Once-through cooling systems, also known as single-pass cooling systems, are expensive and waste large amounts of fresh drinking water. These systems remove heat by transferring it to a supply of clean, cold municipal drinking water that runs through the unit, and then by discharging the used water directly to the sewer. Equipment that may use OTC includes commercial and industrial air conditioners, refrigerators, coolers and ice machines.
Once-through-cooling systems are often used for small commercial cooling loads because they are relatively inexpensive to install and require little maintenance. However, the cost of water to operate a small OTC system for two years is usually greater than the cost of installing an air cooled system that uses no water. For a 12,000 BTU/hour (or 1 ton, roughly equivalent to 1 horsepower) condensing unit, OTC systems use more than one million litres of water per year. A typical restaurant using several units can send thousands of dollars’ worth of clean water down the drain each year.
Options for replacing a OTC system include:
- Air-cooled equipment - install stand-alone air-cooled ice machines and condensing units
- Closed-loop piping - re-circulate cooling water to a remote air-cooled chiller or cooling tower, or connect to an existing closed-loop system serving another area of the building
- Split-system - use heat pumps with remote air-cooled condensers
OTC Replacement in Restaurants
The actual cost to eliminate OTC in a facility can vary widely depending on numbers, sizes, and type of OTC systems currently operating, and conditions that may prevent or complicate direct replacement with equivalent air-cooled systems. Based on many retrofits that have been completed in recent years in Greater Victoria and Greater Vancouver, retrofit costs and utility cost savings are typically in the ranges shown in this Restaurant OTC Retrofit Fact Sheet.
Payback on Replacements
Installation cost and subsequent payback period varies with the complexity of the system. Payback periods for small commercial systems can be as low as 2 years. If you would like an estimated payback period for replacing the water cooled equipment, as well as realizing other potential savings for your business, please contact us to arrange a free water audit at 250.360.3103.
An example of actual water billing information, and water saving benefits from a local restaurant that switched out OTC equipment in 2007.