Dive into our comprehensive guide designed to clarify your doubts on ‘How to Calculate Superheat.’ This article provides step-by-step instructions, practical examples, and essential tips to accurately measure superheat in various systems, ensuring a clear understanding of this crucial HVAC concept.
It is calculated by obtaining the difference between two temperatures. The one temperature is the outlet temperature of the evaporator, and the second temperature is converted with pressure.
The temperature measurement is done by using the contact type thermometer.
The superheat level indicates the level of the refrigerant present in the evaporator. If the superheat is higher than the average level, the refrigerant is less than the required level in the evaporator.
The following are the reason for the lower refrigerant in the system,
- The technician has charged low refrigerant than an actual level requirement
- the device resists refrigerants like orifices, thermocouples etc.
- The heat load on the evaporator is higher than the average level
How to calculate target superheat?
The target superheat of the air conditioning system can be obtained by the following.
The target can be calculated with wet bulb temperature near to evaporator inlet and the outside dry bulb temperature.
After obtaining both temperatures, the following formula calculates the target superheat.
Target superheat = (3 * Wet bulb temperature – 80 – Dry bulb temperature)/2
The instrument used for the indoor wet bulb temperature measurement is a digital psychrometer. The instrument used for outside dry bulb temperature measurement is the digital temperature measuring instrument.
The dry bulb temperature remains same in the most case. The target can vary with the change in the wet bulb temperature. At the time of refrigerant charging, the wet bulb temperature is changing.
To obtain proper refrigerant charging, the target superheat is maintained near the actual superheats.
Lets’s understand target superheat with the following calculation,
Suppose, Wet bulb temperature = 64 ° F
Dry bulb temperature = 86 ° F
An equation to calculate target superheat
Target superheat = (3 * Wet bulb temperature – 80 – Dry bulb temperature)/2
Target superheat = (3 * 64 – 80 – 86)/2
Target superheat = (192 – 80 – 86)/2
Target superheat = (26)/2
Target superheat = 13° F
How to calculate superheat in a freezer?
The calculation of the superheat in the freezer is similar to the refrigerator.
The superheat in the freezer is the difference between saturation temperature and freezer outlet temperature.
A pressure-temperature chart obtains the saturation temperature. The evaporator’s outlet temperature is measured with a digital thermocouple. Take the difference between both temperatures.
The answer to the difference is the value of the superheat for the freezer.
How to calculate superheat in a chiller?
The superheat of the chiller can be calculated with the following steps
- Identify the suction line for measurement of pressure.
- To obtain the pressure of the suction line, Fix the pressure gauge near the condenser coil.
- Attach the thermocouple at the outlet of the evaporator coil. The service port is provided for the thermocouple.
- Note the reading of pressure after the system achieves steady flow.
- Note the reading of the temperature at the same time.
- Convert the reading of pressure into the corresponding temperature using a pressure-temperature saturation chart.
- Take the difference between the corresponding temperature and the evaporator’s outlet temperature reading.
- The answer to the difference is the value of the superheat.
This process of calculating the superheat remains the same for refrigeration and another similar system.
How to calculate superheat on a heat pump?
The heat pump is functioning opposite to the refrigerant. The superheat can be calculated with the following steps.
- Identify the suction line in the system as the suction line always has more cross-sectional area than another line
- To measure the suction line pressure in the system, install the pressure gauge neat to the condenser coil.
- Attach the temperature measuring device to the outlet of the evaporator coil. The service port is provided for the measuring device.
- Note the reading of pressure after the system achieves steady flow.
- Note the reading of the temperature at the same time.
- Convert the reading of pressure into the corresponding temperature using a pressure-temperature saturation chart.
- Take the difference between the corresponding temperature and the evaporator’s outlet temperature reading.
- The answer to the difference is the value of the superheat.
This process of calculating the superheat remains the same for refrigeration and another similar system.
For example :
If the low side pressure reading of the gauge is 120 PSIG.
The corresponding conversion of the pressure into temperature with a pressure-temperature chart. The value of temperature is 42 ° F.
The temperature measurement at the outlet of the evaporator is 50 ° F.
Now, take a difference between the corresponding temperature and the saturation temperature at the evaporator.
Superheat = Corresponding temperature at the low side – Temperature measured at the evaporator
Superheat = 50 – 42
Superheat = 8 ° F
So, With these simple steps, we can calculate the superheat of the system. The superheat in this example is 8 ° F.
How to calculate evaporator superheat?
The evaporator superheat calculation remains the same as in the refrigerator.
It is a difference between the measured evaporator outlet temperature and the corresponding saturation temperature.
The vapour line temperature is measured by identifying the large cross-section of the suction line. The temperature measurement is not the same in the refrigeration and the air conditioning.
The temperature and the low side pressure of the system are measured after achieving the steady flow condition. The measurement of the system will change if measured immediately after starting.
How to calculate superheated steam temperature?
The superheated steam is generally generated in the higher pressure boiler.
The degree of superheat is obtained by using either a steam table or Mollier diagram. The energy is required to raise the temperature of the saturated steam.
The temperature of the superheated steam is always greater than 100 ° C at the standard pressure condition.
How to calculate superheat R22?
The superheat in the system with R22 is calculated by the following equation
Total Superheat with R22 = Corresponding temperature at suction pressure – Temperature measured at a suction line or outlet of the evaporator
The superheat is nearby 10 ° F in most cases. If the superheat is high, then it causes an increase in the heat of compression. This increase in temperature can affect the performance of the compressor. It is required to maintain and monitor the superheat continuously on the system.
How to calculate superheat 404a?
There are two types of superheat in the refrigeration system.
Total Superheat with R404a = Corresponding temperature at suction pressure – Temperature measured at a suction line or outlet of the evaporator
The refrigeration system can be analyzed with evaporator superheat, and the compressor superheat. The evaporator superheat always less than the compressor superheat. The compressor superheat also called the total superheat.
To obtain total superheat for R404, one has to measure temperature at the inlet of temperature with a temperature measuring device. Also, measure the pressure at that location.
The compressor superheat is the sum of the evaporator superheat and vapour line or suction line superheat.
The range of low side pressure for the R404 is nearby 20 psig in the usual case, and the inlet temperature of the compressor is 25° C approx.
For the safe operation of a system with R404 refrigerant, the recommended superheat should be in the range of 20° C to 30° C. If the superheat with R404 is more than the above value, then it can deteriorate the performance of the compressor or system.
The thermal expansion valve is the device used to control the superheat in the refrigeration system. The expansion of TXV can control the evaporator superheat. It can reduce the total superheat at the desired level for efficient working of the system.
How to calculate superheat 410a?
The superheat in the system with R410a is calculated by the following equation
Total Superheat with R410a = Corresponding temperature at suction pressure – Temperature measured at a suction line or outlet of the evaporator
To obtain total superheat for R410a, one must measure temperature at the inlet of temperature with a temperature measuring device. Also, measure the pressure at that location.
I am Deepak Kumar Jani, Pursuing PhD in Mechanical- Renewable energy. I have five years of teaching and two-year research experience. My subject area of interest are thermal engineering, automobile engineering, Mechanical measurement, Engineering Drawing, Fluid mechanics etc. I have filed a patent on “Hybridization of green energy for power production”. I have published 17 research papers and two books.
I am glad to be part of Lambdageeks and would like to present some of my expertise in a simplistic way with the readers.
Apart from academics and research, I like wandering in nature, capturing nature and creating awareness about nature among people.
Also refer my You-tube Channel regarding “Invitation from Nature”
Hi Fellow Reader,
We're a small team at Techiescience, working hard among the big players. If you like what you see, please share our content on social media. Your support makes a big difference. Thank you!