If you're posting a request for installation help, please provide as much info about your system as possible. For example, for help regarding connecting a smart thermostat, please include details about your system including whether you have gas/electric, heat pump, number of heat stages, A/C condenser, etc.

Ecobee3 Not coming on when reaches comfort setting?

steeve725steeve725 Northern ColoradoMember

4 times in the past 2 weeks that I'm aware of my Ecobee3 Thermostat hasn't came on when it reaches my comfort setting.

For example. Today my A/C is suppose to come on when it reaches 73 degrees. I walked past the thermostat and seen it 74.

I have 4 sensors. Here were there readings, 74, 75, 74, and 74 degrees when the A/C didn't come on.

Why isn't my ecobee coming on when it suppose to?

I called and spoke with Tech support, they walked my through checking all my settings and they stated everything looked fine. They stated they where going to have someone look into my problem. They stated if it happened again, to call. I called and was on hold waiting to speak with someone for 25 minutes, and finally left my phone number to be called back. They never returned my call.

My cooling Threshold is set at 0.5. Doesn't that mean when it comes within 1/2 degree it should come on?

I turn my thermostat off at night and open the windows. I notice this happens at the very 1st startup of the day after I turn it on. Is it in some kind of standby mode?

If I increase the temp using my app or the screen it turns the A/C instantly. Isn't that strange.

I have had my thermostat April 2016 and it has worked wonderfully.

It has firmware

My A/C finally came on when it reached 75 degrees? Its suppose to come on at 73 degrees!


  • steeve725steeve725 Northern ColoradoMember

    Pictures attached. One showing the thermostat at 74 degrees, you'll see the set temperature is at 73. The snowflake is still white? The other picture will show the A/C finally came on when it reached 75 degrees, the snowflake is blue.

  • steeve725steeve725 Northern ColoradoMember

    Tech support called me back a long time after I left my phone number and of course after I posted.

    The tech support explained to me about the algorithm.

    My thermostat was in away mode. I have my threshold set at 1/2 degree. When in away mode, the algorithm will add 1 degree to my threshold to help conserve energy.

    So my thermostat is set at 73 degrees, add my 1/2 degree and it brings it too 73.5 degrees, add the away algorithm 1 degree and it now brings it to 74.5, so that is why my A/C came on on 75 degrees.

    On the ecobee3 we see whole numbers, such as 74, 75, etc. We do not see the decimal, such as 74.5, etc.

    When I spoke to tech support the other day, they didn't know what the issue was.

    I guess it matters who you speak to.

    It looks at though my problem is solved.

    I hope if anyone else has this issue, they will read this and understand.


  • EFTCEFTC CanadaMember

    Hm. I wonder if the same issue (add 1 degree to the threshold) in sleep mode regarding the operation of the AC.

  • LarrylLixLarrylLix Northern Southwestern OntarioMember

    I have found this same thing. Many features with the multiple sensors do not function as advertised.

    To experiment, I have disabled all sensors except the stat itself. I find the stat regulates the temperature quite well, except for one time each day where the stat just seems to go to sleep and forget to kick in the A/C until about 1.5C above the setpoint.

    I have the three remote sensors and a CAO wireless Tag setup beside the stat but away from the influence from the stat electronics heat. This tells the real story about some of the flakey operation logic of the ecobee3 stat.

    AS a warning to others let me tell you this:

    Here is why. Typical of many thermostats, instead of using another internal register to fudge the sensor readings, ecobee used the the display register showing on the front of the stat, to do things like compensator/predictor logic arithmetic. This is analogous to the old mechanical thermostats that attempted to prevent overshoot by using a thermal element, running off the furnace solenoid current, to shut off the stat contacts early.

    So when the ecobee3 runs the A/C circuitry, it's internal logic slowly ramps down from the displayed temperature reading on the stat. What this means is, after your ecobee3 runs your A/C for ten minutes, the reading will be 1-2 degrees C lower than the actual sensor and air temperature. It works most of the time but occasionally it send the temperature reading down the tubes at the wrong time and your stat will not run the HVAC equipment when it should. There is another problem making this characteristic worse but I haven't determined it cause yet.

    Anybody doubting this can prove this quite easily for themselves. Just place your sensors close to the stat and observe the operation. My three sensors and CAO Tags indictae a drop of only 0.1-0.2C when the A/C cycles while the stats indicates a drop of 1.0C every cycle.

  • EFTCEFTC CanadaMember

    Hm.. that's interesting. I am experiencing the same thing.

    When AC is running for 2 - 3 h non-stop, I noticed that temperature indicated on the wall unit (E3 wall stat) shows a 3C - 5C difference compared to the actual temperature of the room. At first, I thought there was a leak in the wall where the T-stat is mounted and the draft is blowing cold air to the thermostat. When I reset the wall stat by cutting power to the furnace and restoring the power, the temp on the wall stat will match the actual temp of the room. To prevent the AC from shutting off prematurely, I programmed the thermostat to use the temp from upstairs when I am home or sleeping. The stat will use the temp from the wall unit only when I am away.

    With this setup, the wall stat will not have any impact on operation of AC when I am home or sleeping.

  • LarrylLixLarrylLix Northern Southwestern OntarioMember
    edited July 10

    Yeah, the sensor on the thermostat itself is basically useless for regulating the temperature and my belief is this is why they brought out remote sensors, instead of correcting the original firmware problem that simulate mechanical predictors in the old mechanical stats.

    Having said that I find via a group of other sensors (CAO Tags are claimed to be within 0.3C accurate) that the room, at the stat point stay very stable except for certain times of the day. I believe this time is after the thermostat has been sleeping for many hours. This may be part of the same internal compensation attempt but not showing on the stat temperature. If ecobee would display the resolution of the sensors, as shown in the csv log charts, this would be much easier to diagnose.

    Currently I am running totally on manual sensor selection as I find the Follow Me feature doesn't actually work. If I enable a sensor the average calculated temperature changes immediately to all the enabled sensors whether they see motion or not. Waiting for hours yields the same results. I have contacted ecobee support regarding this and they gave me an example from my own database that was complete crap. Their simple arithmetic was nonsense (they can't calculate an average from three figures they supplied) and the example added up to the same as the stat was sensing anyway. They told me the average had sensors detecting motion were slowly accrued to the average calculation which is incorrect, as proven in many tests by enabling them and disabling them, without the sensors ever seeing motion.

    I found the same nonsense with Venstar stats also. Their tech support person didn't know the difference between sensor calibration and on/off differential. The support techs either don't know or feed you script crap to disguise the technical problem with their firmware.

    One item I that was fed me was their technical description of how the sensor logic works. Two sentences are used to describe the operation logic, that contradict each other in ecobee's information.

    I have created extreme examples to prove the stat temperature "wanders" to give back to tech support but have yet to create a few good examples to prove the sensor follow me doesn't function. As an old retired Instrument Technologist and legal Metrologist I know how to do this stuff.

Sign In or Register to comment.