Unfortunately, the device is problematic. Its temperature sensor (the thermometer) is slow to detect changes in temperature and thus does not function properly. As soon as you turn it on, it works for hours until it realizes that it has reached the desired temperature, even though the analog thermometer shows that the room reached it long ago. Then it turns off, the radiators cool down, the room gets cold, the analog thermometer shows that the temperature has dropped, but the thermostat device still shows a high temperature and does not turn on the radiator burner. You have to constantly monitor it and keep adjusting the temperature up and down so it doesn't burn for hours unnecessarily at first and so the house doesn't freeze afterwards.

Other than that, the screen has a backlight (Siemens ones didn't), it has a small light that blinks (very subtly, of course) when the burner is operating. It has an on button and an off button (Siemens ones don't have this). And it has the ability to be programmed per day. But since it doesn't detect temperature changes, all these features are useless

THE TRUTH is that by measuring the room temperature from 2018 until early 2025, it operated with excellent accuracy of 0.2 degrees Celsius. For the rest that I read have an accuracy of 0.5 degrees, you will definitely 100% freeze! However, after this period of use, the ON/OFF buttons broke in March 2025 from finger pressing, and it should be noted that they always needed a bit more force to work. I fixed them with my own makeshift solution and they work fairly well now, though they still require a bit more pressing than before, but just a few days ago, the background blue light stopped responding. I changed the batteries, but nothing. In other words... "it's done for." Its screen is now dark. However, when I opened the device, I realized that the buttons are ridiculously made and at some point would definitely break since they are made from cheap material for such an unacceptably expensive product like a room thermostat. If nothing else, it should have lasted forever, but know that it will leave you at some point. If they had paid attention to the quality of its construction material, it might have lasted almost forever. So I give it 4 stars because I have to pay for a new one, it is very expensive to buy, and I will need an electrician to install it if I can't manage myself. Money down the drain!

First of all, DO NOT get it in BLACK, you can't see ANYTHING from the shapes on the buttons, painted with gray color... They should be white for full visibility.... But we will get DISSING if we do that even though it's not crazy beautiful... and the lighting is blue and light economical... Anyway, I will order the white cover from the company to be safe... In terms of differential relationship, we are okay even though I used it for half a season... But I have the impression that it requires a little more than a classic Siemens that I had. I will check it with a thermometer this year. As for the menu, it's relatively easy in terms of programs... But so far, I have it on the simple one... I will probably program it this year due to a long absence from home and we'll see... I will come back... 5 stars for the beginning of quality-price ratio... etc... And we'll see... And one last thing, for many devices we can install it (for someone who knows how to install) at 3 volts. So we don't have to change batteries...

Although I use it as a simple thermostat without using a boiler and programming, I will say that it is reliable in terms of temperature.
With 2 digital thermometers for comparison, I saw variations from 0.0 to 0.4, so I consider it to measure very well!
I also heard very good comments from the electrician who installed it for me, it has been working without any problems for several.
Time will tell.
So 5 stars as a first review!

Update 23/12/23
Almost 2 years later, it works perfectly.
I needed to program it but I couldn't do it with the manual. I called the company and in 5 minutes they helped me program it as I wanted. Excellent customer service.
I also learned a detail that helps with programming.
You can't program in minutes, only in whole hours. So I wanted to set it to 5:45 and I set it to 6:00, and instead of 7:30 I set it to 8:00.
But they told me that this specific model has been replaced by the Bs-813P, which you can program with the minutes you want.
Also, the battery lasted easily for 2 years and it is very easy to replace. Just when the battery voltage drops, the screen doesn't light up, probably for energy saving purposes.
Just the fact that it is Greek-made and that you can call the company anytime for any questions, it is worth it and more.
Well done to Olympia Electronics.

First day....we will see what and how...
It needs some corrections in construction and menu...
As for those who mention difficulty, they probably don't know much... With so many functions, you can't just press a button and program it...
I would like a light to flash in yellow when the boiler is turned on, for example...
More vibrant colors on the buttons and maybe larger ones... The screen could light up slightly at intervals for remote control.
The terminals should be changed with clamps instead of those with the blade inside because it is troublesome in the polyethylene cable without tips... The plastic is okay, it looks more upgraded than older components... As for the battery, maybe rechargeable ones could be used and replaced with another device that uses the same ones...
2 analog and one more digital in the same spot, while the temperature drops one degree and more, it still shows the same...
Temperature difference in this one is 0.4 while in other thermometers it is 0.8... It takes time to understand the temperature drop...