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ecobee3 with a Two Stage Heat Pump & Two Stage Furnace

I'm going to be installing an ecobee3 in a few days, and from what I've read, I think it can control what I have, but just wanted to make sure. I have a two stage heat pump and a two stage furnace. The thermostat I have is currently setup with the heat pump as primary and uses both stages and the furnace as auxiliary and always uses its second stage. I'm guessing this is just a limitation of the thermostat. Is the ecobee capable of using both stages of a heat pump and furnace?

Comments

  • lsbrodskylsbrodsky New Bern, NCMember

    Ecobee is good for 2 stages of heat pump and two stages of Aux heat, but how it uses those may not necessarily delight you. For example, Smart Recovery does not use Aux heat, ever, and it only uses Stage 1 of your heat pump. This is the only serious shortcoming I have found.
    Larry

  • That sure is odd. So Smart Recovery isn't so smart, IMHO.

    I wasn't planning on using Smart Recovery. I just like to set a time when I want the heat to turn on, and it sounds like that's the way to go given the hardware I have.

    Thanks for the reply!

  • kevinmcckevinmcc Macomb, ILMember
    edited February 2017

    I use deltas for my 2 stage heat pump, set to minimize AUX usage. I have single stage AUX, but Ecobee3 will work with 2 stage AUX. You do get wider range of lockouts than most thermostats, example I have AUX lockout set to 35F. You can set compressor lockout down to 0F, although I have my compressor lockout disabled. I run my heat pump even in extreme cold. Ecobee3 does have simultaneous operation as well, which can be used if your A-Coil is upstream of (before) the AUX. This allows you to preheat the air with the much more efficient heat pump and finish off with the AUX. I use simultaneous operation, works great with my newer air source heat pump which works down to -10 F without issues.

  • I've had my ecobee installed for a week now, and am pleased with how it can control both stages of my heat pump and furnace.

  • kevinmcckevinmcc Macomb, ILMember

    In the Ecobee user guide there are instructions for the settings that begin on page 25.

    https://www.ecobee.com/wp-content/uploads/2014/09/ecobee3_UserGuide1.pdf

    There are different thresholds and lockouts if you wish to use them.

    Aux Heat Max Temp I have set to 35. I don't know if the Ecobee will turn on AUX if I were ever away and the heat pump failed if this was set below freezing. I don't want pipes to freeze, so I set to 35. If I knew Ecobee was smart and to turn on AUX if them was was near freezing in the house I would set this 20 to 25. For piece of mind, 35 is where I set it and forget it.

    The other setting are pretty straight forward, but if you have questions just post and we'll try to help.

  • @kevinmcc said:
    In the Ecobee user guide there are instructions for the settings that begin on page 25.

    https://www.ecobee.com/wp-content/uploads/2014/09/ecobee3_UserGuide1.pdf

    There are different thresholds and lockouts if you wish to use them.

    Aux Heat Max Temp I have set to 35. I don't know if the Ecobee will turn on AUX if I were ever away and the heat pump failed if this was set below freezing. I don't want pipes to freeze, so I set to 35. If I knew Ecobee was smart and to turn on AUX if them was was near freezing in the house I would set this 20 to 25. For piece of mind, 35 is where I set it and forget it.

    The other setting are pretty straight forward, but if you have questions just post and we'll try to help.

    A question about a "dual fuel air-air 2 stage heat pump with 2 stage gas furnace": I assume that below the "min outdoor temperature", the compressor is disengaged and the 2 stage furnace is used. Right? I am confused as a little later on page 26 in the section it talks about configuring a 2 stage conventional furnace, then says that is it is a heatpump system you can configure the first stage if it is a heat pump?? What has happened to my second stage?

    From page 26----"Furnace This menu lets you configure up to a 2-stage conventional heat source. If you have selected a heat pump as your primary source, this feature allows you to configure the 1st stage of auxiliary heat connected to the system."

  • I know its an alternative, but some modern gas furnaces can be set to auto switch from GAS stage 1, to GAS stage 2 after X min runtime.

    this allows you to have thermostat control compressor stage 1, compressor stage 2, and Aux, than heater controls AUX run time from AUX 1 to AUX 2.

  • kevinmcckevinmcc Macomb, ILMember
    edited March 2017

    Page 25.

    Heat Pump
    This menu lets you configure a heat pump with up to 2 heat/2
    cool stages and a 2 stage auxiliary heat source.

    I have not connected 2 stage AUX. My understanding is Ecobee3 is supposed to do 4 heat stages. When I read the message on page 26, I read that as AUX 1 will be the type you configure, and assumes AUX 2 will be same type, not that you will lose AUX 2.

    Send support an email, they would answer your question with certainty.

    [email protected]

  • LemurTechLemurTech MedfordMember

    @lsbrodsky said:
    Ecobee is good for 2 stages of heat pump and two stages of Aux heat, but how it uses those may not necessarily delight you. For example, Smart Recovery does not use Aux heat, ever, and it only uses Stage 1 of your heat pump. This is the only serious shortcoming I have found.

    I just went through a discussion with Ecobee support about this. From that conversation, it is more accurate to say that although the Smart Recovery feature does not use auxiliary heat, having the Smart Recovery option selected does not mean that aux heat will never be used; it simply won't be used during the period when Smart Recovery is supposed to be active--unless something else triggers it.

  • towprotowpro Member
    edited November 2017

    So does this mean the following is true?
    if I have thermostat set to max compressor 1 run time 10 minutes
    and I turn off smart recovery
    If I am in a smart recovery period, the system will switch from compressor stage 1 to compressor stage 2 after the 10 minutes I specified?

    currently with smart recovery on, if your in a recovery period, it will only run compressor stage 1 to recover, as temps start to drop I can already see compressor 1 running for an hour during mornings.
    this ain't going to cut it as compressor 1 is only 24,000 BTU. Compressor 2 is 36000 BTU and Aux Stage 1 is 48000 BTU
    (note, if its below my compressor cutout setting of 35, AUX 1 compressor heat will not work, it will use only use AUX.

  • kevinmcckevinmcc Macomb, ILMember

    I'd ask Ecobee for sure, but my understanding is Smart Recovery is meant to minimize stage 2 usage and more economically get your home to temperature.

  • that is where they (in my book) ecobee made the mistake. I have 4 stages of heat.
    the first 2 stages are compressor. (stage 1=24K BTU, stage 2= 36K BTU)
    The first 2 stages are set to only will only work above 35 deg.

    If its 36 degrees outside, and thermostat comes into recovery period in morning where 3 deg recovery is called for, if only stage 1 (compressor 1) is used, it will take over an hour for the temp to come up 3 deg.

    If stage 2 (compressor 2) is allowed to come on, this recovery takes around 1/2 the time.

    Which is more efficient? I can't run my heat pump below 35 because of this design where only stage 1 can be used during recovery periods, it would never bring the heat up.

    If I was writing the code, I would take into consideration of "what happened last time it was 36 deg out and we went into recovery". Heck, I might even write code that skips stage 1 and start right out with stage 2, based on learned recovery times.
    or at least write code that follows the owners input, like the setting "max run time stage 1 X minutes". That way if the owner wants the thermostat to stay in stage 1 during recovery, they can leave "max run time stage 1 X minutes" set to auto
    but if they want to stage 1 to advance to stage 2 after 5 or 10 minutes, they can enter it into this spot and thermostat will obey this request even during recovery periods.

  • kevinmcckevinmcc Macomb, ILMember

    Why is your heat pump only working above 35 F? Old unit? I run mine down -5 F without any issues, installed in 2007. Efficiency depends on how many watts per BTU are used per stage. Typically the lower stage should be more efficient although the run time is longer.

  • My system is 3 years old, 18 SEER with 98% propane furnace.
    Stage 1(compressor) =24k btu
    Stage 2(compressor) = 36K btu
    Stage 3 (Aux stage 1) = 48K btu
    Stage 4 (Aux stage 2) = 72K btu

    Before I installed my new system I completed a manual J calculation on my home because I was going to put in Geothermal and I needed to know.
    at 30 deg, Stage 1 (24K BTU) would have to run 70% of the time to heat house.

    During times of smart recovery in the morning from sleeping temp of 65 up to occupied temperature of 68, as long as outside temp is above the compressor lockout temp I have set, the thermostat will only allow the use of stage 1,
    But at 30-25 deg, Stage 1 compressor (24K btu) is not enough heat to change temperature fast enough. I have seen run times of 1 hour to change temp from 65 deg to 68 deg.

    But if Ecobee would honer the setting "max compressor stage 1 run time (10) minutes, and switch from Stage 1 to Stage 2 during smart recovery, I would be able to lower my compressor cutout temperatures.

    Make sense?

    Now most of the time, it seams that since I have turned off smart recovery, some mornings it will switch from Stage 1 compressor to Stage 2 compressor after 10 minutes, but other mornings it will continue to run Stage 1 compressor only.

  • kevinmcckevinmcc Macomb, ILMember

    If your coil is upstream, meaning the return air hits the coil first and then goes through the furnace, you may want to enable simultaneous AUX. You will get the more efficient Geothermal to preheat and the furnace to polish the air. You shouldn't worry about the geothermal running so long, the idea is to run as cheaply as possible which is lower stages, even at longer run times the lower stage will be cheaper. For me I have AUX locked out at 35 F, I try to keep AUX from running as much as possible.

  • lsbrodskylsbrodsky New Bern, NCMember

    I have 2 stage geothermal and 1 stage gas furnace as Aux. When I first got mine and encountered their Smart Recovery shortcoming I disabled SR and observed that the system worked as intended, Stage 1 unless or until the runtime or delta T met requirements for Stage 2, or Aux, depending on the settings. But I like SR getting the house temp up at the right time. Unfortunately, it will only run Stage 1 until the set time. They designed it for economy, not comfort. I suspect if you have a Stage 1 that cannot heat the house from a colder temp then you are an outlier in their design and you will have to live with SR disabled. I have a similar situation in that I want SR to use Aux because natural gas is much cheaper than other Aux fuels and my furnace gets temperature up and toasty quickly. Unfortunately Ecobee has no intent to accommodate SR employing Aux, under any conditions.

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