Have the house builders messed up with the CH programmer? + installing Nest 3

[glen8]

Hi All,

What a week we've had!! Megaflow sprung a leak (9yrs into a 10yr warranty), boiler pcb failed (£250 from baxi!!) and now the plumber tells me the programmer has died.
Thing is, I have a feeling it's not been connected correctly when the house was built. Shouldn't the cable going into 2, be moved into 3?

Basically, when we turn the CH off the water comes on, and when the CH is on the water of off!!! Amazingly we've only just noticed (lived in this house 9yrs lol).

Now I'm focused on this I'm wanting to replacing the entire lot with a gen 3 nest thermostat. Can I pull the programmer off, replace with the nest hub, and then pull the thermostat off and connect the live and switched live together?
The nest is wireless and will control both CH and water via the hub. I'll just power the nest stat from the mains socket with it's USB plug.

Thanks!!

 

[D_Hailsham]

Shouldn't the cable going into 2, be moved into 3?

Yes. Whoever installed just looked at the word "ON" above terminal 2 and didn't see that it was connected to the 'off' side of the CH switch.

The "standard" wiring for programmers is: 1 = HW off; 2 = CH off; 3 = HW on; 4 = CH on. I have never understood why the terminals have been arranged in this way; 1 & 2 for HW, 3 & 4 for CH is much easier to understand and less likely to result in errors.