S40 L40 Smart T Stat Reviews

This thermostat and app are terrible. In fact anyone considering the purchase of a Lennox AC would be well advised to thoroughly investigate the thermostat first. It might be enough of a deterrent to redirect your choice of AC units. We have found our thermostats to not be accurate on temperature measurement and hopefully can be recalibrated. The thermostat does not always accept and keep the temperature that is set for control. Also, we have seen S40L40SmartTStat display one room temperature only to have it immediately jump to a different temperature when we go to make a control setting change on S40L40SmartTStat . We just had 2 new AC units and corresponding thermostats installed 2 days ago. I do not believe these opinions are based on an unfamiliarity with the thermostats as we previously had the previous but similar S30 version on our older Lennox units.

Update - after about a month my feelings are almost the same. Learning to live with this garbage. Why do companies think they have to fix things that aren’t broken? This ‘new and improved’ thermostat was about like the message you get when you open an app - “you have an update”.

I spent over $20k replacing units with variable speed features and had iComfort s30 thermostats which had Apple HomeKit integration. That was great and allowed me to easily use Apple Home or Siri to control my home climate. One of the s30 thermostats failed and was replaced with an s40.

Now I can’t use Apple HomeKit and I can’t use one app. The s40 app is horrible and does not refresh the status unless I change the temp. Need to change mode? Three or four taps just to do that. The cost of the systems and thermostats is not reflected in the feature set, which is lacking! I hate Lennox and I hate that I’m trapped in their Stone Age ecosystem. Why Prakash Bedapudi, why did you remove Apple HomeKit? You have a very unhappy customer!

Setup is terrible. I had issues connecting to the Lennox server and the installers had no idea what was going on. For me, I had to restart the thermostat, while others had to ensure their date/time is correct. Scheduling for energy savings is terrible. During S40L40SmartTStat onboarding, or even outside of the customization and trying to configure a schedule for energy savings, my schedules times and temperatures reset to back to default no matter what I do. It is absolutely the most frustrating thing just trying to configure this just to have it reset back to default. I am so frustrated that S40L40SmartTStat can’t interface with a nice piece of hardware, just to find out both the software and hardware are both hot garbage. Do better Lennox.

Sadly, Lenox is known for its many technical issues. They are also known for releasing their products before they are ready for prime time. This new s40, or i40 thermostat with S40L40SmartTStat only works have the time. For four of my 12 zones it works once every four months. I have to manually go to the main thermostat controller and adjust it. The service technicians at 1-800 Lenox are pleasant enough. That is, Once you get through to them. They do try to help guide you, at least the ones I have had, however they can’t fix the issues. So what good are they then? I have call the installers and they not only charge for a service call, understandable, but they are charging an additional $25 for gas! That should be their cost of doing business. Please do yourself a favor and NEVER purchase a Lenox HVAC system. NEVER. Many better companies, like Carrier and Trane. I so so so wish I had never gone forward this company. Always having issues.

This thermostat is so unhandy to use I can’t believe Lennox actually sells them. I had a new system installed two weeks ago including this thermostat and I still can’t get it to work as advertised. It is very hard to read the instructions on the thermostat because they are so small and faint. It is supposed to be able to be made brighter but I can’t figure out how. There were no instructions with the unit but I did find a 50 page set on line. A little hard to read the instructions on phone while trying to set thermostat. I thought I was supposed to be able to set up schedules on thermostat and change temperature schedule temporarily from my phone but I don’t see how to do that. I tried to change some settings from the thermostat but now it is locked up. I called the dealer and I hope they can fix it. After reading other reviews I am not confident that it will ever work as advertised.

This is a review of S40L40SmartTStat . While the thermostat leaves a lot to be desired, it is no where near as intuitive as the ecobee app, it functions and runs the system.

S40L40SmartTStat, is very outdated. It has a poor design and little customization. When attempting to set a temp there are frequently times when the lag between input and communication to the t-stat “reset” the temp you are trying to adjust to.

Scheduling is not customizable. You are unable to add a time period or a time range.

It seems there is only one user account per t-stat. Individual family members seem to need to use one common account. Because of this, it appears that geofencing is not useful and will not work if multiple people in a home use one account. Maybe I am wrong, but there is no supporting documentation pointing otherwise.

Frankly, you can tell there was little investment by Lennox into a worthwhile t-stat app or t-stat software. They should contract out to a professional app developer and start S40L40SmartTStat over from the ground up. Offer customization similar to ecobee or neat. Offer an updated user interface. And integrate proper user accounts. Finally, adding Home Kit functionality is vital. How many users use S40L40SmartTStat ? Not one has HomeKit functionality.

Disappointed in the software aspect of a very expensive HVAC system.

*this opinion is solely pointed at the software of S40L40SmartTStat and the t-stat. No opinion is given on the functionality of the HVAC system itself.

Upgraded from the original white frame unit that was damaged to the S40. This is a very, very expensive >$1200 replacement thermostat. The screen is so dim on its highest brightness setting it cannot be seen in a day light room. You will need to download this software to control the thermostat except at night. The technician needed to use the smart phone app just to set it up. Now I see the zoning control system has bugs. Though each zone can be accessed and adjusted individually they cannot to be individually programmed. Editing the seasonal settings for any one zone changes the seasonal settings in all other zones. This has got to be a bug. This is basic to zoning management that even the original thermostat did properly. Come on Dave. You discontinued both prior thermostats. How long have you been selling the S40 and it has basic zone control bugs. Glad to see Lennox is updating the software frequently.

I had a Lennox system installed in mid-2024. I added S40L40SmartTStat to control the thermostat remotely, and it has worked well until recently. In the last few days when we were gone, there were times that the thermostat app said the thermostat was offline. When I got home and looked at the WiFi settings on the thermostat, all the connections were green but S40L40SmartTStat still said there was a connection problem. The help screen is worthless, since it only covers cases where a connection shows as red while looking at the physical thermostat.
Has anyone else run into this? I continue to look at this a little more closely. I am happy with our Lennox HVAC system, but very disappointed with S40L40SmartTStat.

When i followed steps to link my Alexa to the Lennox account Alexa couldn't find the device.i was about to refit the nest when I finally realized Apple had a new update for ios which once completed required an update to the alexa app and it was finally able to find the thermostat in alexa giving voice control. I only gave it 3 stars since my nest used to track cycle time history which this no longer does. Also, the screen is pretty dim even on its highest setting for a well lit home. It also doesn't estimate time to target temp like nest did. It does provide the authorized installer service update notices which nest didn't do which I huess is helpful.

My installer originally included the S30 in my proposal and I was most impressed by performance reports available on the website.

It’s just simply stunning that the same feature is not available for the S40. Removing such a feature is inexcusable and I didn’t even think to check for this when we changed to the S40 just prior to install (S30 no longer readily available).

I expect that this will be added in the very near future and hope that it’s not for the reason other reviews have stated (Lennox not wanting to make as much information available).

It’s adequate, but it’s basic. Our new hvac is a significant upgrade from our previous one, and I am surprised that the required S40 thermostat is such a downgrade from our previous one. Lennox has all sorts of data about how the system is functioning, how much, when, etc. S40L40SmartTStat would be an excellent place to provide that info (like Ecobee), but instead they send an email with a *very* basic data summary a couple of weeks after the end of the month. Also, the thermostat and app are both surprisingly sluggish to respond to touch, which is the only way to use them.

The S40 definitely helped the installers when they were trying to make the duel fuel system working properly.

But the lack of HomeKit really is detrimental to iOS users. I can no longer set up the WiFi using WAC, which is painful considering my horrifically long passwords. My family doesn’t have an easy way to change the temps from their phones anymore because we’re all using the single Home app.

Also coming from an E30 (which I only had for a day), it’s weird that S40L40SmartTStat feels like a step backwards. Knowing nothing about Lennox beforehand, I thought the installers were downgrading me. There’s just an excessive amount of clicks to do the same thing (such as changing the schedule). The immediate screen info was much more useful on the E30 compared to this one as well (such as the use of auxiliary heat).

A plus side to S40L40SmartTStat is it feels a little more polished (such as the loading spinner). But the number of clicks to do or see anything is a huge step backwards. If you want to hide things for simplicity, then why have a big screen on my wall?

In any case this is a smart device that supports Apple devices, it should support HomeKit

Although this is supposed to be S40L40SmartTStat for the new S40, there is still verbiage from the older S30 app which Lennox has not updated. Also, the Smart Away (geofencing) feature works only occasionally on the iPhone. After 3 complaints, Lennox Customer Support said a future update (timeline unknown) would fix it. I am not sure whether that was a way to stop my constant calls or whether they were really on it. If the latter, I don’t see any official statement anywhere. (In the meantime they are selling a product promising features we paid for that don’t really have exist. Lawsuit anyone?). But I gave 3 stars as the HVAC system itself seems solid, and the rest of S40L40SmartTStat is more or less okay (once you get around unclear wording of some choice options).

This thermostat does what it’s supposed to do well, in the sense that it will make the temperature in the house warmer or cooler. However, I have two issues with it. One is just a matter of getting used to in that the temperature of my house feels two degrees cooler than what the thermostat displays. I solved this problem by adjusting the setting up by two degrees.

The lack of a vacation mode is more problematic, and this matters less on departing than on returning home. It can take a solid 24 hours to bring the house to the right temperature after a trip. In winter I set it to 55 degrees and in summer I set it to 85 degrees. I want to program the heating or cooling to begin the day before I get home and to set this up before I leave. I don’t want to have to remember to pull out my phone to adjust this a day before returning home. It should be automated and that’s easy enough to program, but it does not allow this unfortunately. I hope this becomes possible in the future!

Coming from an our old house with an S30, we just replaced a poorly installed contractor grade York system in a one YO new construction home with a Signature series Lennox system coupled with the S40 thermostat. S40 certainly seems more robust and consistent than our old S30 when it comes to communication links and initial setup. I did like the Home Screen UI on the S30 better as it gave more at glance info for the mode the system was operating in or what schedule was being used, if the system was ramping between points, etc. On the S40, I have to dig thru menus to figure out those same settings. The info is there but it’s just not intuitive. My biggest ding on the S40 in comparison to the S30 are the number of steps allowed in schedules. The S40 limits schedules to 4 steps throughout the day. That’s very limiting and impractical given todays reality of daily routines coupled with dealing with power company peak and non-peak rates.

Overall S40L40SmartTStat is mostly functional. The big issue for me is that the smart away function often doesn’t trigger based on geofencing. I went in a trip yesterday over 100 miles away for half the day and the thermostat never recognized that I was away.

As another reviewer mentioned, the proximity option does not work as desired. With the proximity option toggled on, I will need to really wave my hand in front of the device in order for it to recognize and wake up. But then, I’ve noticed that over time the screensaver will never appear like it is always awake.

The sleep options under current temperature does not seem to reflect in S40L40SmartTStat when the sleep hours are active. I have sleep time starting at 11pm, when 11pm comes there is no sleep icon next to the sensor I have designated as my sleep time sensor. Hours later it seems to finally appear in S40L40SmartTStat but not at the correct time.

There are some nice to have items as well, such as being able to see which stage cool/heat is running, having humidity displayed along with temperature in the my Home Screen so I don’t need to click on each sensor to view the humidity.

Being able to configure alerts for humidity would be helpful as well, such as a phone notification when a sensor measures over a customized humidity level.

With the older S30 unit I used to be able to monitor my HVAC’s performance on my computer. You could tell how efficient the system was running that way by monitoring on your computer. But now Lennox changed it up and you can no longer monitor performance and see just how your system was working because they knew that that computer feature control gave the consumer power to complain about poor performance, so they eliminated that feature, which is why I am very disappointed with this new system. Lennox needs to get on the ball and get back to what it was which was a good system but now the old system got them into a tight situation because consumers were complaining knowingly that their unit was not performing properly. This was a bad step by Lennox and I wish they would change it. They took a step backwards and I resent that. I don’t think I’ll buy Lennox again.

Have had problems from day1 with this thermostat. We understand when the unit was first installed that it was a prototype and may have problems. The delivery schedule of production versions was over a month in the future. We accepted the prototype because the project took over 3 months to complete without the thermostat. The thermostat has been intermittent since installed, but when it works it is great! We have found that controlling the heat pump with the Lennox computer app works very well. We just hope that the installer will replace the unit so control can be returned to the thermostat.

I owned the prior iComfort thermostat which worked, but wasn’t always the most intuitive or easy to set up / program.

The s40 is a miracle! Great display, settings, it’s accurate, and integrates my communicating Lennox equipment beautifully.

S40L40SmartTStat is much improved as well. I never used the old app much. This new one is so nice - including the status and settings and ease of control - it’s a breeze to program and there are a ton of options inside of it.

Allergen defender mode
Accu weather
Pollen / mold / grass counts and more.
Digital humidity control (no more humidistat!)
Home and away modes for energy savings
Allows for extra sensors to be added throughout the home for extra temp readings and added balancing

I’ve owned Trane, Carrier and Lennox and I’ll never own anything but Lennox.

Even when I forget to turn down (if heating) or up (if cooling) the temperature setting before leaving home, the thermostat is easy to change with my cell phone, or it can be set automatically with “AWAY” setup. Works great to save energy and reduce our electric utility bill.