LUXPro P521U Programmable 5-2 Day Thermostat for Home Use; 2 Heat, 1 Cool

I gave a rating of 4 for the thermostat and it got to 4 because tech support was a 5. The wiring diagram in instructions and online (the same) did not accommodate my old thermostat wiring and terminals. Certainly not the direct replacement I read online. Tech Support saved the day and provided help that was accurate. All is working fine now....thanks Tech Support. Product is good...Tech Support better

I bought this to replace the dial honeywell on my hot water baseboard zone. I have old age eyes, so every time I looked at the dial, I couldn't tell what the temperature was, or what the setting was without grabbing reading glasses and a flashlight. The honeywell was off 4 degrees, so when it said it was 66 degrees, it was really 70 degrees. I kind of knew it, but confirmed it with this new thermostat, and an accurate lab thermometer. I like how you can adjust the swing on the temp, from 0.25 degrees, up to 2.25 degrees. It gives you some degree of adjustment depending on whether you want tight temperature range, or less frequent heat/cool cycles. This is the same as the 500U model available at Lowes, which I also purchased. Still waiting on trim plates to be available as the circular honeywells and old chomotherms are just a bit larger, and you'll need a trim plate, or a paint brush. Very easy to program. As others mentioned on the other similar models, when you push the buttons on the front, the backlight comes on with a very high pitched sound barely audible, but it goes away after the backlight dims, in about 5-10 seconds.

There is a known bug with these, the infamous "Low Battery" bug. For about a year they work great, battery gets low, replace and move on. Then about a year or so along you'll see the low battery thing, but this time changing batteries doesn't help, neither does using the internal reset button. Only recourse it to replace it. So you ask, why keep using it if it's so bad, answer, cause you can't find programable thermostats for a 4 wire hydronic heating system anywhere, three wire or four, doesn't matter, the ones I need are just not there. So, I put up with these disposable ones cause when they do work they work well. The first time I had the low batter issue a few years ago tech support was quick to send me a replacement and I returned the bad one. Yeah, they just ignore you now. I suppose I could drop 20k+ for a new heating system, ah, ha, ha, no.

Keeps a nice consistent temp.

Works as expected, was easy to install, the backing plate was easy too. Have been running with it for 10 months without a hitch. I did have to replace the batteries once already which seemed fast to me, but I can't remember if they were new or used batteries. I have it programmed for weekdays vs weekends with the A/C changing during 'peak' hour for power.

Another reviewer complained that there was a substitution of a tx500ua instead of the p521u. In fact these are the same product, apparently marketed differently. On luxproducts.com the unit pictured even has both model numbers. The unit I received does have temperature differential setting (as well as all other p521u features), despite being marked tx500ua.One note on installation; the hardware reset button is exactly where the thermostat wire wants to sit. You must be careful to keep the wires tidy and ensure they don't stick out far enough to hit the reset button or the unit will not work.Update...I was initially happy with this thermostat, but I started noticing that once the temperature had stabilized it would short cycle (come on for only a few seconds), and keep cycling very frequently. I started to keep track of cycles to see how bad it was behaving. It would come on for 30-60 seconds, and then be off for only 1-4 minutes before cycling back on. I attempted to adjust the settings from 3 to 2 cycles per hour, but this didn't help.Thinking it was defective I had Amazon send a replacement, but I experienced the same issues with the new unit. These thermostats are supposed to "learn" how fast your house heats up so it can calculate an appropriate on-time to maintain certain cycles per hour, but I feel like the algorithm is wonky.On the plus side, Lux customer service was very responsive and have sent me model TX1500Uc/P621Uc as a replacement. This one is the old school temperature swing style, so I am optimistic that it will behave normally.All this being said, I cannot recommend these cycle duration "learning" style thermostats, but can recommend Lux as a company.

A bit finicky but otherwise works well. Slightly confusing install directions.

I live in South Florida and my A/C runs 24/7 for most of the year. My system is 18 years old and I attribute the longevity of it to the old Lux programmable thermostat that I've had on it for many years. It allowed me to set start temperature a few degress above the desired temperature which reduced the starting and stopping. For example, if I wanted to maintain 72 degrees I could set it to start the A/C at 74 degrees and run until 71 degrees is reached. This reduces starting and stopping which lowers your electric bill and extends the life of your equipment. This unit advertises that it will do this but once it arrives you get a notice in the box that it they have changed the operation to no longer include this feature. The new one allows you to set the number of starts per hour. Well I don't know about you but I don't have a clue about how many starts per hour will make me feel comfortable or how that will affect the temperature swing. The new algorithm sucks. Also expect unintended operation. When you first power it up it will start your A/C when it's not called for and then stop and never start again until you switch the switch to off and back to cool. I'm left with zero confidence in this unit. Maybe I'll get to like it over time.

This product works very well. The backlight is much more even than others I have owned, making it much easier to read from a distance. The fact that you can set the temperature spread was the deal-maker for me, and because of that feature it works so much better than the previous thermostat, which was turning the stove on and off too rapidly.There are just two small reasons that I give it 4 stars instead of 5:1) I wish the display were a bit larger to better see from a distance -- the big current-temp digits are large enough, but the rest are too small to see except when close up; and2) I find the programming is not entirely intuitive. The basic daily programming is easy, but other features are not. For example, the EMER button is poorly named, positioned, and described in the manual -- one section of the manual says it has no function without a heat pump while another section explains how it accesses certain setup functions. It is the first thermostat where I have found myself regularly reading the manual to recall how to do something. This is not a deal-killer because once you have the settings how you want them you can just forget it. I'd still buy this model again in spite of this because it really has a wonderful array of features, even if they are a bit difficult to access.

Cheaply made. Not the same rigid construction as the previous one. Has that look and feel of cheap “made in China “ construction. Not satisfied at all.