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Is 2-stage control worth the extra wiring?

njbairnjbair Cleveland, OhioMember

I just bought a new home with a high-efficiency furnace. Both the heating and cooling are 2-stage. The wiring to the current thermostat is basic 4-wire (no C wire). I bought a used Ecobee 3 (1st generation), which includes the PEK for 4-wire installations. Replacing the thermostat wire would be a relatively short, easy pull.

My question is, what would I gain by wiring up the Ecobee 3 for 2-stage control?

Answers

  • I guess it depends on how smart your furnace controller is. I installed a new 2-stage Lennox and ecobee 3 in August. I have the ecobee controlling the stages but it isn't doing it very "smartly". It always engages stage 2 after the furnace has run 10 minutes. My furnace has the same ability to adjust stage control after a fixed delay. I hope that ecobee does implement some smart/predictive logic in the stage control in the future but mine isn't doing it at this point.

  • njbairnjbair Cleveland, OhioMember
    edited January 2016

    @Greencat said:
    I guess it depends on how smart your furnace controller is. I installed a new 2-stage Lennox and ecobee 3 in August. I have the ecobee controlling the stages but it isn't doing it very "smartly". It always engages stage 2 after the furnace has run 10 minutes. My furnace has the same ability to adjust stage control after a fixed delay. I hope that ecobee does implement some smart/predictive logic in the stage control in the future but mine isn't doing it at this point.

    I think I read a thread along those lines here while searching for an answer to this question. Are you sure your furnace's switches/jumpers are configured to hand over stage control to the thermostat?

    Either way, I suppose the potential is there for Ecobee to extend this functionality, whereas the furnace controller is not going to get any smarter. Given that it's a pretty short, easy pull, I'll probably go ahead and run the extra wires. Thanks for your help.

  • @njbair Yes, I've verified the stage control setting on the furnace. I've also used the test feature built into the ecobee3 to verify stage 2 activates when commanded from the ecobee (The test feature is great).

    The ecobee has a more flexibility than the furnace too. You can set the ecobee to engage stage 2 at a set temp delta and/or by time. Another strange behavior I notice is that the ecobee does not use stage 2 during smart recovery. Mine runs for about an hour every morning to recover 4 def f and only uses stage 2 if it hasn't hit the set temp AFTER the recovery period.

  • @Greencat said:
    Another strange behavior I notice is that the ecobee does not use stage 2 during smart recovery. Mine runs for about an hour every morning to recover 4 def f and only uses stage 2 if it hasn't hit the set temp AFTER the recovery period.

    That makes sense to me. When it is in smart recovery it has the luxury of being able to predict How long it'll take to get to temperature and alot of time to do it in. So why not heat it slowly so that when you wake up/get home your house is nice and evenly heated? Now if it takes longer than anticipated to get to temperature, or you surprise it and manually change the temp or trigger smart home, then it should kick on the second stage to get you to temperature right away cause you are probably more concerned with getting the house close to the right temp than having it evenly heated.

    The only exception to this is if you change a threshold such as "max stage 1 runtime" then it should follow that rule.

  • @Greencat said:
    Another strange behavior I notice is that the ecobee does not use stage 2 during smart recovery. Mine runs for about an hour every morning to recover 4 def f and only uses stage 2 if it hasn't hit the set temp AFTER the recovery period.

    I have to recant this observation. This morning, during the recovery period, stage 2 was called 10 min into the period. Also, even though it was colder outside than yesterday it waited longer to begin the recovery period, like it was planning to use stage 2. Maybe part of it's learning?

  • njbairnjbair Cleveland, OhioMember

    @Greencat said:
    I have to recant this observation. This morning, during the recovery period, stage 2 was called 10 min into the period. Also, even though it was colder outside than yesterday it waited longer to begin the recovery period, like it was planning to use stage 2. Maybe part of it's learning?

    According to this post in another recent thread, some furnaces may be engaging stage 2 on their own even with Ecobee controlling it. If that's the case, would the Ecobee know that stage 2 has kicked in? Maybe the Ecobee thinks stage 1 is going the whole time, which could seriously throw off its efforts to learn your system.

    I'll have to get mine wired up and see if it tries engaging Stage 2 on its own.

  • @njbair said:
    According to this post in another recent thread, some furnaces may be engaging stage 2 on their own even with Ecobee controlling it. If that's the case, would the Ecobee know that stage 2 has kicked in?

    I only know stage 2 was running from the ecobee Home IQ system report. But you're right, the ecobee wouldn't know if the furnace were engaging stage 2 on its own. And it would definitely mess with any learning of heating rates. The data in the IQ report only shows when the ecobee is calling for stage 1 and 2.

    I can see someone overlooking the fact that they need to disable the furnace control of stage 2. My Lennox furnace has a switch to select whether the tstat or furnace controls stage 2 and I have it set to tstat. I can tell on my furnace what stage is running with the diagnostic LED display on the furnace. I did that to verify proper stage operation after the ecobee install and to verify the variable speed fan was sequencing properly. I have never noticed a case where stage 2 is running and my tstat or ecobee app said it was still calling for only stage 1.

  • lannister80lannister80 ChicagoMember
    edited January 2016

    @njbair said:
    I'll have to get mine wired up and see if it tries engaging Stage 2 on its own.

    Mine is wired up for 2 stages and the furnace obeys the Ecobee. Always. There's a jumper on the control board that's set to "thermostat control" instead of "furnace control", and it I haven't ever noticed it to misbehave.

    Rheem

  • My AC there only a slight improvement in efficiency for stage 1 over stage 2 when cooling. Really depends on your AC unit and your preference to blower speed. I prefer quiet of stage 1 myself over the stage 2 roar.

  • gizbuggizbug ChicagoMember

    Has your ecobee and your 2 stage Lennox been working good since your last post?

  • @gizbug said:
    Has your ecobee and your 2 stage Lennox been working good since your last post?

    Yes, no issues with my Lennox. My ecobee3 is on fw 3.7.0.936 still. It really hasn't been cold enough to need stage 2 yet. I looked through the logs and see it has only used stage 2 a couple times recently and both were after the transition from Night to Home modes.

  • gizbuggizbug ChicagoMember

    The installer said I do not have 6 wires, only 5, so I guess I'm stuck with furnace controlling 2nd stage

  • gizbuggizbug ChicagoMember

    It looks like he used the adapter, and he took the 5th wire, common, and put it as w2. Seems to be working (ecobee3 controlling stage 2). He never done it before but it seems to work...

  • I was fortunate to have 6 wires but also wanted to control a humidifier so I used the PEK and one spare wire for W2 and as a single wire accessory control (C from the humidifier to C on the control board).

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