I just had a new air con unit installed, and am annoyed/displeased at one of its "features": when you push the ON button on the remote the wall-mounted unit responds with a double-beep and the fan starts blowing, but the outdoor compressor doesn't kick in until a three-minute delay.

My air con technician is pretty fluent in English, but not 100%, so maybe I misunderstood, but I think he said the delay on compressor start is to conserve energy by avoiding a big surge if both the indoor and outdoor units started at the same time. Huh? If that WERE the case, why not just delay the compressor start for 5 or 10 seconds?

Can anybody offer a better explanation of this unwanted "feature" of my shiny new air con?

It's a feature to avoid the compressor motor from overloading. If the unit is running and gets shut off for some reason, maybe a power glitch, it takes the compressor some time to unload. The unit doesn't know if it has been running or not, so it uses the three minutes from a fresh start up too.

It's a feature to avoid the compressor motor from overloading. If the unit is running and gets shut off for some reason, maybe a power glitch, it takes the compressor some time to unload. The unit doesn't know if it has been running or not, so it uses the three minutes from a fresh start up too.

Reasonable enough reason. :-)

But how come any of my previous air cons could distinguish between a re-start and a start. i.e. Push the start button, and the compressor immediately kicks in. When manually turned off and back on right away (or, on a power glitch), it would wait the three minutes. I've had lots of air con units that behaved this way. Why is my new one so stupid and why is it a Feature? <grumble, grumble>

It's a feature to avoid the compressor motor from overloading. If the unit is running and gets shut off for some reason, maybe a power glitch, it takes the compressor some time to unload. The unit doesn't know if it has been running or not, so it uses the three minutes from a fresh start up too.

Reasonable enough reason. :-)

But how come any of my previous air cons could distinguish between a re-start and a start. i.e. Push the start button, and the compressor immediately kicks in. When manually turned off and back on right away (or, on a power glitch), it would wait the three minutes. I've had lots of air con units that behaved this way. Why is my new one so stupid and why is it a Feature? <grumble, grumble>

I would guess that they saved some baht by NOT putting in the additional circuitry. For the compressor to know, there would need to be some sort of pressure switch in the system to let it know if the compressor was unloaded or not.

Well, my little saga of annoyance has taken a nice u-turn.

My original post was based on observation of how the system worked upon installation. The system did, in fact, upon startup pause three minutes before the compressor turned on, and did so even when the system had been switched off for thirty minutes or so.

On Sunday, however, I was delighted to observe that after pressing the "on" button, the compressor started within about three seconds. Much better!

The air con technician and crew are here today to install the other two units. I demonstrated the new, more acceptable, behavior of the compressor of the first unit. He just shrugged and said maybe because the unit was newly charged with refrigerant, the compressor was confused and erroneously sensed that it was in a re-start state where it had to wait three minutes to turn on. Sounds semi-reasonable.

So, I needled him mercilessly about his previous implausible energy-saving reason for not turning on within three minutes.

So, end of story: the system works just as I think it should. Turns out I didn't buy a "stupid" system.