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Problem with Smart Thermostats

LarrylLixLarrylLix Northern Southwestern OntarioMember

After a few brands of thermostats that went back to the stores I have discovered a problem with most smart thermostats.....The electronics produce heat. This is aggravated by using radio transmitter to talk WiFi or any other protocol.

You say...just adjust the calibration to compensate? Well that is what the manufacturers do, and also what causes the problem.

Here is an example. Your room is at 72F = 22C, but the electronics in your stat heats the sensor up a few degrees to 75F = 24C.

The QA tech in the factory saw this and adjusted the stat sensor to read 72F or 22C.

So you take it home and mount the new beauty on your wall, and set all the settings to where you want. It reads 72F or 22C and you are comfortable.

Now your HVAC cuts in and the slight breeze in the room hits the thermostat. The same thing can happen from an open door, leaky windows, internal wall draughts, or a ceiling fan. That very slight heat discussed above, from the electronics gets blown away somewhat, and the senor returns to it's rightful place, with the bad calibration now showing 75F of 24C.

But the actual room temperature hasn't changed...!

Now your thermostat does it's job and turns on the HVAC to cool or heat the room. That's it's job. Now you are cold or too hot and adjust the thermostat setpoint.

But it doesn't stay. The breeze stops later and now you feel too much the opposite and wonder why you have to adjust the setpoint back to where it started.

It the stat doing it's job? NO! But most people have no idea what is going on and either, they are insensitive to heat changes (and paid $340 for a stat??? duh), they try to ignore it, or they take it back to the store and install their old not-too-smart thermostat and forget all the new-age hype.

I have found TekMar thermostats not too bad for this, Venstar ColorTouch T7900 units extremely affected , Honeywell TH7950WF somewhat affected, and ecobee3 quite good for this. However the ecobee3 has another sensor display wandering problem where they use the display register to fudge the cycle compensation, forcing it to cycle on what then appears to be a finer response resolution.


  • phd777phd777 Member

    What if you don't use the internal temperature sensor on the ecobee3 and just use the wireless sensors?

  • LarrylLixLarrylLix Northern Southwestern OntarioMember
    edited July 11

    That removes the operational problem but not the thermostat displaying the problem.

    You may also be subject to more temperature overshoot. I am using my ecobee3 with the remote sensors only right now until the whole thing is understood further.

    AFAIC the ecobee3 follow me feature is a complete flop and doesn't function. Support has argued but suppled bogus examples from my data.

    Right now, so far, I am thinking a combination of one sensor and the stat sensor may be a good compromise.

  • EFTCEFTC CanadaMember

    You are correct. "Follow Me" occupancy detection and Read room temperature based on pre-set sensor has always been in conflict with each other. As far as I know the issue was present when the 1st gen of E3 was introduced to the current E3 and probably the E4.

    When you have "follow me" turned on, it is not known whether sensors that detect occupancy overrides the pre-programmed sensor. There is little to no indication that Ecobee is averaging only the readings from sensor that detected motion or all the sensors that are pre-programmed. Turning off "Follow Me" is supposed to force the E3 to average temperature from pre-programmed sensor but that isn't always the case.

  • LarrylLixLarrylLix Northern Southwestern OntarioMember
    edited July 14

    Ecobee seems very evasive on this feature. The docs are nonsense and their description contradicts itself in places. The website information is always lagging at least 1.5-2 hours behind the current time, making it hard to determine what is going on. Then the webpage only displays temperatures in 0.5C resolution making the finer changes from calculated averages etc, hard to check.

    When downloading the historical data from the website, all temperatures are to 0.1C resolution. However, they have not included the sensor enable status information, making the Occupancy status field useless for any troubleshooting analysis to detrmine if Follow Me actual works. I informed their Tech Support their evaluation could not be properly done due to the missing status and they stopped responding to me. Another stat tech support that doesn't understand their own product or docs.

    July 13, 2017..Ecobees latest stunt includes changing the historical chart crosshairs to a four arrowhead cursor so that exact times cannot be determined from webpage charts showing operation history. You have to guess how long, and what time, things happenned now.

    Ecobee seems to be spending more time and money attempting to cover up good analysis of the stat, and webpage problems, than they are resolving them. I have yet to find an acual ecobee forum for hep from them. Any attempt to find help always leads to their canned answers from docs, very poorly written, and evasive of the issue promoted in the titles/searches.

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