This issue can occur, especially when we replace a compressor and only focus on the motor’s electrical power, without verifying its cooling capacity.
Let’s take a look at four common cases that may arise:
Case 1: Capillary tube longer than necessary When we install a capillary tube with a length greater than required by the system, we achieve greater control over the refrigerant mass flow. This means there will be more restriction to the refrigerant passing through the capillary tube. The longer the tube, the greater the restriction. As a result, more refrigerant will remain on the condenser side, primarily affecting the system’s high pressure.
Although there may also be variations in low pressure, the main impact will be on high pressure. This, in turn, affects the compressor’s power consumption, as an increase in high pressure means the compressor has to work harder.
Case 2: Capillary tube shorter than necessary In this case, when the capillary tube is shorter than it should be, we have less control and less restriction of the gas flow. This allows the gas to leave the condenser more easily and reach the evaporator. As a result, the high pressure drops significantly.
Although the low pressure is also affected, as more refrigerant reaches the evaporator, the main impact will be on the high pressure. If the high pressure drops too low, condensation in the condenser may not occur correctly, altering the refrigeration cycle and affecting the system’s performance.
Case 3: Capillary tube with a larger diameter than necessary When we keep the length of the capillary tube fixed and increase the diameter beyond what is recommended, the system also experiences issues. In this case, the greatest impact is seen in the low pressure. Although high pressure is also affected, the low pressure loses stability the most.
If the diameter is excessively large, there will not be enough restriction in the capillary tube, causing the low pressure to drop drastically. This can also cause a noticeable reduction in high pressure, affecting the compressor’s power consumption.
Case 4: Capillary tube with a smaller diameter than necessary Finally, when we install a capillary tube with a diameter smaller than required, the main impact is again on low pressure. Although high pressure is also affected, the most noticeable change will be the reduction in low pressure.
A smaller diameter increases the high pressure, which immediately increases the compressor’s power consumption. This can lead to inefficient operation and higher energy consumption.
Summary and recommendations When replacing a compressor, it is essential to verify its cooling capacity, expressed in BTU/hour, kilocalories/hour, or watts. The capillary tube we install must match the new compressor’s cooling capacity and operating temperature, not just the motor’s power.
