Diagnose Walk-in Cooler & Freezer Refrigeration Problems

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.

Malfunction Possible Causes Solution
Power is on, but control board does not display.
  1. Phase loss or fuse blown.
  2. Power phase open or transformer shorted.
  3. Control board failure.
  1. Check wiring for breaks and replace fuse.
  2. Check Transformer output voltage (12V)
  3. Replace cold storage room control board.
Control board displays, but compressor does not run.
  1. Compressor relay tripped.
  2. Hi-Lo pressure safety switch shut down.
  3. Defective contactor or coil.
  4. Cold room temperature is lower than operation setpoint.
  5. Internal thermal overload tripped.
  6. Compressor malfunction.
  1. Determine reason and take correct action.
  2. Determine type and cause of shutdown and correct it before resetting safety switch.
  3. Repair or replace.
  4. Reset operation temperature setpoint.
  5. Wait until compressor cools down for reset.
  6. Check compressor motor winding.
High discharge pressure.
  1. Dirty Condenser coil.
  2. Fan not running.
  3. System overcharged with refrigerant.
  1. Clean walk-in cooler and walk-in freezer condenser coils.
  2. Check fan motor and its electrical circuit.
  3. Reclaim excess refrigerant.
Low discharge pressure.
  1. Insufficient refrigerant in system.
  2. Low suction pressure.
  1. Check for leaks; repair and add charge.
  2. See corrective steps for low suction pressure.
High suction pressure.
  1. Excessive load.
  2. Expansion valve overfeeding.
  1. Reduce load.
  2. Regulate superheat.
Low suction pressure.
  1. Lack of refrigerant.
  2. Plugged suction filter.
  3. Evaporator dirty or iced.
  4. Fan not operating.
  5. Expansion valve underfeeding.
  1. Check for leaks. Repair and add charge.
  2. Replace suction filter.
  3. Clean and defrost.
  4. Check fan motor and circuit control.
  5. Regulate superheat.
Large difference between actual cold storage room temperature and set point on control panel.
  1. Incorrect room temperature.
  2. Sensor placement, wire too long.
  3. Sensor contactor open.
  1. Re-position sensing point of temperature sensor.
  2. Enlarge wire section.
  3. Reconnect sensor.
Heavy frost builds up on evaporator fins. Too much time between defrost cycles or incomplete defrosts. Manual defrost and adjust defrost cycle.
High temperature alarm.
  1. Overload and door open excessively.
  2. Bad refrigeration performance.
  3. Heavy frost build-up on evaporator.
  1. Reduce load and door opening.
  2. See corrective steps for discharge and suction pressure malfunctions.
  3. Manual defrost and adjust defrost cycle.
Coil not clearing off frost during defrost cycle.
  1. Heater malfunction.
  2. Not enough defrost cycles per day.
  1. Check heater operation.
  2. Adjust defrost control.
Ice accumulating in drain pan.
  1. Heater malfunction.
  2. Not enough defrost cycles per day.
  1. Check heater; replace if necessary.
  2. Clean drain line.
Display screen flashes, unit emits humming noise. Observe alarm indicator. See alarm indicator for remedy.

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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Comments
  • Brian January 27, 2012 at 1:29 pm

    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

  • ttuIV May 28, 2012 at 8:21 pm

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

  • TOM September 3, 2012 at 10:59 pm

    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.

  • Paul October 25, 2012 at 9:27 pm

    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?

    • Walk-In Freezer October 25, 2012 at 9:46 pm

      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.

  • Pawan Chona January 30, 2013 at 9:20 pm

    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?

  • David February 4, 2013 at 2:48 pm

    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.

  • sam February 16, 2013 at 9:20 pm

    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.

  • j April 7, 2013 at 12:23 pm

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

    • David April 24, 2013 at 2:53 pm

      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.

  • Dave April 11, 2013 at 11:40 am

    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.

    • David April 24, 2013 at 1:46 pm

      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.

  • gm June 17, 2013 at 1:39 pm

    hello,
    I have a problem with the light in my walk in the fixture seem to be filling with water every 3-4 days and burns the lamps. I dont know if im not using the correct fixture or lamp.If that is the problem what fixture should i buy yo replace it ? thank u

  • taffy nazzal June 24, 2013 at 3:57 pm

    1 have a display walk-ins cooler 5hp 3 phase condensing unit R-134A every 3 hours the line set ice frozen don’t except freon charge .

  • William September 21, 2013 at 8:54 pm

    HELP!!!! I am working on a walkin cooler that uses air to defrost the evaporator fins. I am getting 3psi on the low and 124psi on the hi. inside the evaporator room it willnot drop lower than 45F. I have changed out the TXV and cleaned out the condenser and the pressures have dropped even more! I did a pump down test and the compressor did barely hold. I’m just not sure if I have a “wet” system that’s throwing me off or something else. grrrrr! I humbly welcome advise. Thank You.

    • David September 23, 2013 at 10:35 am

      Your system may be low on charge and need more freon or there could be moisture problems. You could write a comment with specific model and serial numbers of the refrigeration unit, that might help with the diagnosis.

  • greg October 1, 2013 at 11:40 pm

    what happens if there is a puncture in the the evaporator fins and it is leaking Freon. Can it be repaired?

    • David October 8, 2013 at 1:04 pm

      @Greg It may be possible to repair it but it’s not recommended. Talk to a refrigeration repair service, but some won’t bother because it is very time consuming and the results of the repair are often sub-par.

  • Ryan October 19, 2013 at 8:05 am

    Hi , Looking for some advice on this. I have a few large walkin freezers, that i use to store meat preoducts in plastic containers. I am noticing freezer burn on some of the products. I have the freezers on timers so they do not run 24 hrs a day. I am wondering if its the flucuating temperatures due to the timers being on and off that could cause the freezer burn (-20 deg c to -2 deg C) or if its the fact the it could be to cold in the freezer (-20c).

    Thanks

    • David October 21, 2013 at 12:10 pm

      @Ryan It could be how the meat is being packaged. Even if you are using plastic containers that are meant for freezer use, if the food isn’t packed properly it will get “freezer burn”. If you can’t get the air out, the air “burns” the food. So make sure that you are removing as much of the air as possible when freezing food (adding another layer of plastic to seal the top of whatever is going in the containers may help). If you are not maintaining a fairly constant temperature in the freezer, that could definitely be the cause. In addition to looking at the timing intervals and the temperature fluctuations caused by that, if the freezer has heavy traffic, if the door is left open for long periods of time, if you put hot food directly into the freezer etc; these things could all cause significant fluctuation in temperature which could result in freezer burn.

  • David N. November 21, 2013 at 2:04 pm

    I have a walk in refrigerator that when i flip the switch to turn it on the motor does not come on all i hear is a click please help.

  • abby December 4, 2013 at 2:55 pm

    hi david,
    I have a problem with a freezer room unit, the evaporator keeps icing up i have checked the defrost timer and my sensors i cant find any problem with that plus my pressures are ok only problem with this is that it doesnt go past negative 10. sir can tx valve can be the problem.

  • evan price January 2, 2014 at 11:56 pm

    My walk in compressor seems to be running and not shutting off. It gets to freezing and still keeps going. Any ideas why? Ive been turning it off by hand to keep it from burning the compressor up. Any help wouldbe appreciated.

  • eric January 6, 2014 at 6:55 pm

    Have a walk in cooler running head pressure 100 over 15 but not cooling and temperature outside is -15 has a hot gas bypass and crank case heater it’s run sight glass has a trickle of liquid any ideas

  • diego January 9, 2014 at 6:19 pm

    I have a walk in freezer working two days frozen suction line to the compressor and sweating i think is overcharge i have 12 degrees f inside the box client said the box before was 0 degrees someone can help me

  • Clay February 3, 2014 at 8:27 pm

    I have a walk in freezer and the threshold under the door came off exposing a wire. the wire broke off at both ends under the door. Now the door freezes shut. Can I repair the problem? The local commercial freezer repair company said it would cost approximately 780.00 to fix.

    • David February 4, 2014 at 8:11 am

      This is something you may be able to fix yourself for much cheaper.
      At walkincoolerparts.com there is custom sized heater wire and installation instructions. However, you will want to find a wire similar to the one that’s already in your door and threshold so it fits properly. Door thresholds are also repairable. You might call the manufacturer of the walk-in to see what kind of wire they recommend.

  • sameer March 4, 2014 at 9:23 am

    I have a 24ft chiller for milkshakes ect the problem is one the bottom 2 levels it’s icing up the goods system runs R22 any ideas

  • steve shobe March 26, 2014 at 5:36 pm

    I have a freezer that is rusting on ceiling and wall panels in front of the fans. We have checked the roof and seams to make sure that the moisture is not coming from the outside. What we believe the problem is they are leaving the door open for too long and daily placing hot pots of soup in the cooler to cool. Please tell me what we are missing. Also once we have fixed the problem can the inside panels have the rust removed prepped and painted? Or What else can be done with them.

    • David March 31, 2014 at 4:00 pm

      Steve,
      Unless your walk-in has a stainless steel interior, the condensation from soup (tomato especially) is very acidic. You could, but the real problem is there may not be any NSF approved paint that can cover the rust and you may not meet certain health codes. We will have an article posted on condensation and icing problems posted sometime in April.

  • Fred April 2, 2014 at 11:13 pm

    I have a walk in cooler.. I have to set my t stat at 28 to maintain a 36 degree temp.. Any suggestions?

    • David April 4, 2014 at 8:50 am

      As long as your thermometer is working, it sounds like the thermostat may be out of calibration and needs to be replaced.

  • Rich C April 11, 2014 at 12:42 pm

    Walk-in not cooling compressor clicking on and off
    Is this a sign of a blown compressor?

    • David May 19, 2014 at 4:07 pm

      Probably not. Just check for leaks in your system.

  • steve daubenmire April 15, 2014 at 8:48 pm

    hi pressure line leaving receiver frosting up,can you explain what it may be.

    • David May 19, 2014 at 4:06 pm

      Check for restrictions. It could be ice or some kind of debris blockage in that area.

  • wilson May 19, 2014 at 7:40 pm

    i have a walk in freezer i built 5 years ago it has worked fine all this time up tell 2 weeks ago it lost power on one side of the breaker. replaced the breaker and it worked fine for 2 weeks.
    now it is still cooling and running for the most part the compressor starts up and a couple seconds later it shuts off the compressor. i got it to run fine by dropping the box temp at the thermostat to -20 to -10 it is keeping the box between -5 to 7 it ran like that working fine for 2 days now the compressor is turning on and right back off it runs for 30 sec to 3 min. it dos have a little ice buildup on the suc line for about 2 inches past the isolation at the compressor.
    any info will help suc pre is 20psi liq line is 120psi ish going to recheck them today

    • David May 22, 2014 at 9:53 am

      It sounds like you might have developed a leak and are low on charge. That would explain why the walk-in is not holding temp. As for the tripping the breaker you should check and make sure all the coils are clean and getting good air flow. If you’re not a refrigeration tech, get it checked out by one.

  • Stan July 4, 2014 at 8:13 pm

    Wondering if you stack pallets of ice under the evaporator coil will that keep your freezer from pulling down and causing the coil to get heavy frost running R-22 it is an ice cream freezer set point -12 degrees superheat 5-10 degrees
    Strainer clear power head new, check valves good, t.x.v new , CDS valve pressure 12 psi from rack to evaporator coil. Liquid solenoid valve guts new defrost 4 times a day for 24 min with a 13 min drip time my termination and temp sensor are correct. The freezer is having a hard time recovering down to a negative temp they have pallets of ice stacked up to the coil

  • James August 20, 2014 at 10:05 pm

    How can you tell if a expansion valve is not working well

    • David August 25, 2014 at 3:18 pm

      It’s common to think the expansion valve is defective, when it’s in fact another issue. Check out this article to make sure that’s where the issue lies.
      ehow.com/way_5915627_expansion-valve-troubleshooting.html

  • kevin August 23, 2014 at 4:31 pm

    I have a large walk in cooler at my mortuary. The compressor unit is located on top of the cooler in the attic space. I have a continual puddle of water on the floor. I do not see any type of drain on the machine to drain the water off. There is a small “bottom” under the coils ( I don’t know if this could be classified as a drain pan or not.. Nonetheless, there isn’t an outlet for the water. Help…

  • torres August 23, 2014 at 10:45 pm

    Walk-in-cooler is freezing the lines what can the problem be

    • David August 25, 2014 at 8:49 am

      It may be a problem with your thermostat or defrost timer. Or you may be low on freon or have a leak. You should get a service tech to check it out to determine the issue.

  • Matt September 18, 2014 at 6:05 am

    My freezer periodically makes a high pitch noise. Everything looks clean, good air flow all around unit and fans. I basically turn motor off for 10-15 minutes and turn aback on and noise goes away, this happens about 3 times a day just started about a week ago.

    • David September 22, 2014 at 9:31 am

      It sounds like the motor bearings may be failing.

  • pankajakshan October 9, 2014 at 1:22 pm

    How do you remove ice from the chiller unit without spraying water?

  • Kristy November 2, 2014 at 8:34 am

    I have a new outdoor walk in freezer. It’s early November temps are falling now my unit won’t keep correct temp. I have found it up to 30 degrees. What can I do!!!???

    • David November 3, 2014 at 4:52 pm

      So it holding temp until recently? What is the thermostat set on and have you checked the temp with another thermometer? Where is this located and have you cleaned the outside condenser coil?

  • Jeremy November 22, 2014 at 11:13 pm

    Have a problem with a walk in freezer door. The door gasket heaters work well, and the gasket seals good, too good, because the vacuum in the space prevents you from opening the doors! Are walk-in boxes ever fitted with vacuum breakers so you can open the doors??

    • David November 24, 2014 at 8:07 am

      Most walk-in freezers have a heated pressure relief vent to prevent this sort of issue. You should be able to cut out a hole and retrofit one on your walk-in.

  • Benj November 25, 2014 at 1:41 pm

    Hi! Ive got freezer issues!! Its a danfoss, blue star unit controlled by Eliwell ID 794 control unit! My problem is it was shutdown six months ago in perfect working order as the blue star unit is only three months old and now when I’ve came to switch it back on there’s absolutely nothing!! Ive been through all the control settings as programmed by the company that installed it and nothing’s changed! Also if I click the relays in the control panel manually the compressor fires up as do the fans and the blower unit!! Any help ideas with this rather frustrating problem greatly appreciated,thanks

    • David November 25, 2014 at 3:53 pm

      I’m sorry, we don’t have anyone familiar with the refrigeration unit you have.

  • Elizabeth December 4, 2014 at 11:15 am

    I have a walk in freezer that keeps shutting off in the early hours of the morning, the only way to restart it is the main switch. Any suggestions?

    • David December 5, 2014 at 8:45 am

      Did you have any other details on the refrigeration unit or its condition?

  • michelle tynes January 19, 2015 at 3:20 pm

    I have an older walk-in cooler. Last week it froze up and we turned it up to defrost and turned backup it worked for a while but about a week later it stared to heat up it was blowing 52 degrees so we added freon. when that didn’t work we replaced the blowers. What else could be wrong??

    • David January 20, 2015 at 8:29 am

      How long did you have it turned up to defrost it and did it get completely defrosted before you turned it back down? What temperature are you holding the cooler at? How much Freon did you add and what made you think it was low?

  • chris February 26, 2015 at 5:56 pm

    R-22 walk-in cooler that wont pull down below 65
    outdoor ambient= 85
    box temp= 65
    High side pressure=180psig
    Low side pressure=15psig
    Super heat=45
    sub cooling=30
    Compressor amps low
    normal evap and cond fan operation
    Sight glass full
    no temp drop across filter drier or solenoid valve

    • David March 2, 2015 at 9:52 am

      Super heat is way too high. Check to see if you have a bad thermal expansion valve.

  • louis March 16, 2015 at 7:58 pm

    the compressor for my walk in cooler has two fans for the condenser. once and went I can change the motor now later the other fan is gone I need to change is motor. the compressor it keeps cutting off. is it because one of the condenser fans are not operating?

    • David March 17, 2015 at 9:13 am

      Yes, if both fans are not operating properly that will cause high head pressure and shut the system down.
      You should have them replaced and the whole system checked by a qualified service tech.

  • Rajib April 24, 2015 at 8:19 am

    I want to know about chiller freezer

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