I have a 2 zone system that intermittently shows temp 2 degrees or so above set point; on one or the other thermostat, day or night. At some point, the condenser kicks back on and everything works fine. Outside temp doesn't matter, it will keep it 70 inside with it 100 outside. The problem is obviously the condenser not coming back on immediately when the thermostat demands cooling. When the temp is above set point, the blower is running, but the condenser unit isn't. Again, after a bit, it does kick back on and bring the temp back down.


Your A/C system, your zone controller, and/or your thermostat could have a time delay to prevent the system from turning on and off too often. Short cycling the compressor can be bad for it, so the controllers typically enforce some kind of delay.

The actual delay will vary depending on the controller, so you'd have to get model numbers, etc, and research which device has which delay to figure out exactly what's causing it in your system. There can also be a delay built in before switching from cooling to heating, but that's not what you're running into here.

  • I agree with jphil1618 if the system was running in the 3-8 minutes prior it is most a short cycle delay but would add a defrost timer on the evaporator especially if you have a dehumidifier mode. There is also a dead band setting on most units the set point plus or minus 1-3 degrees to prevent the system from being commanded on off two often both of these can be adjusted in most units some with the thermostat some with switches or jumpers on the control board.+ – Ed Beal Jul 22 '19 at 20:41

Some electric utilities install a load switching device on residential customers' A/C condensers. The device allows the utility to remotely turn off the condenser intermittently; this allows them to shed load on parts of their grid to meet generation or transmission targets/limits (sometimes called demand response). In theory these are activated only on the hottest days.. such as those being experienced in many parts of the US in the past week. Often there's some financial incentive from the utility to entice customers to participate in the program.

If your condenser is equipped with one of these devices it would be visible on the outside. Look for a plastic box mounted to the condenser unit or possibly to the building wall near the condenser. One such device is made by Energate and is pictured below. A person in the home would experience basically what you've described: the blower continues to run, but there's no cooling for a short time, and then things return to normal.

Energate load switch device

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