Pioneering the Long Journey to U.S. Hydrocarbon Refrigerant Approval

With the well-known destructive effects of hydrofluorocarbons and HFC/HCFC refrigerants on our planet’s ozone layer, natural refrigerants offer a sustainable alternative that has been advocated through corporate initiatives such as Refrigerants, Naturally!, and is seeing increasing adoption in many parts of the world.  However, no freezer for sale in the United States was able to offer 100% natural refrigerants until last year, when Stirling Ultracold received U.S. EPA and UL approval to introduce an all hydrocarbon-based refrigerant cooling system in the SU780UE ultra-low freezer.

But this major milestone certainly didn’t happen overnight!

A 3-Year Process
We started our U.S. hydrocarbon refrigerant approval Stirling achieved SNAP approval process in August 2012 by presenting an initial submission through the EPA’s Significant New Alternatives Policy (SNAP) program for the “proposed use of ethane in ultra-low freezers non-mechanical heat transfer applications.”  This was followed by final submission a year later, a completeness letter, a public posting of the “proposed rule inviting comment” in 2014 and a final publication in April of 2015.

This process also involved compliance with the UL 471 Standard, as one of the EPA’s conditions for use of ethane in very low temperature refrigeration equipment.

Questions to Ask About Hydrocarbon Refrigerant ULTs
We welcome recent announcements that other ultra-low freezer manufacturers will now be offering natural refrigerants in their ULTs sold in the U.S.  Having already navigated through the rigorous U.S. approval process, we do suggest asking some questions about each manufacturer’s specific application of natural refrigerants and their expected time to market:

  • What refrigerant is used in the upper and lower stages?
  • What is the mass of the refrigerant in each stage?
  • Is the total mass of refrigerant less than 150 grams?
  • Has the freezer been submitted to UL for listing?
  • Has the application been submitted to SNAP? If so, what stage is the submission in the SNAP process?

Been There, Done That
At Stirling Ultracold, we’re pleased to see the industry moving toward natural refrigerants and are proud to have led the way in providing a 100% hydrocarbon refrigerant alternative in the U.S.   If you’re interested in a natural refrigerant ULT solution for the U.S., there’s no reason to wait.  Just contact us at or 740-274-7900.

The Real Answer to ULT Compressor Failure: No Compressor

Step back from the haze and hype swirling around our industry and ask yourself this simple question . . . Why are many ultra-low freezer manufacturers focused on providing backups and workarounds when a compressor fails? The obvious answer to this question is two-fold:

1. Based on experience, everyone in our industry assumes that compressors will fail at some point.

2. The biological materials stored in ULT freezers are incredibly valuable – virtually priceless to the researcher using the samples.

It is the acceptance of #1 and acknowledgement of the risk inherent in #2 that should lead ultra-low freezer buyers to question the “status quo” of using compressor technology, period. Every day, we see researchers trusting their priceless samples to the lowest ULT bidder and using an aging, failure-prone technology that is known for disrupting the preservation process.

Compressors needn’t be the “necessary evil” they have become in our industry when there is a field-proven, cost-competitive alternative. Of course, I’m referring to the free-piston Stirling engine that powers our freezers.

A Superior Technology with the Industry’s Best Standard Warranty
While the sustainability and energy saving benefits of Stirling freezer technology are increasingly acknowledged, the reliability advantages of the Stirling engine are not as well known. The superior design and quality of the Stirling cooling engine provide the foundation of our industry-leading 7-year standard warranty. You can read the blog post Myth #2: Energy Efficiency Must Compromise Reliability to learn more about this. Also, refer to the table below which compares key reliability factors of compressor cooling systems to the Stirling engine: