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Ecobee 3 Temperature Accuracy

BPMBPM AlbertaMember

I have put 2 thermometers next to the ecobee 3 on the wall and separate rooms, (they remain constant with very little difference in temperature among them), and my set point differential set at .3 Celsius. I am getting from furnace fire on/off, not counting the high efficiency furnace blower time before shut down, a swing of over 2 Celsius of actual air temperature although the thermostat is reading 1 Celsius. Has anyone else actually measured the air temperature by the E3 as opposed to just trusting what the thermostat number tells you. Thanks



  • my0gr81my0gr81 coldnadaMember

    The ecobee3 displays an average of all the sensors that are enabled. To read the temperature at the thermostat, you need to go into the systems menu and look at the sensor for the thermostat.

  • BPMBPM AlbertaMember

    This is not using the sensors as of yet, as I want to make sure the E3 is measuring the temperature correct in the first place. As mentioned, it is the thermostat alone on the wall with an accurate stand alone thermometer. As an example today, I had swing from system start to finish of 2.5 Celsius with a set point differential at .3 Celsius. A 2.5 Celsius swing on what is supposed to be .3 give or take +_.5 according to specs. Way off!!!

  • I had a 1C difference between my old stat and the e3, but it fixed itself over the course of a few days. Once I added the sensor it started to do the same thing, it wasn't the average temp at the home screen but the temp when you look in the settings that was off by a few C.

    I disabled the sensor and then just enabled th senor and the temp returned to the correct values.

    I would try to adjust the temp and see if it starts to read the correct temp when it reaches the set point, i also remember restarting the e3 and letting it calibrate.

  • aweber1njaweber1nj NJ, USAMember

    I left the thermostat I was replacing (a high-end Honeywell) lying on a table next to the ecobee3, and I found that the temp was identical between them (every time I looked).

    Don't know.

  • BPMBPM AlbertaMember

    Thanks for all your input however, my questions pertains to the accuracy of the thermostat based on a temperature measuring device other than another thermostat that may not be accurate. Has anyone used 1, 2 or 3 thermometers that read close to each other then looked at the temp on their thermostat. Mine overshoots over 2 degrees from set point even though the E3 says it has shut off at the correct temperature, the actual room temperature is 2 Celsius higher. Again if 2 or 3 different thermometers all read the same overshoot and the E3 reads 2 Celsius lower, I would have to think the thermometers of actual air temperature are correct not the E3 reading.

  • my0gr81my0gr81 coldnadaMember

    BPM said:
    Thanks for all your input however, my questions pertains to the accuracy of the thermostat based on a temperature measuring device other than another thermostat that may not be accurate. Has anyone used 1, 2 or 3 thermometers that read close to each other then looked at the temp on their thermostat. Mine overshoots over 2 degrees from set point even though the E3 says it has shut off at the correct temperature, the actual room temperature is 2 Celsius higher. Again if 2 or 3 different thermometers all read the same overshoot and the E3 reads 2 Celsius lower, I would have to think the thermometers of actual air temperature are correct not the E3 reading.

    A thermostat has to have a temperature measuring device (known as a thermometer), hence another thermostat's reading is just a valid as a stand alone thermometer.

    Going back to your question, the E3's thermometer is more sensitive and changes are displayed more frequently than what I have seen in other thermostats or thermometer. I have small digital combo thermometer/hygrometer sitting right above the E3's housing and while they settle to the same temperature, I do find that the E3 shows more changes instantly with airflow such as when the patio door is opened to let the dog out. Perhaps the E3 uses those instantaneous readings to make assumptions about smart recovery or about when to call for fan only rather than heat. I do find that on average over a period of time, the E3's thermometer is accurate when compared to the readings of other thermometer in the same air space.

    Have you called support and asked to be sent a replacement if you think the thermoter in your thermostat is off?

  • BPMBPM AlbertaMember

    Thanks for your response. It is not a matter of the temperature being accurate while their is not a call for heat, it is when the heat cycle is active. Before a call for heat, the thermostat and thermometer read the same, it is when the heat starts that the thermometer increases by over 1.5 Celsius before the E3 changes from start point to the next .5 Celsius increase in temperature. Therefore by the time the E3 shuts off the heat cycle, my thermometer is 2.5 Celsius higher, (actual room temperature), than what it shows on the E3. I would have to say that the E3 has a problem in sensitivity for reading temperature at first 5 minutes of heat cycle. By the way my fan setting is set to always on so the airflow issue is not even a variable here.

  • my0gr81my0gr81 coldnadaMember

    or the E3 is too aggressive in compensating for the inevitable operational temperature change due to the current flow during a call for heat. Check your firmware version, if it lower than, then you may want to contact support for an update.

  • BPMBPM AlbertaMember

    I have the current firmware. As mentioned previously, the initial 5-10 minutes or so the reading on the thermostat is way off the actual room temperature shown by the thermometer. Once the E3 shown temperature reaches set point, the E3 shuts down fairly quickly and within specs, It would be great to know if anyone else has experienced the overshoot by actually using a thermometer(s) as opposed to just saying my E3 shut off it must be working properly or it is the same as my other thermostat etc.. Thanks

  • kain2thebrainkain2thebrain VirginiaMember

    I just installed my ecobee3 today, and I saw the same issue. I called customer service, and they let me know that when the ecobee3 first starts up, it will try to read the same temperature as it was last at...in the case of a new model, it would be the calibration temperature. over time, it would move towards the actual room temperature. my old thermostat was reading 66F, and the ecobee started out at 80F, dropping slowly over the course of an hour or so till it hit the actual temp.

  • chrisyngchrisyng calgaryMember

    When I first installed my e3 I noticed that every time the fan turned on, either with a call for heat or for ventilation, the temp reading for the main sensor started to go down..this was due to the location of my thermostat picking up draft from the vent .. this caused my heat to stay on longer than normal. When the fan stopped, main temperature rapidly went back to normal room temp readings (as verified with 2 separate digital thermometers) .. I brought my remote sensor down and placed it by the thermostat, shut off the main thermo and relied on the remote thermometer to sense the temp in the room. I found that the remote sensor was not affected by fan turning on and I was not overshooting my set point..
    What I did to fix my issue and make the e3 less sensitive to the drafts was to block half of the port to the temp sensor at the bottom of the e3.. I just used a bit of clear tape and covered up half of the opening. After doing this, my e3 works perfectly. No longer drops temps when the fan kicks in, no longer overshoot calls for heat, and gives temp readings that match up to my other thermostats..

  • BPMBPM AlbertaMember

    Thanks again all for your input. My E3 has been installed for over a week and I have turned down the heat, disconnected to reset and let calibrate to room temp, which it does, to eliminate that as a concern. As mentioned, I eliminated drafts as well as I have my fan always on and of course fan speed increases when furnace fires up. Also as mentioned earlier, the problem lies with the thermostat taking 1-1.5 Celsius increase in actual room temp before it registers a .5 Celsius increase on the E3 which then by time the thermostat stops the call for heat it has created an overshoot problem by 1-1.5 Celsius or more.

  • maybe open a ticket with support with your findings so they can look into it further. It might also help if we knew what firmware you are on, mine updated a few days ago to 3890.

    I wish there was a changelog for the firmware so we know whats changed, maybe it fixes your issue?

  • ecr72ecr72 Auburn, CAMember

    my0gr81 said:
    or the E3 is too aggressive in compensating for the inevitable operational temperature change due to the current flow during a call for heat. Check your firmware version, if it lower than, then you may want to contact support for an update.

    I think this may have something to do with your issue. I noted in another thread that when a call for AC happened on mine the physical temp of the E3 went up and the internal sensor did not compensate properly and read the temp higher than it should have. Maybe the new firmware has some better correction algorithms. Now that I'm using heat, I'll need to check the temp of the internal sensor and see if there are any similar issues.

  • mtherrmtherr CanadaMember

    I sent the following to support this morning.... :(

    I installed my Ecobee3 last night. For about 1/2 hour, it was calibrating. Then, the displayed temperature came very low (15C while it was 20C) in the room. I adjusted the temperature correction parameter to correct this and then it fluctuated between 18 and 25.

    This morning at 4:30 it was showing 18 (in line with my other devices). It went down to 17 and started heating for a few minutes and then it was showing 25 (at 5am) while the real temperature is 18. Temp correction parameter is already at around +3.5. At 5:30 it is showing 20 degrees. I can assure you that the temp in my house did not vary much during that time.

    Humidity sensor is also problematic. It was showing 65% while it was 45% in the house. Earlier this am (30 minutes ago) it was showing 30% (15% under) and now it is showing 53%

  • BPMBPM AlbertaMember

    I appreciate your input. Although that isn't satisfactory, my concern still has to do with the accuracy in on/off temperature and overshoot. I have over 2 Celsius difference when the E3 is set to the lowest (.3 Celsius) set point differential. In other words, thermostat reads correctly to what I want my settings to be, but, the actual room temperature is way different with way more fluctuation than the E3 is showing. I find it hard to believe there aren't others that have experienced something like this. Is it just a case that people hang this on their wall and because it reads that it is working they are satisfied? Do any of you realize how much in energy costs you are using because the E3 is keeping things running longer than it should. Wasn't this supposed to save everyone money? So far the Smart in Smart thermostat is only smart for the electrical and gas companies!!!!

  • my0gr81my0gr81 coldnadaMember

    I thought I was clear that my experience (including measurements with other thermometers) was that it was accurate. Some of the ones that replied on this thread also provided the same feedback, and we tried to help troubleshoot what the issue with your E3 might be.

    You appreciate the input and you are not satisfied that it addresses your issue, that's fair. But that doesn't mean we are experiencing the same and we are clueless about it. Please give us more credit than this.

  • BPMBPM AlbertaMember

    Seriously my0gr81, you sound like you are an employee of Ecobee!! If someone is stating their facts and you offer support, it is appreciated, However, there has only been one response with someone actually saying they used an accurate measuring device, YOU, to notice if their E3 was accurate or not. Apparently, it seems that there is more than one instance on here that it is inaccurate or problems with the E3 temperature reading. You shouldn't try to bully someone on here who is seeking assistance whether the E3 they own is accurate when theirs is not, it doesn't look good on you. Just as an example, when I first posted about this problem, you stated about how the sensors take an average when in my initial post, sensors weren't even a part of the problem, they weren't hooked up. Mine has not corrected and or so called fixed itself with the latest firmware or any other suggestions that might be on here in over a week.So, if you believe that you are the guru of the E3 and what you say is the way it is and there are no other possibilities or experiences that people may have, then you are in the wrong place.

  • ChrisD24ChrisD24 Salisbury, NCMember

    I haven't checked my thermostats accuracy but I know the remote sensors are correct. I'll have to see how accurate mine stat itself is and report back.

  • BPMBPM AlbertaMember

    Thanks ChrisD24, that is all I am asking is for people to check just the thermostat reading compared to actual room temperature from start of cycle to end of cycle and see what the total temperature difference is in comparison to their set point, set point differential and E3 reading with a calibrated thermometer as opposed to another thermostat etc.. As an example, my set point is 22.5 Celsius, my set point differential is .3 Celsius, my Thermostat comes on at 21.5, (calibrated thermometer and actual room temperature), which is outside specs and shuts off at 23.6 Celsius, (calibrated thermometer and actual room temperature), which is outside specs, while the E3 says 22 Celsius to start and 23 Celsius at shut off. Just so I do not get any questions about residual fan heat after the thermostat shuts off, this has been accounted for. Thanks

  • ecr72ecr72 Auburn, CAMember

    I think you're going to have a hard time finding people with a calibrated thermometer like you're requesting here. I do think there is something "off" with the internal temp sensor on the E3 and that the internal temp rise of it's power circuitry when making a call is the root cause of the issue, but these are just hunches based on some rather crude tests performed with a non-calibrated digital thermometer and non-calibrated IR temp gun while running AC, not heat. The internal temp rise on my E3 caused the internal sensor to read higher than the room temperature by a considerable amount and kept running the AC much longer than it should, so I agree with your comment about the potential lack of cost savings. My short term fix was to have the E3 ignore the internal sensor and rely on three external ones. A week later it cooled off and I didn't need AC anymore so the testing stopped. If I can find some time, I will see if I have a similar issue with the heat calls too.

  • BPMBPM AlbertaMember
    edited November 2014

    Thanks for your response. One thing I could point out is that in my case, I am more curious on the temperature swing, that is, any thermometer could work so far as the temp is looked at when unit first starts and also when unit has finished, furnace or air on to off and take note of the temp swing compared to what the E3 change is. An example is if a digital room thermometer goes from 21 to 24 and the ecobee goes from 22 to 23, we have a problem with accuracy somewhere. After all, there sure seems to be a lot of views on this topic yet not a lot of people actually testing their own unit to find out the accuracy.

  • ChrisD24ChrisD24 Salisbury, NCMember

    I don't have my old Honeywell as I sold it when I had my ecobee Si - so all I have left is the Si. Since it can't operate without being connected to power, I had to use an indoor/outdoor thermometer I had.

    So far the thermometer always shows 1 degree higher that the stat (not the average on the display). That doesn't mean the thermometer is wrong or the stat is wrong - each could be decimals away making one show a whole degree higher and the other a whole degree lower. But they are consistent 1 degree off when idle.

    My stat is on an interior wall in a hallway near a return where they usually recommend they be - but it is located right outside from the master bedroom (which sees little to no sun) vs the entire house which sees sun. Since master bedroom is cold in the summer and cold in the winter by a few degrees when the heat runs the temperature on the stat (both the old Si and the 3) drop in temps - which I assume is from sucking cold air from the master. During that time it seems the thermometer remains the same - but when it stops it they both show the same temp. So I ASSUME the thermometer doesn't update as often - but I don't know. :)

    Bottom line, I don't see my stat increasing in temp when running.

    One thing I did do was seal the hole behind the stat. I did this when I had an issue with the Si sucking air through the hole. I just took a piece of spray foam that dried and compressed it enough that I could stick it in the hole.

  • BPMBPM AlbertaMember

    ChrisD24, thanks for checking what you could it is appreciated. However, my problem is with the actual house temperature increasing by over 2 degrees Celsius from furnace on to furnace off and my E3 (stat) only showing a total increase of 1 degree Celsius. My stat isn't increasing in temp to coincide with the actual real room temp. On Home IQ or what ever data Ecobee has, shows the stat is working great although in real time usage, it does not show the correct temp to actual room temp.

  • ChrisD24ChrisD24 Salisbury, NCMember

    You're welcome - Just to note I was checking the stat temp by going into the sensors menu, not comparing the temp on the stat display.

    So I understand your saying the stat temp (not what's on the display) only increases by 1 from on to off? What about the remote sensors, are those turned on at all? If you have them on but unchecked in the settings - I believe it averages them instead of using occupied/unoccupied...I'd have to check.

  • mlbowdenmlbowden Harrisburg, PAMember

    I just installed my E3 three days ago. I have noticed that the sensor temperature (not the displayed temperature) on the thermostat is 5 degrees lower than a standalone digital thermometer. In addition, the humidity displayed by the thermostat is 15% higher than the digital thermometer. The remote sensors are more accurate than the sensor in the thermostat itself. If this a problem with the thermostat?

  • ltn268ltn268 Montreal, CanadaMember

    mlbowden, I experienced or most of us experienced the same issue as you. I have asked ecobee support about this and the answer was:

    Yes. The ecobee temperature sensor is sensitive to small changes in temperature/humidity RH% caused by the air draft in/out of the wall cavity behind the thermostat. Depending on the type of home (bungalow vs. 2-story) wall cavities that are indirectly connected to an unconditioned attic will be either significantly warmer/colder depending on the time of season. Or if the wall cavity is directly used for the R/A system this will also be a cause for the ecobee to sense the minute changes. Either way this can cause the heating/cooling system to cycle longer than normal. The simple and most effective solution is to seal the hole behind the thermostat. A seal that provides an vapour barrier and stops all drafts is best. Electrical or plumbers putty works best, it will conform around/between the wires to provide a reasonable seal.

    I have not tried the recommended suggestion. For the time being, I excluded the main thermostat sensor and use only my remote sensor.

  • GeekGeek Toledo OhioMember

    I have been lurking here as I have the same temperature accuracy and variation issues.

    Ecobee's above technical response was the "Ahh Haa!" post.
    I removed the EB3 and caulked the big wire feed hole to block the small in/out airflow that occurred when the fan came on or when a high wind blew.


    The temperature reading is much more stable, the system is not overshooting/undershooting by up to 6F, and the temperature graphs are smooth.
    Prior to that I had the EB3, Remote, and old Honeywell on the wall and the EB3 was reading 2F low so I put a correction factor in the EB3 configuration.

  • @BPM, Whats the latest on your situation? Any update or did you find a fix?

  • BPMBPM AlbertaMember

    Sleepy, responded with PM

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