cascading refrigeration

Cascade refrigeration, a rela­tively new industrial cooling tech­nology, has proven itself as an eco­nomical, energy efficient and safer option to traditional ammonia-based systems.

More U.S. food processors, food ser­vice, and cold storage warehouse opera­tors have embraced this technology dur­ing the past decade. Why? Utilizing one refrigerant in a single system – in applications with extreme high and low operating pressures – is proving to be inefficient. Alternatively, a cascade system uses two different refrigerants (such as carbon di­oxide and ammonia) with a heat exchang­er as the interface, which will minimize the upper and lower pressure differentials.

In fact, ES! Constructor’s experience with cascade refrigeration systems suggests that refrigeration performance continued from page 1 improves by 3 to 16 percent (over ammo­nia systems) depending on operating con­ditions and design. In particular, these sys­tems deliver excellent BHP/ton for rooms operating between -20° F to 0° F.

Operating costs – involving both new and retrofit installations – also have been impressive. Likewise, maintenance costs have been in line with ammonia plants. ESI initially was concerned that there may be more maintenance but with proper training, this has not proven to be the case.

ESI has found that cascade refrigeration technologies carry about the same initial price (or no more than 10 percent) as cen­tral ammonia systems and deliver a return on investment within the first two years.

Safety is always important. In a cascade refrigeration application, no ammonia en­ters the building where product and work­ers are located. The entire ammonia charge is located and isolated within the equip­ment room. Moreover, the total ammonia charge is approximately 60 to 80 percent less than a central system.

There are two ways to defrost the air units in a cascade refrigeration system. For the past 10 years or so, it has been primar­ily electric defrost. More recently (past four years), the hot gas defrost approach has been worth the additional piping and valves to increase efficiencies.

An ammonia technician will probably not notice it is an Ammonia/CO2 plant un­til they walk into the mechanical room and look at the equipment configuration and pressure/temperature set-points. Most am­monia technicians can be fully proficient with six to eight hours of training, which is offered through the Industrial Refrigeration Technical College (IRTC).

Want to consider this new technology? ESI Constructors can help building own­er-operators collect base bids for ammonia – and then price cascade refrigeration op­tions for apples-to-apples operating com­parisons. We are convinced that cascade is the best all-around option for performance, safety and savings.

By Michael McGinnis & Timothy Nguyen
Article co-authored by Michael McGinnis, President of Innovative Refrigeration along with Timothy Nguyen, Regional Vice President with ES/ Constructors, Inc. The two have a combined 50 years of experi­ence in the food, beverage and cold stor­age warehouse industries.