How to measure SUPERHEAT and SUBCOOLING! HVAC/R Training Video.
How to calculate SUPERHEAT and SUBCOOLING on your air conditioner or refrigerator? R22 R410a R134a R404a

What Is SUPERHEAT & SUBCOOLING? Video Link!
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PRODUCT/TOOL LINKS BELOW
Fieldpiece Real-time Superheat and Subcooling for A/C and Refrigeration
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Yellow Jacket Mechanical Manifold Gauge Set
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Fieldpiece SC260 Clamp Multimeter With True Rms
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Yellow Jacket Service Wratchet Wrench
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Hello everyone & welcome to JMT & todays lesson will be on "How to calculate superheat/subcooling & why is it important?"
(INTRO)
Thank you to everyone tuning into JMT & to begin our lesson, we are going to quickly go over what is superheat and subcooling?
If you havent watched my previous video on "What is superheat/subcooling", Id highly recomened watching that video before continuing on this one.
The numbers or answers won't do you any justice if you don't understand what they represent.
To make it short & simple, superheat is the temperature ABOVE its saturation temp. & subcooling is the temperature BELOW its saturation temp.

Lets begin with calucating SUPERHEAT in real life.
We are going to begin by taking our refrigerant gauges and connecting them to our HVAC system.
To calucate superheat, we are going to focus on the low side of the system.
Once are gauges are connected, we are going to have our pressure readings.
Lets say the low side has a back pressure of 60 PSIG & we are working on a R22 system.
We are going to take out our P/T chart and match 60 PSIG with the corresponding temperature for R22.
60 PSIG for R22 is 34 degrees F.
34 Degrees F. is our saturation temperature.
Next we can take our pipe clamp thermometer and take a temperature reading of the suction line.
In this example, our suction line temperature is 44 degrees F.
Our superheat is the difference between our saturation temperature and our suction line temperature.
The suction line is the pipe leaving the evaportor and entering the compressor.
SUPERHEAT= Suction line temp(44 Degrees F.) - Saturation temp(34 Degreees F.)
SUPERHEAT= 10 Degreees F.
As refrigerant leaves our evaportator and travels down to the compressor, there is an INCREASE in temperature and that differece is our SUPERHEAT.

Next we can begin to calculate SUBCOOLING in real life.
To calucate subcooling, we are going to focus on the high side of the system.
Once our refrigerant guages are connected, we are going to have our pressure readings.
For example, lets say we are reading a 200 PSIG head pressure for an R22 system.
Our next step is to convert that pressure into temperature using a P/T chart to find our saturation temperaure.
200 PSIG for R22 is 102 degrees F.
Next we can take our pipe clamp thermometer and take the temperature reading of the liquid line.
The liquid line is the pipe leaving the condenser and entering our metering device.
In this example, our liquid line temperature is 90 Degrees F.

SUBCOOLING= Liquid line temp(90 Degrees F.) - Saturation temp(102 Degrees F.)
SUBCOOLING= 12 Degrees F.
As refrigerant leaves out condenser, there is DECREASE in temperature and that difference is known as our SUBCOOLING.

Subcooling is normally used so that when the cycling refrigerant reaches the expansion device, its totality is in its liquid form, thus, allowing the valve to work properly.

Having a balalnced superheat and subcooling will insure the system is running eficently thus providing a longer life to your HVAC/R system with less potential break downs.
Measuring supheat & subcooling is another tool you can use for troubleshooting the equipment.
Each reading you get is another clue to finding the true problem.
Rule of thumb for superheat is 8-12 degrees F. & rule of thumb for subcooling is 12-15 degrees F.
These values might vary from one manufacturer to another depending on the type of equipment you are working on.
8-12 Degrees F. for superheat & 12-15 Degrees F. for subcooling is a safe bet and its key know these values.
This is the way you will learn in school and this is the way it was done back in the day.
There are many tools on the market to make these calculations for you that save a lot of time & effort to make your day easier.
In the video description, there will be a list of tools with links to purchase them that will calculate these values for you as well as tools I recommend.

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