Fuelled by increasing market interest in environmentally friendly systems and practices, and a goal of preparing the global market for greater hydrocarbon acceptance, the first collaborative project was Manitowoc’s 500-pound ice maker. To convert the ice maker to natural refrigerants, Danfoss replaced a compressor using R-404a, a hydrofluorocarbon (HFC), with a new compressor designed for R290, a hydrocarbon (HC).

Knowing it would also help reduce energy use, Danfoss chose to install one of its S Series compressors (SC18CNX) for R290, which features a reliable, compact design and a motor with specially-optimized valves and internal motor protection. The SC compressor offers high cooling capacities, low noise levels and low energy consumption at high ambient temperatures (113o F).

To further improve the efficiency of the ice makers, Manitowoc installed a specially-designed Danfoss TU thermostatic expansion valve, which helps to optimize the charge and regulate the injection of the refrigerant. Manitowoc also replaced the condenser with a new Danfoss microchannel condenser.

“This project was a tremendous step forward in working with alternative refrigerants,” commented Greg Erickson, field marketing manager at Manitowoc Ice, Inc. “The decision to offer units operating R290 was primarily driven by some of our large accounts’ internal demand to become more environmentally friendly. We are currently looking at other natural refrigerants like CO2, but R290 provides the great energy efficiency benefits that our customers are also demanding.”

Production Capacity
Typically, replacing R-404a with natural R290 causes production – the volume of ice harvest within each 24-hour period – losses up to 10%. However, by increasing compressor displacement with R290, reducing operating pressure with microchannel heat exchangers and optimizing component selection, Danfoss and Manitowoc were able to maintain ice production capacity of the R290 systems at the same level as R404a systems, while staying within the 150g charge limit.

Though the introduction of hydrocarbon refrigerant was first and foremost intended to create an environmentally friendly system promoting sustainable practices, the lower pressure ratio and discharge temperatures of R290 combined with the high-efficiency compressor and components work together to save 20 to 30% more energy than comparable ice makers. This is a direct benefit to customers who are also motivated by a reduction in energy costs over time.