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Lux 7-day 24-Volt Programmable Thermostat Rectangle

20 Reviews
  • Universal compatibility for all system types
  • Each day of the week can be programmed differently
  • 2 Or 4 user selectable periods per day


The TX9100U is a 7-day programmable thermostat that allows you to create a unique program for every day of the week. Features programmable air filter life timer, easy to view back lit display enhances both the design and ease to use.
  • Universal compatibility for all system types
  • Each day of the week can be programmed differently
  • 2 Or 4 user selectable periods per day
  • Energy usage monitor
  • Special day program
  • Programmable air filter life timer
  • Keyboard lockout for unauthorized users
  • Adjustable vacation hold – set for 1-30 days
  • Smart recovery – enables the set temperature to be reached by the programmed time
Weight 0.5 lbs
Dimensions 1.4 × 7.1 × 10.4 in

Latest reviews

  1. Michael77

    I replaced my old Trane Weathertron Heat Pump thermostat with this Lux thermostat. Installation was simple just make sure you carefully read the directions. It took me around 5 minutes for installation. I like that the features are not too complicated. The filter setting is nice to have because I never recall when I put in the filter. Also good that it’s on a timer(2-5min) so if the ac or heat cuts off and you decide to change the temp, it will wait the desired minutes to turn back on not automatically thus lessening the chances of damaging the compressor to the unit. This thermostat was well worth the price considering how much I was quoted from a HVAC tech that wanted to install a Honeywell programmable in at over $200.

  2. pwils025

    I searched for a product that was affordable and reliable and this seems to be the one. I’ve had it for 1 month now and it’s worked without any issue. Installation was very easy since I only use it for a single stage gas boiler. Simple Red/White wire hookup. Programming was simple and the instruction manual was an easy read. Like others mention, it makes a low pitched sound when the back light is on but not loud enough to annoy me. The light turns off after 10 seconds so it’s OK. My only concern are the hinges on the front cover door seem a bit flimsy and only time will tell if they are durable. This unit does a great job of keeping my first floor at the set temp. I would prefer if the clock/settings ran off power instead of 2 double AA’s.

  3. NW-Buyer

    We already had a programmable thermostat for our multi-stage heating and cooling system. Its main flaw was that it required reprogramming at the beginning and end of holiday periods when people were home on weekdays. A lot of button presses were required! The LUX TX9100U eliminated that annoyance with its Special Program. Now, after a one time setup, all that’s required is switching to the Special Program and entering number of days.

    Pressing of any button activates the back light, which makes the display easily readable. There are many other features. An instruction manual, written by a fluent English speaker, comes with the thermostat and is available on the LUX website. It includes eight wiring diagrams covering several system configurations. There are French and Spanish sections, too.

    The thermostat has managed heating flawlessly in several weeks of use.

  4. Phil222

    My old Honewell thermostat gave up the ghost and I was reluctant to buy an electronic one. In my last house the new ones were not as good as my old ones. There have been great improvements in the last few years I see! This thermostat was easy to install and would have been easier to program if I had remembered about the feature to copy and repeat settings from one day to the next! It pays the read the instructions but it is hard to remember all the features. This thing just works, and works well. It seems to be keeping the house at a steady temperature much better than the old one. I can’t explain why except that the old one must have been in worse shape than I realized. Anyway, I shouldn’t have worried and delayed. This is a great thermostat, especially for the money.

  5. David

    I purchased an older Lux thermostat for my Heat Pump. However, there were many (mostly minor) issues that led to returning it and purchasing the brand new Model (LTX9100U). This model has fixed all of the minor design problems in earlier models. It now shows both setpoint and room temperature simultaneously. Both offset and swing are adjustable and the Heat Pump is controlled perfectly.

    Initially, I was skeptical that such an all-purpose thermostat existed, which is why I first went for a Lux specifically labeled for Heat Pump use. However, the instructions are excellent, backed by responsive customer care. It does take the instruction manual to set some of the more obscure (infrequently used) settings, which is why I didn’t rate ‘Ease of Use’ excellent. For day-to-day use the Lux LTX9100U is superb. For the price it is unbeatable. I don’t hesitate to recommend to anyone wanting a digital thermostat, without paying a fortune and who is willing to tackle installation themselves.

  6. NewThermostatPurchaser

    We purchased this LUX thermostat perhaps a month ago. I’ve seen so many mixed reviews for Honeywell thermostats, as well as not particularly liking their look, that I steered away from them. The other manufacturer we looked at was White-Rodgers, who I’ll admit also has some nice thermostats. LUX won out for the following reasons:

    1. Simple design, particularly when closed
    2. Screen has a backlight that can be activated (but is not ALWAYS active)
    3. Able to handle multi-stage heating and cooling, though we’re not fortunate enough to have such fancy gear yet
    4. Adjustable temperature swing and offset–it allows me to manage the temperature controls better
    5. Filter life monitoring is nice
    6. Big display which shows all the relevant information
    7. LUX is a smaller company headquartered in the U.S.

    There are some negatives:
    1. Even with single-stage equipment, when heating, the thermostat indicates the second stage is active (not a big deal)
    2. As mentioned in another review, the backlight activation does produce a high-pitched whining. Since the light’s only on 15 seconds, it’s fine.
    3. Installation took longer than advertised. The installation manual is very good, but could use some clarifications.
    4. It’s a little deeper than the old thermostat, though it’s also smaller in terms of width and height.

    Overall, I would gladly buy this thermostat again. Time will, of course, tell how good it is in the long haul.

  7. Roosta

    This device has an impressive number of features included. It covers every need we have. However, some of the device’s features are not very intuitive to use. If you have a need for the deeper features and the patience to learn them, then this is a great device. You may pay a lot more to get something more “user friendly” with this many features.

  8. jaid

    Have only had this for a month. It replaced a previous Lux model that lasted about 10 years, but then failed to send signal to our A/C unit. This unit is packed with features, and is working well so far. Two minor complaints: 1- High-pitched buzzing sound when screen is lit up. 2 – Difficult to open and close panel.

  9. GaryH

    Installation and programming was straight forward following the instructions carefully. The feature that brings the house to the desired temperature by the time a set time is reached is nice. It works well for us coming home on winter nights but not so well waking winter mornings. But, this is most likely due to our 25 year old heat pump. The old thermostat that this one replaced was a little above my eye level. So, a minor quibble is that the screen is not as easily readable from below as it is from above. Another minor disappointment is that the product’s clamshell package arrived in just a padded envelope instead of in a box. I tried to buy at our local store, but none had it in stock, so I had to buy online. Our heat pump’s cooling mode is single stage, but the display says stage 2 when the cooling mode is running. Since it seems to work fine, I haven’t bothered checking with Lux tech support yet. So far, it’s a good thermostat at a fair price.

  10. hondacbx2000

    Easy to program. I have a forced air system and I like the speed dial makes programming so easy. Also the ability to adjust the swing so the house does not go cold then warm. I did increase it by one because the furnace did cycle more than I wanted. It works very well. I liked the price as well

  11. Chico

    I just got this Lux thermostat model TX9100Ub. Prior to installing I sent a picture of my wire set up with my old thermostat and shared with them the make and model of my central system. I received my answer before I logged at 06:30 am. I matched the wires and it began to work. When I realized that the heat pump was not sending hot air I called and they walked me through the set up for my my electrical heat pump. Now I am warm and cozy. Tried other manufacturers and the products were a bust. The Lux is working great, customer service is superb, the price of the thermostat is much less compared to others with the same amount of functions and, unlike the expensive ones, this one is working.

  12. McCello

    I purchased this thermostat online after finding I was unhappy with a similar priced Honeywell that was carried in the store. The LUX offers a key feature that other brands don’t: a temperature swing setting. This allows you to set a temperature swing anywhere from .25 deg to 2.5 deg in increments of .25 deg I believe (Check the manual for exact numbers). On extremely hot days this allows the AC compressor to work for a longer and rest longer rather than cycling every 5-10 minutes (like it does with the Honeywell). If you can stand a 2 degree fluctuation in temperature inside, you can save your compressor the work. For example, if you set a 2 degree swing and set your desired temp for 76 deg on a hot day, the AC will kick on when the temp reaches 77 and run until it reaches 75. Other thermostats kick on when it reaches 77 and kick off when it gets back to 76 causing the compressor to cycle too often in my opinion. There are a couple other features that are nice that similar price models don’t typically have. The only downside to this thermostat was that it isn’t the most user-friendly. I don’t mind this, but others may prefer something with fewer buttons that “just works.”

  13. River-Man

    The thermostat was not as easy to install as I thought it would be. I have replaced baseboard electrical heating units before so am somewhat familiar with how the whole system works. The directions/pictures did not really explain to me how to determine what type of thermostat I was replacing, being an older, oil furnace. I ended up using the most common set up and it seems to be working fine.

  14. NickName88

    I bought this thermostat a few years ago. At the time, it had the short cycling problem that has been mentioned by other reviewers, and was replaced by the manufacturer under warranty. All of a sudden, in the last month or so, it has started eating batteries. I assumed that the batteries were somehow defective, so I bought a brand new pack and found that it still completely drains them in less than a week. I am disappointed that this thermostat seems to have multiple defects.

    One minor annoyance: The front panel has a flip-down cover over the controls. It is supposed to be possible to pull a tab on the top of the thermostat to open the cover. Unfortunately, it is easer to completely remove the thermostat from the base than to open the cover, so I always end up with the hole unit in my hand instead of having the cover opened.

  15. Broosedamoose

    Purchased this to replace one similar to it. I couldn’t believe how expensive these have gotten since purchasing the original about ten years ago! However, this one was reasonably priced and package said it did everything I need it to do. It was a direct replacement for my other one and is really simple to set up. The backlit screen is cool but not necessary. They could have skipped this feature and offered it at a lower cost! Overall, it’s a great thermostat if you just want a basic programmable unit. Doesn’t have any bells and whistles to make it confusing to program and the large screen makes it easy to read.

  16. hItec

    This LUX LTX 9100u has a Swing feature that allow me to control my second floor temperature exactly as my first which I had never been able to achieve with a HoneyWell 5-2 programable digital thermostat for 13 years which went bad last week. Good value + excellent design. very happy with this purchase that fixed my 13 years of problem with Honeywell.

  17. Craig

    I can’t believe anybody can be happy with this programmable thermostat. It may have a great display BUT
    the time and temperature variation to shut down is horrible. In AC operation the temperature variation must drop
    by 4 or 5 degrees before shutting off the fan even after I tried to change the program in the Menu. So although it is set to go off when reaches 72 or 73 it continues to operate until you are freezing.

    Very bad technical product! Returned and bought another Honeywell, It works great with very tight temperature and time variation. Go Honeywell and forget the good looking LUX!

  18. Roger982

    returned due to furnace running every 5 minutes for only about a minute.

  19. Indi

    I’m just an average homeowner whose pretty handy around the house. I have installed several thermostats in my homes over the years so this shouldn’t have been too confusing.
    The first problem…The temperature I set the thermostat to does not reflect the actual temperature in the area that the thermostat is in. For example, since the basement is not used all the time so I set the temperature at 65° in all modes. I raise the temperature as needed. Here’s the problem. The actual temperature on the thermometer reads 62.1°. I changed the setting to 66° and the thermometer now reads 63°.

    Another problem is opening the control panel door to change settings. It’s very hard to open this door. Every time I do open it to adjust the settings, it tends to pull the entire unit out of the electronic circuit instead of just opening the door.

    Finally, I have a 2-wire system. Can’t be much problem there, right? But the directions are not really written for the average homeowner (moi.) I tried the first wiring diagram and nothing worked. Then I tried the second and it did work.

    I definitely wouldn’t buy this unit again. The unit it replaced is no longer available, and was the easiest thermostat to install and program. However, I’ll live with the inaccuracy as long as it’s already installed and working. Don’t fell like going back to to replace it.

  20. Chuck

    Easy setup and installation this replaces my old one I had for 23 years.
    Programmed for 7days and 3 different times a day for our convenience.
    Works like a charm no problems at all.

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