• Diagnosing Walk-in Coolers & Freezers Problems

    May 31st, 2011 U.S. Cooler

    A systematic approach to walk-in cooler and freezer maintenance is the technician’s best guide.

    The ubiquitous walk-in cooler or freezer is an essential part of many cafeterias, restaurants and convenience stores. It is also a large energy user in these facilities but is rarely considered until problems emerge.

    Problems include failure to maintain pressure and compressor failure, both of which can result in expensive losses to the products stored in the cooler. These problems, as well as unnecessarily high energy use, can be avoided by observing equipment and taking corrective action.

    Evaporators
    Moisture from the air freezes onto the evaporator coils (the cooling coils in the freezer) and forms an insulating barrier to heat transfer. Airflow also decreases as the passages narrow due to ice buildup. Each evaporator has a defrost cycle to melt frost/ice that has built up on the evaporator coils. Water from the melted ice is drained from the freezer . . . ideally.

    It’s not unusual, however, to find evaporators in a state of poor maintenance. For many evaporator units, the ice isn’t melted, or the water isn’t properly drained, resulting in a block of ice taking over the evaporator. When the coil freezes, heat transfer is greatly reduced resulting in the compressor working harder and longer. It works harder because the suction pressure drops making the compressor work at a higher differential pressure, thus requiring more power. It works longer because heat transfer is reduced. When ice buildup is excessive, the compressor will run all the time and the freezer temperature setpoint will not be maintained.

    As the ice melts, the water has to drain out of the freezer. This doesn’t always occur. Trapped water that freezes can do significant structural damage to a freezer; especially older ones where cracks allow water to seep in, then freeze and expand. Stalactites and stalagmites of ice appearing in your freezer are reason for swift action to avoid costly damage.

    Condensers
    The condenser coil of the refrigeration system removes heat from the system. It’s not unusual to find condensers located in enclosed spaces or spaces with inadequate air flow to remove heat from the space. The temperature around the compressor rises resulting in higher head pressure for the compressor, which again increases compressor power.

    To effectively remove heat, the condenser should be placed in a well-ventilated area where the temperature is controlled to allow heat to be removed easily. Enclosed spaces will require openings for cooling air intake and exhaust. In many cases, a fan will be required to move enough air through the space. If the condenser heat is never needed, it should be exhausted directly outside if possible.

    In cases where it may be used for space heating — such as for a nearby dry storage room — controls may be installed to direct the flow indoors for heating, and outdoors when heating is not required.

    Condenser coils should also be checked regularly for cleanliness. Dust and debris will act like ice buildup on an evaporator coil. This will insulate the heat transfer surface and reduce airflow, which will make the compressor run harder and longer. In extreme cases, compressors may fail.

    Refrigerated Space & Shell
    Although the space itself doesn’t have any mechanical parts or equipment, it shouldn’t be ignored. The shell of the cooler or freezer should be inspected regularly for leaks and loose insulation or panels. Leaks and other voids in the shell can cause excess moisture to accumulate, potentially causing even bigger problems. The door is also a key component of the cooler. Doors must be sealed properly to eliminate air infiltration which increases the cooling load and may cause moisture buildup within the space and on the evaporator. Frost buildup on the door itself is a common occurrence when the door heater fails and has a tendency to either freeze the door shut or keep it from closing. Proper care should also be taken when placing items inside the space. If the space is overcrowded with items, or items are placed in front of the evaporator fans, the circulation of air is greatly reduced along with the performance of the refrigeration system.

    Maintenance Helps Avoid Energy Waste & Repairs
    Operations and maintenance issues should be addressed to avoid excessive energy use and costly repairs, as well as potential product loss. Additional maintenance issues can be reviewed in the Walk-in Cooler/Freezer Diagnostic Protocol table shown below.

    Eric Borchardt, EIT, LEED AP, is an energy engineer for Michaels Energy, a nationally-recognized energy efficiency consulting company, with offices throughout Wisconsin. Michaels Energy is a division of Michaels Engineering. He can be reached at 608/785-3318; or by email at, EJB@michaelsenergy.com

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    12 responses to “Diagnosing Walk-in Coolers & Freezers Problems”

    1. I have R-414 compressor. It works for few days (2-3 days) and it stop and does not run until I shut off the power breaker and put it back on. Then it works for few days and stop.
      When it stops usually early in the morning (aroung 4 or 5 in the morning)
      presure setting :cut in 20 and cut out 20

    2. the compressor is protecting itself, could be a false contact at the power source

    3. WATER DRAINING OCCURRING ON THE SIDE AND FRONT OF FREEZER AREA SPILLING ONTO THE TILE FLOOR. THE HEAT CABLE LINE HAS BEEN CHANGED, BUT IT’S STILL HAVING THE SAME PROBLEM.
      ONE SUGGESTION BY THE REPAIR PERSON WHO CHANGED MY HEAT CABLE LINE SAID THE PVC PIPE FROM THE WALK IN COOLER THAT GOES TO THE WALK IN FREEZER WALL MAY BE BUSTED. ITS HARD TO TELL UNLESS YOU RIP OF THE METAL WALL THAT SEPARATES THE COOLER FROM THE FREEZER UNIT.

      WHAT ELSE COULD IT BE????? I NEED EXPERT ADVICE.

    4. Do you have a rule of thumb for how far boxes should be kept away from the evaporator in a walk-in cooler or freezer?

    5. It’s not recommended to stack anything in front of the evaporator fans. This is necessary to have good airflow and even cooling throughout your walk-in. If you absolutely need to stack things in front, it should have at least 5ft of airspace… but it’s best to have that area as clear as possible.

    6. How much freeon gas go 8door display walking cooler. Some body who work for my cooler said he put 27lb. gas on the comp. or motor. Is this is possible?

    7. It depends on the length on the length of the lines going into the cooler, the size of the evaporator coil and the size of the receiver tank on the condensing unit. Can’t say for sure, but it’s possible they could’ve put that much in.

    8. walk in freezer everything runs ok only its not blowing cold air inside the box the lowside of the compressor reading is 10psi and the amps on each lead shows 2.2 amps what is it that my lowside pressure is so low please let me know what I should look for to fix this problem I have been working on the freezer for week still at first nothing was running at all slowly one by one everything started running only not blowing cold air at all.

    9. Accumulation of ice on ceiling 2 feet in front of evaporation coil. How do you prevent

    10. I have a large walk in freezer. Ice only forms on bottom corners of evap. All defrost heaters OK, pan heaters OK. Drain tripped to full size and correct heat trace and drain is clear. Defrost termination and fan delay OK. System has been verified to be grossly oversized. Any ideas on ice.

    11. Dave, unfortunately an oversized refrigeration system is inherently going to have icing problems. Outside of purchasing a correctly sized system, I’m not sure there’s much you can do about it.

    12. J – Here are a few tips to get you started. Check the drain line and pan for proper drainage. Check the fan delay and make sure it is keeping the fan off adequately for condensation dripping condensation off the coil before the fans come back on. Check the defrost timer & termination and make sure it’s allowing adequate thrust to defrost the coil properly and that termination is not shutting off too quickly.

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