Refrigeration Defrost
This article is intended to introduce the defrosting methods in refrigeration equipment. More specifically in freezers. The majority of all freezers have a defrost cycle of some sort. In general the sequence of operation is the same, although components differ from unit to unit in many cases. We will explore the defrost cycle and the why it is necessary for freezers to have them. By the end of reading this you should a basic understanding of why defrost cycles are necessary, the primary methods of defrosting, as well as how they are initiated and how they are terminated.
Understanding Refrigeration Defrost Cycles – Why it’s Needed
The basic principle of refrigeration is to remove heat from the desired space or product, then get rid of the absorbed heat outside of the refrigerated area. The component responsible for absorbing the heat from the refrigerated area is called the evaporator coil. This component is nothing more than multiple loops of copper and aluminum with a fan motor to move air through it. The idea is to allow low temperature refrigerant, generally in the negative degrees, to absorb the heat from the air traveling through the evaporator coil. Continue reading “Defrosting Methods in Refrigeration” →
Beverage Air Freezer Temperature is Rising – CFG36-1
A client stated that the his freezer temperature was rising however upon arrival we found the unit operating normally with a temperature of -3*F. I increased the temperature control setting to see if I could get the unit to cycle off. The current setting was at # 6. Turned the temperature control knob to setting to # 3 when unit cycled off. Reset temp control back to # 6 to turn refrigeration system back on. Checked the compressor amps and checked system pressures. Continue reading “Evaporator Fans Running During Defrost” →
Compressor Sounds Rough on Victory Freezer
Model# VSF-2
Technician Notes:
I found the unit operating but the compressor sounds rough like it has internal damage. I did not feel any heat coming off the condenser unit and the u-bends felt slightly warm. Connected my stubby gauges to the system and found the suction pressure was really low at approximately 6 psig. I decided to add refrigerant to further diagnose the system. I found the suction pressure struggling to increase passed the 6-8 psig range and the head pressure rising past 200 psig. Based on these pressures I determined that the capillary tubes were restricted. I also found oil on the side of the compressor rotor lock, which indicated that it was most likely leaking from this area. The area around rotor lock and compressor Continue reading “Freezer Compressor Running Rough” →
Kolpak Walk-in Freezer with Defrost Issue – Evaporator is Covered with Ice
After arriving at the location and speaking with client, I found the walk-in freezer temperature at approximately 50*F. Noticed that the evaporator coil was covered with ice, blocking air flow. Looks like a possible defrost issue. Went to the roof top and found condenser operational. Placed unit into defrost and check to see if defrost heaters were pulling amps. Clamp meter reading 6 amps during defrost. Data plate stated 6.3 heater amps. Allowed defrost to operate to melt ice from coil. After ice removal placed defrost timer at 3 pm. After 15 minutes of operation, timer clock did not move from the 3 pm position. Continue reading “Walk-in Freezer with Defrost Issue” →
Follett Freezer Temp is High – Under Counter REF5 / 00926626
Customer complaining that the Follett Freezer temp is high and has been for a few days. Found the unit temperature at 50*F. Checked all components and found they were operating normally. Installed my stubby gauges to check refrigerant pressures and found the suction pressures lower than normal. Unit discharge line and condenser were barely warm to the touch. Determined that unit was low on charge and therefore must have a leak. Returned with service gauges and nitrogen then pressured system to 125 psig. Searched for leaked using my leak detector. Unable to locate any solid detections. Doubled checked with leak bubbles and still unable to locate any leaks. Bled off nitrogen and pulled a quick vacuum. Recharged system with refrigerant per weight on data tag. Added leak dye to system. Informed client of leak issue and that we would return in a couple of weeks from now to allow leak dye to circulate and hopefully help us pin point where leak is in the system. Returned to the location and started search for leak dye. Found a little dye underneath evaporator coil. Called factory and checked the units warranty status and part availability. Checked unit charge and pressures looked normal. No need to add any additional refrigerant. Spoke with customer about findings and quoted repair. Customer said he would call us to make repair if approval was given. Unit is currently operational and temperature was at -3*F before leaving.
For additional information on this use click on the PDF: Follett Freezer Service Manual
Kolpak Walk-in Freezer not Getting Below 25*F
Found box temperature above 30*F. Evaporator fans were not running and the liquid line solenoid was buzzing, indicating it was getting power and should be allowing for refrigeration to the evaporator. Went outside to check the condenser and found it running. After further investigation, found the unit’s suction pressure was extremely low. Checked the low pressure control and saw that it was set to cut out at 15 psig, however the suction pressure was below 10 psig. Switched off the unit at the disconnect and noticed oil along the liquid line. Found the copper line had rubbed on the metal framing and had worn a hole creating a leak. Pumped the unit down via the receiver king valve and grabbed the turbo torch. Patched the hole with solder and replaced the liquid line drier. Removed the old low pressure control and replaced it with a new peanut style control. Pressured system and checked for leaks. Pressure held and was unable to locate any leaks. Pulled a vacuum and charged the system with virgin R404a. Turned the disconnect back on to test operation. Continued to charge the system until the sight glass was full and superheat was above 5*F. Pumped down the system once more to be sure the low pressure control was working correctly. Unit turned off at 13 psig. Also insulated a portion of the suction line to prevent sweat from dripping onto electrical box. Went back inside box and found evaporator fans running and box temperature at 18*F and dropping. Confirmed door thermometer was calibrated correctly and set the thermostat to 0*F. Explained my findings to the customer and recommended the evaporator be replaced because the fins were deteriorating. Checked the box temperature once more before leaving and it read 10*F on door thermometer.
To learn more about Kolpak click on the PDF: Kolpak Refrigeration Manual
Troubleshooting a Trauslen Freezer – G12010 Tech Support Needed
Started troubleshooting the Trauslen freezer by opening the evaporator compartment and found the evaporator coil iced up. Turned the unit into defrost and found the heating elements not getting hot. Checked the amperage of the elements and no amps being drawn. Applied direct power to heater relay to close switch and heaters started working, pulling 4.3 amps. Found the controller was not sending power to the heater relay. Went through parameters on the controller and found the evaporator sensor temperature displaying was completely off the chart. Checked the resistance of the sensor and it did not match the temperature / resistance chart in the service manual. Determined the evaporator coil sensor was bad which was causing the unit not to enter the defrost cycle. De-iced the evaporator coil and replaced the evaporator sensor. Placed stubby gauges on service ports and checked the refrigerant charge. Both high and low side pressures running normal. I confirmed the coil sensor temperature in controller to be sure it was reading correctly and it was. Also found some controller parameters had been changed. Spoke with a Traulsen tech support person to run through controller settings and set them back to factory defaults. Tested the freezer’s defrost and operation one last time to confirm everything was working like it should. Watched the box pull down and completed job.
To learn more about the Traulsen freezer click on the PDF here: Traulsen Operation Manual