All right, so a common confusion is the difference between td and delta d, and it makes sense why there would be a common confusion about this, because they both actually mean the same thing. Td means temperature difference or temperature differential and delta t means the delta in temperature, which just means the difference in temperature, so they mean exactly the same thing, but in the trade we use them to mean pretty specific things. Now you may find that some people will say td when they mean delta t, but, generally speaking, if you read most of our industry, textbooks and most of the jargon among the field has these being two different things. So let's define them so that way.

Hopefully you don't make this simple mistake when we say td we're often talking about an evaporator coil td, and that means the difference between the saturated suction temperature, otherwise called suction saturation or evaporator temperature, which is specifically the temperature that the refrigerant is boiling inside the evaporator Coil the temperature that is changing state inside the evaporator coil compared to the air, that's passing over the evaporator coil, so on ac we would call that the return temperature and refrigeration that would often be the box temperature. So that's the temperature of the air as it goes into the evaporator coil. The difference between that and the temperature of the refrigerant boiling inside the evaporator coil. That temperature and air conditioning is typically 35 degrees.

And i'm just going to focus on air conditioning here, because this isn't a refrigeration, video but typically 35 degrees is kind of your standard baseline td that you're going to see. And that means that your evaporator coil inside, when it's boiling, when it's at that suction saturation temperature, is going to be about 35 degrees lower than the return air temperature. If the system is working properly, which is where we get that 40 degree, evaporator temperature number from 75 degree return temperature, which is a common comfortable temperature inside subtract 35 from that you end up with a 40 degree, evaporator temperature. So that's that 35 degree, td delta t is the term that we use for the difference between the return air temperature and the supplier temperature and obviously that's going to be lower.

Now i could give you a delta t that a lot of people repeat they'll say something like between 16 and 22 degrees. It's a pretty big range, because there are a lot of things that affect delta t. You get a lot of variation in delta t based on airflow how much airflow you have going over the coil air mass. So what is the weight of the air which does change and then also the amount of humidity or moisture content in the air? Also changes? What your delta t target is going to be so, when you're calculating delta t to figure out what your target is, what you want to hit for a properly operating system, it's best to look at a target delta, t calculator.

We've got one on our website or in our app, but also recognize that even that is a moving target, because, when we're calculating delta t's, we're making a lot of assumptions about what your air flow is and what that. How that air flow and cfm relates to the capacity of the equipment, so there's a lot of variables there, but when we say delta t. The main purpose of this video is just to isolate that we're talking about the difference between the return air temperature and the supply air temperature. When we say evaporator, coil td, we're talking about the difference between your suction saturation, evaporator temperature and the error and the return going over it.

So hopefully you found that helpful. Don't make the mistake that i made many times and saying td. When i mean delta, t or delta t, when i mean td thanks for watching thanks for watching our video, if you enjoyed it and got something out of it, if you wouldn't mind hitting the thumbs up button to like the video subscribe to the channel and click, The notifications bell to be notified when new videos come out. Hvac school is far more than a youtube channel.

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