Your suction pressure is likely high because the evaporator is being overfed with refrigerant.
Here's a breakdown of the common causes for high suction pressure:
Potential Causes of High Suction Pressure
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Overcharging the System: The most frequent cause. When you add too much refrigerant to the system, it results in the evaporator being overfed. This means more refrigerant is entering the evaporator than it can effectively handle, leading to a higher pressure on the suction side.
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Oversized TXV/EXV (Thermal Expansion Valve/Electronic Expansion Valve): If the TXV or EXV is too large for the system's cooling load, it will allow too much refrigerant into the evaporator, also resulting in overfeeding and higher suction pressure.
How These Issues Increase Suction Pressure
Both of these issues ultimately cause an excess of refrigerant circulating in the low-pressure side (suction side) of the system. Because more liquid refrigerant is present in the evaporator, the pressure rises.
Troubleshooting High Suction Pressure
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Verify Refrigerant Charge: Use gauges and temperature readings to accurately assess the refrigerant charge in the system. Compare readings to the manufacturer's specifications. If overcharged, carefully remove refrigerant until the pressures are within the correct range.
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Inspect Expansion Valve: Check the size and operation of the TXV or EXV. Make sure it is properly sized for the system's cooling capacity. If it is oversized or malfunctioning, replace it with the correct component.
By addressing these potential causes, you can diagnose and correct high suction pressure in your system.
