Thermostat Cycling

Installed the Intelligent Thermostat (ADC T-3000) on Wednesday evening. Immediately noticed the ambient temp was reading four degrees higher (74) than my previous thermostat(70). I just adjusted the set point up a few degrees and didn’t think much of it. Over the next 24 hours the thermostat cycled my heat pump over and over attempting to cook the house. It would run for maybe five minutes and then cut off, wait maybe five minutes, then restart. The ambient temperature kept climbing and the unit kept this on and off routine without ever getting close to the set point temperature. Each time the thermostat would go to orange display with “Protect 5 Min” on it. After attempting to correct in settings last night, I switched the thermostat back to my original to avoid damaging the compressor from so much cycling. It then ran for over an hour to cool the house from the 79 degrees it had reached to the 70 degree set point.

Everything was wired exactly like it was on the old thermostat. Blue to C, Orange to O, White to W, Yellow to Y, Red to RH (selected RH only on menu to create digital jumper to RC), and Green to G. Any way this could be a faulty unit out out of the box? With the ambient temperature off significantly and the cycling, it makes me think that unless there’s some advance setting I’m not aware of.

That wouldn’t be affected by any setting, I don’t believe, and not necessarily from any wiring mistake. From

System Protect is a 5-minute delay prior to calling for heating or cooling to protect the system from short cycling. It is only applied if the thermostat has detected an unexpected relay state internal to the thermostat during a call.

System Protect is intended to cover rare cases of power issues with the HVAC system. If System Protect is being seen frequently or appears on every call for heat or cool, it points to poor HVAC performance or pre-existing incompatibility. Frequent System Protect delays can be resolved by installing an isolation relay.

The info above is direct from ADC documentation. What model of heat pump are you using? When was the air handler installed?

An Isolation Relay is likely necessary in this case. If you are seeing the protect message repeatedly and the thermostat is cutting off the pump prior to reaching the set point I think that is going to point to the voltage being out of expected range. The ADC-T3000 is more sensitive to this than other models I am familiar with, and it will require an isolation relay where the T2000 wouldn’t.