Should I retrofit my R-22 coils for R-410A?

Posted by Al Nord on Oct 12, 2020 12:00:14 PM

Today, most new air conditioning system components that would have used R-22 prior to its regulation are now designed to operate with R-410A, but R-22 systems, such as commercial split systems for example, still exist. This means that when a coil reaches the end of its service life, the system engineer has a decision to make: replace the system or convert the existing equipment to operate on R-410A.

Ideally, the solution would be to replace all the system's components. But ideal approaches often find themselves at odds with what’s feasible. The purpose of this article is to outline some important considerations for an R-410A retrofit when a total system replacement just doesn’t make sense.

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What are the arguments against retrofitting? 

Like many other HVAC topics, the conversation around R-410A retrofitting is rife with strong opinions. The goal of this article isn’t to pick a side, rather it’s to communicate that things aren’t always black and white/cut and dry/third cliché.

Okay, so on to those strong opinions. There are two primary arguments against retrofitting:

  1. Tube-side materials in R-410A coils need to be thicker due to the higher operating pressures associated with R-410A relative to R-22.
  2. An R-410A coil would need to be larger than an R-22 coil to meet the same performance.

In our experience, these claims aren't so much inaccurate as they are incomplete, lacking some of the important nuances and context needed for a comprehensive understanding.

On the first concern, we’re not arguing that there’s not a difference in operating pressure between the two. There is – roughly 130 PSI for R-410A evaporators compared to about 70 for R-22. Rather, we’re saying that for the majority of instances, coils designed for R-22 can withstand the higher pressures that come with a switch to R-410A.

Some exceptions would be for residential coils designed with very thin manifolds or large condenser coils with large manifolds too thin for R-410A's operating pressures. Coils fitting that description would need to be replaced. But for most R-22 coils designed for light commercial applications - i.e. ½” OD tubes and smaller with wall thicknesses of .014" and above are sufficient for the operating pressure of R-410A systems.

On concern number two, it’s been our experience that the performance disparity between coils for R-410A and retrofitted R-22 coils is negligible for the majority of typical HVAC applications.

Okay, I think retrofitting makes sense for my system. What do I need to know?

Changing your system’s refrigerant is a big task, and there are potentially significant consequences that can result from poor execution. In short, if you decide that an R-22 to R-410A retrofit makes sense for your application, it must be done properly. Fortunately, there’s no shortage of information on the ins and outs of properly executing a retrofit. This PDF from Johnson Controls is an excellent example, and provides a terrific list of best practices for ensuring successful execution.

If you have any questions about your retrofit, your system, or HVAC-R in general, give us a call. We’re here to help.

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