Ice machines produce various kinds of ice for a range of applications. The types of ice produced are cube, flake, crushed, and nugget.
- Cube ice is clear and comes in several shapes—rectangular, crescent, pillow-shaped, pure cube, or other regular shapes. The largest dimension is about 1.25 inches (3.18 centimeters). Pieces of cube ice range in weight from 0.16 to 0.50 ounces (4.8 to 14.0 grams) and contain minimal amounts of liquid water. More than 80 percent of ice machines sold in the US make cube ice.
- Flake ice comes in chips or flakes that contain up to 20 percent liquid water. Flake ice tends to conform to the surface of items that rest on it and is typically used in supermarket display cases, on fishing boats, or anywhere food needs to be preserved for short periods. Flake ice may also occasionally be used in soft drinks.
- Crushed ice consists of small, irregular pieces made by crushing larger chunks of ice. Its primary use is for keeping drinks cool.
- Ice nuggets, made by extruding and freezing slushy flake ice into small pieces, are also used primarily to cool drinks.
For more about types of ice and the machines that make them, see Chapter 43 of ASHRAE’s 2014 ASHRAE Handbook.
Types of machines. Ice machines can be mounted above a storage bin or integrated with an attached insulated bin, a style known as a self-contained unit (Figure 1). Integrated units are the simplest to install but usually come with a fixed capacity. The capacity of nonintegrated units can be increased by stacking additional ice makers on top of the first machine or by placing two machines side by side on top of a larger bin.
Figure 1: Ice maker
Ice makers often come with the ice-making equipment integrated with the storage bin, as shown here. Stainless steel resists corrosion and provides an attractive look.
Ice makers are also classified as batch or continuous in operation. Batch models tend to produce ice that is purer than its source water because the freezing process removes impurities. In continuous units, chemicals tend to remix in an ice/water combination. Controls for batch ice makers are more complicated: They must end the freezing process at the proper time to start a thawing cycle and resume the freezing process after the ice has been harvested.
Condenser types. Ice makers are available with three different types of condensers:
- Air-cooled ice makers generally use the most energy but are less expensive than water-cooled models. They also use less water.
- Water-cooled models tend to be more efficient than air-cooled units. There is no addition to air-conditioning loads because the heat removed in making the ice is discharged outside the building.
- Remote air-cooled condensers transfer the heat generated by the ice-making process outside of the building. Like water-cooled units, they reject heat outside of conditioned spaces and therefore do not increase air-conditioning loads. They also reduce noise levels inside by up to 75 percent, but there are extra installation costs for running lines to a remote location. Remote condensers can use remote compressors for further efficiency gains.
Bin types. Ice-storage bins are available in a range of sizes, usually with a full-width door that allows users access to the ice. Bins are usually sized to hold 10 to 12 hours’ worth of ice production. Larger bins are available for applications in which ice is only changed once or twice a week, such as supermarket displays. Sealed, sanitary units are also available, but they're much more expensive than standard units. They are often used in hospitals, motels, and restaurants, and for any operations in which ice comes in direct contact with food or drink.
Water heat recuperation. Some ice makers direct the incoming water behind the evaporator plate or over the ice to use the heat of the incoming water to assist in the ice-harvesting process. This step also serves to prechill the incoming water and cuts energy use significantly.
Water treatment system. Ice makers can be run directly from tap-water supplies, but some applications may require additional water treatment. In general, if the total chemical content of the incoming water is greater than 400 parts per million, auxiliary water treatment is recommended.
Self-cleaning systems. A relatively new option among ice makers is the self-cleaning machine. Typically, ice makers are cleaned and sanitized every two to six weeks, which requires emptying the bin of ice, adding cleaning solution, switching the controls to a cleaning mode that circulates the cleaning solution through the machine, and then producing enough ice to be sure the machine is cleared of the solution. Self-cleaning models automate most of these steps.
Energy-efficient units. In 2013 Energy Star updated its specification requirements for ice machines. These initial levels cover only air-cooled ice makers and those that make cube (not flake or nugget) ice. The Energy Star program has stated its intention to include flake and nugget machines once a test standard is available and adequate data are collected for deriving performance requirements. Energy Star hosts a Commercial Food Service (CFS) incentive program with local utilities, which offer rebates for energy-efficient machines. Rebates typically range from $100 to $500. For more information, see the Energy Star CFS website.
The Consortium for Energy Efficiency (CEE) has also created voluntary standards for commercial ice maker energy and water efficiency updated in 2015. The CEE standards, along with a list of ice makers that meet the standards, are presented on the webpage CEE High Efficiency Specifications for Commercial Ice Machines. Both Energy Star and CEE specifications are great certification schemes to follow when shopping for ice makers. Table 1 compares levels of energy consumption for a sample machine that makes 800 pounds of ice per day at current and planned federal efficiency standards, along with those required by Energy Star and the CEE. To get the maximum cost-effectiveness and greatest payback, CEE Tier 1 or Energy Star labels are typically the best bets, and CEE Tier 2 units may offer increased savings at additional cost.
Table 1: Comparison of Energy Star and CEE efficiency with federal standards
Because federal efficiency standards and Energy Star or CEE qualification criteria vary depending on the amount of ice a given machine is able to produce each day, data for a representative machine producing 800 pounds of ice per day is shown for the sake of comparison.
In some cases, high-efficiency ice makers have little or no incremental cost versus less-efficient models, yielding very short (or even immediate) simple payback periods. In other situations, simple payback periods may be as long as 10 years or more, making the equipment less cost-effective (Table 2). It’s important to pay close attention to both expected energy savings and incremental costs when purchasing a new machine to ensure that you’re getting the most cost-effective option.
Table 2: Sample calculation of energy cost savings for ice makers
Ice makers are available with a wide range of efficiencies. This sample calculation compares hypothetical air-cooled commercial ice makers with a capacity of 1,200 pounds (544 kilograms [kg]) of ice per day and an average production of 800 pounds (363 kg) of ice per day. The base model has a typical low efficiency (as defined by the Food Service Technology Center of the Gas Technology Institute). The other ice makers listed have efficiencies that meet the thresholds for each of the Consortium for Energy Efficiency tiers as well as for Energy Star, the current federal efficiency standards, and the 2018 federal standards.