Heating, Ventilation, and Air Conditioning (HVAC) systems are necessary to ensure that our internal surroundings remain in ideal comfort conditions.
For these systems to function at their optimum, it is essential to look at several conceptual definitions relating to the field.
The following article will explain the main terms related to HVAC and their importance and relevance to the overall efficiency of the system.
Refrigerant Pressure
Condensing Pressure
The high-side pressure can also be referred to as the condensing pressure, head pressure, or discharge pressure, and represents the pressure under which the refrigerant turns from gas to liquid.
This pressure is a must for the heat exchange in the condenser system and is one of the main factors in the selection of a turbine system.
Ideal condensing pressure should be maintained for heat rejection and proper function of the system.
Evaporating Pressure
The low-side pressure, suction pressure, or back pressure also known as the evaporating pressure, is the pressure that is exerted at the evaporator to transform the refrigerant from the liquid phase to the vapor phase.
This pressure should be regulated to allow maximum draw of heat from the indoor air, a factor that strengthens the cooling ability of the system.
Useful HVAC Definitions
Superheat (S/H)
Superheat is the measure of the temperature of a refrigerant vapor above the saturation temperature, which occurs at a specified pressure range.
It is normally measured at the evaporator outlet or the suction line and is the arithmetic difference between the actual gas temperature and saturation temperature.
Superheat is used to prevent the liquid refrigerant from getting back to the compressor, where it might cause some serious harm, and also to ensure that the refrigerant extracts heat as it cools the system.
Subcooling (S/C)
Subcooling may be defined as the temperature drop between the saturation temperature and the actual temperature of the liquid refrigerant.
Subcooling varies with the type of refrigeration system in use, but a guide is that the refrigerant should be about 10 degrees below the minimum boiling temperature.
Subcooling enables the refrigerant to stay in the liquid phase and not to start boiling before it achieves its desired location, hence enhancing the efficiency of the system.
What is Vapor Saturation Temperature (VSAT)?
Vapor Saturation Temperature (VSAT) refers to the temperature of the refrigerant vapor at its saturation level, that is, at the phase where the refrigerant is both liquid and vapor.
This is so during the phase change in the evaporator, where the refrigerant undergoes boiling, or in the condenser, where it undergoes condensation.
It is important to note that VSAT is an effective measure of the temperature of the evaporator coil.
A temperature that goes below 32ºF affects the condensation systems, and this reduces efficiency or creates operational problems.
Suction Line Temperature (SLT)
Suction Line Temperature (SLT) is the temperature of the refrigerant vapor at the inlet section of the suction line that leads to the compressor.
SLT is a gas, having lower pressure as well as temperature than the liquid phase. SLT management plays an important role in system optimization and its performance, so its control is crucial.
The correct range of SLT depends on the type of refrigerant and the cooling coefficient that is preferred for the machine.
Temperature Differential (ΔºT)
Temperature differential (ΔºT) measures the difference between the air temperature from the supply vents (cooled air) and the return grille (air needing cooling).
Ideally, the supply air should be 15-20°F cooler than the return air.
ΔºT indicates how much heat the AC removes from the air. Both excessively high and low ΔºT values can indicate system inefficiencies.
Additional Key Concepts
Refrigerant Charge
The term charge usually describes the quantity of refrigerant present in the air conditioning system.
Refrigerant gas is critical in the operation of the appliance, and its levels need to be correct.
When the charge is over or under the optimum, then the system becomes inefficient, and a lot of power is wasted, and at times, the power can even be damaged.
Heat Transfer Efficiency
The heat transfer coefficient is the effectiveness of the system in transferring heat with the refrigerant to the air or water surrounding the system.
Proper heat exchange helps enhance cooling and heating and, thus, lowers energy and costs.
Compressor Functionality
The compressor is central to the activities of the HVAC system Since it pumps refrigerant and ensures its circulation at the right pressures.
Compressor health is a critical aspect of the whole system’s health. Proactive maintenance checks and monitoring of the compressor can help avoid failure and increase the lifetime of the equipment.
Airflow Management
Ventilation control is aimed at ensuring that the air flows in the right direction within the HVAC system.
This involves proper cleaning of the filters, ducts, and vents and guaranteeing there is proper airflow in and out of the system.
Proper airflow management enhances the IAQ and systems performance.
Thermostatic Expansion Valve (TXV)
The Thermostatic Expansion Valve (TXV) controls the amount of refrigerant that passes through the evaporator.
It controls the rate of the gas that is circulated so as to regulate the superheat and, at the same time, avoid passing liquid refrigerant to the compressor.
A well-working TXV increases the efficiency of the system and its life span.
Seasonal Energy Efficiency Ratio (SEER)
The Seasonal Energy Efficiency Ratio (SEER) is used to determine the efficiency of the specified heating and air conditioning unit during the cooling season.
Systems with higher SEER ratings are generally more efficient and, therefore, cost less to operate.
Knowledge of SEER ratings assists in the procurement of energy-efficient HVAC systems.
Maintenance and Monitoring
The proper functioning of the HVAC systems should be maintained appropriately with the help of proper checkups and monitoring of the system.
This involves some checks such as the level of refrigerant, examination, and cleaning of components, and control of the system settings.
Routine maintenance will be cheaper than repairing the system when it has broken down and help in increasing the lifespan of the system.
Conclusion
It is important for those who design, specify, install, operate, and maintain HVAC equipment, systems, and installations to be familiar with these important definitions and concepts.
Understanding concepts such as refrigerant pressure, superheat, subcooling, and vapor saturation temperature, among others, makes homeowners and technicians make their HVAC systems efficient and gain the desired comfort as well as save on energy.
For further details on HVAC terms and systems maintenance, do not hesitate to call Finest Heating & Air; we are your HVAC solutions provider.
Let our professionals assist you in getting the most out of your heating and cooling systems.
