Buying and operating tips—walk-in refrigeration

What should you consider when buying or operating a commercial walk-in refrigerator or freezer?

Buying tips

Buy the right size unit.
Think about how much space is available in your kitchen, and what capacity your operation requires.

Look for a model with a remote compressor/motor condenser system.
These are more expensive to install and maintain, but they add less to indoor cooling costs and noise pollution.

Choose high-efficiency components.
By incrementally and independently reducing the load on the compressor, a high-efficiency refrigeration compressor, evaporator fan motor and condenser fan motor can each improve system energy efficiency by five to 10 percent.

Opt for energy-efficient demand-defrost controls.
This feature allows you to initiate defrost cycles in a variety of ways, such as measuring temperature drop, frost accumulation or humidity levels. All of these methods are more effective than using a simple timer to initiate defrosting, and can improve energy efficiency by up to six percent.

Select a model with anti-sweat heater controls.
Anti-sweat heaters keep external display doors free of condensation in high humidity conditions. Anti-sweat heater controls that sense humidity can be set to turn off heat in drier weather and can improve system energy efficiency by two to four percent.

Buy or retrofit a unit with floating head pressure controls.
In outdoor air-cooled condensers, these controls take advantage of low air temperatures, allowing the head pressure to vary with outdoor conditions. This reduces compressor load, extending the compressor’s life and reducing energy use by three to 10 percent.

Explore options for sub-cooling the liquid refrigerant.
Further cooling the liquid refrigerant lowers the temperature of the evaporator, substantially increasing the refrigeration system’s cooling capacity and overall efficiency. This can be done naturally, with an oversized condenser or mechanically, either with a remote cooling system or by running a refrigerant line from a central system. 

Ask about an evaporative condenser.
A unit using an air-cooled condenser can be equipped with a moistened filter to cool ambient air as it enters the condenser. This increases the cooling condenser capacity and cools the liquid refrigerant, which reduces the compressor load. An evaporative condenser can reduce energy use by three to nine percent.

Use a liquid pressure amplifier.
This small refrigerant pump raises the liquid line pressure. This reduces capacity loss at low head pressure, improving efficiency and ensuring lubricant circulation through the compressor. A liquid pressure amplifier can reduce energy use by as much as 20 percent and, with air-cooled condensers, efficiency gains increase as outside temperatures drop.

Ask about heat recovery.
The operating cost of a walk-in refrigerator or freezer can be partially offset by recovering heat from the refrigeration system for use in water heating and space heating. Ask an HVAC professional whether your unit is suitable for heat recovery.

Operating tips

Energy efficiency is compromised in commercial walk-in refrigerators and freezers by parasitic loads: demands on the refrigeration system from items other than those meant to be cooled. Examples of parasitic loads include interior lighting, fans and pumps, heat gains through insulation, air changes from open doors, and even personnel and machinery operating inside the unit.

Some parasitic loads use energy twice: directly from the electrical system to power fans and pumps, and indirectly through heat gain, which must be removed by the refrigeration system. 

Many of the following tips will help reduce the effect of parasitic loads:

Read the owner’s manual.
It will provide model-specific tips for optimum efficiency.

Check the insulation.
Regularly inspect the unit’s insulation and replace it when necessary.

Set and confirm optimum temperatures.
Regularly check the room’s temperature and adjust thermostats accordingly.

Use energy-efficient fans and pumps.
Fit these components with variable speed drives and run only when necessary.

Cut back on lighting.
Replace existing fixtures with energy efficient alternatives and turn off lights whenever possible.

Keep outdoor cooling coils shaded.
Direct sunlight can overheat the coils, reducing efficiency and even causing mechanical failure.

Clean the condenser coils and fan regularly.
Accumulated dust and debris can restrict airflow, causing the motor to work harder and use more energy. Ensure that the condensation drain is not blocked.

Open doors only briefly.
Cold air spills out quickly, forcing the cooling system to work harder to achieve the desired temperature. Restrict personnel and machinery operating inside the unit.

Install a strip curtain and automatic door closers on high-traffic units.
These features help reduce heat loads that can overwork the compressor.

Let food and containers cool before putting them inside.
Avoid adding unnecessary heat to the fridge or freezer compartments.

Keep door seals clean and tight.
If a sheet of paper placed in the door slides around or slips out, or if light from a flashlight placed inside can be seen through the seals, replace the seals. (Use the flashlight test on oven doors, too.)

Conserve water with a cooling tower.
This component pumps warm water from a water-cooled condenser through spray nozzles onto the tower fill material. As the water evaporates, it assists in cooling the condenser, meaning that the unit uses less municipal water.