My ecobee3 continues to cool/heat even after reaching temperature. I frequently have to manually turn my ecobee off, when it cools/heats to our set temperature (say, 75 degrees) and then keeps cooling/heating. It knows the equipment is running too!
How can I fix this to avoid wasting power and making the house too cold?
Anytime the equipment is on outside of the selected setpoints, it will be due to the 'smart recovery' feature. The thermostat continues to accumulate data taking into account the outdoor weather and the efficiency of your system in the past and uses that for 'smart recovery'. This feature pre-cools or pre-heats the home to bring it to the desired temperature for the start time of your next scheduled change. The higher the difference in setpoints between 2 schedules, the earlier/longer the system may run to achieve that set-point for the upcoming schedule.
If you would like to disable this feature, you can do so by going to MENU > SETTINGS > PREFERENCES > SMART RECOVERY COOL/HEAT and disable this. Or you can make modifications in your schedule to not have any big drops in temperature.
(Please note, disabling smart recovery will cause the thermostat to only turn on the cooling/heating after the next schedule changeover).