Question

Should I follow my service company's advice and replace my current AC unit with a new "environmentally friendly" Freon unit?

Asked by Gaby Mendelsohn
Charleston, SC

My service company wants to replace my current (and broken) air conditioning unit with a new “environmentally friendly” Freon. In addition, the technician says that I need a new indoor coil even though the current one is not broken. What does that mean and should I buy it?

Answer

Steve Saunders

Answered by Steve Saunders

Irving, TX

TexEnergy Solutions, Inc

June 2, 2010

Except for the impact on your pocketbook, the replacement and upgrade of your HVAC system is probably good.

Your service technician is correct in that you need to switch refrigerants (from R-22 to R-410a) and to make the new refrigerant work right in your home’s new AC unit, you will also need a matching evaporator (indoor) coil that is properly sized and has the correct device to properly meter (make the AC work right) the refrigerant in your system.

An energy efficient, properly sized outdoor and indoor AC system will operate at lower utility cost (helping pay for the cost of the installation), be more comfortable, and have a lesser impact on the environment. This is a good recommendation.

Some background: You are caught in the middle of two long-term public policy initiatives. Ultimately, both of these policy efforts will save you money and help the environment.

Trend 1: Environmentally sensitive Freon

You may or may not remember that we used to worry about the hole in the ozone layer. This is because the products we bought (not just ACs, but many consumer and business products) were made with a process that released harmful gases into the atmosphere. The fears were that these gases impacted the ozone layer in the earth’s atmosphere. The ozone layer reflects a large amount of the UV (ultraviolet) rays from the sun. The UV rays are particularly harmful (in large quantities) to human skin and, if not partially deflected, they would cause increased danger to public health.

If you are old enough, you will remember that we went through this change with car air-conditioning systems in the mid-1990s. I recall it as frustrating at the time, but there was a hard shut-off of AC systems on cars and in about three years the transition had been made and public awareness and perceptions accommodated the change. Essentially, the move was made, and after a brief flurry of activity and angst, the issue ceased to be problem for the vast majority of people.

The transition in residential and commercial HVAC systems began about the same time as with cars. Because of the vastly more complex and diverse business operations of building, installing and maintaining HVAC systems, the mandatory HVAC changeover had a very long lead time. That lead time ended this January (2010) and HVAC manufacturers can no longer manufacture HVAC compressor bearing units that contain the older ozone-depleting R-22 (technically this is HCFC-22). This change also impacts your indoor evaporator coil (remember that HVAC in most applications is a split system with part of the unit outside and part inside).

Now, to get a properly operating system, you must have an indoor unit that matches up with the indoor unit you have. Each indoor unit has what is called an “expansion device.” This expansion device helps feed the Freon to the coil in a fashion that maximizes the performance of the unit. The new 410a Freon has different performance characteristics than the old Freon and must have a device that is properly matched with the new refrigerant. There are several ways to achieve a proper metering, but the best is to replace the indoor evaporator coil. In part, that is the best way because of Long-Term Trend #2.

Trend 2: More efficient HVAC systems

The HVAC equipment manufacturer, to meet federal law, must make more efficient HVAC systems. The legal standard of appliance efficiency is NAECA. This is an acronym for National Appliance Energy Conservation Act -- and this law sets the minimum efficiency performance for many types of appliances.

For residential and small commercial air-conditioning systems, this means that the current minimum performance of HVAC efficiency is a SEER of 13. (SEER stands for Seasonal Energy Efficiency Rating.) The most recent change in efficiency standards came in January of 2006.

As a general rule, the higher SEER levels require more pounds of Freon to make them work more efficiently. More Freon means the air-conditioning systems outside your home (commonly called “the box”) are larger. But because the split AC systems have a matching indoor system, the indoor coil must also be larger to properly handle the amount of Freon effectively as well.

Conclusion

Because of the two long-term policy trends, it is best to replace your evaporator coil on the inside at the same time as you replace the air-conditioning unit on the outside. Your service technician did you a favor by recommending both a new unit with environmentally friendly refrigerant and a new and properly matched indoor evaporator coil. You should take the tech up on the offer.

Other Options

There are options. Except for very specific applications, I recommend none of them. But, for a complete education on this subject, I mention the major things you might hear about and consider:

  1. Replace the compressor and not the whole air-conditioning unit and evaporator coil. The AC compressor manufacturers can still make a compressor that works with the old-style R-22 systems. You can, essentially, rebuild your existing system on a part-by-part basis and Band-aid it together to keep it running as time progresses. I doubt you will save money long term with this solution. In fact, your total cost will probably increase substantially. It may save short-term cash.
  2. Use a “drop in” Freon, an alternative to R-22. This might be a good solution. I have no factual information on the real-world performance. But I have spoken with the research engineering department of a major compressor manufacturer who indicate that they believe “drop in” Freons will not have the same capacity as existing R-22 systems. Less capacity means a reduced ability to cool your home when you need it, leading to longer run times, higher utility bills and discomfort at extreme temperatures. I do not like this solution, but there are some proponents.
  3. Replace the AC outdoor unit, keep the existing indoor unit but change the “expansion device.” This is a “tricky” solution. Generally, I would say that it would lead to disappointing results. Certainly, I would strongly recommend that you do not try this without the advice of a very well trained professional service person or company.

Prediction

We are going to repeat all the impacts of refrigerant replacement and for (essentially) the same two trends. I believe that sometime in the next decade or two, the R-410a refrigerant will be replaced with an even better alternative.

Current public policy is (and is likely to remain) focused on reducing our dependence on fossil fuels. The low-hanging fruit is improving the energy efficiency of our existing homes and buildings. Expect to see continued emphasis on equipment efficiency. In all likelihood, we will move to regional efficiency standards. The geographic areas that are cooling-dominant will have requirements for more efficient air-conditioning systems. The northern and mountain climates will have standards requiring more efficient furnaces.

The other trend relates to atmosphere again. This time we are focused on carbon emissions. Today, the debate rages about the efficacy of climate science, the impact of human activity on climate and carbon build-up, and the costs of acting vs. the costs of not acting. I make no pronouncements as to the answer to any of the key questions.

But R-410a has the same chemical composition as some of the items currently under regulation review by the EPA for their impact on carbon emissions. My best guess is that the country and the world will eventually work to reduce carbon impacts and that reduction will be felt on the type of air-conditioning systems we have in our homes.

My prediction is that we will find (over time) another refrigerant that has the performance characteristics to allow for higher efficiency performance on HVAC equipment and, at the same time, a lower impact on carbon than the refrigerant that is the current national standard. This is likely to be painful, but perhaps less painful than the alternatives.

 

For more information:

You should also read Danny Kelly's Ask A Pro Q&A, "What are the best ways to reduce my electric and propane consumption for heating and air conditioning? What should we do first?" to learn more about improving your home's energy efficiency.

Tagged In: heating cooling

Do you have a question about greening your home? GreenHomeGuide invites you to Ask A Pro. Let our network of experienced green building professionals – architects, designers, contractors, electricians, energy experts, landscapers, tile & stone specialists, and more – help you find the right solution.