For example, a system operating with a 23 percent refrigerant undercharge could result in a 52 percent efficiency loss. A dirty condenser coil can increase system energy consumption by up to 37 percent.

Here is the basic formula used to calculate the electrical cost to operate a system:

Cost = (kilowatts consumed) x (hours in use) x (cost per kWh)

For example, if the utility company charges $0.14 cents per kWh, a system that consumes 5 kW and operates for 10 hours a day will cost a customer $7 per day to operate ($0.14 per kWh x 5 hours x 10 kW).

This formula shows us that run time is a major factor in calculating system operating costs. Therefore, looking for ways to reduce run time can result in sufficient energy savings.

One way of preventing excessive run time is making sure a system’s cabinet is in good shape. A poorly maintained cabinet can and will cause a system to run longer.

Check the door gaskets and hinges to ensure the door closes properly and creates a sufficient seal with the cabinet. Torn or worn door gaskets need to be replaced and broken or loose door hinges need to be repaired.

One trick of the trade used by some technicians is to take a dollar bill and place it between the door frame and gasket. With the door closed, the bill should not fall. Next, pull on the bill. It should be snug and require a little force to pull it from between the gasket and door frame. If it’s loose or falls, there is not a good seal between the gasket and door frame. Try this trick on several sections of the door to make sure the entire door seal is good.

On low-temperature systems, check the defrost system. Ensure the defrost cycle is terminating properly. Problems with the termination circuit can lead to excessive defrost periods, leading, in turn, to excessive run times and
wasted energy.

A common issue found on walk-in freezers is a bypassed termination switch from a previous repair, which may lead to a timed defrost cycle instead of a temperature or pressure termination. Also, check the number of programmed defrost periods; perhaps the number of defrost periods per day can be reduced. (Be careful when making this change; however, reducing the number of defrost periods can cause inadequate defrosting of the evaporator and lead to an iced evaporator and an increase in the cabinet’s temperature.)

Another area to examine on low-temperature systems is the temperature controls. A defective or misadjusted temperature control can cause a system to operate at a lower case temperature, which can lead to excessive run times. Operating a freezer at a lower temperature may not be perceived as a problem, but is a waste of energy. Operating a system at minus 20?F costs more money than operating it at minus 10?F. If minus 10?F is adequate for the product being stored, then operating the system at minus 20?F is a waste of energy.

Examining the ways to reduce the energy consumed by a system can be a major benefit to both your customer and your company’s bottom line. So, the next time you service a refrigeration system, see if you can save your customer some money, too.

Publication date: 5/4/2015

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