Walk-in cooler and freezer units may seem to be among the more simple items of equipment in a store but regular maintenance and some basic housekeeping procedures are essential to keeping them running. Following these guidelines for operating walk-ins ensure that they preform properly and that problems are avoided.
As with any type of mechanical device or refrigeration system, preventative maintenance for walk-ins is indispensable. Although walk-ins are essentially large insulated boxes connected to either single-unit or centralized refrigeration systems, they are themselves made up of various parts and materials. Proper attention paid to how well the different parts work keeps them working longer.
Four sets of basic steps should be performed regularly. These include steps for inspection, proper lubrication, adjustment and ensuring proper airflow.
Inspection. First and foremost, however, before any of these procedures are performed care must be always taken to keep floors clean and free of spills and any ice buildups. Walk-in floors can become slippery and hazardous if allowed to become wet, greasy, or icy. Particular attention should be paid to walkway surfaces including metal floors and diamond tread plates. Any spilled liquids and food particles should be wiped up using warm water and mild detergent. The area should then be thoroughly rinsed with a small amount of hot water before being dried with clean towels.
One final point to keep in mind about taking care of spills or any other cleaning is to never use corrosive or abrasive cleaners. The cleaning product manufacturer should always be checked with for information on any potential reaction with different metals and finishes.
The first thing to check when inspecting a walk-in is for any condensation. Water condensation must never be permitted to drip onto the walk-in floor. Any condensation that’s found may be an indication of a problem with the walk-in’s condensate drain line. Refer to your refrigeration system instructions for proper condensate drain line installation and maintenance.
Walk-in doors are the next thing to inspect. Door hardware and the sweep gasket should be checked monthly for ease of operation. The sweep gasket must be adjusted to allow free movement and proper seal. Any damaged hardware should be replaced immediately to prevent permanent damage to door.
Frost or condensation appearing around the doorjamb, or heated pressure relief vent, usually indicates an electric heater that’s not working. The power supply and electrical connections, or the heaters themselves, may be the problem. These should be checked and replaced when necessary.
Doors on walk-in freezers include some additional components to check on a regular basis. They typically contain resistance heaters controlled by a simple rhea-stat. Used as frame heaters, they are located under the jamb guard in a sealed track and as sweep heaters they’re in a cavity on the adjustable sweep assembly and a heated pressure relief port. A temperature control device cycles then whenever refrigeration may be inoperable. The normal set point is approximately 85F for “on” and 105F for “off.” Continuous operation of the heaters protects the door from icing and damage.
Service doors may also be equipped with a magnetic gasket that uses an accordion PVC material with a magnet on the flat outer service. This gasket meets and seals against the metal jamb guard material. It’s vital that this gasket be kept clean—using simple soap and water—and clear of obstructions for a proper door seal.
Cooler/freezer doors can have both have magnetic gaskets and adjustable sweep gaskets. The doors on walk-ins operating under 32F will have heaters to prevent condensation from forming icing. The cooler doors (for walk-ins operating 35F and above) will usually not need heaters.
The pressure equalization (or relief) port is critical to the efficient operation of a walk-in cooler. Also know as a PRV (pressure relief valve), they equalize pressure when doors are opened and closed and during the defrost cycle of the refrigeration equipment. PRVs come in a variety of forms and sizes depending on the cubic feet of the walk-in but most often are simply spring-loaded flappers. They should regularly be checked that they are working properly and that they are clear of obstructions to ensure proper operation.
Along with checking the doors, anti-skid strips should also be checked on a monthly basis. Abrasive-coated anti-skid strips are typically factory installed on ramps. Because of the importance of these for safety, their effectiveness should be maintained. Additional strips are usually available from the manufacturer and should be replaced whenever they begin to show signs of wear.
Finally, regular inspections should include all refrigeration equipment for proper functioning of evaporators, drain pan heaters, defrost controls, and drain line heaters. Manufacturers generally provide instructions for what to specifically look for when checking refrigeration systems.
Proper lubrication. The moving parts of a walk-in should receive annual attention at a minimum. These include door hinge bearings, latches, and inside releases. At least once a year these should be lubricated with petroleum jelly.
Adjustment and airflow. Some components of a walk-in periodically need adjustment as time goes on. Door sweeps, for instance, need to be kept properly adjusted in order to compensate for wear or uneven floors. All hardware and fasteners, including attaching screws, need to be checked and tightened to ensure that they are firmly anchored. If any of these ever malfunction, the owner’s manual should be checked for warranty terms and what actions to take.
Maintaining unrestricted airflow across the condensing unit and making sure the condenser coil is kept free of any dirt at its inlet (usually behind) and outlet (usually in front) is essential to the operation of the walk-in. Depending on the application, product or other items may be stacked nearby or around the condensing unit. Care should always be taken to make sure the airflow across the condenser is unrestricted. It is also important to make sure that the condensing unit drain lines run free and clear.
As basic a piece of equipment as walk-ins are, it’s of the upmost importance that they be accurately maintained in order to ensure reliable operation. By following a program of preventative maintenance owners can avoid problems and enjoy proper performance.
Q: How does a refrigerant distributor function?
A: Distributors are used on multi-circuited evaporator coils. By using multiple circuits in evaporators, the pressure drop through the evaporator is minimized. The purpose of the distributor is to provide equal feeding of the refrigerant to each individual circuit. Because of this, it’s important for each connecting tube from the distributor to the evaporator to be of equal size and length. Also, it’s recommended that distributors be installed in a vertical position, to maintain equal flow under low load. There are two commonly used distributors: nozzle or venturi. The nozzle type (below right) uses an orifice plate to generate pressure drop, which creates the turbulence to provide equal feeding of the circuits. The venturi type (above right) uses an internal venturi design to provide equal flow to the circuits. The venturi doesn’t rely on turbulence to equalize the feed to the circuits; it has a much lower pressure drop through it. In either case, an externally-equalized expansion valve should always be used with a distributor, because of the pressure drop which the distributor generates.
Copyright 2008 Emerson Climate Technologies, Inc. All rights reserved. Used by permission.