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Posts from the ‘Making Sense’ Category

Making Sense of Servicing CO2 Transcritical Booster Systems

Amidst increasing regulations to phase-down hydrofluorocarbon-based (HFC) refrigerants, global adoption of CO2 (R744) as a natural alternative is on the rise. But to successfully perform service on a CO2 system, mechanics will need proper training and a deep understanding of the refrigerant’s unique properties.

Seven Keys to Servicing CO2 Systems

Our 13th Making Sense webinar, Seven Keys to Servicing CO2 Systems, offered a basic primer on CO2-based refrigeration and discussed the many implications of servicing a CO2 transcritical booster system. The webinar was presented by Andre Patenaude, director of CO2 business development for Emerson Climate Technologies.

Andre introduced common CO2 system architectures — secondary, hybrid cascade and transcritical booster; the latter is the only system that relies completely on CO2 as its only refrigerant. He explained that CO2’s global adoption has largely been driven by its effectiveness in cooler climates due to its low critical point of 87.8 °F. This is primarily the reason that subcritical systems (where the ambient temperature is typically below 87.8 °F) have been successful to date. It’s also the reason that CO2 transcritical booster system technology (above 87.8 °F) is evolving to enable operation in warmer climates.

In addition to low critical point, Andre explained two other primary differences between CO2– and HFC-based systems:

  • High triple point (where three phases of refrigerant co-exist) — the triple point temperature for CO2 is -69.8 °F, but the pressure is relatively high at 60.4 psig. Technicians need to avoid approaching that point, or the CO2 refrigerant will turn to dry ice in the system. This is why systems need to be charged with vapor CO2 first in order to reach sufficient pressure (145 psig) before switching to its liquid form to complete the charge.
  • High pressure — historically, CO2’s high pressure has been the primary concern for adoption. At supercritical mode, on a hot day above 87.8 °F, the pressures on the roof (condenser) could be as high as 1,400 psig, with temperatures approaching 240 °F. To handle those conditions, stainless steel piping is required. A pressure-reducing valve is also needed to lower the pressures to a point where it’s similar to working with an HFC system (400–500 psig).

Because CO2 transcritical booster systems lose efficiency in warmer climates, several techniques are used to offset the impacts of high ambient air temperatures.

  • Spray nozzles — condenser that mists water to cool air across condenser coils
  • Adiabatic gas cooler — wet pads lining the outside of condenser are used to cool air and keep the system from going into transcritical mode
  • Parallel compression — flash tank feeds an independent compressor with increased suction pressure and smaller motor
  • Subcooling — cools the gas to increase efficiency
  • Ejectors — a means of using high-pressure gas energy to reduce evaporator superheat and increase suction temperature

Andre stressed the importance of having a plan to deal with power outages, including designing systems with generators and standby condensing units to keep CO2 pressures from building up during system shutdown. In fact, retailers should test the effectiveness of their response by performing a trial power outage.

Most importantly, service technicians should be well-trained to understand the intricacies of dealing with CO2-based refrigeration systems.

To hear this webinar in its entirety, please visit the webinar archives on our MAKING SENSE website.

New MAKING SENSE Webinar Covers Seven Keys to Servicing CO2 Systems

When it comes to refrigerants, a change is in the air. The EPA’s pending SNAP ruling to delist R-404A and other commonly used refrigerants is yet another reminder of the uncertainty that permeates the refrigeration industry. But in this regulatory climate where refrigerants with high global warming potential (GWP) are being phased down, CO2 (R-744) is emerging as a viable natural alternative.


For food retailers seeking to circumvent ongoing regulatory compliance challenges, R-744 represents one of the few future-proof refrigeration options available today. With a GWP of one, virtually zero ozone depletion potential and the technology in place to support broader adoption, R-744 has a tremendous upside. But, its high pressure and unique refrigeration properties will mean a change in typical operating and maintenance procedures. As a result, service technicians will need to educate themselves and become familiar with R-744’s characteristics.

Our next MAKING SENSE webinar will address these considerations. Presented by Andre Patenaude, Emerson Climate Technologies’ director of CO2 business development, “Seven Keys to Servicing CO2 Systems” will take place on July 14 at 2 p.m. EDT. This informative session will explore the many operating implications of CO2-based refrigeration systems from a service technician’s perspective and help them prepare to effectively deal with the refrigerant’s unique properties. In this complimentary webinar, you’ll learn about:

  • Dealing with the high pressure of R-744
  • Understanding R-744’s critical and triple points
  • How to improve CO2 system efficiencies in warm ambient environments
  • Managing power outages
  • Dealing with the standstill pressures of R-744
  • Preparing the service technicians with the proper equipment (gauges, hoses, etc.)
  • R-744 cylinder storage, charging and maintenance best practices

To make sure your service team is prepared to handle CO2 in refrigeration, register now to join us July 14 from 2–3 p.m. EDT. We’ll help you MAKE SENSE of CO2 and allow you to take advantage of the industry’s most future-proof refrigerant alternative. Learn more and register by visiting our website at:

MAKING SENSE of the Technology Used to Meet Future DOE Energy Regulations


Whether you’re an OEM, wholesaler, contractor, design consultant or end user, you’ve probably become increasingly aware of the of the Department of Energy’s (DOE) new minimum energy efficiency regulations in the commercial refrigeration industry. Although the effective dates for the DOE’s rulings are not until 2017 and 2018, many OEMs have proactively been preparing to improve the efficiency of their refrigeration equipment.

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MAKE SENSE of Technology Alternatives That Can Help You Meet Future Energy Regulations


In the feature story of our second edition of E360 Outlook magazine, we talked about how the Department of Energy (DOE) has mandated significant energy consumption reductions for walk-ins, reach-ins and ice machines by 2017. Complying with these new regulations will require equipment changes that utilize new technologies and innovative refrigeration strategies in each application.

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Live From AHR: Making Sense of Embedded Electronics

Panel Provides Insights on Interoperability of Electronics in HVACRAHR Expo Live Webinar

While exhibiting at the 2015 AHR Expo, Emerson Climate Technologies held its eleventh installment of the company’s Making Sense webinar series.

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