Relief valve arrangements for CO2 refrigeration systems

4 Mar 2021 16:00 to 17:15


Listen to the webinar recording here 

All those registering for the webinar will receive a recording of the broadcast even if they are unable to join the live meeting.


Download the Paper

The paper is available to download here



What you will learn

  • The unusual properties of carbon dioxide and their consequences.
  • Why relief valves are fitted to refrigeration systems.
  • Requirement of CO2 relief valves venting from an EN378 perspective.
  • Considerations when designing relief valve venting systems.


The adoption of transcritical carbon dioxide systems in refrigeration has presented several new challenges to system designers, installers and maintenance teams.  The correct, safe way to arrange relief valve piping is one of them.  There are two polarised schools of thought; that relief valves can be treated in much the same way as for any other refrigerant or that relief valves need a unique installation arrangement different from any other refrigerant.  Clearly both positions cannot be correct, or can they?

This paper starts with an overview of the purpose and function of the pressure relief valve and then examines the reasons why carbon dioxide requires to be treated differently.  It reviews some of the previously published literature and describes some case study examples of the ways in which systems are installed.  Results of tests are also presented and analysed.  The wording of current standards on the topic is examined and a proposal for new wording is suggested.

The paper will hopefully be helpful to people in all sectors of the refrigeration, air conditioning and heat pump markets where carbon dioxide is used.



Andy Pearson FinstR, Group Managing Director, Star Refrigeration

Andy is one of the leading names in the refrigeration and engineering industry, and his work is world renowned. He is a respected voice in the sector and has edited books on ammonia and carbon dioxide for the International Institute of Refrigeration, as well as being a lead author for UNEP’s Refrigeration, Air
Conditioning and Heat Pumps Technical Options Committee from 2006 to 2014. He also contributes a popular monthly column to the ASHRAE Journal and writes extensively on subjects related to industrial refrigeration, particularly with regard to ammonia and carbon dioxide, safety, energy efficiency and system design improvements.


Steve Benton FInstR, Director, Cool Concerns 

Stephen is a down to earth practical engineer with a vast range of experience and is owner and director of Cool Concerns. His refrigeration talents are many, from fault diagnosis and repair through understanding and interpreting complex standards to the development of RAC systems on flammable refrigerants. He is a time served apprentice who has learned by doing, asking, reading and googling. He sits on several European standards committees, helping to update and revise standards we use in the RAC industry.


Andy and Steve are both members of the Institute of Refrigeration’s Technical Committee and are active in CEN TC182, ISO TC86 and the BSI’s refrigeration safety committee, RHE/018, of which Andy is currently the chair.