HVAC

HVAC Basics - Delta T #2

Name: HVAC Basics - Delta T #2
Uploaded: 2025-05-29T14:03:49Z
Duration: 1 min 56 s
Description: In this video, we break down why patience is key when checking an HVAC system’s temperature difference. Learn why a true 15–20° delta T takes time to stabilize, what a low or high reading might mean, and how taking the time to do it right prevents unnecessary callbacks and keeps residents comfortable.

In this video, we break down why patience is key when checking an HVAC system’s temperature difference. Learn why a true 15–20° delta T takes time to stabilize, what a low or high reading might mean, and how taking the time to do it right prevents unnecessary callbacks and keeps residents comfortable.

Best Practices

Thermostat

Diagnostic

Mark Cukro

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Transcript

Now that the AC is running, we should have ideally a 15 to 20 degree difference. However, we just turn the unit on, so we go to one of the vents, we check with our thermometer, and this is 58 degrees, okay? Which means right now it's a 12 degree difference in temperature. However, if I check this in a couple of minutes, it's already going down to 57.

So what this means is after 10 or 15 minutes of running, the AC system should go from the same temperature, air. So the air coming out being 15 to 20 degrees cooler. Another common mistake technicians make is they either check it and they're like, Hmm, that's pretty good, and they leave. It takes five, 10, or 15 minutes for the system to stabilize and get in a running cycle where it makes a difference in temperature between 15 to 20 degrees.

I know it's easy to get in a rush, but don't be in a rush. If you do it right the first time, you won't have to come back and do it again. So check everything. Make sure the air is coming out of all of the vents. In the, uh, resident's home and that the temperature is 15 to 20 degrees cooler. So this temperature is dropping, which means it's going to continue to drop.

Now, if you're supposed to have a 15 to 20 degree difference in temperature, and the temperature difference is 25, 27, 30, that's not good. That means airflow. It is probably too low or something else could be an issue or a concern. So remember, air conditioners don't make cold air. They remove heat. The absence of heat is what we feel is cooler.

The temperature difference should be 15 to 20 degrees when it's properly running, charged, and cleaned. And make sure the indoor unit and the outdoor unit both come on. They work. Check the heat, check the temperature. Start at the thermostat and you will be able to find the root cause of the issue.

Troubleshoot faster in less time, yet less callbacks and everyone will be glad for it.