All commercial air conditioning systems contain a component known by the general name of a metering device. Thermostatic expansion valves are the most common type of metering device. These valves reduce the pressure of the refrigerant as it enters your evaporator coil. This sudden pressure drop lowers the refrigerant temperature drastically, allowing it to absorb more heat.
Expansion valves work by means of restriction. Yet if the amount of restriction grows too great, insufficient amount of refrigerant will enter the evaporator coil. As a result, the efficiency of your system plunges, leading to overworked compressors and an increase in your cost of cooling. Other mechanical problems may also stem from a serious restriction.
As the owner of a commercial property, you should possess at least a basic understanding of thermostatic expansion valve restrictions. This article provides vital information about one of the most common causes of a restricted expansion valve: compressor oil. By increasing your knowledge of this issue, you can better protect your system against inefficiencies and breakdowns.
Caused by an Oil-Clogged Expansion Valve
Oil can accumulate in the expansion valve in one of two primary ways. First, it could be caused by an excess of compressor oil in the system. This issue frequently arises when refilling the oil reservoir of a compressor to compensate for the gradual oil loss that affects a system. An excessive amount of oil will migrate through the system with the refrigerant if too much oil is added.
When this oil reaches the expansion valve, it frequently backs up or deposits, causing restrictions. Even if oil concentrations do not exceed the maximum recommended level, such restrictions may be imposed. In this case, the issue could be the result of a phenomenon known as refrigerant flooding.
Flooding occurs when liquid refrigerant enters the compressor while it is in operation. There, the liquid refrigerant combines with the oil, causing the two to combine into a foamy mass. As this mixture flows into the compressor and then throughout the system, it causes abnormally high oil levels to enter the expansion valve.
Your commercial refrigeration expert can evaluate your beverage display cooler, including a temperature survey, to determine if it is worthwhile to repair the appliance. With the proper replacement components, an older beverage cooler with sentimental value can often be preserved.
Effects of an Oil-Clogged Expansion Valve
Oil clogging has two major negative effects on the expansion valve. First, it limits the quantity of refrigerant that can pass through at any given time. Simply put, the oil deposits coat the walls of the tailpipe and tubing of the valve, thereby reducing their interior dimensions. Consequently, the amount of refrigerant that can pass through the valve is diminished.
The thermal bulb of the expansion valve is also negatively affected by oil clogging. The thermal bulb located in the tailpipe of the expansion valve measures the temperature within the evaporator coil. If the temperature becomes excessively high, the bulb opens the expansion valve, allowing additional refrigerant to enter the evaporator coil.
As oil coats the interior of the tube and the thermal bulb itself, it becomes more difficult for the bulb to accurately register the true temperature. The oil coating tends to insulate the tube, causing the bulb to register a higher temperature than is actually present. As a result, the bulb prematurely opens the expansion valve, allowing excessive refrigerant into the coil.
As the volume of refrigerant in the evaporator coil increases, the exiting refrigerant's superheat decreases. This increases the likelihood that the refrigerant will turn back into a liquid on its way to the compressor, leading to the refrigerant flooding discussed previously. This flooding exacerbates the problem of oil clogging the expansion valve.
Ultimately, expansion valve restrictions reduce the efficiency of your HVAC system, resulting in higher cooling costs. For efficient and effective cooling, the flow of refrigerant through the expansion valve must remain unimpeded.