Introduction
Cold rooms have one main function to keep whatever is in them consistently cooled. Faulty refrigeration equipment in a cold room can lead to inefficient cooling, which could spell trouble for the perishable items stored in it. The smartest thing to prevent this from happening is to maintain the cold room maintenance checklist to ensure it is running as efficiently as possible. An efficient cold room also reduces energy costs.
Regular Maintenance is the key
The simplest way to prevent a breakdown is through regular cold room maintenance schedules and keeping an eye on how things are running, trying to spot potential problems before they develop into full-scale disasters. During a preventive maintenance session, there are several things that can be checked, which could lead to premature failure in the future. It only takes a few minutes if done correctly. Remember to disconnect all power and check with a voltmeter.
Electrical Connectors
Check the electrical connectors to ensure that they are tight with no free play. Loose connectors can cause poor voltage resulting in overheating of the connectors and the motor. Look for discoloration of the terminals and conductor insulation which will indicate overheating. If present, fix it immediately. Check if there are any loose wire strands in the wire terminal or at the contactor. Ensure the wires are dressed properly so as to prevent any shot circuit.
The picture on the left shows the state of wiring where insulation has worn out due to overheating and needs to be redone during maintenance. The picture on the right shows wiring in good condition.
The above Is a thermo graphic image that gives an indication of the amount of heat generated that is not visible to the naked eye? The highlighted portions in the image give an indication of excess heating in the wires and the contactor points. Excess heating of wiring can lead to accidents.
Contactor Inspection
Contact will overheat if they transmit too much current, if they do not close quickly and firmly, or if they open too frequently any of these situations will cause significant deterioration of the contact surface and the shape of the surface. Erratic operation and failure will follow quickly. To check the contacts, just look at them, same minor pitting as well as a black oxide coating is normal, but severe pitting or any melting or deformation of the contact surface is a sure indicator that it needs replacement.
Measuring Voltage and Current
Measure voltage across the three phases R-Y, Y-B and B-R.
The voltage measured across the phases will enable calculation of voltage unbalance. Voltage unbalance decreases motor efficiency by causing extra heating in the motor. Heat also affects equipment life by increasing the operating temperature which decomposes the grease or oil on the bearing and de-rates the motor winding,
Measure the current across the phases. The current should be as per the manufacturers rated current mentioned on the date plate.
Condenser
A dirty Condenser coil will have a reduced ability to transfer heat to the outside air, and this can lead to a less effective cooling system. A dirty condenser coil no longer provides adequate cooling
The condenser plays a vital role in the cooling process by condensing the refrigerant and removing heat from the air, during regular operation, the coil will collect dirt and grime that, over the long run, will diminish the unit’s ability to perform.
Dry or wet cleaning depending upon the requirement should be carried out during preventive maintenance.
Liquid Line Oil sight glass
The sight glass is provided to show if the liquid line is full of liquid or if it has bubbles, which means it is a mixture of liquid and vapour.
A clear glass in a running system generally means a full line of liquid. The moisture indicator on the sight glass shows if the system is dry or if it has moisture content.
Filter- Drier
A filter-drier in a refrigeration or air conditioning system has two essential functions: one,to adsorb system contaminants such as water that can form acids,and two,to provide physical filteration.
Measure the temperature at the inlet and outlet of the filter-drier:if there is a temperature drop at the outlet ,it means a clogged filter drier, which must be replaced.
Compressor checks
Winding insulation and grounding
Overtime, this compressor winding insulation can break down due to high temperatures caused by poor power supply quality or excessive operating temperatures. Check the resistance of the windings to make sure they are within the manufacturers specifications. Check the winding to ground resistance to make sure that the winding insulation is good. If the meter is capable of reading millions of ohms and you can manage to obtain a value for the resistance, check it against the specifications, if it is below the specified value, the winding insulation is beginning to fail
Oil level
If the compressor is equipped with oil sight glass, observe the oil level and see if and how it fluctuates during operation. As long as the oil stays visible within the sight glass, it is acceptable, but check the manufacturer’s specifications to be sure. If it fluctuates beyond the sight glass, it can indicate that large amounts of oil are leaving and may not be returning in a regular manner. If the oil is above the sight glass, it can indicate that the oil charge in the system is excessive.
Outdoor insulations
Proper insulation maintains consistent refrigerant temperatures, allowing the expansion valve and nozzle to work properly insulation on the suction line will ensure cooler refrigerant return gas temperature to the compressor for more cooling. This also keeps the compressor motor cool, if the insulation has detoriated or is torn, replace the insulation.
Cold Room Checks
Door Leaks
Even though the produce may stay frozen in a walk in freezer, the refrigeration machinery may be working much harder than it needs to. This may be because of air infiltration from the door.
When hinges, latches, door locks, gaskets or seals are in poor condition, the door of the unit may not be airtight. Test the door gasket by inserting a paper while closing the door. You should feel some resistance when you pull out the paper.
Panel leakages.
Check for air leakages inside the cold room. They could be because of air infiltration due to leakages in the panels or panel joints. These leakages need to be closed by applying silicon sealant.
Door Heater
If the gasket is freezing and sticking to the door frame, the freezer door heater wire may be burnt out or not strong enough to sufficiently heat up the trim
Door Closer
A roller at the top of the door closer may not be catching the hook enough to close the door. Sometimes a simple adjustment or bending can get the hook back into the position to come into contact with the roller.
Door View Port
Check if the heater connected to the view port is operational. If it is not operational, it can lead to condensation on the door view port, also check for leakage from the view port.
Product stacking
Clear the space around the equipment. Air flow blocked by debris or stacks of stuff can impose a strain on the unit. Causing it to run inefficiently and even overheat. Reduced air flow can also increase power consumption, advice the customer to remove the material stacked in front of the coil to allow proper air.
Liquid flood-back
Flood back can be a serious problem if the refrigeration system is not properly maintained. If an evaporator coil freezes because of lack of maintenance, refrigerant may not evaporate properly. The liquid may then return to the compressor and cause serious damage to it.
- Causes of liquid flood back
- Defrost Heater malfunctioning
In case of a freezer unit, if the heater in the indoor unit is faulty, ice in the indoor unit will not melt thereby leading to ice buildup. /check the heater operation: after defrost, if the ice has melted in the indoor coil, it is an indication the heater is operational.
Improper Defrost interval
Indoor unit defrosting takes place at fixed intervals and for a fixed time. Defrost interval and defrost interval and defrost duration are set at the controller. At times the parameters in the controller are changed by mistake and can lead to ice buildup in the indoor unit. Check the parameters and rectify if needed as per the manufacturers guideline.
Sensor Location
Check if the coil sensor location is in line with manufacturers guidelines, defrost termination, depends on the time of a reaching the desired coil temperature, whichever occurs earlier, if the coil sensor is wrongly located, it would not measure the correct coil temperature leading to improper defrost. This can lead to ice buildup on the indoor unit coil.
Drain pan Heater and Drain Heater
As the ice melts water has to drain out of the freezer. This does not always occur. Trapped water that freezes can cause significant structural damage to a freezer. Ensure that the drain pan heater and the drain heater are operational.
Dirty indoor coil
Periodic cleaning of the indoor unit will lead to proper heat transfer in the indoor unit. If the indoor unit is not cleaned properly it would lead to ice buildup in the indoor unit, leading to liquid flood back to the compressor.
Conclusion.
For a business that depends on the sales of perishables or health products, cold room maintenance services is vital for it to work at its best. Refrigeration breakdowns can be costly, inconvenient and stressful, while regular maintenance cannot guarantee that there never will be a breakdown, it will help to prevent minor issues turning into major disasters.
It is important to engage a highly trained team to ensure that the refrigeration unit is running as it should and is not in danger of imminent breakdown. Regular cold room maintenance cost may seem like an ongoing expense your business could well do without, but being proactive with standard health checks can potentially reduce costs and stress in the long run.
