R-22 vs. R410-A
We have heard it for a few years now. The doom and gloom about the changes that are coming to the apartment industry for HVAC. Chances are, you have heard different things that come along with it. No matter who you ask in the industry, everyone has their own opinion about the change and what is involved.
First, let’s clear the air and get to the bottom of why this change is happening. But more importantly, let’s take the necessary steps to prevent premature replacement of units. Here is the information you need to understand the new refrigerant, why the changes are being made, and what tools you will need to tackle replacement efficiently.
History of R-410A
Since 1985 it’s been well documented that the ozone layer surrounding the earth has been diminishing. Scientific evidence suggests man-made chemicals are responsible for creating the hole in the ozone layer and that they’re likely to add to global ozone depletion.
Ozone Depleting Substances (ODS) have been used in many products which take advantages of their physical properties. For example, Chloro Fluoro Carbons (CFC’s), have commonly been used as aerosol propellants and refrigerants.
However, since highlighting that the chlorine in CFC’s attributes to the demise of the ozone layer, the ‘Montreal protocol on substances that deplete the ozone layer’ was negotiated and signed by 24 countries and the European Union in 1987. The protocol calls for all parties to scale down the use of CFC’s, halons and other man-made ODS.
R410A is a type of refrigerant – a liquid coolant that makes air conditioning possible. R410A was developed as an alternative to R22 (Freon), which will be phased out over the coming years in response to international environmental concerns.
R410A contains no chlorine, so it’s not damaging to the atmosphere’s ozone layer. As an added benefit, independent testing have shown that R410A allows higher heat transfer than R22, resulting in more efficient operation. So choosing an air conditioner with R410A not only makes sense environmentally – it also makes sense from an economic standpoint.
The Essentials of R-410A
Technicians with R-22 experience will need to become familiar with working with high and low side pressures that are much higher when using R-410A. A typical R-22 system operating normally with a head pressure of 260 psig at a 120-degree condensing temperature and a low side pressure of 76 psig at a 45-degree evaporator saturation temperature will find the equivalent pressures in an R-410A system to be much higher.
A normally operating R-410A system with the same condensing temperature of 120 degrees and a 45 degree evaporator saturation temperature will have a high side pressure of 418 psig and a low side pressure of 130 psig.
Although refrigerant 410A is a near-azeotrope and has a slight temperature glide, there is no need to correct for refrigerant dew point and bubble point differences. Superheat and sub cooling calculations can be calculated the same way we have always done with R-22 refrigerant. The only difference will be the higher pressure-temperature relationship when reading the temperature-pressure chart. The temperature glide for R-410A is only .3 degrees Fahrenheit and can be ignored and fractionation is not a concern.
Compression Ratio & System Efficiency
At first glance, one might ask the question, with 410A operating at higher pressures are the compression ratio higher and the efficiency less? The answer is no, the compression ratio is about the same or slightly lower than that of R-22 and the efficiency is higher. Compression ratio is the absolute high side pressure divided by the absolute low side pressure. The compression ratio is affected by the pressure differential between the high and low sides of the system not how high both pressures are. Using the previous examples comparing the operating pressures of an R-22 system to an R-410A system, the R-22 system would have a compression ratio of 3.02:1, while the R-410A system would have a compression ratio of 2.98:1. The actual efficiency gains from R-410A are due to its superior thermodynamic values over R-22. Under identical operating conditions the discharge temperature on a 410A system may actually be lower than on an R-22 system.
With all else being equal, it is possible to manufacture an R-410A air conditioning system that is physically smaller using less refrigerant and a smaller compressor than an R-22 system of the same capacity and SEER rating.
Compressors used on 410A air conditioners use thicker metals to withstand the higher operating pressures. Therefore, only a compressor designed for 410A should be used with 410A. The ideal compressor type for use with 410A is a scroll built to withstand the higher pressures. The scroll compressor has the advantage over the reciprocating compressor when comparing volumetric efficiencies and internal heat transfer losses between the suction and discharge ports. Scroll compressors compress the refrigerant in stages through the use of up to six individual pockets in its scroll assembly while reciprocating compressors raise the pressure from the suction pressure to the high side pressure in a single stroke. In addition, the scroll compressor’s suction and discharge openings are farther apart than those in a reciprocating compressor thus decreasing heat transfer losses between the suction and discharge ports.
The internal pressure relief valves inside the compressor opens at a pressure between 550 & 625 psig on compressors designed for R-410A service. Compressors designed for R-22 service have internal pressure relief valve settings that open between 375 & 450 psig. So only compressors rated to work with R-22 should be used with R-22 and those rated for use with R-410A used with R-410A.
The metering device used in a 410A system must be about 15% smaller in capacity as opposed to a metering device used in an R-22 system of the same capacity. It is imperative that only a metering device designed and properly sized for R-410A be used on an R-410A system. In fact, no parts designed for R-22 use should be used on a 410A system.
Refrigerant lines used for R-410A must be properly sized for R-410A systems. It is possible to use existing refrigerant lines from an R-22 system in an R-410A system installation if they are of the correct size however, they must be cleaned of all debris and oil. This process is done with nitrogen and a flush kit. The minimum size lines that can be used are 5/8 suction and 3/8 liquid. The best practice is to replace the lines with new copper liquid and suction lines to ensure they are clean and do not have any weak areas that could be a problem at the higher operating pressures of 410A. Once lines are brazed in, a vacuum must be pulled down to 500 microns. This is a much deeper vacuum requirement then R-22 and must be measured with a micron gauge.
Driers & System Accessories
The desiccants used in R-410A systems are the same as those used for most other refrigerants. Zeolites, molecular sieve type desiccants work on the principle of a material with small pockets or areas that adsorb moisture by the process of capillary action. This type of desiccant seems to work well with all modern refrigerants including R-410A. The metal shell containing the filter-drier however, must be thicker to withstand the higher pressures of 410A. Therefore, only use filter-driers rated for use on R-410A. R-410A filter-driers are those rated for pressures no less than 600 psig.
R410A- The Refrigerant of Tomorrow
Many of new heat pump and air conditioners today use the EPA recognized, chlorine free R410A refrigerant. Because of R410A contains no chlorine, its ozone responsible. R410A is better for use in higher efficiency equipment because of the greater heat transfer rate than R22. Using R410A refrigerant in your next systems not only makes sense environmentally, it can also help you with energy cost savings.
The Current Standard of R22 Freon
Acting in accordance with an international treaty called the Montreal Protocol; the U.S. Environmental Protection Agency (EPA) has mandated the eventual phase out of R22 through the Clean Air Act. By January 1st, 2010, the manufacturing of heating and cooling equipment using R22 will be prohibited. By 2015, a 90% decrease in production of R22 refrigerant will occur and by 2020 the production of R22 Freon itself must cease. The main reason for this regulatory action is that R22 is a hydro chlorofluorocarbon (HCFC) compound, which contains ozone-depleting chlorine.
It seems that the industry has focused a lot on what to do about the replacement instead of how to efficiently take care of existing equipment. Filter changes and cleaning evaporator coils are common items to take care of but what is being done about the outdoor unit? We are bogged down with tasks that take us away from completing a full tune up but take these steps in March/April and you will cut down your work orders and after hours calls by 50% !
- Clean the condenser coils all at once. Take a day and go around to each building and spray coil cleaner on all units and then rinse them off with a water hose. What this does:Keeps your head pressure down and allow the outdoor coil to absorb more heat from inside and keeps heat transfer efficient. It also makes the amp draw go down on the condenser motor keeping the fan from burning up.
- Check all mechanical parts inside the unit. Check the contactor to make sure it is not burned up. Check the capacitor by testing the microfared reading to ensure it is not weak and will quit on you soon. What this does:The contactor allow the voltage to pass through to the unit and make it run. The capacitor alternates current through the fan and the compressor. Think of a battery on a car. Without it-the unit doesn’t run.
- Check amp draw on the fan and the compressor. On the data plate, there are specific readings for each part. The compressor will have a running load amps (RLA) and a lock rotor amps (LRA). The running load amps are the amps that are being pulled while the compressor is running. You should never exceed the number on the data plate. The lock rotor amps are the amps it takes to start the compressor. This rating will be extremely higher than the running load amps. Try not to get them mixed up or you can drive yourself crazy. What this does:This will enable the technician to be proactive and catch a bad part before it actually goes bad.
- Check the charge. This is a common task done and a property can go through quite a bit of Freon in a summer. Add the correct amount needed to get the resident cooling. If you notice a leak, make a note of it. Once you get caught up, go back and try to find the leak. What this does:By finding and fixing the leak, you are not only saving yourself time on a call back for Freon, but you are saving the compressor. When a system is low on Freon, the amp draw goes up on the compressor and wears out the windings. Low refrigerant is the number one cause of compressor failure!