HVAC

HVAC Basics - The Thermostat

Name: HVAC Basics - The Thermostat
Uploaded: 2025-05-29T13:24:47Z
Duration: 1 min 25 s
Description: This video walks you through a crucial but often overlooked HVAC diagnostic step—timing the fan operation in both cooling and heating modes. Learn how delays can indicate issues with relays or sequencers, and understand how heat pump behavior changes with temperature differences. Simple steps, smart troubleshooting.

This video walks you through a crucial but often overlooked HVAC diagnostic step—timing the fan operation in both cooling and heating modes. Learn how delays can indicate issues with relays or sequencers, and understand how heat pump behavior changes with temperature differences. Simple steps, smart troubleshooting.

Best Practices

Thermostat

Diagnostic

Mark Cukro

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Transcript

Now we waited for the fan to go off, so we know that it called for cooling while a fan was in auto mode, and that part works. Now we're gonna go from auto to on, and now there will be a time delay for the fan to come on. One of the most common things technicians forget to do is to exactly time how long it takes for the system to go on and off.

Now I know that the fan works when it goes from auto to on. I put it back to auto and I wait for it to cycle and turn off while I'm timing it. If it takes too long, I have an idea what the issue is. If it turns off too quickly, it's probably the same component, which is a fan relay or a time delay, fan relay, or a sequencer, which are basically all the same thing, but they look different.

They're configured differently now. It took about a minute for the fan to turn off. Perfect. That means the time delay is working. Now I'm gonna move it from. Cool to off to heat. Now here's the deal. If it's a heat pump and you turn the heat on, if the difference is more than three degrees, the backup electric heat strips also come on as well as the unit that's outside.

So you have to know that about heat pumps. So we have two degree difference. We're going to wait and see how long it takes for the system to come on the outdoor unit to come on, and then we'll check the airflow and check the air temperature with our thermometer.