Why would an AC compressor overheat if turned on right after being turned off; not same as leaving it on?

Question

I'm wondering why my window AC unit has a 3 minute wait before activating the compressor when first turned on (to avoid overheating it, I believe).

What is different about leaving the compressor on and turning it off and then back on?

Answer 1

Well, when you first turn on the a/c, the compressor is now under pressure. It takes a few minutes for the pressure in the system to equalize on both sides of the compressor when it shuts off. Hence the terms the Hi side and Lo side. The compressor will not start under pressure. Most units are built this way in order to prevent damaging the compressor. All a/c's are built this way. Both central systems and window units. This will cause amperage to go up, circuit breaker to trip and Hi limit temperature switch to shut off compressor. , This would eventually cause compressor to fail. It is a safety feature put on the units in order to protect the compressor and the customer's investment.

Answer 2

An ac has both high and low pressures separated by a metering device while operating. By turning the ac off and immediately back on the pressures do not have time to equalize. The compressor motors do not have the power to overcome the head pressure so they shut off on overload until pressures equalize and the unit cools.

Answer 3

the answer above is right on, compression ratio is huge(low suction + high discharge) compressor starting amp draw is much less with pressures equalized.



The 3 minutes isn't that long is it!?!? haha