Target Superheat Chart + Calculator, Formula, R22, 410A Examples

When diagnosing air conditioners, you will probably need to consult the target superheat chart. Here we are going to take a structured approach to how to calculate and use target superheat. Namely, we are going to go through these 4 very useful resources for target superheat:

• Target Superheat Formula. In order to calculate target superheat, we use an equation that includes wet bulb (WB) temperature and dry bulb (DB) temperature.
• Target Superheat Calculator. Using the formula, we have designed a calculator that determines target superheat. You just input both temperatures (WB and DB), and you get the target superheat.
• Target Superheat Chart. With the formula and calculator, we can calculate what superheat should be on 80°F day, 90°F day, 100°F day, and so on. The superheat chart includes target AC superheat for 55°F to 128°F outdoor temperature (DB temperature) and for 50°F to 76°F indoor evaporator temperature (WB temperature). You will find the chart that summarizes all total superheats further on. Note: Due to popular demand, we have also created the Target Superheat Chart PDF (in .pdf form) that you can freely download, print, and take with you on the job (for any kind of refrigerant – R-22, R-410A, R-134A, you name it).
• 2 Target Superheat Examples For R-22 and R-410A refrigerants. To illustrate how to use target superheat, we will look into a 3-ton 16 SEER R-22 example and a 5-ton 14 SEER R-410A example.

Alright, let’s first explain why we need target superheat:

Target superheat is the total superheat an air conditioner should have. We usually measure total superheat using this method; then we have to compare the measured superheat with the target superheat. Target superheat depends on the outdoor temperature (and indoor evaporator coil temperature):

• At higher outdoor temperatures, we will have lower total superheat. Example: At 66°F indoor WB temperature and 95°F outdoor temperature, our target superheat is 11.5°F.
• At lower outdoor temperatures, we will have higher total superheat. Example: At 66°F indoor WB temperature and 80°F outdoor temperature, our target superheat is 19.0°F.

When we have both measured total superheat and target superheat (usually from the chart below), we compare them, and can have one of these 3 scenarios:

• Total superheat is higher than target superheat (high superheat situation). In this case, we usually need to add refrigerant (R-22, R-410A, R-134A, or whichever refrigerant the AC uses).
• Total superheat is lower than target superheat (low superheat situation). In this case, we usually need to remove the refrigerant.
• Target superheat is the same as target superheat with about +/- 2°F accuracy (normal superheat). This is what we want to get; in this case, the AC charge is adequate.

Let’s start by checking the target superheat formula, and then we will proceed with the calculator that calculates target superheat automatically, and the target superheat chart. At the end, you will find the R-22 and R-410A examples that best illustrate how to find and use target superheat in practice:

Target Superheat Formula

It is important to understand that target superheat depends on only 2 temperatures:

1. Dry Bulb Temperature. This is the outdoor temperature measured with a thermometer. We also refer to it as outdoor ambient temperature or OP temp for short.
2. Wet Bulb Temperature. To measure WB temp (indoors), we use a temperature sensor covered by a wet cloth and place it on the return side of the evaporator coil. It’s basically a measure of the lowest temperature that something can be cooled to through the evaporation of water (hence “wet” bulb temperature).

Note: Target superheat does not depend on the type of refrigerant. As we will see in the R-22 and R-410A examples at the end, target superheat for a system using R-22 and the target superheat for a system using R-410A (or any other refrigerant) are the same. Only the DB and WB temperatures determine the target superheat.

Here is the formula we use to calculate superheat:

Target Superheat = (3 × T_{Wet Bulb} – 80°F – T_{Dry Bulb}) / 2

It’s not all that simple, but it’s also not all that complex. Let’s look at one example to illustrate how to use the target superheat formula.

Example: What is the target superheat for an R-134A refrigerant at 90°F and at 70°F indoor wet bulb temperature? We just insert both temperatures in the equation like this:

Target Superheat (R-134A) = (3 × 70°F – 80°F – 90°F) / 2 = 20.0°F

As we can see, the target superheat here is 20.0°F. You can check the target superheat chart below and see that you get 20.0°F there as well.

We calculated this example manually. However, it’s just easier to use this superheat calculator that does the same calculation for us:

Target Superheat Calculator

Here’s how you can use this calculator. Let’s take the previous example with R-134A refrigerant. Slide the 1st slider to ’70’ since our indoor WB temperature is 70°F, and slide the 2nd slider to ’90’ since we have a 90°F outdoor DB temperature. Here is the result:

Our target superheat is 20.0°F, just as we have calculated manually.

Now, there are many different WB and DB temperature combinations. You can play around with the sliders in the calculator to calculate them. Most often, however, we use this simple target superheat chart with pre-calculated target superheat temperatures:

Target Superheat Chart

This superheat chart is quite long and wide; you can scroll left and down to see all of it:

As you can see, we can now tell how much total superheat should be on a 100°F day, for example. This depends on the indoor wet bulb temperature like this:

• At 60°F indoor WB temperature (on 100°F day), our target superheat is 0.0°F.
• At 62°F indoor WB temperature (on 100°F day), our target superheat is 3.0°F.
• At 64°F indoor WB temperature (on 100°F day), our target superheat is 6.0°F.
• At 66°F indoor WB temperature (on 100°F day), our target superheat is 9.0°F.
• At 68°F indoor WB temperature (on 100°F day), our target superheat is 12.0°F.
• At 70°F indoor WB temperature (on 100°F day), our target superheat is 15.0°F.
• At 72°F indoor WB temperature (on 100°F day), our target superheat is 18.0°F.
• At 74°F indoor WB temperature (on 100°F day), our target superheat is 21°F.
• At 76°F indoor WB temperature (on 100°F day), our target superheat is 24°F.

Realistically, you are likely to measure indoor WB temperature between 64°F and 70°F on a 100-degree day. That means that the target superheat on a 100-day is between 6.0°F and 15.0°F.

In the same way, you can use this target superheat chart to determine target superheat for 55°F to 128°F outdoor temperatures and 50°F to 76°F indoor WB temperatures. Since superheat doesn’t depend on the type of refrigerant we use, this chart can be used as target superheat chart for R-22, R-410A, R-134A, and all other freons.

Here is the promised PDF version of this target superheart chart (you can freely download it, print it, and use it for AC diagnostics):

Alright, let’s look at R-22 and R-410A target superheat examples to illustrate how we use this chart in practice:

R-22 Target Superheat (1st Example)

Let’s say that we have a 3-ton 16 SEER air conditioner that uses R-22 refrigerant. We want to figure out what the target superheat for this R-22 system is. The measured outdoor temperature is 83°F, and the measured indoor WB temperature is 61°F.

Here’s how we calculate the R-22 target superheat for these conditions manually:

Target Superheat (R-22) = (3 × 61°F – 80°F – 84°F) / 2 = 9.5°F

We can see that, in these conditions, the R-22 target superheat is 9.5°F. You can manually calculate this as we did here. The much easier way is to use the calculator above or consult the target superheat chart.

It works the same way for R-410A refrigerant. Here is the solved example:

R-410A Target Superheat (2nd Example)

Alright, let’s say that we have a 5-ton 14 SEER unit that uses R-410A refrigerant. In order to calculate the target superheat, we have measured two required temperature; outdoor dry bulb temperature is 105°F (105-degree day), and the indoor wet bulb temperature is 69°F. What is the target superheat for R-410A in this situation?

Let’s use the target superheat formula and calculate this manually:

Target Superheat (R-410A) = (3 × 69°F – 80°F – 105°F) / 2 = 11.0°F

We see that the target superheat for R-410A refrigerant in this system is 11°F. You can use the target superheat calculator above to get to this result much quicker.

We hope that the formula, calculator, and especially the all-encompassing chart, together with these R-22 and R-410A examples, you help you in all target superheat calculations. With the target superheat chart in PDF form, you don’t even need to calculate it; you can just read it off the chart.

If you have any questions, you can give us some numbers in the comment section below, and we will help you out as best we can. Thank you.