Read around and some say it could be a blown fuse which this turn off of the display is telling me but I don’t get why the two lights would be on? I read this forum https://www.diynot.com/diy/threads/upgrading-lp522-to-nest-wiring-diagram.502626/ - and found it really useful and how is easy it was. Also, whilst there maybe a nomenclature in the wiring centre lid stating the suggested function of each terminal, often it is ignored. I assume too, that the existing thermostat is actually controlling the heating at the moment. I've seen some installations where there's a thermostat with a cable in, but it wasn't connected to anythng at the other end. I know there are plenty of threads about this but I still can’t seem to hit this one on the head. I had an LP522 in place in my new house and am trying to hook up a new Nest to it

Another possibility is that the room thermostat and /or programmer have been moved at some point and the wires extended from another junction box using wires with a different colour. I have considered changing my own thermostat, but mothers house had so many problems with wireless link, so not keen on wireless, at the moment using Nest Gen 3, as it sends info through the same two wires as it gets the 12 volt power, so all done with two wires boiler area to main house. But Nest Gen 3 does not connect to TRV heads, it said it did, but alas that's not true, but mainly the problem is house design, late mothers house worked fine without linking TRV's, but this house hall cools too slow. Much depends upon the layout of the various components in your home, if the system has been modified or moved in the past, the personal preferences of the installer, and the materials they had to hand. Lots of variables really.

LP522Si

And all central heating should come from the same 230 volt supply, otherwise and UPS system to keep it running will not work. However my TRV's with this house (oil fired) have not worked anywhere near as good as with late mothers house (modulating gas) how much down to how pipework installed and how much down to on/off boiler I don't know. My initial feeling is that a fuse went off in the junction box and that’s caused the programmer to go blank with the two lights lit to denote a replacement fuse is required? Not sure why the heating and and potentially HW stayed on though. The HW didn't work on the Nest, which was a surprise. So I just took a wire off, and it now works fine. It was great to have hot water in the morning without getting out of bed and pressing a button. However, my CH wasn't working on the scheduler, or the dial. Another thing is that the hot water was a lot hotter than it usually was but perhaps this was because the water was left on for longer than it usually does. The only things that seem to show are the two lit LEDs denoting that the hot water and central heating boost are on. I’ve attached a really bad picture to show the green lights that are lit.

boiler turned off in case heating was left on as I can’t see if it is on the display (but could hear it working) Allowing different programmes for weekdays and weekends and independent timing of each channel. LP522 provides the ability to control central heating even more efficiently. No longer do systems have to switch on as early at weekends as they do on weekdays. Finally the old thermostat needs to be decommissioned. The simplest way is to leave it in place and put both wires in the same terminal so that they are electrically connected.random turning off of the display of the programmer console Drayton Lifestyle LP522 with two lights denoting HW/CH boost are on Unfortunately, whilst the wires have to terminate at their correct points for the heating to work, there is no fixed way of getting them there. I have seen 100's of installations over the years and I'm pretty sure no two of them have been installed exactly the same. I decided to get a Nest 3rd Gen (Learning Thermostat) after reading the forums on here. I'm in a rental property with no thermostat and I want to save money on heating, and I figured I could probably take this with me if I move (I also like tech). It's not a total disaster, as pressing the manual button does work - but that doesn't make sense as clearly it can and does operate the CH. I assume you are asking this for simplicity of installation, it's a bit of a fudge to leave the LP522 in place, but you could. The simplest way would be to leave the heating set to be permanently 'on' at the LP522 and replace the old mechanical thermostat with a WiFi controlled 'wired' smart thermostat.