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” →
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