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When I turn off the AC it continues to blow cold air for several minutes. I realize this may be an energy savings feature, but I'd like to know if it is possible to disable it. In other words, what I'd like is for "Off" to be immediate off. I realize this is not something I may be able to do on my own, not really expecting to. I want to know if an HVAC technician would be able to modify this setting.

I apologize in advance, I have very little HVAC knowledge, but I am able to list the following installed components:

  • Carrier Split-System Condensing Unit - 38HDR
  • Carrier Gas Furnace - 58MCB
  • Nest Thermostat (Airwave is disabled)

Btw - I have the same problem with heating, not just cooling.

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    Looks like your furnace has an adjustable blower off delay from 90 - 180 seconds, so you'll be limited to that. While some units don't use the delay when in cooling mode, it sounds like yours does
    – Tester101
    Commented Jun 20, 2015 at 12:36

3 Answers 3

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This is basically a safety feature. In the case of heating, if the fan turned off immediately after turning off the thermostat, the heat buildup in the heat exchanger could cause it to eventually crack and leak carbon monoxide into your house, so the fan continues to blow until the heat exchanger sufficiently cools. In the case of the A/C, there's no danger of carbon monoxide. But if the various coils in the A/C were allowed to heat too rapidly, that could also cause their premature failure, so the fan continues to blow air across them until they're within a few degrees of ambient. If this were able to be disabled and you could find an HVAC tech to do so, I wouldn't hire him or her, nor the company for which they worked.

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  • DV because, though generally good advice, incorrect for OP's system and question.
    – jay613
    Commented Jun 25 at 17:42
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Read the manual!

Your question is mainly about cooling. You can set the power-off delay for cooling in your system to 5 seconds. That's very close to what you want!

You can set the power-off delay for heating to as little as 90 seconds.

You can do this yourself, or a technician can do it in 5 minutes.

You should not try to bypass these limits. You should follow the instructions in the manual to (almost) make the changes you want.

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You could just pull the breaker at the unit and it will shut off immediately and then put it back in. However, I would guess there is probably a good reason that it takes a while to shut off. Most likely protecting the unit from some wear and tear

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  • Why pull the breaker? Just turn it off/on - switch if there is one, breaker if there isn't.
    – manassehkatz-Moving 2 Codidact
    Commented Jun 25 at 17:53

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