Finding Target Superheat

Bert teaches the Kalos techs some strategies for finding target superheat on systems with fixed-orifice metering devices (not TXVs).

Whenever we take readings, we should start by knowing what we want our readings to look like; we should know what to expect of a system that is working properly so that we can recognize abnormalities in our readings. Superheat is an especially critical reading because it can let us know a system's risk of flooding the compressor, if the evaporator coil is being fed efficiently (as opposed to overfed or underfed), and the evaporator load, and it can help us diagnose problems with TXVs (on TXV systems). We can measure superheat on the suction line or discharge line, but those superheat values are very different and can tell us different things about the system.

Suction line superheat readings that are too high can indicate that we are starving the evaporator, and low superheat readings can indicate that the system is feeding too much refrigerant into the evaporator coil (or that the coil is otherwise not absorbing heat sufficiently). When you have a metering device problem, like a wide-open TXV, the saturation point is a lot higher than it should be because the pressure stays higher and keeps the evaporator coil warmer.

A common rule of thumb is to achieve a 10-degree target superheat for fixed-orifice systems, but the target is variable because the superheat isn't constantly monitored and manipulated by the metering device (unlike a TXV system). On a fixed-orifice system, the target superheat will decrease as the outdoor dry-bulb temperature increases.

[kelbymasey]

I appreciate his approach to teaching. Good job!

[bulentyavas]

First of all, I wish you success in your work. We will benefit greatly from your training and other study VIDEOS, but we would be very grateful if you could add Turkish to the subtitles. Greetings. I was able to write this article by translating it from translator. Thank you.

[carrieresammy]

Appreciate the insight. Too many people feel like they know what range superheat should be which is fine, but if you’re not testing, you’re guessing!

[thrshr]

Awsome to watch and appreciate the tips/tricks/skills you are sharing with us all! Thanks!!!

[juancarlosfernandezmontero]

Greetings from Costa Rica.
Well explained.

[rpsmith]

Excellent video! Very good presentation! Thanks!

[rickhimes]

Where is this school? This guy is a great instructor.

[markharmon]

I wonder if this method of finding targe superheat would work on a vehicle. Having trouble getting proper cooling from a 2008 Jeep Grand Cherokee I replaced the evaporator, dryer and TXV on a couple years ago, and it never has worked right. Evacuated and weighed in correct amount of refrigerant, but unsure exactly how much oil is in the system. Perhaps that's part of the problem, thinking of evacuating again, draining all oil from wherever I can get it out of easily, and starting over. Suggestions welcome, it's been many years since HVACR school in the Navy, and just the occasional job like this since. I just tuned up my JB vacuum pump and micron gauge (good for 15 micron verified by two separate micron gauges) and ready to try again. I think part of the problem last time was the vacuum pump wasn't pulling down remotely enough, and with my micron gauge contaminated, couldn't tell at the time.

[jericosha]

Why did Bert say to input the tonnage into MQ? Isn't return wetbulb and outdoor drybulb enough?

[seekn]

I use the Emerson checkcharge app. It asks for vapor pressure vapor line temperature. And indoor wb outdoor db

[BigDon]

Does target super heat calc also work for the duct less mini split systems?

[mr.invisible]

How do you determine target superheat on water source heat pumps? Do you replace outdoor dry bulb with inlet water temp?