Measuring Superheat

Superheat is the temperature of a gas above its boiling point.  As you should already know, measuring superheat is one of the basic skills necessary for any service technician working on modern air conditioning equipment.

In this lesson, you will learn how to properly measure and adjust superheat.  

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HVAC Industry Standard:

  
Proper adjustment of superheat is essential to gain full efficiency of an Air Conditioning unit.  

The following link gives a general overview of industry standards:

click here to view standards

                                                                                                            

Background Information:

Proper superheat adjustment is necessary to ensure that proper energy efficiency is obtained.  

The process of adjusting superheat involved removing or adding refrigerant to a system until the correct superheat is obtained.  

Improper superheat is not only detrimental to system efficiency, but can also lead to compressor damage.

Click the following link to read more about compressor damage caused by slugging:

http://www.danfoss.com/NR/rdonlyres/CA85447B-C096-459F-B861-3BFD680DBC28/0/FSN008web.pdf 

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Lesson:  what you will need:                                                       

• Identify the Air Conditioning unit you will be using.

  This will be same unit you were using in the previous lesson.  If you do not have one assigned, please send me a message and one will be assigned to you.

  Next:

  

  Install your gauge set onto the unit.  If you are having trouble, review the lesson on gauge installation. 

  Now:

  Install your electronic thermometer probe to the suction line near the service port:

  

   Now:

  Record the suction pressure and the suction line temperature. 

  If you don't read and record them accurately, your calculations will be incorrect. 

   Refer to your Pressure/Temperature Chart.

  
  Of course, you will refer to a full size chart:                                                                              

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  Using your chart and the pressure found on the gauge, find the corresponding evaporator temperature.  Again, you should have learned this in a previous lesson.  If you are having trouble please refer to the following video:

   The math is simple:

  SH = SLT - ET

  This means.....Superheat is equal to Suction Line Temperature Minus Evaporator Temperature.
  
  

  Suction Line Temperature...Is very easy to read.  It is displayed directly on your digital thermometer.

  Evaporator Temperature....Is a little more difficult.  You must read the pressure and convert to a temperature using your P/T (Pressure/Temperature) chart.

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  What now????

  We are trying to get our system to have a 10 degree Fahrenheit superheat. 

   

  What did you get??????

  If your superheat was too high then you need to add refrigerant. 

  If your superheat was too low then you need to remove refrigerant. 

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  Making adjustments.

  *Please remember that when making adjustments in the refrigerant charge, it takes several minutes for the temperatures and pressures to stabilize*

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  Conclusion:

  You should now be able to read and adjust superheat to obtain optimum system performance.  In the next lesson we will explore the different superheat charging charts that each manufacturer produces.  

  This lesson simply asked you to get to 10 degrees because that is a safe superheat which will not damage the AC units found in the Lab.

   

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  Grading Rubric

  Lab Report : Finding Evaporator Superheat

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  Teacher Name: Scot Martin
  
  
  Student Name:     ________________________________________
  
  

  CATEGORY	4	3	2	1
  Safety	Lab is carried out with full attention to relevant safety procedures. The set-up, experiment, and tear-down posed no safety threat to any individual.	Lab is generally carried out with attention to relevant safety procedures. The set-up, experiment, and tear-down posed no safety threat to any individual, but one safety procedure needs to be reviewed.	Lab is carried out with some attention to relevant safety procedures. The set-up, experiment, and tear-down posed no safety threat to any individual, but several safety procedures need to be reviewed.	Safety procedures were ignored and/or some aspect of the experiment posed a threat to the safety of the student or others.
  Procedures	Procedures are listed in clear steps. Each step is numbered and is a complete sentence.	Procedures are listed in a logical order, but steps are not numbered and/or are not in complete sentences.	Procedures are listed but are not in a logical order or are difficult to follow.	Procedures do not accurately list the steps of the experiment.
  Calculations	All calculations are shown and the results are correct and labeled appropriately.	Some calculations are shown and the results are correct and labeled appropriately.	Some calculations are shown and the results labeled appropriately.	No calculations are shown OR results are inaccurate or mislabeled.
  Conclusion	Conclusion includes whether the findings supported the hypothesis, possible sources of error, and what was learned from the experiment.	Conclusion includes whether the findings supported the hypothesis and what was learned from the experiment.	Conclusion includes what was learned from the experiment.	No conclusion was included in the report OR shows little effort and reflection.