What is low superheat high subcooling of your AC and does this condition reduce the cooling capacity? If you want to maintain the efficiency and longevity of your cooling device then I invite you to check this article where I will tell you how to fix this issue.
Let’s get started!
An Insight into Low Superheat High Subcooling: Meaning and Major Causes
Let’s briefly go over the basic essentials you need to know about low superheat high subcooling:
- Low superheat: It takes place when there is too much refrigerant in the evaporator, and it cannot evaporate quickly enough.
- High subcooling: This happens when there is an excess of liquid refrigerant in the condenser, often due to an obstruction or overcharge. It results in higher-than-saturated-liquid temperatures in the liquid line.
This may be due to high refrigerant charge, limited airflow in the condenser coil, and impaired metering device. In order to fix this, you need to remove liquid so that both of the problems can get back to their original state.
But there’s a lot more you should know in order to optimize your system. Continue reading below to find out additional causes of this issue and their easy fixes! Let’s dive deep into this informative guide!
4 Reasons Why Your HVAC Has Low Superheat
Low superheat and high subcooling are critical indicators of an imbalance in the coils. This imbalance can be attributed due to either not enough heat or too much refrigerant.
Several issues can lead to low superheat in air conditioning systems, including:
Excess refrigerant in the AC system
Reduce refrigerant levels as needed
Evaporator airflow restriction
Replace air filters and the blower wheel
Metering device overfeeding
Insulate the TXV sensing valve properly
Insufficient heat load on coil
Clean both filters and the coil
Oversized AC system
Consider opting for a properly sized AC unit
Now that we have gone through the table, let’s explore each problem in detail!
1. Excessive Refrigerant in the AC System
Excessive refrigerant can lead to a problem – low superheat absorption in the evaporator coil. This affects your air conditioning system performance.
- Low superheat is typically absorbed during the refrigerant evaporation process.
- Too much liquid refrigerant can damage it, and it’s meant for squeezing gas.
- The presence of excessive refrigerant may be attributed to a malfunctioning TXV valve
2. Limited Air Flow to the Evaporator Coils
When insufficient airflow reaches the evaporator coil, it absorbs less heat, potentially causing low superheat. This airflow restriction can be caused by:
- Dirty Coil: A dirty coil or dust on the coil’s surface significantly diminishes its available area for heat exchange. Consequently, there is a reduced interaction between the coil and the incoming air.
- Clogged Air Filter: An air filter that is obstructed also hinders the airflow towards the evaporator coil. Since the air must go through the sieve before it gets to the dirty coils, any blockage or reduced airflow space within the filter restricts the amount of air that can reach the coil. As a result, heat absorption as done by the evaporator becomes limited.
Thus, by adhering to these practices, the issue of low superheat can be effectively rectified.
3. Regulation By the Metering Device
When metering tool insulation is insufficient, it allows the refrigerant to flood the evaporator coil, causing trouble.
4. Oversized AC Unit System
When dealing with an oversized AC system, there will not be enough heat load for the vaporization of the refrigerant at the evaporator coils. This situation can result in the occurrence of low superheat.
3 Reasons Why Your HVAC Has High Subcool
Subcool measures how much of the refrigerant surpluses to the condenser unit, resulting in a high subcool. This can be due to several underlying problems
Remove excess refrigerant
Small/ malfunctioning metering device
Callibirate metering devices
Liquid pipe Blockage like a wavy line
Ensure lines don't have any blockage
The causes of high subcooling can be summarized in the following section:
1. Overcharging the System Will Cause a High Subcool
Normal subcooling refers to the expected level of subcooling in a refrigeration or cooling system. Excess refrigerant in the system hinders the proper condensation and evaporation processes. As a result, the condenser unit experiences a backup.
2. Faulty Metering Device
Device problems, such as Metering device faults being undersized, head pressure control system glitches, or issues with the thermostatic expansion valve can lead to elevated subcooling.
3. Restriction of the Liquid Line
Water line blockage disrupts refrigerant systems, reducing cooling efficiency and increasing energy use.
For a better understanding, I would recommend you check out the following helpful video.
Low or High Superheat on an AC: How To Know Which One Plagues Your System
Discovering superheat’s secrets involves a straightforward method: evaluating heat charge and refrigerant levels.
For precise readings, you will need to check:
- Specialized pipe thermometer;
- Temperature-to-pressure conversion chart.
In a standard system, at the evaporator, it’s about 10°F, and a warmer 20°F to 25°F in proximity to the compressor. In the HVAC system, if the temperature difference at the evaporator is less than 10°F and <20°F overall, then superheat is considered low.
For nonoptimized system performance with high superheat, it’s high when readings exceed 10°F at the evaporator and are also greater than 10°F near the compressor.
- To check the suction line temperature, it’s essential to use a thermometer to employ a reliable method for diagnostics.
- Measure the suction pressure.
- Applying the temperature-pressure chart for conversion.
- Calculate the temperature difference.
Why Does My System Have Low Superheat with High Subcool
Now that you understand what leads to low superheat and high subcool, let’s see when they happen together. This condition results exclusively from the excessive refrigerant in the AC system, leading to both low superheat and high subcooling.
Low Superheat or High Subcooling: Which One Is It?
For a thorough subcooling assessment, begin by measuring the liquid line temperature in proximity to the condenser. Subsequently, employ the pressure-temperature chart for precise conversion of top pressure into temperature
An Insight Into Service Standards
These standards may outline best practices for diagnosing and correcting issues related to low superheat or high subcooling. Technicians are trained to follow these standards to maintain system efficiency and safety.
What can cause low superheat?
Low superheat can be caused by low heat load, high levels of refrigerant charge, and low evaporator coil airflow.
What if my subcooling is too high?
If your subcooling is too high, then this means there may be an overcharge or a malfunctioning metering device. In order to fix this, you need to remove excess refrigerant from the system and replace the metering device.
How do you fix high subcooling?
You can fix high subcooling by getting rid of the extra liquid refrigerant charge from the system. Alternatively, you can also check for any blockage in the liquid line and cater it for proper flow. Lastly, you may need to replace your metering device.
The final say is that low superheat high subcooling can harm system optimization. Low superheat and high subcooling occur mainly when the refrigerant charge is high or the faulty metering TVX or AEV device.
You can overcome the issue by removing the excess refrigerant charge, repairing the metering device, and cleaning up the condenser coil to avoid any restrictions in the line. Also, consider cleaning dirty filters and motors, to allow for increased airflow into the coil.