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Ecobee4 - Operational question/temperature variance

Hey Everyone,

I have installed two Ecobee4 units to replace my two current thermostats. Couple different things going on that hopefully someone can chime in on.

Information about HVAC system (House is a year old):

-(2) Lennox single stage heat pumps w/ electric heat
-Outdoor temps have been ranging from the teens to low 30's
-Both areas behind the thermostats have been sealed to the best of my ability with plumbers putty (there wasn't that large of a hole to begin with)
-Downstairs Ecobee is on living room wall
-Upstairs Ecobee is on hallway wall
-Default settings are pretty much being used on the thermostat (I did reduce the compressor min outdoor temp)

First thing that I am noticing is that when the thermostats call for heat, the logs indicate that the temperature continues to drop over the next 15 minutes. So I checked the air coming from the registers and noticed that when air starts flowing on a heating cycle it is in the low 60's. It takes a bit for the temps to get up in the upper 70's...but by that time the temperature at the thermostat has dropped another 1-2 degrees. Aux heat will kick in and run with the heat pump and then the house will regain temperature. This is happening on both the first and second floor...but is more apparent on the second floor. Is that normal of a heat pump? Or did I do something wrong with installation or in the settings?

The other item I am noticing in that the upstairs thermostat is always 1-2 degrees lower than the room sensor and a third party thermometer I have upstairs. I had the sensor and the thermometer placed in the hallway on a tripod in close proximity to the thermostat and there was still this variance. The thermostat has been replaced already because before I was getting a larger variance.

Thanks in advance.

Comments

  • lsbrodskylsbrodsky New Bern, NCMember

    Where is the return air for your system(s)? Is it possible that it is pulling in any outside air before the heat pump(s) can catch up?

  • @lsbrodsky said:
    Where is the return air for your system(s)? Is it possible that it is pulling in any outside air before the heat pump(s) can catch up?

    The downstairs return vent is on the same wall as the thermostat and the upstairs has a return vent at the end of the hallway in the ceiling and in an room off the end of the hallway (on the ceiling as well). Is that what you are referring to?

    I don't think it would be pulling in any outside air...unless there was a gap or hole in the line in the attic space?

    I thought maybe it was blowing cool air due to a defrost cycle...but it happens every time the heating cycle starts (according to the Ecobee logs)

  • lsbrodskylsbrodsky New Bern, NCMember

    I am not an HVAC guy, just a guy with technical background. As I see it, even if the HP's were not working, the air coming out should be no colder than room air, but you are saying it is colder than room air. I cannot imagine your reversing valves are operating in cool then heat, each time, so I would want to rule out a path for outside air.

  • @lsbrodsky said:
    I am not an HVAC guy, just a guy with technical background. As I see it, even if the HP's were not working, the air coming out should be no colder than room air, but you are saying it is colder than room air. I cannot imagine your reversing valves are operating in cool then heat, each time, so I would want to rule out a path for outside air.

    I will definitely check my return lines for any external air infiltration...I just felt like this never happened with my original thermostat...maybe I'm wrong.

  • lsbrodskylsbrodsky New Bern, NCMember

    You probably did not have the ability to monitor it as well with your old one, but you never know...

  • Hypothetically, if I turn my fan to "on", the temperature coming out of the registers should be very close to the temp at the return vent, correct? If it is much cooler, then I should assume I do have some sort of leak.

  • lsbrodskylsbrodsky New Bern, NCMember

    Makes sense to me

  • wolfpack2013wolfpack2013 NCMember
    edited January 8

    Here is my old wiring and new wiring. Does this look correct to everyone? Just want to make sure no functionality was lost. The black jumper I assume was for the emergency heat setting, which just activated the strips via the white wire.

    https://drive.google.com/open?id=0B-vuWNlxRxQwMTc3YVJCQWpFSUtQNmxoaUFlaVUyb2R3Ti0w

    https://drive.google.com/open?id=0B-vuWNlxRxQwZWhRSkRPdTRpRUZfU2JaYkhUUXpBVHpRR1lv

  • Okay, I just set the fan to "on" and the temp coming out of multiple registers is the same as the temp going into the return.

    So, I can confirm there is no ambient air being sucked into the system.

    Any thoughts?

  • lsbrodskylsbrodsky New Bern, NCMember

    Have you tried changing the setting for the reversing valve, energize on cool or heat?

  • @lsbrodsky said:
    Have you tried changing the setting for the reversing valve, energize on cool or heat?

    Wouldn’t that run the heat pump in “cool” mode though?

    The temperature does eventually increase out of the vents. It just is blowing cold when it starts up in the “heat” cycle.

    Are there some other settings I should be checking? Maybe my heat pump is cycling too much and for some reason defrosting all the time. I have no clue...I am just throwing stuff out there.

  • lsbrodskylsbrodsky New Bern, NCMember

    Well, why weren't they running too much with the old thermostats and also defrosting? How old are your heat pumps? Any newer heat pump is not going to have a problem with the temps we have had recently, but an older one might. But if that is the case, you should be able to see that it stops heating periodically and goes into defrost. Is that something you can see in the chart? Any different behavior now that it has warmed up outside?

  • lsbrodskylsbrodsky New Bern, NCMember
    edited January 8

    I am hoping that Kevinmcc will jump in here overnight; he is clearly the expert.

  • wolfpack2013wolfpack2013 NCMember
    edited January 9

    Thanks for your help so far with this.

    The home is a year old. So the heat pumps are brand new.

    I have attached the run time report for the upstairs unit. I can tell that this is not the most efficient way to run a heat pump system...but I am unsure what settings I need to adjust. Looks like it has been running a little better since the temps warmed a bit today.

    https://drive.google.com/open?id=1CDFqjus6Zl83tVom1aRaItq9iPYSX7t5

    Here is an example of what occurs when a heating cycle starts

    https://drive.google.com/open?id=1rBrf190gnwxQwU2lsljuiHKd6a6ke9Ei

  • SneakXSneakX MontrealMember

    Hi,

    According to your charts it seems to be working correctly, only the heat pump is struggling a little bit in the teens to keep the house warm (nothing wrong here, I am in the same situation). If you want to reduce the AUX usage you could raise the Compressor to Aux Runtime, seems to be set at 30 minutes. Mine is set at 150 minutes. You could try 60 minute as a beginning point. Wiring looks correct too IMO.

    You could also try to reduce the Heat differential temperature to 0.5 F instead of 1 F, the heat pump will start more quickly but it should reduces the delta between hi and low ambiant temps.

    If it is not conclusive, you still can easily put it back at 1 F.

  • lsbrodskylsbrodsky New Bern, NCMember

    When I look at this data, I see a heat pump that does not have much punch at the lower temps. Clearly Aux is needed to maintain temp in your house. Back in the day, that was exactly the case for heat pumps. I have read that newer units supposedly perform better at the below 20F regime, which was always the qualitative turning point. Your unit just isn't putting out much heat it seems. Is your refrigerant charge OK?

  • wolfpack2013wolfpack2013 NCMember
    edited January 9

    @SneakX said:
    Hi,

    According to your charts it seems to be working correctly, only the heat pump is struggling a little bit in the teens to keep the house warm (nothing wrong here, I am in the same situation). If you want to reduce the AUX usage you could raise the Compressor to Aux Runtime, seems to be set at 30 minutes. Mine is set at 150 minutes. You could try 60 minute as a beginning point. Wiring looks correct too IMO.

    You could also try to reduce the Heat differential temperature to 0.5 F instead of 1 F, the heat pump will start more quickly but it should reduces the delta between hi and low ambiant temps.

    If it is not conclusive, you still can easily put it back at 1 F.

    I think I have both the "Compressor to Aux Temperature Delta" and "Compressor to Aux Runtime" set to"Auto". If I change the runtime to 60 mins, should I leave the Temp Delta setting on "Auto" still?

    The setting is currently at 0.5 degree heat differential according to my thermostat.

    The issue I am concerned about is the fact that when the heat cycle begins the thermostat readout continues to drop...that would only happen if I was adding air into the home that was cooler than the current interior temp. For some reason, the system pumps 60-65 degree air from the vents for a while before it gets up to 80-85 from the vents. That is why it calls for heat at 67.5 degrees but the temp still continues to fall until 66.3 degrees. I am really confused on that.

    @lsbrodsky said:
    When I look at this data, I see a heat pump that does not have much punch at the lower temps. Clearly Aux is needed to maintain temp in your house. Back in the day, that was exactly the case for heat pumps. I have read that newer units supposedly perform better at the below 20F regime, which was always the qualitative turning point. Your unit just isn't putting out much heat it seems. Is your refrigerant charge OK?

    The system can generate temps from the registers of 80-85 degrees with the heat pump only...what I am noticing is that it is pumping out temps of 60-65 degrees when a heating cycle starts up. That is what causes the interior temperature of the house to continue to drop after the thermostat has called for heat. I have no idea why it is doing that...and I am unsure how to troubleshoot that issue.

    I assume the refrigerant charge is ok. I would need to get a HVAC contractor out here to verify.

    Is the fan coming on before it is supposed to? Is it running a defrost cycle and the electric heating strips are not getting engaged?

  • kevinmcckevinmcc Macomb, ILMember

    Your refrigerant may need to be checked. Possible you have a sticking TXV. Heat pump usually do take a several seconds to get up to full temperature, but should not be taking 15 minutes. Something is definitely not quite right with your system. I would have a HVAC contractor check everything out.

  • Okay, thanks. I will have someone come out.

    I also did the fan "on" test this morning again and this time it started blowing 56 degree air and the inside temp was 68 degrees. It slowly began to raise to around 62 and then I shut it off. So there is a possibility that I have a leak in the duct work.

  • lsbrodskylsbrodsky New Bern, NCMember

    Indeed, it cannot find 56 degree air inside a 68 degree house. But you best get the system checked professionally. The savings in aux heat will pay for the service call.

  • LarrylLixLarrylLix Northern Southwestern OntarioMember

    I have watched this for years across many brands of stats.

    Stop using the indicated temperature on the stat as an indicator!

    Almost every stat I have encontered does this compensation calculation, where they fudge the sensing results using the register for the indicated temperature on the front of the stat. The sensing has a slow decrease in temperature as it calls for HVAC. They all do it.

    If your stat calls for heat at 22.0C, as it runs the heating the indicated temperature drops by 0.1c, 0.2C and more the longer you run it. Of course the room temerature may be starting to warm up but the stat doesn't want to short cycle the heating appliance and turn it off right away, so it fudges the sensed temperature by subtracting an increasing value from the register that just happens to be shown on the front.

    You cannot use the temperatue indicated on the stat for any critical observations!

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