The cables to the nest must be live as the circuit wont complete otherwise as the programmer doesnt switch on.
What ? the call for heat starts at the programmer and is then sent to the nest, when the nest switches on temp fall the boiler comes on.
The cables to the nest must be live as the circuit wont complete otherwise as the programmer doesnt switch on.
There are only two possibilities.The boiler has always come on whether there's batteries in or out of the heat link
then it's very likely that the old thermostat wasn't connected to the boiler. Probably disconnected and just left on the wall when an older heating system was replaced with a combi.I believe my old thermostat never worked
Then it is not wired correctlyThe boiler has always come on whether there's batteries in or out of the heat link
There are only two possibilities.
Either the wiring at the heatlink is incorrect
or more likely, the wiring isn't connected to anything.
Given this:
then it's very likely that the old thermostat wasn't connected to the boiler. Probably disconnected and just left on the wall when an older heating system was replaced with a combi.
As it's a combi boiler, the old programmer needs to be removed and the new Nest heatlink installed in it's place.
Looking at the pictures there is a supply to boiler then three core and earth going to programmer, and at programmer a three core and earth, unless there is a wiring centre some where between the boiler and the programmer then can't see how anything is connected to the system as well as programmer?
Had same here, and it asked the question what did the previous owners do? To switch on central heating needed to turn on programmer did not matter if DHW or CH as only two wires so both options did the same, then out of house and into garage under house and plug in the pump. It seems the heating did not work after garage turned into flat.
It seems the programmer only does CH in your case, so simply replace programmer with Nest.
Nice try with the diagrams but there's a lot of info missing. A withe always has two ends, so there will always be an even number. Your diagram has 3 brown ends, where's the 4th end? Same for the black wires, and there's only 1 grey end. Anyway, this is how the Nest should be connected. Everything else goes.
View attachment 186181
In the bin.where would the programmer fit into this?
In the bin.
The Nest is all that's required. It's a programmer and thermostat all in one device.
...So the programmer becomes a useless ornament on your wall that has no function.The programmer is left on as instructed in the setup guide.
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