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Comment by glitchc | Hacker News Reader

A general note: Arbitrarily cutting and restoring power is a bad idea for a compressor. See the first answer at this link for a detailed explanation:

https://diy.stackexchange.com/questions/145791/how-bad-is-it...

In a nutshell, it takes time for the refrigerant pressure to equalize. An AC with a thermostat will have a timer to prevent an immediate restart after a stop.

Another option is to introduce hysteresis into your control loop as the TFA author has done: Use a distinct power threshold from your off threshold. By setting the power on a couple of degrees higher than the cutoff, it will give the refrigerant pressure time to settle.

To the author: I agree with the other posters. Looks the AC already has a thermostat, just no automatic fan control.

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Author here. Thanks for the heads up. From my experience, after it turns off, it tends to stay off for about 30-45 minutes. I hope that's long enough to avoid issues. The comment in the link mentioned delaying 3-5 minutes.

And yep, It was my bad to misunderstand the first knob. I should have read the manual instead of assuming. I added a note to the post.

Certainly more than enough, it only takes a few minutes as mentioned. You could probably lower the temperature gap further.

I did something similar to the TFA but instead of switching the power on and off, I signal it with instructions to cool to the minimum and maximum temperature. (This was easy in my case because it has an infrared remote which I can emulate.) I’m assuming that any logic required to be mechanically sympathetic to the compressor is built into the AC’s own controller.

IME compressors usually have a thermal cutoff . If you do try to start them up too early, you'll know - it won't turn and the cutoff will kick in. Not great for your motor or premises wiring, but it has been designed for.

To the OP, don't regret doing this at all. Thermostats on air conditioners are generally subpar, since they're located on the unit itself. If you want to use the "auto fan" mode to keep noise down, then there ends up being large temperature swings. I think this is because the air stops circulating, while the air near the unit stays cool due to the cold coils.

I've got a plan to automate a dehumidifier Real Soon Now, and I'm planning on using a plug with current monitoring. This way I can sense when the compressor has shut off on its own and then wait several minutes for efficiency's sake.

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