What Is Superheat and Subcooling In HVAC?

Superheat and Subcooling are technical readings in an HVAC that measure the Freon (refrigerant) reading. Superheat measures the Freon boiling point in gas form while subcooling measures the Freon in liquid form below the evaporation level.

To calculate superheat and subcooling measurements, a specific Mathematical chart is used, and the process is mostly done by an HVAC technician.  This is usually done when the technician is diagnosing your HVAC for overheating or flooding of the Freon.

You can still learn how to calculate these measurements on your own as part of learning how your air conditioning unit works.

What is Superheat HVAC?

Superheat is a temperature value measured of vapour (steam or refrigerant) above boiling point. The reading will show the amount of refrigerant going through the evaporator and whether it is sufficient.

When the reading is too high, it means that the refrigerant is not sufficient, so the system will be inefficient. On the other hand, when the reading is too low, it means that too much liquid is going to the evaporator. This can damage the compressor as the liquid might cause flooding.

How to Measure Superheat

The first step here is to measure the compressor suction pressure.  With the suction pressure measurement, you can follow the chart to see the corresponding saturation temperature.

NB: Allow the HVAC to run for 15 to 20 minutes so that you can get accurate results. When taking the temperature of the Freon, use a temperature probe.

What is Subcooling

This is when the refrigerant is cooled at a temperature lower than the minimum temperature required. Many reasons can cause subcooling to occur, including underfeeding, overcharging, restricted meter device, or faulty head pressure control. The effect of subcooling is reduced system efficiency and overcharging of the system.

Checking the Subcooling

You will need a temperature probe and gauge to take the measurements.

For accuracy, take measurements near the condenser coil of the liquid line.

Always use the manufacturer’s readings as the guide.

Benefits of Superheat and Subcooling Measurements

Superheat and subcooling are important measurements to determine the performance and efficiency of your HVAC system. It is important to check these measurements during the routine servicing by your technician.

Here are some benefits of regular checking:

Improved Efficiency

Superheat, and subcooling readings are important to help improve the efficiency of your system. Inefficiency is usually caused by inappropriate refrigerant levels, so regular checking might help you determine the right step to take.

If your HVAC has become inefficient, talk to your technician about checking the refrigerant levels, and you will notice a huge improvement.

Easy and Fast Diagnosis

Repairing your HVAC can take a lot of time when trying to pinpoint the issue. Most technicians are not aware of the exact problem just by checking your air conditioning system. They need to check the superheat and subcooling readings to point out the problem accurately.

Evaporator and compressor issues have similar characteristics, so it might be confusing to know the exact issue without checking the measurements.

Avoid Overheating

Overheating can damage your entire system, and it is usually caused by low refrigerant levels. When refrigerant levels are low, the compressor starts overheating, and the first thing that you will notice is efficiency.

Overheating can be quite detrimental, as it can damage other parts of your HVAC, leading to costly repairs.

What causes High Superheat and Low Subcooling

Liquid Line Restriction

The refrigerant passes through a liquid line in the HVAC system. The normal flow of the liquid means that you will be able to maintain optimum levels of the refrigerant. However, if there is a restriction or a blockage that restricts the flow, problems will be inevitable.

Malfunctioning Metering System

The metering system of the HVAC is posed to control the amount of refrigerant passing through the liquid line. If there is a fault and proper control is not happening, you are likely to experience high or low refrigerant levels. This will lead to high superheat or low subcooling.

Excessive air in the Evaporator Coils

The amount of air flowing in the evaporator coils should be regulated to keep the refrigerant levels optimal. Unfortunately, sometimes there is excessive air in the evaporator coils, and this causes the refrigerant to evaporate.

Limited Airflow in the Evaporator

Apart from excessive air in the evaporator coils, limited air can also be a problem. The air levels should be regulated so that the refrigerant remains at the right level.

The Role of Freon in your HVAC

The refrigerant (Freon) is an important part of your HVAC system. Therefore it is crucial to maintain the right levels for the efficiency of your system. Freon is a cooling agent, responsible for keeping your home cool during the summer months.

If you are not a technician, it’s not advisable to attempt to change Freon on your own. This is because it can lead to more damage to your unit.

Here are some benefits of refrigerant:

Protects the HVAC from Overheating

Freon is known as a cooling agent. It is responsible for preventing overheating in the HVAC unit. Without proper levels of Freon, your HVAC unit will undoubtedly overheat, leading to damage.

During the routine servicing, you can check your Freon levels. The technician can drain the fluid and replace it when necessary. Keeping clean fluid and maintaining optimum levels is important for the efficient performance of your HVAC system.

Better Performance and Efficiency

For better performance and efficiency, you need to have enough Freon in your HVAC. It will prevent your HVAC from overworking, giving you the level of efficiency you desire. With clean Freon and the right levels, it is possible to achieve optimal efficiency.

Are Superheat and Subcooling Important?

Superheat and Subcooling are important concepts in HVAC performance. However, if you don’t have the technical knowledge on how to calculate the measurements, it might be stressful to try to figure it out on your own.

Fortunately, consulting a technician regularly will help you monitor your superheat and subcooling. Experts admit that it is impossible to achieve optimum measurements, but you can still keep your HVAC in good condition.

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