs, and some Liquid Conditioners.
If you have any questions, contact your Technical Sales Manager at email@example.com
or (513) 326-5252.
Several national companies purchase used environmental chambers and resell them in the used chamber market. You may even find a CSZ chamber for sale from time-to-time. Since January 1, 1996, a manufacturer can’t place CFCs into their new equipment. And our customers already know that they shouldn’t accept HCFCs in new equipment. However, used chambers can be sold with CFCs in their refrigerant systems. But, your cost of refrigerants and service may be very high. The production of CFCs today represent recycled and reclaimed refrigerant, and while it is still available, it is costly and in some areas, hard to find. Ask for used equipment that has been refurbished with the new CFC-free refrigerants.
A new refrigerant will be introduced in the 1996-1997 timeframe that replaces HCFC-22 with an ozone-friendly HFC. This refrigerant is SUVA AC9000 and is comprised of 23% HFC-32, 25% HFC-125, and 52% HFC-134a. It is an equivalent in performance, but slightly higher in pressure than the HCFC-22 it replaces. We mention this because some environmental chambers were sold several years ago (and currently by other manufacturers) with HCFC-22 on the high side. Therefore, it may be tempting to use this HFC to replace HCFC-22. Be cautious! HCFC-22 was designed primarily as an air conditioning refrigerant and it results in relatively low capacity and higher discharge temperatures at the higher pressure ratios found in environmental chambers. As long as you must flush the system to remove the mineral oil and replace it with a POE, we recommend a switch-over to HFC-404A although that means a thermal expansion valve change also.
If you have any questions about refrigerants, contact your Technical Sales Manager at firstname.lastname@example.org
or (513) 326-5252.