Thinking About Installing a CO2 System in Your Grocery Business? Here’s What You Need to Know
Supermarkets and grocery stores contemplating new construction or renovation of existing refrigeration systems have more options than ever with the rise of natural refrigerants — including CO2. With the renewed focus and more aggressive regulations on the phaseout of HCFCs and HFCs, the need for a low-GWP alternative refrigerant is greater than ever. Early in their development, CO2 systems were challenging to install and maintain in the real world, and their costs were prohibitively expensive. That has all changed.
Today, CO2 systems are not only possible but are truly competitive alternatives to synthetic refrigerant systems. They offer tremendous environmental benefits, meet or exceed regulatory requirements and “future proof” companies’ investments in their systems, as regulations become more widespread and formalized.
Despite its advantages, there are still a lot of questions, misunderstandings and concerns about CO2 — how it works, safety concerns, installation and maintenance costs, and so forth. CoolSys has emerged as a leader in CO2 system engineering, installation and maintenance, with experience installing over 150 CO2 systems across the country. We recently sat down with Bryan Beitler, vice president and chief engineer at CoolSys, to get his perspective on the topic and learn from his experience and expertise.
Bryan, how often are you involved with the design and/or installation of CO2 systems in supermarkets? Approximately how many have you installed to date?
As a company, we are involved with the design and install of CO2 systems on a regular basis. Be it designing new systems, installing or remodeling existing, or providing service and maintenance, somewhere throughout the company, there is an employee interfacing with a CO2 system on a daily basis. They are becoming more and more a part of our routine.
When did you install your first CO2 system? Briefly describe the application.
The first CO2 system we designed and installed was in 2010 in Southern California. The application was a supermarket, and the design was a subcritical system with an R134A top cycle over CO2. The system combined a scroll parallel LT rack and used a pumped CO2 supply for low-temperature and medium-temperature fixtures.
What did you do to prepare for this first installation? For example, did you take additional training classes? Work closely with the OEM? Did you feel prepared and/or nervous about it?
CoolSys was the engineer of record for the refrigeration and mechanical plans for the project. However, we worked very closely with the rack OEM, as it was their rack design we incorporated into the project plans. We traveled to their facility with our mutual customer to review design details, they were on site during installation and start-up, and they were critical in making sure we were aware of any nuances that were new or foreign to our field technicians. We tried to surround ourselves with as many supporting entities as possible to make sure we were prepared in advance and to avoid surprises.
What is different about designing/installing CO2 systems, compared to traditional HCFC/HFC refrigeration systems? How are system components the same/different?
The heat transfer process is still quite similar. However, there are some unique aspects related to safety, system pressures and the refrigeration cycle that are worth noting. As CO2 is a higher-pressure refrigerant, it is important for the designer and installer to select and install components with pressure ratings that match the system design. Tubing, valves and all components must be rated for use in a higher-pressure application. The designer must understand the proper components to specify and must also provide clear design details that ensure there is an uninterrupted path to the safety relief valve for the refrigerant to follow in the event of a pressure excursion. Electronic expansion valves are used exclusively in DX applications, so one must incorporate a controls plan that provides an emphasis on fixture controls for each evaporator.
What factors are taken into consideration when deciding whether to install a transcritical or a subcritical CO2 system?
Transcritical systems were introduced to the U.S. market over the last five years. They have allowed the industry to apply CO2 in warmer climates without having to use a subcritical top cycle, if used with adiabatic gas cooling or ejector systems. This eliminates having to have a separate refrigeration top cycle, which may be a cost factor. Energy considerations related to operation in transcritical mode versus subcritical are being studied, as is the cost-effective balance among climate zones, hours of transcritical operation and first costs associated with a transcritical system versus a subcritical system. Those who are making design and lifecycle cost decisions need more data to use as guidance. Some end users have also looked at the pool of trained CO2 service technicians in a particular area as part of the process of determining which systems to install. From the perspective of overall cost of operation, the more hours a transcritical system runs subcritical, the more favorable the energy costs will be.
What are some of the best practices that contractors should follow when installing a CO2 system? Are there any challenges to working with these systems? Common mistakes that contractors should try to avoid?
Many of the installation techniques we use for traditional chemical refrigerants apply to CO2. Having a clean system is paramount; flowing nitrogen of the right proportion allows this to occur. If high-pressure iron copper piping is used, one must ensure that all fittings and tubing are of a similar high pressure rating. Pressure testing takes on a different dimension, where test pressures must align with the ratings of the system. Having a helium leak detection system available for leak checking prior to evacuation is important for hard-to-find leaks. Charging methods are somewhat different than those for chemical refrigerants, as one must ensure there is adequate vapor pressure in the system prior to introducing liquid; otherwise, the resulting dry ice formation inside the system can ruin your day! Making sure the correct grade of CO2 is used is critically important. Most manufacturers recommend Coleman-grade, which has a purity level that is favorable to beverage-grade CO2. The supply chain may not always have backup Coleman-grade CO2 available, so having a discussion with your customer related to establishing a backup charge is important. To maximize evaporator efficiency, ensuring that the EEV controllers are performing correctly upon startup sets the tone for good product temperatures and efficient operation. Depending on the EEV controller manufacturer, each valve may have a transducer, suction temperature sensor and coil inlet and outlet temperature sensors to calibrate and check. Control systems are a key element of any refrigeration system operation — and even more so with CO2.
Do refrigeration contractors need additional training in order to install/service CO2 systems? If so, what type do you recommend?
We have found that the best training has come from the equipment manufacturers. Be it on the job site, in advance of the job or at the manufacturer’s facility, the OEMs have provided the best view into how their systems are to be installed, how they function and how they should be controlled and maintained.
RETA (Refrigerating Engineers and Technicians Association) has developed a technician certification program that is available to any service technician. The course takes one through CO2 basics then expands on various types of systems, safety, design, etc. This could be a useful element to any technician training program.
The nonprofit NASRC (North American Sustainable Refrigeration Council) has a website with lots of information from an educational perspective for technicians and contractors. Training manuals are available from a variety of OEM manufacturers, as well as component manufacturers, in their resource library. Educational information is available to anyone interested.
Will contractors face a steep learning curve when working with CO2 systems for the first time? At what point did you start feeling more comfortable with the technology?
The first experience is always an exciting one. We have spent many years doing similar refrigeration applications with chemical refrigerants. However, from an engineering perspective, having CO2 enter the market has been a breath of fresh air. It did take an investment in time to thoroughly understand the first projects; however, use of lower-GWP refrigerants is the responsible direction to go as an industry. It is still “just refrigeration”; the cycle just looks a little different. It is important to visit systems that are already in operation, take advantage of what is on the internet for supporting documents, talk with those who have had experience, and rely on the component manufacturers to support their products. Repetition goes hand-in-hand with comfort levels. The more you install and the more technicians who are involved, the greater the comfort level.
What do you know now about CO2 systems that you wish you knew earlier?
These systems will be a big part of our future, in both commercial and industrial refrigeration. They are safe. The installation techniques are similar to those for chemical refrigerants, and the systems control and operate quite well. However, they cannot be simply left alone to run without maintenance. We did not foresee the progression of system designs from the first techniques to current. Some of the earlier systems involved pumped CO2, use of thermo-syphon techniques in liquid-vapor separators and auxiliary chillers on CO2 vessels. We now have booster systems with parallel compression, adiabatic gas coolers and ejector systems. In 10 years, we have gone from a quite simple flooded/pumped approach in a subcritical system to “transcritical,” a word none of us thought too much about five or six years ago! The manufacturers have made significant progress transitioning their products through the evolution process, adding many product and efficiency improvements along the way. We still have to understand and maintain the early systems as a contractor to keep them running in good order, but we must adapt to the new as well. And make money! All aspects have been rewarding and challenging. Our company has been fortunate enough to operate along the leading edge and gain experience and knowledge of these systems as they evolved.
Some contractors/technicians may be nervous about working with the higher pressures in a CO2 system. What advice would you give them that might allay those fears?
It could be worse in other industries from a pressure perspective! The keys to mitigating fear or nervousness are proper training, proper tools and equipment, making sure technicians have a lifeline to reach out to when they get into a jam, starting out with basic instruction in safety and system operation, and repetition.
CO2 systems enable supermarkets and grocery stores to meet or exceed mandates for environmental protection and to get ahead of the ongoing phase-out of systems that rely on synthetic refrigerants. For example, the U.S. Congress passed the American Innovation and Manufacturing (AIM) Act in December 2020. The legislation mandates a reduction in HFC refrigerant production to 85% of 2011-2013 rates over the next 15 years and highlights the importance of CO2 from a lifecycle perspective and beyond.
Because the technology is so new, it is important to seek out refrigeration professionals who have real-world experience in engineering, installation and maintenance of CO2 systems. As a leader in CO2 technology, CoolSys possesses that experience and expertise — and we’re ready to help you with your new construction or renovation of existing systems!