How to retrofit an ageing HFC system with transcritical CO₂

Transcritical CO₂ refrigeration systems have been steadily gaining traction in North American supermarkets, particularly in Canada. For retailers seeking to use a low-GWP, energy-efficient refrigerant and to future-proof their system against regulations on synthetic refrigerants, transcritical units are seen as an increasingly viable option.

In an existing store, a retailer seeking to remove the refrigerant R22, for example, would simply look for a drop-in replacement refrigerant (typically an HFC) rather than replace an entire direct expansion (DX) system, including cases, with a transcritical system. It has become an article of faith that these systems only make sense in new stores rather than in existing stores with an operating refrigeration system.

Alternatively, retailers intent on replacing a high-GWP HFC would go for a lower-GWP HFC as a drop-in. This is certainly true for new or medium-age DX systems and even for ageing systems.

Some retailers — such as Whole Foods Market in a store in Sacramento — have somewhat deviated from this scenario by retrofitting an existing store with a cascade CO₂ system. But transcritical systems have remained a less attractive option for retrofits, due to the work and costs associated with refashioning an existing store to support the high pressures of CO₂.

Sobeys bucking the trend

However, Sobeys, Canada’s second largest retailer — and North America’s largest retail user of transcritical refrigeration — is rewriting the retrofit script for transcritical systems.

Transcritical refrigeration is Sobeys’ standard system. As of September 2015, 78 Sobeys stores in eight provinces (63 in Quebec that operate under the IGA banner) use CO₂ transcritical booster systems with heat reclaim. Each year, another 15 to 20 stores — both new and renovated — are equipped with the systems. Some of these stores are franchised operations.

Of course, ‘renovated’ can mean total renovation of the store. But in some cases, Sobeys stores have seen fit to focus a renovation on replacing an existing refrigeration system with a transcritical model.

For example, over the past two years, Systemes LMP, a transcritical OEM based in Laval, Quebec, has retrofitted two Sobeys IGA stores in the Montreal area (one a franchisee) with a transcritical system, and is in the process of retrofitting another Sobeys corporate store in Ontario, with one more corporate retrofit in Nova Scotia in the pipeline. The retrofits were all prompted by the need to replace aging R22 compressor racks.

Changing the refrigerant to a lower-GWP gas would not suffice in these stores. “You would still have a potentially high leak rate because all of the lines and rack fittings are old,” said Jeffrey Gingras, vice-president of sales at Systemes LMP. “A leak is a leak even when you have a lower GWP refrigerant. I think it is important to evaluate the age of the equipment before doing a refrigerant retrofit.”

In addition, these changes align with Sobeys strategy to standardise on transcritical systems as a long-term, future-proof, energy-efficient solution that puts the stores outside the reach of future regulatory measures. Sobeys gave LMP the opportunity to retrofit the stores to further prove the merits of transcritical CO₂ refrigeration, said Gingras.

Retrofit at night to avoid sales losses

The Montreal area stores include one in Sainte-Thérèse, a suburb of Montreal, and one in Sherbrooke, about 128.7km east of Montreal. Systemes LMP finished retrofitting the former store in July and the latter about 1.5 years ago, according to Xavier Marle, director of operations for Systemes LMP. The transcritical systems are both running successfully.

In both cases the retrofits were done “with no loss of sales,” said Marle. “We converted to CO₂ while the stores were running, slowing transferring the circuits every night.” While refrigerated cases have to be changed at night, when customers are not around, piping and overhead work as well as much of the work in the compressor rooms can be done during the day.

For these stores, the majority of the original cases were modified with electronic expansion valves and new evaporators to accommodate the CO₂ refrigeration, and re-piped to the new rack. Upon completing the transcritical installation, Systemes LMP decommissioned the existing R22 racks, took them apart and removed them.

The original systems did not include monitoring, but the retrofits are being closely monitored to make sure the new systems are making the most of the heat reclaim function. The stores in both Quebec and Ontario feature heat recovery, which is used for space and hot water heating.

Time commitment

The cost of a transcritical retrofit can be difficult to define, said Gingras. “When you’re going to all- CO₂, you have to change everything. All the lines, all the cases, all the racks – everything’s got to be changed. Putting a price on the start-up time, organisation and team work required to make sure this all works without causing any downtime for the store is pretty difficult.”

But he acknowledged the longer time commitment involved. “You have to rip out a whole system to install a new one,” he said. “Basically it’s two jobs in one. I would say a normal installation would take around three to four months, and this takes eight to nine months.”

A longer version of this article will appear in the next issue of Accelerate America magazine.