Drayton 123070 LP522 (Mk4) 2 Channel Programmer, White

Product Information

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. 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? 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. 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.

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. Which model you choose will depend upon how the old thermostat is wired. Not all room thermostats have a neutral connection and just have a live and a switched live. If yours doesn't have a neutral, you would require a battery operated replacement. Such as the Tado wired thermostat. The two switching wires from the existing thermostat simply connect to the NO and COM terminals and that's it, wiring done. If you do have a neutral present at the thermostat you have the option of a battery or mains powered thermostat.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. 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)

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.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. 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 Drayton LP522 as well as heating control includes another channel for control of hot water heating. So that would still continue to work as it does now. 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.